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Comparison of insect pest complexes in different Philippine dryland riceenvironments: population densities, yield loss, and managementJ. A. Litsinger; E. M. Libetario a; A. T. Barrion a; R. P. Apostol b

a Philippine Rice Research Institute (PhilRice), Maligaya, Science City of Muñoz, Nueva Ecija, Philippines b

International Rice Research Institute, Metro Manila, Philippines

Online Publication Date: 01 April 2009

To cite this Article Litsinger, J. A., Libetario, E. M., Barrion, A. T. and Apostol, R. P.(2009)'Comparison of insect pest complexes indifferent Philippine dryland rice environments: population densities, yield loss, and management',International Journal of PestManagement,55:2,129 — 149

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Comparison of insect pest complexes in different Philippine dryland rice environments:

population densities, yield loss, and management

J.A. Litsingera*, E.M. Libetariob, A.T. Barrionb and R.P. Apostolc

a1365 Jacobs Place, Dixon, CA 95620, USA; bPhilippine Rice Research Institute (PhilRice), Maligaya, Science City of Munoz,Nueva Ecija, 3119, Philippines; cInternational Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines

(Received 12 February 2008; final version received 5 November 2008)

In the Philippines most of the dryland rice pests are distinct from those of wetland culture. Partitioned-growth-stage yield loss studies revealed the highest losses in dryland rice were due to sown-seed and seedling pests (ants,field crickets, mole crickets, and termites) as well as root feeders (white grubs and root aphids) and early seedlingpests (seedling maggot and flea beetle) more than the common foliar wetland pests. Losses (5–71%) were highestin the sites with the smallest rice area in which pests were concentrated and the poorest soils (which constrain yieldcompensation) along a continuum of dryland rice habitats. Crop management practices such as overseeding andfertility management can mitigate potential losses to a large degree. Therefore integrated crop management playsa central role in integrated pest management in dryland rice cultivation where the use of insecticides should beminimized for economic and environmental reasons.

Keywords: rice insect pests; yield loss; slash and burn; upland rice; integrated crop management; pestmanagement; crop compensation

1. Introduction

Dryland rice is a cultural type distinct from themore common wetland culture where direct rainfallis the only source of water and japonica-basedvarieties, rather than indica ones, are normallycultivated in non-bunded fields. Dryland rice,representing ca. 13% of rice area worldwide (Guptaand O’Toole 1986), is neither puddled nor pondedand the soils are aerobic (Morris 1986). ThePhilippines ranks fifth among SE Asian countriesin dryland rice area (Gupta and O’Toole 1986); itsupports 15% of the Filipino population (Garrityet al. 1993).

Arraudeau and Harahap (1986) conducted aworldwide survey among dryland rice scientists andproduced a long list of constraints beginning withpoor soil, frequent water stress, fungal diseases,nematodes, weeds, and lack of adaptive and manage-ment responsive varieties. They also listed a widearray of insect and vertebrate pests that contribute tolow yields, but these were considered of lesserimportance. Grist and Lever (1969) and Fujisakaet al. (1991) also mentioned birds, rodents, wild pigs,monkeys, squirrels and even elephants and rhino-ceroses as dryland rice pests, particularly near forestswhich are habitats for most of these animals. Thedegree to which the aforementioned pest constraintsare manifested is mainly linked to the type of drylandhabitat; the latter can vary dramatically in terms of

slope, soil type, rainfall pattern, and surroundingcrops and flora.

Litsinger et al. (1987b) reviewed the worldliterature on dryland rice insect fauna and notedlife-history strategies based on polyphagy, dormancy,and/or dispersal abilities, as dryland rice is dom-inantly a single rice crop system. Key insect pests ofthe wetlands, i.e. brown planthopper Nilaparvatalugens (Stal), green leafhopper Nephotettix virescens(Distant), and yellow stemborer Scirpophaga incertu-las (Walker), are specific to Oryza spp. and cannotsustain themselves in a dryland rice environment. Dueto the short rice season, they must re-migrate eachseason from nearby wetland sites. Several soil insectscommon in the drylands have life-cycles of up to ayear or more in duration. More dryland rice pestsenter periods of dormancy than wetland pests.Armyworms, butterflies, and locusts have greaterdispersal powers than most wetland insect pests, withthe exception of rice planthoppers and leaffolders(Denno et al. 1991).

In the Asian literature, there have been few trialsin which yield losses were measured, but all research-ers used the insecticide check method. Other yield lossstudies have been conducted in Latin America andAfrica where dryland rice is the most important riceculture (Litsinger et al. 1987b). In Thailand, Kata-nyukul and Chandartat (1981) recorded losses of only5% (range 1–13%) from 1976 to 1979.

*Corresponding author. Email: [email protected]

International Journal of Pest ManagementVol. 55, No. 2, April–June 2009, 129–149

ISSN 0967-0874 print/ISSN 1366-5863 online

� 2009 Taylor & Francis

DOI: 10.1080/09670870802604054

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Downloaded By: [Litsinger, J. A.] At: 12:37 1 May 2009

Earlier studies in the Philippines documented theinsect pest fauna and measured losses by theinsecticide check method in Batangas and CamarinesSur provinces (IRRI 1975, 1976a). Those studies wereundertaken in habitats with favourable soils andmore permanent agriculture based on thoroughtillage. Losses incurred by traditional tall Daggeand Kinanda varieties were very high, averaging31 + 17% (2.4 vs. 1.8 t/ha) over nine fields. Studieswere also carried out in dryland fields on the borderof the irrigated experimental farm of the Interna-tional Rice Research Institute (IRRI), the conclusionbeing that most insects found in the drylands werealso present in the wetland area (Pathak and Dyck1975).

There is a continuum of dryland rice habitats thatrepresents stages in settlement, economic develop-ment, and population growth in a locality (Litsinger1993). It begins with pioneering farmers settling intorecently logged rainforests; they then cultivate dry-land rice by slash and burn or swidden agriculture(Morris 1986). As the area becomes more denselypopulated, animal power is used to pull tillageimplements. Still further population increase bringsnearby markets and crop diversity increases wherecash crops are rotated with rice.

In this report we argue that each of thesesuccessive stages in land use leads to different pestcomplexes and population intensities. We also expandon earlier trials in the Philippines. Multi-year croploss assessments were undertaken in four farmcommunities, each representing a different environ-ment along the continuum. These differed fromprevious studies as losses now were partitioned byrice growth stage. Also more attention was given torecording pest complexes, as researchers lived at thesite as opposed to making periodic visits, and sosampling could be done more frequently. We alsoreport on the results of trials which were alsoundertaken to develop practical crop productionpractices centred upon cultural controls as well asminimal usage of insecticides following an integratedcrop management approach.

2. Materials and methods

2.1. Site descriptions

Two research sites (Claveria and Tupi) were estab-lished in Mindanao Island under the influence of theInter-tropical Convergence Zone climate, and afurther two were established in Luzon Island (Sinilo-an and Tanauan) with a monsoon climate. Together,all sites represented an environmental and cropcultural continuum from subsistence, low input, slashand burn systems on sloping, acidic, and eroded soilssown with traditional varieties, to high input,diversified agriculture on flat volcanic soil sownwith modern rice and cash crops.

2.1.1. Siniloan

This slash-and-burn site was established in Magsay-say village located mid-way between Siniloan andReal municipalities in the Sierra Madre mountains ofthe Laguna and Quezon provincial border in highlyeroded, acidic soils (Gonzaga et al. 1986). Traditionalrice is sown in holes made with a dibble stick in Julyamong smouldering tree stumps. Rice fields are small(ca. 0.1 ha) due to the high labour demands, asperennial grasses quickly invade requiring tedioushand-weeding. Farmers do not use either inorganic ororganic fertiliser.

2.1.2. Claveria

Claveria in Misamis Oriental province, near Cagayande Oro City, is located on an escarpment along thelower slopes of Mt Balatukan volcano. This highlyeroded and acidic soil site is representative of arecently deforested stage; the forest has been replacedby perennial grasslands, leaving only scattered treesin a relatively steep terrain. The farmers’ priority is tofirst plant maize in fields prepared by animal-drawnimplements including the mouldboard plough. Rice issown in rows in May or June made with a furrowopener which also serves for inter-row cultivation ofweeds in the early growth stages. There is moreuncultivated than cultivated land in the site. Farmershave their own tall, traditional japonica type varieties,which they cultivate with few purchased inputs.Further site description can be found in Litsingeret al. (2002).

2.1.3. Tupi

Tupi is a town in South Cotabato province, lying onfavourable, young, and only slightly acidic volcanicsoils. This third stage is more populated and on flatterrain with few uncultivated areas (IRRI 1990).Farmers typically apply 30 kg/ha of N and P;uncharacteristically for dryland rice sites, farmersgrow a mix of modern semi-dwarf varieties along withhigh value traditional types.

2.1.4. Tanauan

The principal crops in Cale village, Tanauan town inBatangas province are maize and dryland rice as wellas a wide array of vegetables for the nearby Manilamarket. The nearby Taal volcano erupts regularly tospread new ash over the landscape. This fourth stagerepresents a highly favourable soil in a populated areawhere farmers engage in the growing of high-input,diversified croppings where fields are intensively tilled(IRRI 1976b). The topography is gently sloping,and farmers prevent the slight erosion with livingfencerows. Farmers are economically well off from

130 J.A. Litsinger et al.


the sale of vegetables, and can afford an average of110 kg N/ha on rice where lodging can occur duringripening stage during typhoons. Due to its preferredtaste and grain type, farmers prefer to grow atraditional variety rather than to purchase rice inthe market.

2.2. Rice crop management

UPLRi5 dryland rice variety bred by the Universityof the Philippines was used in all sites except Siniloan.This semi-dwarf is a cross between indica and japonicatypes, and is high tillering and of medium maturity(130–140 d). The traditional rice Benernal in Siniloanwas grown at a seeding rate of 50 kg/ha whereas inother sites the rate was 100 kg/ha. Siniloan farmersplaced three to four seeds per dibble hole 20–25 cmapart. Each hole was covered with soil and steppedon. All trials were superimposed on farmers’ fieldsunder their own agronomic management. In additionto yield loss treatments, the trials included someimproved agronomic practices in the experimentaldesign. In all but the slash and burn site, land wastilled with animal-drawn ploughs. Furrows weremade with a wooden implement (lithao), and seedwas broadcast and raked into the furrows with aspike-toothed, box-harrow and covered by a finallevelling. In Tanauan 90 kg N/ha was applied in twoequal splits as a side dressing during hilling up and atpanicle initiation. Prior to seeding in Claveria andTupi, P was placed in the open rows at 25 kg/ha andcovered. A side dressing of 25 kg N/ha occurred at14 d after crop emergence (DE) before the first inter-row cultivation followed up by a second top dressingof 25 kg N/ha before panicle initiation. Farmershand-weeded as needed. In Tanauan and Tupifarmers undertook dry season ploughing for weedcontrol, in the latter site a number of times. Nocooperating farmer applied any pesticide to drylandrice crops. Grain yield was taken from five samples of5 m2 cuts taken in a stratified grid within the 100-m2

plots. The grain was dried to 14% moisture.

2.3. Treatment descriptions

2.3.1. Partitioned-growth-stage yield loss trials

The insecticide check, partitioned yield loss methodwas conducted following Litsinger et al. (1980). Therewere eight treatments in Claveria (seven seasons) andTupi (four seasons) to quantify losses in six growthstages. The first treatment was termed the ‘completecontrol’ where the objective of a regimen of insecticideapplications was to suppress all groups of insect pests.Sown seeds were protected with a systemic insecticide(6 g a.i. carbosulfan STD/kg seed) from ants, fieldcrickets, and mole crickets as well as seedling maggotand flea beetles that attack young seedlings. Carbo-sulfan was added to cassava flour then mixed into a

paste. Seeds were then added to be coated with themixture, and finally they were dusted with cassavaflour for easier handling after drying overnight. Next,a soil insecticide (1 kg a.i. Lindane (gBHC) granules/ha) was placed in the seed furrows directed againstroot-feeding white grubs and termites, and a secondapplication was side-dressed at hilling up. Litsingeret al. (1983) showed that this insecticide had highefficacy against white grubs. Reproductive stage soilprotection was 0.75 kg a.i. carbofuran granules/haplaced in shallow furrows 40 and 70 DE for root-feeding aphids and mealybugs. The reproductive stagewas also protected by an additional treatment ofweekly foliar sprays (0.4 kg a.i. monocrotophos/ha)for stemborers, plant- and leafhoppers, and leaffolders.Ripening stage protection against rice seed bugs was10 g a.i. deltamethrin EC/ha sprayed twice weeklyfrom panicle emergence to hard dough. The secondtreatment was an untreated check. Foliar insecticideswere applied in 19 l, lever-operated, knapsacksprayers fitted with cone nozzles. Spray volumeincreased from 300 to 500 l/ha as the crop grew.

Each of a succession of treatments eliminated oneof the complete control treatments in order topartition the loss among growth stages. Rice growthstages were described by Yoshida (1981). The thirdtreatment eliminated the seed treatment, the fourtheliminated the soil applications of gBHC granularinsecticide, the fifth eliminated the reproductive stagecarbofuran granules, the sixth eliminated the repro-ductive stage sprays, and the seventh treatmenteliminated ripening stage sprays.

In Tanauan, yield loss was calculated in the talltraditional Dagge rice over five seasons in separateexperiments and from the improved UPLRi5 rice inexperiments over three seasons. The partitioned yieldloss treatments consisted of a complete control whichprotected five growth stages. The first stage was thesown-seed where 4 g a.i. bendiocarb/kg seed made asa water slurry without the cassava flour. A soiltreatment consisted of diazinon granules at 1 kg ai/haapplied in the seed furrows. A third was vegetativefoliar protection with 1 kg a.i. monocrotophos/hasprays at 10-day intervals (25, 35, 45 DE) and thefollow on to protect the reproductive stage (55, 65, 75DE), and then by 1 kg a.i. gBHC EC/ha at milk, soft,and hard dough stages.

The complete control treatment in Siniloan (twoseasons) included increasing the dosage of the seedtreatment to 0.4 kg a.i. carbosulfan/ha. This wasfollowed by weekly sprays of foliar insecticides:0.75 kg a.i. monocrotophos/ha during the vegetativeand ripening stages and the mixture of 0.75 kg a.i.chlorpyrifos þ BPMC/ha from panicle initiation toheading. Only the total yield loss was determined inSiniloan where the complete control was compared tothe untreated check, as no growth stage partitioningwas carried out to keep the trials small.

International Journal of Pest Management 131


Total yield loss was calculated as the differencebetween the complete control treatment and theuntreated check. To calculate percentage, total losswas divided by the full protection yield and multipliedby 100. Yield losses from each of the partitioned-growth-stage treatments where insecticide wasomitted were calculated in the same way and thenadded. As the two totals were seldom mathematicallyequal, losses for each pest group or crop stage wereapportioned based on the total loss from the completecontrol.

2.3.2. Crop management treatments

Plots of integrated crop management practices wererandomised among the yield loss plots in the on-farmtrials. Their purpose was to generate recommenda-tions for farmers, and their inclusion each seasonallowed an iterative process of technology develop-ment for each site. These treatments included varia-tions in seeding rate, inorganic and organic fertiliser,and insecticide protection either as soil and/or seedtreatments.

Six potential recommended practices were com-pared in Siniloan: (1) was a high input practice todetermine the yield potential that involved organicfertiliser plus lime mixed into the soil in each dibblehole to raise soil pH thus making applied P moreavailable in the highly acidic soils. Insect control wasan insecticide seed treatment (0.25 kg a.i. carbosulfanST/kg seed). The seeds were slightly moistened toallow the seed treatment (ST) formulation to stick tothe seed coat. Foliar insecticide protection was0.75 kg a.i. monocrotophos EC/ha weekly duringthe vegetative stage to flowering, and 0.75 kg a.i.Brodan EC (BPMC þ chlorpyrifos)/ha during milk,soft dough, and hard dough. (2) The same as(1) except it lacked the seed protection. (3) Thisincluded only the insecticide seed treatment plus ashplaced in the seed holes plus 23 kg N/ha from ureaapplied on the soil surface 14 DE. (4) This consistedonly of the ash and 23 kg N/ha. (5) This received theseed treatment plus the ash. (6) This consisted onlythe seed treatment. (7) The untreated check (i.e.control).

In Tupi and Claveria similar treatments werecompared which involved two seeding rates (50 and90 kg/ha) and a soil insecticide treatment 0.25 kga.i. Lindane G/ha and an insecticide seed treatment(0.3 kg a.i. carbosulfan ST/ha). Two fertilisertreatments also were compared: the first lackedinorganic fertiliser; the second was 50-25-0 with theN application split at 14-25 DE during inter-rowcultivation and before panicle initiation, and P wasapplied basally during land preparation. The inclu-sion of these treatments varied from season toseason to enable us to find the best performingtreatment.

In Tanauan a crop management trial was con-ducted in 1976 with 12 treatments replicated in sixfarmers’ fields. Four of the treatments involvedincremental increases in the seeding rate from 50 to125 kg/ha. Four other treatments were conductedat 50 kg seed/ha that tested two seed and twosoil treatments. The seed treatments tested twochemicals – carbofuran ST and dieldrin WP – bothat 0.5 kg ai/ha dosages. The two soil treatments werecarbofuran G at 0.5 and 2 kg ai/ha dosages. Twoother treatments tested the seed treatments at a higherseeding rate of 100 kg/ha while the last two treat-ments tested the soil insecticide dosages, again at the100 kg seed/ha. Data taken were plant stand (ten 3-mrow samples) and yield (two 10 m2 cuts).

A follow-up trial was conducted in four farmers’fields over 3 years (1978–1980) with UPLRi5 sown at100 kg/ha where a seed (0.30 kg a.i. carbosulfan ST/ha) and a soil (0.75 kg a.i. diazinon G/ha) treatmentwere compared to an untreated check. Crop manage-ment treatments were analyzed economically todetermine marginal returns and benefit:cost ratio(B:C) following the method of Smith et al. (1988)using 1986 prices for agricultural inputs and includinga 12% interest per annum for inputs and labourpriced at $0.10h, the wage in rural Philippines at thetime. Unmilled rice was valued at $0.128/kg. A B:Cratio of 42 is considered a favourable return oninvestment.

2.4. Experimental design

Field trials were conformed to a randomised completeblock design with farmers as replicates. New farmercooperators were selected each season, as the resultswould become recommendations for the farm com-munity as a whole. Farmer cooperators were selectedon a staggered basis evenly along each season’splanting curve. Plot sizes were 100 m2 with theexception of the slash and burn site, where theywere 10 m2, the largest obtainable size of uniformfield conditions free of tree stumps.

2.5. Arthropod and crop sampling

Identification of arthropods was undertaken by oneof us (ATB). Voucher specimens were deposited inthe IRRI Entomological Museum. On each samplingdate a team of at least two staff participated in datacollection. The stratified grid method was used tosample plants or arthropods from each quadrant ofall plots. Data collection sites were randomly selectedwithin each quadrant. One person recorded the dataon a clipboard while others did the counting withmechanical tally counters. Plant stand was recordedweekly from the first through the fourth weeks bycounting the number of plants along the rowmeasured in 1–4-m sections. Insect damage was also



assessed at the same time. Seedling maggot wascensused by damaged tillers (deadhearts) and molecricket by damaged plants. Root pests such astermites, root aphids, and mealybugs were recordedin 50 plant samples with each plant being uprootedand the root system inspected. Stemborer deadheartsand whiteheads as well as leaffolder damaged leaveswere censused 50, 70, 90, and 110 DE from 10samples of 5-m rows. In these cases the number oftillers and leaves was counted in each 5-m row. Plant-and leafhoppers were sampled in the crop in Tanauanusing a motorized D-VAC1 suction machine that wasswung side to side a distance of 1 m and walked ameasured 25 m to give a sample size of 25 m2.Sampling was done weekly in four fields from earlyvegetative stage to 2 weeks before harvest. Rice seedbugs were sampled by taking 25 pendulum sweepswith a 38-cm diameter insect net at milk, soft, andhard dough stages. Damaged grains were determinedvia the acid fuchsin staining technique (Litsinger et al.1981).

2.6. Light trap collections

Pairs of kerosene metal light traps were used, madeby Laguna fishermen with the lamps enclosed in aglass housing (Litsinger et al. 1979). Farmers weretrained to manage the light traps by depositing eachnight’s catch in vials of 70% alcohol. Trained staff didthe identification and counting with the aid of astereomicroscope. Light traps were placed two pervillage in rice fields out of sight from one another andunobstructed by trees within a radius of 100 m.Enough kerosene was used to enable the lamps toburn throughout the night. The height of the flamewas standardized across sites by wick length. Collec-tions in the four dryland rice sites were compared tothree rainfed wetland and three irrigated sites wheresimilar research teams worked. Two irrigated siteswere separated into areas that represented thestandard synchronized double-rice cropping and amore intensive cropping (2.5 crops in 5 years) plantedasynchronously (Loevinsohn et al. 1988). Countswere summed over six months that represented themean period of a seasonal rice crop. This was done sothat rainfed single crop areas could be compared toirrigated double crop sites on a per crop basis. Inirrigated sites data were summarized for each wet anddry season crop based on the planting pattern eachyear. Data presented are averages of all of the cropsduring the specified years for each species.

2.7. Statistical analysis

All statistical analyses were performed by SAS withP � 0.05 as the criterion for significance. Resultswere subjected to one-way ANOVA. Treatmentmeans were separated using the paired t-test for two

variables or the Least Significant Difference (LSD)test for more than two variables. Means are shownwith standard errors of the mean (SEM) using apooled estimate of error variance.

3. Results

3.1. Insect pests

3.1.1. Siniloan

The most injurious group of insects in the slash andburn site were sown-seed and seedling pests whichreduced plant stand 91% in 1984 and 27% in 1985.The first group included ants, dominated by theubiquitous Solenopsis geminata (F.), that removedseeds, while field crickets fed on the germinatingseeds. Foliar pests attacking young seedlings wereseedling maggot Atherigona oryzaeMalloch and a fleabeetle Chaetocnema basalis (Baly). The rice seedlingmaggot caused 42% deadhearts in 1984 but rose to440% deadhearts in 1985 (Table 1). The 2-mm fleabeetle adults caused shot hole leaf damage to 46% ofyoung seedlings leading to death of many in 3–5 days.Its normal hosts are grasses (Barrion and Litsinger1986a).

As rice was planted in such small areas of burned-off forest there were fewer species in this pest complexcompared to other sites. This was due to both thesmall size of fields and lack of alternative hosts.Absent were sown-seed and root pests, such as rootaphids, mole crickets, white grubs, mealybugs, andtermites. Foliar pests such as plant- and leafhoppers,stemborers, and defoliators were also missing.

The crop suffered periods of moisture stressmanifested by leaf rolling. These conditions encour-aged a leaf-feeding thrips Stenchaetothrips biformis(Bagnall) to multiply causing stippling by removingphotosynthetic area, but their numbers were soonsuppressed by heavy rains (Barrion and Litsinger1986b). Two leaffolder species were encountered withMarasmia exigua (Butler) being more prevalent thanCnaphalocrocis medinalis (Guenee) as the former hasa wider host range (Barrion et al. 1991). Light trapcollections recorded leaffolders year-round and theypeaked during rice harvest in the lowlands 15–20 kmaway, showing their high migratory capability.Damage was non-economic, however. Rice seedbugs Leptocorisa oratorius (F.) and L. acuta (Thun-berg) were recorded at relatively high densities (4.1/m2). The latter is less associated with rice areas andhas a wider plant host range. This was the highestdensity recorded among 11 research sites representingdryland, rainfed, and irrigated wetland ecosystems(Litsinger 2008).

Kerosene light trap collections showed low tomoderate densities of brown planthopper and greenleafhoppers along with one of their major predatorsCyrtorhinus lividipennis Reuter (Table 2). Yellowstemborers were also caught in low levels. Despite



Table1.

Effectofincreasinginputlevelsofnutrients,soilamendments,andinsecticideonyield

ofBenernaldrylandrice

grownin

slash

andburn

culture,Siniloan,Lagunaprovince,

Philippines,1985.a

Treatm

ent

Treatm

entinputs

(dosageper

hectare)

Plantstandd

(no.plants/30hills)

14DE

Leafbeetle

(%damaged

leaves)14DEe

Seedlingmaggot

(%deadhearts)

28DEe

Yield

(t/ha)f

Nutrients

(kg/ha)

Soilamendments

Insecticidetreatm

ent

1.Highinput,

fullprotection

46N,28P,14K

500kglimeþ

3tchicken

manure/ha

0.4

kga.i.carbosulfan

ST/haþ

weekly

foliarspraysc

206+

24ab

8.3

+4.9

a17.4

+4.5

a0.48+

0.25a

2.Highinput,

foliarprotectiononly

46N,28P,14K

500kglimeþ

3tchicken

manure/ha

Weekly

foliarspraysc

142+

15c

7.8

+5.1

a42.4

+23.2

c0.47+

0.26a

3.Low

input,seed

treatm

entonly

23N

Ash

b0.25kga.i.carbosulfanST/ha

221+

26a

12.4

+8.6

a28.8

+11.3

ab

0.42+

0.24a

4.Low

input,

noprotection

23N

Ash

b162+

11c

38.9

+13.2

b30.6

+16.3

b0.45+

0.21a

5.Low

input,

seed

treatm

entonly

Ash

b0.25kga.i.carbosulfanST/ha

204+

27ab

13.5

+9.9

a18.9

+9.0

a0.20+

0.08b

6.Low

input,

seed

treatm

entonly

0.25kga.i.carbosulfanST/ha

162+

16c

11.2

+7.2

a15.7

+5.4

a0.21+

0.07b

7.Untreated

149+

19c

45.7

+20.3

b37.0

+15.2

b0.06+

0.05c

P5

00001

500001

500001

500001

F5.32

4.84

5.92

4.98

df

10

10

10

10

aAverageoffourreplications.In

acolumn,means(+

SEM)followed

byadifferentletter

are

significantlydifferent(P�

0.05)byLSD

analysis.DE¼

daysafter

cropem

ergence.

b½

cupper

dibble

hole

derived

from

forest

trees.

c0.75kgaimonocrotophosEC/haweekly

duringthevegetativestageto

panicle

initationandduringripening,0.75kgaiBPMCþ

chlorpyrifos(BrodanEC)/hafrom

panicle

initiationto

flowering.

EC¼

emulsifiable

concentrate

(liquid)form

ulation.ST¼

seed

treatm

ent.

d30dibble

holessampledper

replication.

e50hillssampledper

replication.

f 25-m

2samplesper

replication



Table

2.

Abundance

ofinsectsandvariablesofrice

croppingintensity

byrice

culture

asdetermined

from

kerosenelighttrapssetupin

12locationsin

thePhilippines,1979–1992.

Riceculture

aTown

Province

No.

crops/yr

Area

inrice

(%)b

Seasonaltotalper

lighttrapper

locationc

Brown

planthopper

N.lugens

Whitebacked

planthopper

S.furcifera

Green

leafhoppers

Nephotettix

spp.

Zigzag

leafhopper

R.dorsalis

White

leafhopper

C.spectra

C.lividipennis

mired

predator

Scirpophaga

spp.

Stemborers

dOther

stem

borers

e

Dryland

Siniloan

Laguna/Q

uezon

1.0

3185+

78d

451+

144c

425+

158b

41+

7c

Claveria

MisamisOriental

1.0

9262+

75d

130+

37b

75+

29c

190+

73c

37+

19b

45+

11c

178+

98c

Tupi

South

Cotabato

1.0

14

2,908+

864c

498+

115b

1,449+

398c

1,802+

161b

80+

22b

1,780+

272b

170+

43c

315+

87bc

Tanauan

Batangas

1.0

20

130+

78d

1,700+

367b

860+

452c

720+

294c

50+

23c

Rainfedwetland

Solano

Cagayan

1.0

60

491+

217d

1,527+

527b

3,218+

2,320b

312+

103ab

595+

269b

437+

133c

131+

36c

Manaoag

Pangasinam

1.0

85

289+

94d

321+

81b

2,179+

538c

305+

79c

475+

66c

0c

Oton/Tigbauan

Lloilo

1.0

85

1,824+

528cd

1,012+

215b

2,440+

770c

1,016+

612bc

458+

185a

455+

314b

997+

108b

38+

30c

Irrigated(synchronous)

Victoria/

Sta

Maria

Laguna

1.9

90

214+

79d

1,366+

896b

629+

426c

195+

95c

410+

168b

413+

88c

35+

35c

Cabanatuan/

Zaragoza

NuevaEcija

2.0

80

154+

14d

361+

77c

305+

17c

0c

Koronadal

South

Cotabato

2.0

70

1,677+

345cd

549+

152b

2,279+

617c

855+

169c

93+

17b

706+

252b

662+

83bc

405+

46b

Irrigated(asynchronous)

Jaen

NuevaEcija

2.0

80

15,224+

238a

9,207+

2,561a

137+

59c

0c

Koronadal

South

Cotabato

2.4

70

11,168+

1,849b

4,043+

1,117a

3,158+

501b

2,961+

389a

145+

21ab

7,169+

720a

2,519+

430a

751+

123a

P50.0001

50.0001

50.0001

50.0001

50.0001

50.0001

50.0001

50.0001

F37.01

6.76

5.54

24.02

3.12

17.46

19.91

17.92

df

49

40

49

40

32

36

49

45

RiceCulture

Average

Dryland

871b

776b

709b

904b

59

1,103b

77b

247

Rainfedwetland

868b

953b

2,612ab

661b

385

525b

636ab

56

Irrigated(synchronous)

682b

957b

650b

551b

93

558b

460ab

147

Irrigated(asynchronous)

13,196a

4,043a

6,183a

2,961a

145

7,169a

1,328a

376

P50.0001

0.04

0.02

0.02

0.12ns

0.007

0.04

0.07ns

F40.95

6.15

6.30

12.09

7.33

37.03

3.04

0.76

df

11

811

75

611

9

aSynchronyrefers

tofarm

ers’plantingdatesandsynchronyoccurs

when

farm

ersplantwithin

aperiodofonemonth,theaveragegenerationalperiodofmost

insect

pests

(Loevinsohnet

al.1988).

bCircumference

of1km

2centeredaroundeach

lighttrap.

cDailycounts

from

kerosenelighttraps.Nodata

indicatesthattheinsect

inquestionwasnotmeasured.

Inacolumn,means(+

SEM).followed

byadifferentletter

are

significantlydifferent(P

40.05)byLSD

analysis.

dS.innotata.S.incertulas.

eChilosuppressalis,Sesamia

inferens,Maliarphasp.



these catches that were equivalent to a number ofwetland sites where moderate damage levels occur onalmost each crop, such densities did not translate intosignificant infestations in the slash and burn area, asdeadhearts or whiteheads were rarely encountered.

3.1.2. Claveria

Stand loss averaged 14% in the vegetative stage, morefrom sown-seed and root pests (Table 3), mainly antsagain dominated by S. geminata. Germinating seedpests were mole cricket Gryllotalpa orientalis Burme-ister and field crickets, while root pests were whitegrubs, termites, root aphids, and mealybugs. Thesubterranean termite Macrotermes gilvus (Hagen)prefers wheat to rice as a 100-m2 trial plot (var.Trigo) sown within a rice field was totally denuded inthe seedling stage. Densities in rice reached 7 termites/50 plants with minimal damage to rice.

The seedling maggot averaged a modest 6%deadhearts. After tillering their numbers declined, asthe larvae can only attack developing tillers. Defolia-tion from general defoliators including C. basalis fleabeetle was subeconomic. The most common defolia-tors were leaffolders that averaged only 1% damagedleaves, the most common being M. patnalis Bradleyfollowed by M. exigua and C. medinalis. Also notedwas the armyworm Mythimna separata (Walker)which did negligible damage.

Three species of root aphids built up in numberswith crop growth reaching 1.8/plant. Tetraneuranigriabdominalis (Sasaki) was most common followedby Geoica lucifuga (Zehntner) and Rhopalosiphumrufiabdominalis (Sasaki) in fields where numbers werehigh, plants turned yellow and became stunted. Thecommon root mealybugs were Trionymus sp. andPseudococcus sp. where only token numbers occurred(1/50 plants).

Stemborer damage as deadhearts or whiteheadswas 51% where species composition determined bytiller dissection showed striped stemborer Chilosuppressalis (Walker) to be the most dominant (72%of collections) followed by yellow stemborer (11%),white stemborer S. innotata (Walker) (10%) andfinally pink stemborer Sesamia inferens (Walker)(6%). Larvae were reared to distinguish between theScirpophaga species. Rice seed bugs were a mixture ofL. oratorius and L. acuta averaging 1/m2.

White grubs also fed on roots having the greatestdetrimental effect on seedlings averaging 8/10-m rowafter harvest. The two most common species Leuco-pholis irrorata (Chevrolat) and Holotrichia mind-anaoana Brenske had synchronized 2-year life-cycleswhich on odd-numbered years resulted in the lastinstar larvae being in the field at the time of cropplanting (Litsinger et al. 2002). Females ovipositduring land preparation predominantly in evennumbered years when only the less damaging young T

able

3.

Insect

pestdensities

onfarm

ers’drylandrice

fieldssownto

UPLRi5

inClaveria,MisamisOrientalandTupi,South

Cotabato,Mindanao,Philippines

1984–1990.a

Site

Crops

(no.)

Years

Plantstandreduction(%

)21DEb

Seedingmaggot

(%deadhearts)

21DEb

No.per

50plants

40DEd

Stemborer(%

)b

Leaffolder

(%damaged

flagleaves)b

Ricebug

(no./m

2)e

Whitegrubs

(no./10-m

row)

atharvestf

Sown

seed

pests

Root

pests

Combined

cTermites

Root

aphids

Rootmealy

bugs

Deadhearts

50–70DE

Whiteheads

Claveria

71984–90

11.0

+2.3

9.3

+1.6

14.3

+1.9

5.8

+1.1

7.3

+2.9

88+

30

1.0

+0.6

0.6

+0.3

0.5

+0.2

1.2

+0.3

1.0

+2.1

8.4

+2.8

Tupi

41986–87

1989–90

8.4

+3.9

8.5

+3.8

13.6

+2.8

8.3

+2.0

9.9

+5.4

172+

33

00.5

+0.3

0.7

+0.3

6.5

+2.8

1.0

+0.9

7.2

+5.6

aEach

year4–8fields(replications)

weremonitoredfrom

insecticideuntreated100m

2plots.DE¼

daysafter

cropem

ergence.Data

are

means+

SEM.

b0-m

row

sample.

cSampledfrom

theuntreatedcheck.

dPlants

dugupto

10cm

depth

androots

insepected.

eData

are

meansfrom

sampling25m

2duringmilk,soft,andhard

doughstages.

f Plants

dugupandsoilinspectedto

20cm

depth.



larvae affect the crop. Three other species were alsofound feeding on rice but in much lower densities:H. flachi Brenske, Adoretus luridus Blanchard, andAnomala humeralis Burmeister.

Claveria had the lowest light trap collections ofany of the sites (Table 2), as it was the most isolatedfrom wetland areas. Plant-/leafhoppers were rarelyencountered on the crop. As with Siniloan, stemborerspecies balance favoured genera other thanScirpophaga.

3.1.3. Tupi

An average stand reduction of 14% resulted fromboth sown-seed and root pests in this favourabledryland site (Table 3). The main seed pest was S.geminata, along with mole and field crickets. Seedlingmaggot damage averaged 8% deadhearts but other-wise the seedling stage was not significantly infestedby insect pests, as flea beetle damage was barelynoticed. Root pests were white grubs and termites.White grubs continued to gnaw away on rootsthroughout the crop season; the same five species asfound in Claveria were recorded. They averaged 7 per10-m row at harvest. Termites averaged only 1 perfive plants. Other root feeding pests were root aphidswhich averaged 43 per plant and thus were one ofthe most important pest guilds. Root mealybugs,however, were not recorded.

Stemborers were mainly Scirpophaga dominatedby white stemborer although there was a species shiftin the province prior to the study due to El Ninoclimate change (Litsinger et al. 2006a). Damagelevels, however, were extremely low with deadheartsand whiteheads 51%. Leaffolders averaged 7%damaged leaves dominated by M. patnalis (55% offield collections) and C. medinalis (45%). Rice seedbugs were low in number (1/m2).

Light trap densities of the major rice pests weregreatest in Tupi among the dryland rice sites and evengreater than many other wetland rice sites (Table 2).The exception was whitebacked planthopper Soga-tella furcifera (Horvath) which was more abundant inTanauan due to its close proximity to Lagunawetland areas. Densities of brown planthopper,zigzag leafhopper Recilia dorsalis (Motschulsky),and Cyrtorhinus mirid were highest in Tupi exceptfor one or two of the asynchronously plantedirrigated rice sites. Green leafhopper numbers werehigh in the dryland sites but lower than the irrigatedwetland sites. Stemborer densities were also highestamong the dryland sites but much less than at thewetland sites. The ratio of Scirpophaga to non-Scirpophaga stemborers favoured the latter, equal tothe other dryland sites. The most abundant wasMaliarpha sp. with 63% of the catch followedby S. innotata (26%), C. suppressalis (9%), andS. inferens (2%).

3.1.4. Tanauan

Insect pest species richness and their densities inTanauan were only higher than in Siniloan. Sown-seed and root pests (white grubs and termites) eachreduced stand 9–11 and 11–10%, respectively, whenmeasured individually and for each varietal type(Table 4). When both contributions are combined,stand reduction ranged from 14 to 16% for Daggeand UPLRi5, respectively. S. geminata was probablyresponsible for most of the loss of seed followed bymole and field crickets. Only one species of whitegrub L. irrorata was encountered and is a major pestof sugarcane in nearby fields. Farmers cite termitesdominated by M. gilvus along with Coptotermes spp.as major dryland rice pests. Termites are permanentresidents of the uplands as their nests extend belowthe plough pan and feed mainly on maize stalks andrice straw. Farmers, however, overestimate theimportance of termites but do not sufficiently valuethe other pests. Seedling maggot was also present butat very low numbers during the vegetative stage.

Several defoliating Lepidoptera were recorded,based on periodic field collections during the 1976–1980 seasons mainly in the reproductive stage. Fromthe total collection of 635 larvae and pupae, the mostabundant was greenhorned caterpillar Melanitis ledaismene Cramer (46% of the total) followed byarmyworms M. separata (17%) and Spodopteramauritia acronyctoides Guenee (16%) plus riceskipper Pelopidas mathias (F.) (13%) and brownsemi-looper Mocis frugalis (F.) (9%). However, theamount of defoliation from these species neverreached economic levels.

The light trap catches showed that among the fourdryland sites Tanauan had supported high levels ofplant- and leafhoppers, second only to Tupi (Table 2).The highest light trap densities were of whitebackedplanthopper followed by green and zigzag leafhop-pers which were mirrored in field sampling (Figure 1).Densities peaked in the late reproductive stage anddeclined toward crop senescence with the abundanceof Cyrtorhinus predator trailing that of its prey.Abundance of yellow stemborer from light trapcatches was equivalent to that at other dryland sitesexcept Tupi. Cyrtorhinus numbers were also moderatedespite its major prey (planthoppers) being abundanton the crop.

Plant- and leafhoppers were more abundant onDagge than on UPLRi5 (Table 4). Numbers werehigher on the traditional variety than on the modernvariety, and at times small patches of hopperburnwere noticed in some fields. Of the green leafhoppers,most individuals (83%) were N. virescens, as theremainder being N. nigropictus (Stal) indicating thatthe site was still within the dispersal range of riceinsect pests moving from wetland areas. Cyrtorhinuspredators were also prevalent, their numbers building



up over the season and peaking after the planthop-pers (Figure 1). Spider densities were at 1–2/m2

throughout the crop season. The most commonspiders were Argiope catenulata (Doleschall) (Aranei-dae), Clubiona japonicola Boesenberg et Strand(Clubionidae), Pardosa pseudoannulata (Boesenberget Strand) (Lycosidae), Tetragnatha javana (Thorell),T. mandibulata Walckenaer, and T. nitens (Audouin)(Tetragnathidae).

Three species of rice stemborer were recovered byperiodic stem dissections (n ¼ 703 larvae) withS. incertulas the most abundant (74%) followed byS. inferens (19%) and dark headed stemborerC. polychrysus (Meyrick) (7%). The combined da-mage as deadhearts was minimal 52%, with white-heads only slightly 43% (Table 4). Damage washigher on Dagge probably because as it was the tallervariety it elongated more, making it more susceptible(Bandong and Litsinger 2005). These levels were alsosubeconomic. S. innotata does not occur on Luzon.

The high nitrogen usage encouraged three leaf-folders, M. patnalis being the most commonlyencountered while M. exigua colonized first followedby C. medinalis. Damage was greatest at the flag leafstage, averaging 17 and 10% damaged leaves ontraditional and modern varieties, respectively. Fewliving larvae were found upon opening up foldedleaves indicating high rates of predation. Rice seedbug numbers were moderate averaging 1/m2 over theripening stage which damaged 57% of rice grains.

3.1.5. Comparison of rice agro-ecosystems

Kerosene light traps operated over standardized cropseasons in 12 sites measured the activity of a narrowspectrum of rice insect pests, mainly plant-/leafhop-pers, stemborers, and Cyrtorhinus mirid that preys onhoppers. The overall analysis shows that brownplanthoppers were just as prevalent in dryland as inother synchronously planted wetland sites (Table 2).The same was true of whitebacked planthopper forwhich there are no resistant rice varieties. Brownplanthopper was found at low levels in three of thefour dryland sites despite susceptible varieties beinggrown. At Tupi the incidence was as high as inirrigated areas and only less in the two asynchro-nously planted irrigated areas where genetic resis-tance had broken down. The low levels in Manaoag(IR36), Victoria (IR42) and Cabatanuan/Zaragoza(IR42, IR52) indicate that the rice varieties planted atthe time were resistant to brown planthopper. AtIloilo farmers grew a mixture of traditional types andIR36 which was resistant. Tupi farmers selectedmodern semi-dwarfs that, however, were notresistant.

Green leafhoppers were most abundant in Tupiwith the lowest incidence in Claveria but in none ofthe dryland sites were varieties resistant to greenT

able

4.

Insect

pestdensities

onfarm

ers’drylandrice

fieldssownto

traditionalandmodernrice

varietiesin

Tanauan,Batangas1976–1980.a

Plantstand(%

reduction)21DEb

No.per

25m

240DEd

Stemborers

bRicebugde

Variety

Crops

(no.)

Sown

seed

pests

Root

pests

Combined

cNephotettix

spp.

N.lugens

S.furcifera

R.dorsalis

C.spectra

Cyrtorhinus

predator

Deadhearts(%

)

Whiteheads

Leaffolder

(%damaged

flagleaves)b

No./m

2Damaged

grains(%

)

Whitegrubs

(no./10-m

row)

atharvestf

50DE

70DE

Dagge

59.1

+1.4

11.4

+2.2

14.1

+4.7

78+

47

143+

90

1,318+

763

158+

141

8.1

+2.5

31.4

+10.1

0.4

+1.4

1.6

+0.5

2.6

+0.8

17.3

+5.1

1.3

+1.6

4.1

+0.6

1.2

+0.9

UPLRi5

310.7

+3.0

9.8

+2.4

16.4

+5.3

34+

834+

12

310+

218

27+

17

7.3

+1.7

23.2

+2.2

0.3

+0.1

0.5

+0.2

1.5

+0.6

9.6

+4.0

1.3

+0.9

3.7

+0.5

1.7

+1.5

aEach

year4–8field(replications)

weremonitoredfrom

insecticideuntreated100m

2plots

foreach

variety.

DE¼

daysafter

cropem

ergence.Data

are

means+

SEM.

b10-m

row

sample.

cSampledfrom

theuntreatedcheck.

dSampledbyD-V

AC1

suctionmachine.

eData

are

meansfrom

samplingduringmilk,soft,andhard

doughstages.Damaged

grainsweredetermined

bytheacidfuchsinstainingtechniqueofthefeedingsheaths(Litsinger

etal.1981).

f Plants

dugupandsoilinspectedto

20cm

depth.



leafhopper grown. In the case of dryland sites, cropapparency was low due to a long dry fallow and inirrigated sites genetic resistance prevailed. Modernrices are resistant to green leafhoppers, as can be seenin Laguna and Cabanatuan/Zaragoza among theirrigated sites. However, resistance had broken downin the asynchronous areas. Generally the lowestincidence was in both dryland and irrigated synchro-nous sites with high numbers in rainfed wetland andasynchronous irrigated areas. The short season dry-land rice environment suppressed green leafhopperbuild up whereas in synchronous irrigated sitesresistant varieties were responsible. There are noresistant varieties for zigzag leafhopper and white

leafhopper Cofana spectra (Distant). The highestzigzag leafhopper incidence was the asynchronoussites, but was also recorded in Tupi, and there wereno differences between dryland, rainfed wetland, andirrigated (synchronous) cultures. Also, there was nosignificant difference between rice cultures for whiteleafhopper. The mirid predator densities mirroredmore the brown planthopper than any other preyspecies.

The lowest incidence of Scirpophaga stemborerswas recorded in the dryland habitat, whereas thehighest catches were recorded in Koronadal fromwhite stemborer in the asynchronous area. The ratioof non-Scirpophaga to Scirpophaga was positive only

Figure 1. Abundance of planthoppers, leafhoppers, spiders, and a mirid predator on a traditional dryland rice varietydetermined by weekly suction sampling with a DVAC machine in Tanauan, Batangas, Philippines, 1980. Data are averages of25 m2 samples in each of four fields where rice was sown in June and harvested in October. WBPH, whitebacked planthopperSogatella furcifera; BPH, brown planthopper Nilaparvata lugens; GLH, Nephotettix spp. green leafhoppers; ZLH, zigzagleafhopper Recilia dorsalis, and the mirid predator Cyrtorhinus lividipennis.



in the dryland sites. Differences among habitats fornon-Scirpophaga species were not significant. Skew-ing the results were three sites wherein only Scirpo-phaga stemborers were found. Koronadal had highincidence of Maliarpha sp. stemborers in bothdryland and irrigated sites.

3.2. Yield loss

3.2.1. Siniloan

The slash and burn crop suffered greatly from bothbiotic and abiotic stresses, foremost of which was theeroded acidic soil which reduced root growth, thuswhen periodic water stress occurred the plants werenot able to extract moisture from deep in the soil.Biotic stresses were mainly diseases and vertebrateand insect pests to the extent that in 1984 there wasno grain harvest. Most serious was leaf and neck blastdisease (Pyricularia oryzae Cav.) followed by rats andbirds and an array of insect pests. Also, those plotsthat grew best from added soil amendments and goodinsect control suffered greater yield loss than thepoorer-growing ones due to lodging from typhoons.At harvest, plant height and biomass were insignif-icantly different between treatments. Less blastoccurred in the second year which produced a grainharvest that illustrates how complex quantification ofyield loss is when multiple stresses are involved. Thefarmers’ practice was the untreated (treatment 7)which yielded 60 kg/ha, barely returning the seedsown (Table 1). If insecticide seed treatment isprovided, a yield of 210 kg/ha occurred resulting ina loss of 0.15 t/ha or 71% (treatment 6 vs. 7) fromsown-seed and seedling pests. However, if the farmerfollows the recommended practice of adding 23 kg N/ha there is no yield loss from insect pests (treatment 3vs. 4) because of crop compensation. The besttreatment yielded 480 kg/ha, that is the technicalyield potential, which was also reached by applyingonly 23 kg N/ha plus ash without insecticide. Therewas no additional yield benefit from foliar sprays,thus the measured yield loss from insects came fromcontrol of the sown-seed and seedling pest guilds.Clearly, the degree of loss is highly influenced byagronomic practices.

3.2.2. Claveria

Claveria resulted in an average loss of 0.79 t/ha or23% as the difference between the fully protectedcrop (3.43 t/ha) and the untreated (2.64 t/ha) grownunder farmer management (Table 5). Using thepartitioned yield loss method, losses (t/ha) werehighest from white grubs and termites (0.31) followedby root aphids (0.21), sown-seed/seedling pests (0.16),rice seed bugs (0.09), and stemborers (0.03). The totalyield loss equalled 22.8%: that breaks down to 8.3%for white grubs and termites, 6.6% for root aphids, T

able

5.

Yield

loss

determined

bypartitioned

growth

stage,

insect

pestguildinsecticidecheckmethodin

farm

ers’

fieldsin

Claveria,Misamis

OrientalandTupi,S.Cotabato,

Philippines

1985–1991.a

Site

Crops

Years

Yield

(t/ha)

Yield

loss

(t/ha)

Yield

loss

(%)

Complete

protection

Untreated

Total

Whitegrubs

term

ites

Seed/seedling

pests

Rootaphid

Stemborer

leaffolder

Ricebug

Total

White

grubs/

term

ites

Seed/

seeding

pests

Root

aphid

Stemborer/

leaffolder

Ricebug

Claveria

71985–91

3.43+

0.21a

2.64+

0.16b

0.79+

0.24

0.31+

0.18a

0.16+

0.21ab

0.21+

0.17ab

0.03+

0.10b

0.09+

0.08ab

22.8

8.3

5.0

6.6

0.7

2.2

P0.01

0.04

F6.36

3.17

df

73

73

Tupi

419871989–91

3.46+

0.19

2.96+

0.32

0.50+

0.16

0.10+

0.08

0.11+

0.08

0.19+

0.15

0.09+

0.07

0.01+

0.04

15.0

3.3

3.5

5.5

2.5

0.2

P0.21ns

ns

F1.61

0.57

df

39

39

aYield

loss

wasdetermined

asthedifference

betweenafullprotectiontreatm

entthatprotected

fivegrowth

stages

andassociatedpestguildswithinsecticides

selected

fortheireffi

cacy

andphytotoxic/

phytotonic

neutrality

Fivetreatm

ents

sucessivelyomittedinsecticideprotectionso

thatlosses

could

beattributedto

thatgrowth

stage/guild

See

textfordescriptionsofinsecticides,dosages

andtiming.Alltrialswereconducted

infarm

ers’fieldswitheach

fieldasareplication.

Means+

SEM

inarow

notfollowed

byacommonletter

are

significantlydifferent(P�

0.05)byLSD

test,ns¼

notsignificantlydifferent



5.0% for sown-seed pests, 2.2% for rice seed bugs,and 0.7% for stemborers.

3.2.3. Tupi

Interestingly the yield potential in Tupi was similar tothat in Claveria despite these being better soils inTupi. The four crops in Tupi recorded a 0.50 t/ha or15% loss as the difference between 3.46 and 2.96 t/hafor full protection and the check (Table 5). Yield losswas lower than in Claveria, even though pestcomplexes and densities were similar. The rankingof yield loss differed, in that the greatest loss was fromroot aphids (0.19 t/ha or 5.5%), sown-seed/seedlingpests (0.11 t/ha or 3.5%), white grubs and termites(0.10 t/ha or 3.5%), stemborers (0.09 t/ha or 2.5%),and rice seed bugs (0.01 t/ha or 0.2%).

3.2.4. Tanauan

In Tanauan the modern variety out-yielded thetraditional variety under the same management inboth the comparison of full protection (4.01 vs.2.90 t/ha) and untreated (3.61 vs. 2.85 t/ha) (Table 6).With Dagge there was an insignificant differencebetween the protected (2.90 t/ha) and the unprotectedcheck (2.85 t/ha); total loss was too low (5%) for usto have confidence in assigning significance appor-tioned across each pest guild. There was, however, asignificant yield loss in UPLRi5 of 0.40 t/ha or 18%between protected and unprotected treatments. Thishigher loss was spread fairly evenly between guildswith most due to white grubs/termites and sown-seed/seedling pests (5.9% each), and least in the ripeningstage (2.3%). The 4.1% loss in the reproductive stagewas probably from whitebacked planthopper.

3.3. Crop management

3.3.1. Siniloan

The slash and burn crop was protected with a seedtreatment as an initial recommended practice whichwas tested together with several agronomic andinsecticide interventions including organic and inor-ganic fertiliser amendments and foliar sprays. Withcarbosulfan seed treatment, yields increased signifi-cantly from 60 to 210 kg/ha, giving a marginal returnof only $0.60/ha (Table 1). The highest yield with theleast amount of inputs was obtained from applying23 kg N/ha and ash to reach 450 kg/ha and amarginal return of $42 and B:C ratio was a highlyfavourable 6.1. Adding the seed treatment did notincrease yield, neither did adding lime, chickenmanure, doubling the N rate from 23 to 46 kg/ha,or foliar insecticide sprays. This agronomic recom-mendation probably increased the crop’s compensa-tory ability against insect pest damage, but it maychange if and when the yield potential can be T

able

6.

Yield

loss

determined

bypartitioned

growth

stage/pestguildinsecticidecheckmethodin

farm

ers’fieldsin

Tanauan,Batangas,Philippines,1976–1980.a

Varietytype

Crops

Years

Yield

(t/ha)

Yield

loss

(t/ha)

Yield

loss

(%)

Complete

protection

Untreated

Totalyield

loss

Whitegrubs/

term

ites

Sownseed/

seedlingpests

Reproductive

stage

Ripening

stage

Total

yield

loss

White

grubs/

term

ites

Seed/

seedling

pests

Reproductive

stage

Ripening

stage

Traditional/

Dagge

51976–80

2.90+

0.08

2.85+

0.06

0.05+

0.07

0.02+

0.02

0.01+

0.02

0.01+

0.01

0.01+

0.02

1.7

0.8

0.3

0.3

0.3

P0.734ns

F0.117

df

63

Modern/

UPLRi5

31978–80

4.01+

0.16

3.61+

0.35

0.40+

0.38

0.13+

0.12

0.13+

0.12

0.09+

0.10

0.05+

0.06

18.2

5.9

5.9

4.1

2.3

P0.165ns

F2.02

df

35

aYield

loss

wasdetermined

asthedifference

betweenafullprotectiontreatm

entthatprotected

fourgrowth

stages

andassociatedpestguildswithinsecticides

selected

fortheireffi

cacy.

Fourtreatm

ents

successivelyomittedinsecticideprotectionso

thatlosses

could

beattributedto

thatgrowth

stage/guild.

See

textfordescriptionsofinsecticides,dosages

andtiming.Alltrialswereconducted

infarm

ers’fieldswitheach

fieldasareplication.

Means+

SEM

inarow

followed

byadifferentletter

are

significantlydifferent(P

50.05)byLSD

test,ns¼

notsignificantlydifferent



significantly raised, i.e. with a blast resistant variety,better soil management, or improved vertebrate pestcontrol.

3.3.2. Claveria

The crop management variables tested were inorganicfertiliser, seeding rate, as well as insecticide soil and/or seed/seedling treatments. The lowest yields resultedwithout addition of either fertiliser or insecticideproducing equally low levels (2.4 t/ha) at both the 50and 90 kg/ha seeding rates (Table 7). The minimalinput to raise the yield significantly above theuntreated level was the adding of inorganic fertiliser(50-25-0) at the 90 kg seed/ha rate producing 2.6 t/habut a negative marginal return of $9/ha. The nextyield plateau was reached at a seeding rate of 50 kg/ha, 50-25-0 fertiliser level, and an insecticide seedtreatment which improved to 2.8 t/ha, but only ameagre marginal return of $7/ha with a B:C ratio ofonly 1.2. The addition of a soil insecticide treatmentto this last practice did not further improve yield. Thefully protected plots produced the highest yields(3.4 t/ha) among all treatment combinations andout-yielded the fertilised control at the same seedingrate by 0.80 t/ha. This treatment was not a potentialpractice; but it merely showed that there was morescope for improvement. Thus the most profitablepractice for the farmer was to not apply anyagricultural inputs due to the meagre yield responseof added N and P.

3.3.3. Tupi

Almost the same mix of management practices wastested in Tupi as in Claveria. Lowest yields againwere in the unfertilised and non-insecticide treatedplots at either 50 and 90 kg/ha seeding rates (2.4–2.5 t/ha) (Table 7). There was no benefit ofincreasing just the seeding rate from 50 to 90 kg/ha without fertiliser or seed treatment. The mosteconomical return was at 50 kg seed/ha withinorganic fertiliser (50-25-0) and insecticide seedtreatment with highest marginal return of $90/haand 3.0 B:C ratio. Adding only fertiliser had agreater benefit as yields increased 0.53 and 0.66 t/hain the 50 and 90 kg/ha seeding rates, respectively,although not significantly. Economically there was amarginal return of $44/ha and B:C ratio of 2.8from use of inorganic fertiliser at 50 kg seed/hawithout seed treatment. If the farmer increased to90 kg seed/ha with fertiliser but without seedtreatment, the marginal return became $64/ha andB:C ratio rose to a more favourable 3.1. Profit washigher with an insecticide seed treatment however.No further benefit was realized from applying themore expensive soil insecticide treatments, indicat-ing less pest pressure than in Claveria. In Tupi thefull protection treatment did not yield more thanthe seed treatment or use of fertiliser. Thereforethere was no significant benefit from any insecticideprotection on a well fertilised crop at 90 kg seed/ha,again indicating crop compensation.

Table 7. Yield response to crop management practices on dryland rice production, Claveria and Tupi, Mindanao,Philippines, 1984–1990.

Insecticidetreatment

Seedingrate

(kg/ha)N-P

(kg/ha)

Yield (t/ha)a

Claveria No. crops N Tupi No. crops n

Completeprotectionb

90 50–25 3.41 + 0.23 a 7 28 3.61 + 0.22 a 4 16

Seed/seedling þsoil treatments

90 50–25 2.89 + 0.15 b 4 16

Seed/seedlingtreatment

90 50–25 2.85 + 0.23 b 6 24 3.20 + 0.26 ab 4 16

Seed/seedlingtreatment

50 50–25 2.84 + 0.28 b 3 28 3.48 + 0.24 ab 3 12

Soil treatment 90 50–25 2.65 + 0.17 bc 2 8 3.41 + 0.29 ab 2 8Soil treatment 50 50–25 2.69 + 0.39 bc 3 26 3.37 + 0.37 ab 3 12Untreated 90 50–25 2.61 + 0.18 bc 7 28 3.17 + 0.28 ab 4 16Untreated 50 50–25 2.33 + 0.25 c 3 28 2.96 + 0.32 ab 3 12Untreated 90 0 2.44 + 0.32 3 12 2.51 + 0.30 b 3 12Untreated 50 0 2.42 + 0.28 c 3 12 2.43 + 0.27 b 3 12P 0.007 0.03F 5.50 2.22df 294 135

aEach crop consisted of 4–6 farms ¼ replications (n) and treatments were analyzed on the basis of fields and not crops.

In a column, means + SEM followed by a different letter are significantly different (P � 0.05) by LSD analysis.

Soil treatment was 0.25 kg al/Lindane G/ha, seed treatment was 0.30 kg ai carbosulfan ST/ha.

Fertilizer applied was 50–25–0 with the N application split at 14–25 days after crop emergence during inter-row cultivation and panicleinitiation while P was applied basally during land preparation.bFrom the yield loss trial which treatments were randomly mixed with the insect control treatments each season.



3.3.4. Tanauan

Combinations of seeding rates and insecticide treat-ment of seeds and soil were tested in one season withDagge variety. There was a yield benefit (0.50 t/ha) ofincreasing the seeding rate from 50 to 100 kg/haalthough not significantly (Table 8), but it had ahighly favourable marginal return of $55/ha and aB:C ratio of 8.3. Higher seeding rates up to 150 kg/hadid not increase yield. At the 50 kg/ha seeding rate,insecticide seed treatment resulted in modest butinsignificant yield gains (0.23–0.27 t/ha) that pro-duced a marginal return of only $15/ha and B:C ratioof 1.7. Slightly higher, but again insignificant, gains(0.36 t/ha) were obtained with the 0.5 kg a.i. carbo-furan/ha soil insecticide treatment at 50 kg seed/haproducing a marginal return of $20/ha and B:C ratioof 1.8. The highest yield gain (0.64 t/ha) was obtainedwith the highest rate of soil insecticide treatment(2 kg a.i. carbofuran/ha) at the 100 kg/ha seedingrate producing marginal return of only $7/ha and B:Cratio of 1.1.

In 2 years’ trials (1980–1981) the same seed andsoil treatments produced no significant yield gain inUPLRi5. In the 1979 trial which had more sown-seedand root (white grub) pest pressure, also at 100 kgseed/ha, that included both a seed treatment of0.30 kg a.i. carbosulfan ST/ha (3.68 t/ha) and a soil

treatment of 0.75 kg a.i. diazinon G/ha (3.82 t/ha)resulted in significant yield increase over the un-treated of 3.28 t/ha (P ¼ 0.03, F ¼ 3.54, df ¼ 28).Both insecticide treatments produced similar margin-al returns of $31 and $41/ha, respectively, and B:Cratios of 2.6 and 2.4. The average in untreated plotswith UPLRi5 over the 3 years was 3.6 t/ha; thus, in1979 there was greater insect pest pressure. Thefarmer practice of 100 kg seed/ha without insecticideis probably the most economical practice as farmersare hesitant to use insecticides.

4. Discussion

4.1. Yield potential

Except for the very low productivity of the slash andburn site, yields in the unprotected treatment of theother three sites ranged from 2.6 to 3.6 t/ha; these aremuch higher than the world average of 1 t/ha. Thiseffect is likely attributable to the Philippine climateand soils being as a whole more suitable for drylandrice compared to those of many other countries. Thehighest yielding site was Tanauan with the mostfavourable soils, good crop management, and highestuse of inorganic fertiliser where the low tilleringvariety Dagge averaged 2.9 t/ha, which is equal toyields obtained from similar traditional varieties inthe irrigated wetlands. The high tillering UPLRi5

Table 8. Comparison of different practices on the yield of Dagge rice including increasing the seeding rate, insecticide seedand soil treatment and combinations thereof, Tanauan, Batangas, Philippines, 1976.a

Seed rate

Insecticide treatedPlant standb

no./m-row) 14 DEYieldc

(t/ha)Seed Soil

Seeding rate50 kg seed Untreated Untreated 35 d 2.00 b100 kg seed Untreated Untreated 45 bc 2.49 ab125 kg seed Untreated Untreated 60 a 2.43 ab150 kg seed Untreated Untreated 59 a 2.23 ab

Seed treatment50 kg seed Carbofuran ST Untreated 38 cd 2.27 ab50 kg seed Dieldrin WP Untreated 41 cd 2.23 ab

Soil treatment50 kg seed Untreated 0.5 kg ai carbofuran G/ha 38 cd 2.36 ab50 kg seed Untreated 2 kg ai carbofuran G/ha 41 cd 2.47 ab

Seed treatment þ increasing seeding rate100 kg seed Carbofuran ST Untreated 51 ab 2.27 ab100 kg seed Dieldrin WP Untreated 52 ab 2.19 ab

Seed treatment þ increasing seeding rate100 kg seed Untreated 0.5 kg ai carbofuran G/ha 52 ab 2.51 ab100 kg seed Untreateed 2 kg ai carbofuran G/ha 51 ab 2.64 aP 0.02 0.04F 5.38 4.98df 33 33

aFarmer practice was 00 kg seed/ha without insecticide usage and N was applied at 60 kg/ha in all treatments.

ST ¼ seed treatment formulation, WP ¼ wettable powder, G ¼ granule.

In a column, means + SEM followed by a different letter are significantly different (P � 0.05) by LSD analysis. The randomized completeblock trial was replicated across six farmers’ fields.b20 samples of 1-m rows. DE ¼ days after crop emergence.cTwo 10 m2 yield cuts.



averaged even more 3.6 t/ha under the samemanagement. Its characteristics of high tilleringcombined with blast resistance make UPLRi5 anattractive variety for dryland rice farmers. Tupisoils are similar to those of Tanauan, but farmersapplied less nitrogen, 30 vs. 110 kg/ha, andaveraged 3.0 t/ha with UPLRi5 almost equal toDagge under higher N rates. The two sites with theleast favourable soils achieved the lowest yields.Claveria, with its highly eroded acidic soils and loworganic matter content, averaged 2.6 t/ha. Slashand burn culture, exemplified by Siniloan, recordedthe lowest yields with the farmers only doublingtheir investment in seed.

4.2. Partitioned-growth-stage yield loss

There was no partitioned yield loss data for the slashand burn site due to the difficulty of carrying outmultiple-treatment trials on small and very patchyfields. The mean yield loss figure across the otherthree sites for UPLRi5 was 18.6%, with 5.8%attributed to white grubs and termites, 4.8% tosown-seed/seedling pests (ants, crickets, seedlingmaggot, and flea beetles), 4.0% to root aphids andmealybugs, 2.4% to reproductive stage pests (stem-borers, leaffolders and plant- and leafhoppers), and1.6% to rice seed bugs.

The partitioned-growth-stage method has itslimitations. We noted interactions in the yield losscalculations between pest guilds attributed to thebroad spectrum nature of the insecticides used andthe overlapping growth stages of a number of them.The greatest interaction was evident with Lindanegranules between damage caused by white grubs andtermites (root pests) that would also have affectedsown-seed pests such as ants and crickets. The degreewith which this occurred can be seen in Tables 3 and 4where sampling plant stand in the untreated controls(‘combined’) was 3.3–6.0% lower loss than wasestimated by separate treatments that measuredsown-seed/seedling and root pest protection. Otheroverlapping stages were between root aphids/mealy-bugs and the foliar pest protection for the reproduc-tive stage. In the former the granular insecticidecarbofuran directed at root aphids and mealybugswould have had some systemic activity againststemborers and leaffolders dwelling in and feedingon the above-ground plant parts. The dosage selected(0.75 kg ai/ha) for carbofuran was such that onlytrace amounts would have been taken up by the stemsand leaves from the root zone placement. Anystatistical interaction would have underestimatedloss from reproductive pests.

Additional interactions would have developedfrom use of carbofuran as it has other propertiesthan as an insecticide. In addition to being anematicide it also has been found to have plant

growth hormone like properties (Venugopal andLitsinger (1984). Nematodes are a serious problemin dryland rice (Villanueva et al. 1992), causinghigh losses in their own right. In fact, carbofuran isthe chemical of choice for estimating losses in thenematicide check method, but again the dosageused in our study (1 kg ai/ha) was half used bynematologists (e.g. Plowright et al. 1990) and at thelower end of the dosage range that gives aphytotonic effect. Another mitigating effect wasthat the timing of the first of two applications 40and 70 DE which, being late in the growth period,would have tempered both potential effects. Each ofthese factors would lead to an overestimation ofyield loss. On the other hand, none of theinsecticide treatments achieved 100% control ofinsect pests in the trials offsetting the aforemen-tioned effects.

The low yield loss of 5% on Dagge rice contrastsmarkedly with the results of the earlier studies byPathak and Dyck (1975) where 430% yield loss wasrecorded on similar traditional varieties in the samelocation. Such high losses recorded earlier wereprobably due to the high rate of in-furrow carbo-furan G (2 kg ai/ha) which would have both induceda phytotonic response (Venugopal and Litsinger1984) and significantly suppressed nematodes (Villa-nueva et al. 1992), resulting in overestimates ofinsect losses. Carbofuran was not used in our studyin Tanauan.

4.3. Insect pest complex

The key ecological factors of dryland sites thataffected insect species composition were the resultof: (1) an aerobic soil due to lack of soil puddling andponding, (2) the extensiveness of alternative planthosts (perennial grasslands and presence of maize orsugarcane), and (3) nearness to wetland rice bowls.We conclude that the most significant speciesassociated with loss were adapted to the non-floodeddrylands (ants, field crickets, mole crickets, whitegrubs, termites) or those that survive well on grassyweeds, or on the more dominant maize or onsugarcane (seedling maggot, flea beetle, root aphids,mealybugs, thrips, rice seed bugs, non-Scirpophagastemborers). The most important among this list wereundoubtedly ants which was the only taxon ofeconomic importance acting across all four sites.Root aphids also reached economic numbers in twosites. Seedling maggot was economically important inall sites except for Tanauan which is devoid ofgrasslands. Siniloan has extensive grassy areascomprising the abandoned slash and burn fieldsfrom previous seasons that only slowly return toforest.

Termites appear not to prefer living rice plants, soare not considered economically important pests as



dead plants were not seen. Thrips and mealybugswere present and would have become more abundantif prolonged drought had occurred. Rice seed bugs,like flea beetles, reached economic importance only inSiniloan due to their concentration in small fields.Rothschild (1970) also attributed high numbers ofrice seed bugs in slash and burn cultivation inSarawak to the same factor. Both pest groups havegood local dispersive powers and can seek out smallplantings.

Puddling is a means of transforming a soil into amuddy consistency to allow long-rooted seedlings tobe readily transplanted (DeDatta 1981). This processof tillage and eventual ponding would kill all exceptthe most adapted soil-dwelling insects such as aquaticroot weevils (Lissorhoptrus and Echinocnemus) which,only occur in flooded habitats. Our results show thatdryland soil pests are mainly those that cannottolerate sustained flooding. There are only limitedrecords of soil-dwelling pests such as termites, molecrickets, and ants occurring in the wetlands. Theyexist primarily when there are large bunds thatprovide an aerobic environment from where theycan make temporary incursions into the field duringperiods of low water saturation but cannot sustainthemselves (Way et al. 1998). Flooding is in fact acontrol method for these pests (Litsinger 1994).

Polyphagy is one of the most distinguishing fea-tures of dryland rice insects (Litsinger et al. 1987a) andis exhibited by most of the prevalent species. The onlymonophagous insect pest encountered in significantnumbers in dryland rice was the white stemborer.Whitebacked planthopper has a wide host plant rangecompared to the monophagous but more infamousbrown planthopper which it outnumbered in thedrylands. The host plant range of N. virescens isprimarily Oryza spp., whereas N. nigropictus couldpersist in the drylands on perennial grasses.

The dryland site with the highest measured pestdensities was in Claveria which has large tracts ofwild perennial grasslands which grow quickly withthe first rains of the wet season enabling pest densitiesto build up rapidly. In Brazil for example, theextensive pasture lands surrounding tracts of drylandrice are responsible for build up of a number of pestssuch as spittle bugs which disperse to rice withdevastating effect (Litsinger et al. 1987a). Both Tupiand Tanauan are highly cultivated areas wheredryland rice occupies a smaller footprint than thesurrounding maize and sugarcane; thus, immigrationcan be significant by more dispersive species, i.e.seedling maggot, flea beetles, white grubs, molecricket, field crickets, root aphids, planthoppers,mealybugs, and rice seed bugs. Ho and Kibuka(1983) found that in dryland areas of Kenya whererice was grown in association with maize andsorghum, the principal rice stemborers were thosespecies that fed on all three crops.

Aestivation is a mechanism enabling survivalduring a long dry season and S. innotata has theability to enter this diapause state for up to a year(Litsinger et al. 2006a). No other Asian stemborer hasthis adaptive trait and the ability to diapause isprobably the reason that in Sarawak, Rothschild(1971) found it to be the most abundant stemborer inslash and burn rice. But despite this adaptation, itsnumbers were lower than other stemborer species inthe Philippines as determined from tiller dissections(Jahn et al. 2007). Yellow stemborer enters quiescencein cool climates such as N. India and Bangladesh butnot in the Philippines. Quiescence is not a truediapause state as the insect can resume activityrapidly from rain or land soaking (Islam 1993).Quiescence is different than diapause in that it occursin direct response to an environmental change whileS. innotata enters physiological inactivity in anticipa-tion of the change from short day lengths and cropage (Litsinger et al. 2006a). Dry season tillage in thetwo Mindanao sites acts as a control measure againstwhite stemborer survival. Other species with knowndormancy abilities are Leptocorisa rice seed bugs,white grubs, and rice butterflies (Litsinger et al.1987a).

Light trap data revealed that traditional pestsemanating from wetland culture continually ‘rained’down on dryland rice fields in all four sites essentiallyyear-round (Table 2). Tupi, Tanauan, and Siniloanwere situated relatively near (10–20 km) to largewetland rice bowls, whereas Claveria is more distant.Light trap data showed that dispersal of wetland riceinsect pests, even to Siniloan in the midst of a maturetropical rainforest, occurred when rice was not evenpresent. The most dispersive species are brown andwhitebacked planthoppers, Cyrtorhinus, armyworms/cutworms, locusts, and leaffolders followed by ricebutterflies, leafhoppers, and stemborers (Litsingeret al. 1987a).

Inorganic nitrogen usage and drought stressaccounted for the abundance of some insect pestsamong sites. Tanauan with highest nitrogen usagewould have favoured planthoppers and leaffoldersalong with stemborers, as noted by studies done inwetland rice culture (Litsinger 1994). The beneficialeffects of nitrogen on planthoppers have been higherfecundity, greater survivorship, and increased feedingrates while those for leaffolders were egg recruitment(ovipositing moths are attracted to the most vigorousgrowing fields) and survival (Kraker et al. 2000).Rothschild (1970) also found leaffolders on drylandrice to be more abundant in fields of high N but leastnumerous if the crop were under drought stress.Dryland rice farmers on acid soils such as in Siniloanand Claveria obtained poor results from applyinginorganic fertiliser, thus it is likely these pests werenot numerous in these locations due to poor soils.The 2-year life-cycle of white grubs in Claveria is



attributable to poor nutrition (Litsinger et al. 2002).Higher yield losses in Claveria than in other sites canlikewise be attributed to the lower level of compensa-tion linked to poorer soil nutrition. Litsinger (1993)showed that higher application of nitrogen in wetlandrice resulted in lower losses.

Among the world’s main cereals, rice is leastadapted to drought stress. In most years in all sites,the crop exhibited leaf rolling, a sign of water stress.Studies on insects have shown that high mortalityoccurs if dietary moisture is not adequate (Mochidaet al. 1987). Xylem-feeders in particular are negativelyaffected by reduced turgor pressure. On the otherhand, drought stress favours a number of drylandpests such as mealybugs, aphids, and thrips, as theyfeed on the phloem sap containing N compoundswhose quantities have increased in stressed plants(Rothschild 1970; Williams 1970; Mochida et al.1987; Jahn 2004; Jahn et al. 2005). Drought alsoreleases locust and armyworm populations from thesuppressive effect of their natural enemies (Litsingeret al. 1987a) and increases the number of breedingsites along river banks (Zhang and Li 1999). Locustsand armyworms generally affect dryland rice morethan irrigated rice but were not noted in this study.

Climate played a role in seasonality of pestdensities as can be seen when we compare monsoonversus inter-tropical convergence zone sites. Thelatter climate affects dryland rice by extending hostapparency via longer wet seasons, so favouringpolyphagous and dispersive pests. The two Luzonsites were influenced by the short monsoon rainyseason, whereas the two Mindanao sites with a longergrowing season allowed greater time for pest buildup.Additional generations per year potentially translateinto a exponential increase in pest abundance(Loevinsohn et al. 1988). It is under the longer rainyseasons that changing planting time can have aneffect. With the first rains of the wet season, grassesemerge and farmers tend to sow maize first and ricesecond in Mindanao. Thus reduction of seedlingmaggot can be realised by early sowing of rice,particularly in years of early rains (Litsinger et al.2003). However, there is little scope for farmers toadjust planting time of rice and maize in the monsoonclimate of Luzon.

We have seen that within the dryland rice pestcomplex, typical wetland foliar species do not thriveon nutrient-poor and water-stressed plants, despitethe constant aerial inundation. There is anotherfactor at work. This study has revealed ants to bepests in reducing dryland plant stands, but they arealso have an additional role as predators (Barrionand Litsinger 1980). Way et al. (2002) found thatcolonizing planthoppers could not become estab-lished in dryland rice fields in Tanauan due to antpredation, principally by S. geminata. The fact thatplanthoppers became so abundant in Tanauan in the

presence of ant predation could be that S. geminatawas tending them for honeydew (Way et al. 2002).Further research should clarify what triggers ants toprey on or tend planthoppers. We have alreadydocumented the abundance of Cyrtorhinus in drylandrice (Table 4). The species richness of dryland spiderswas elucidated by Barrion and Litsinger (1981). Riceleaffolders also are heavily preyed upon by S. geminataand carabids in Tanauan (Barrion and Litsinger 1985).Other natural enemy groups such as earwigs (Barrionet al. 1987) and parasitoids (Barrion and Litsinger1987a, 1987b) have also been identified in dryland riceareas. Litsinger et al. (1997) found lower levels ofparasitism of rice butterflies in dryland versus irrigatedwetland rice areas. What needs further study is thenatural biocontrol of soil dwelling pests.

Of the three main rice cultural systems, drylandrice has the least crop apparency, thus rice pests findit difficult to build-up and sustain numbers. Loevin-sohn et al. (1988) and Litsinger (2008) showed thatspatial effects of the area sown in rice and temporaleffects of the length of the dry season were strongdeterminants of pest density. In cross culturalcomparisons, the lowest densities of rice insect pestswere found in single crop sites with the smallest areasplanted which characterizes dryland rice culture.

4.4. Integrated crop management

Despite the high yield losses measured in Siniloan(71%), Claveria (23%), and Tanauan (with UPLRi5)(18%) by the insecticide check method, crop manage-ment trials showed that most loss can be mitigatedthrough use of either modest amounts of inorganicfertiliser (Siniloan) or overseeding in a fertilised crop(Claveria and Tanauan). Only in Tupi was there aneconomic advantage of applying a low dosageinsecticide seed treatment, however this was onlywhen rice was sown on a fertilised crop.

Overseeding is an inexpensive method that antici-pates chronic stand reduction from sown-seed pests.This preventive measure was found by Litsinger et al.(2003) to be effective in overcoming seedling maggotdamage. Overseeding should be more effective on ahigh tillering plant type such as UPLRi5 compared totraditional low tillering varieties. UPLRi5 plantsadjust the number of tillers per plant in response tofertility level and can fill in field gaps. Overseeding isalso environmentally sound as it conserves predatoryants. Way et al. (2002) cited reports where insect pestsresurged in response to insecticide use directedagainst S. geminata. An optimally fertilised crop is awell known method for facilitating compensationfrom insect pest damage and has been found inwetland rice to be an optimal strategy for minimizinginsecticide usage (Heong 1998; Litsinger et al. 2006b).In wetland rice the high tillering semi-dwarfs havebeen shown to exhibit extraordinary powers of



compensation from insect pest damage, particularlywhen the crop is well managed and there are fewother stresses.

An interesting finding in light of the abovediscussion was the lower relative losses of thetraditional Dagge variety than the high tilleringUPLRi5 (2 vs. 18%) under similar pest infestationlevels. One would have expected that losses wouldhave been higher in the traditional variety which hasless compensatory potential. Two factors couldaccount for the findings: (1) Dagge is deeper-rootedand thus more drought-tolerant as the combinationof insect damage and drought stress is known to beassociated with high losses in wetland rice (Litsingeret al. 2005). (2) UPLRi5 is inherently higher-yieldingthan Dagge (Table 6), and may be suffering fromimbalanced fertiliser as only N was provided. P and Kmay not have been limiting for the lower-yieldingDagge. Nutrient stress could have been a cause ofaccentuated yield loss in UPLRi5.

The weak response in Claveria to inorganicfertiliser was probably the reason why, with UPLRi5,there was a minimal response to agronomic interven-tions compared to Tupi and Tanauan sites. There wasnot even a response to increasing the seeding rate,although this did produce a favourable result in anearlier single season trial (Litsinger et al. 2003).Dryland rice in Claveria was under more stresses thusthe crop had less potential to compensate (Litsinger2006b). Tupi soils are more fertile than those ofClaveria which are highly deficient in organic matter(MacLean et al. 2003). Improved crop fertility mayhave had the added benefit of increasing tolerance tonematodes (Villanueva et al. 1992; Prot et al. 1994)and may have been the reason why Tanauan farmersused such high rates of N. Samples of rice rootsshowed that they contained high densities of nema-todes. N application stimulates plants to continuouslyproduce new roots and allows them to grow deeperinto the soil to escape reinvasion. Removing a stresssuch as nematodes would allow the crop to compen-sate more from insect pest damage and water stress;thus, good agronomic management is seen as apreventative strategy.

Due to the many stresses inherent in drylandrice culture, workers have concluded that insectpests are not as important in dryland rice as theyhave been in wetland rice (Gupta and O’Toole1986). But as our study has shown, insect pestlosses can be very high and can vary dramaticallyin relation to site, management, and cultivar.Additionally most losses in dryland rice are causedby a quite different pest complex than most riceresearchers are aware of. Given that many of thepests are soil dwelling and thus out of sight,evidence of their presence and damage is not asnoticeable as their equivalents in wetland rice, thusthey have been largely overlooked.

Acknowledgements

The able assistance of the Claveria site staff: Elsiner L.Dahilog Sr, Quirino S. Baguio Jr, and Nestor T. Labanes.,Tupi site staff particularly Hector Corpuz as well as BeatrizDatijan, Anita Labarinto, and Joseph Siazon, and Tanauanand Siniloan site staff Mariano Leron, Eduardo Micosa,and Carlos de Castro is gratefully acknowledged. We aregrateful for the assistance of Nonnie Bunyi and Josie LynnCatindig at IRRI in providing references and technicalinformation. The contributions of two anonymous re-viewers is highly appreciated.

References

Agyen-Sampong M. 1988. Assessment of on-farm losses inrice due to insect pests. Insect Sci Appl. 6:691–695.

Arraudeau M, Harahap Z. 1986. Relevant upland ricebreeding objectives. p. 189–197. Progress in upland riceresearch. Los Banos (Philippines): IRRI. p. 567.

Bandong JP, Litsinger JA. 2005. Rice crop stage suscept-ibility to the rice yellow stemborer Scirpophagaincertulas (Walker) (Lepidoptera: Pyralidae). Int JPest Manag. 51:37–43.

Barrion AT, Litsinger JA. 1980. Ants – a natural enemy ofCnaphalocrocis medinalis larvae in dryland rice. Int RiceRes Newslett. 5(4):22–23.

Barrion AT, Litsinger JA. 1981. The spider fauna ofPhilippine rice agroecosystems. I. Dryland. PhilippineEntomol. 5:139–166.

Barrion AT, Litsinger JA. 1985. Chlaenius spp. (Coleoptera:Carabidae), a leaffolder predator. Int Rice Res News-lett. 10(1):21.

Barrion AT, Litsinger JA. 1986a. Flea beetle Chaetocnemabasalis (Baly) (Coleoptera: Chrysomelidae), a pest ofslash-and-burn upland rice in the Philippines. Int RiceRes Newslett. 11(4):31–33.

Barrion AT, Litsinger JA. 1986b. Effect of heavy rains onrice thrips. Int Rice Res Newslett. 11(4):31.

Barrion AT, Litsinger JA. 1987a. A larval parasite ofswarming caterpillar and common cutworm in thePhilippines. Int Rice Res Newslett. 12(2):34–35.

Barrion AT, Litsinger JA. 1987b. Strepsipteran parasites ofrice leafhoppers and planthoppers in the Philippines.Int Rice Res Newslett. 12(4):37–38.

Barrion AT, Libetario EM, Litsinger JA. 1987. An earwigpredator of Asian pink stem borer in upland rice. IntRice Res Newslett. 12(1):21.

Barrion AT, Litsinger JA, Medina EB, Aguda RM,Bandong JP, Pantua PC Jr, Viajante VD, dela CruzCG, Vega CR, Soriano JS Jr, et al. 1991. The riceCnaphalocrocis and Marasmia (Lepidoptera: Pyralidae)leaffolder complex in the Philippines: taxonomy,bionomics and control. Philippine Entomol. 8:987–1074.

Cates RG. 1981. Host plant predictability and the feedingpatterns of monophagous, oligophagous, and polypha-gous insect herbivores. Oecologia (Berlin). 48:319–326.

DeDatta SK. 1981. Principles and practices of riceproduction. New York: John Wiley and Sons. p. 618.

de Kraker J, Rabbinge R, van Huis A, van Lenteren JC,Heong KL. 2000. Impact of nitrogenous-fertilization onthe population dynamics and natural control of riceleaffolders (Lep.: Pyralidae). Int J Pest Manag. 46:225–235.

Denno RF, Roderick GK, Olmstead KL, Dobel HG. 1991.Density-related migration in planthoppers (Homoptera:Delphacidae): The role of habitat persistence. Am Nat.138:1513–1541.



Fujisaka S, Kirk G, Litsinger JA, Moody K, Hosen N,Yusef A, Nurdin F, Naim T, Artati F, Aziz A, et al.1991. Wild pigs, poor soils, and upland rice: adiagnostic survey of Sitiung, Sumatra, Indonesia.IRRI Research Paper Series No. 155. p. 9.

Garrity DP. 1984. Asian upland rice environments. p. 161–183. An overview of upland rice research. Los Banos(Philippines): IRRI. p. 566.

Garrity DP, Kummer DM, Giang ES. 1993. The Philip-pines. p. 549–624. Sustainable agriculture and theenvironment in the humid tropics. Washington (DC):National Academy Press.

Gonzaga RR, Roxas NM, Price EC. 1986. Subsistenceupland rice cultivation systems: an economic considera-tion. p. 153–169. Progress in upland rice research. LosBanos (Philippines): IRRI. p. 567.

Grist DH, Lever RJAW. 1969. Pests of rice. London:Longmans. p. 520.

Gupta PC, O’Toole JC. 1986. Upland rice: a globalperspective. Los Banos (Philippines): IRRI. p. 360.

Heong KL. 1998. IPM in developing countries: progressand constraints in rice IPM. p. 68–77. In: Zalucki M,Drew R, White G, editors. Proceedings sixth Australa-sian applied entomological research conference. Uni-versity of Queensland, Brisbane, Australia.

Ho DT, Kibuka JG. 1983. Stemborers in various riceecosystems in Kenya. Int Rice Res Newslett. 8(5):18.

IRRI (International Rice Research Institute). 1975. AnnualReport for 1974. Los Banos (Philippines): IRRI. p. 216.

IRRI. 1976a. Annual Report for 1975. Los Banos(Philippines): IRRI. p. 227.

IRRI. 1976b. Annual Report for 1975. Los Banos(Philippines): IRRI. p. 366–369.

IRRI. 1990. Annual Report for 1989. Los Banos (Philip-pines): IRRI. p. 96–98.

Islam Z. 1993. Diapause in rice yellow stem borer,Scirpophaga incertulas (Walker) (Lepidoptera: Pyrali-dae), in Bangladesh. J Plant Protect Trop. 10:163–175.

Jahn GC. 2004. Effect of soil nutrients on the growth,survival and fecundity of insect pests of rice: anoverview and a theory of pest outbreaks with con-sideration of research approaches. Int Org Biol ControlBull. 27(1):115–122.

Jahn GC, Almazan LP, Pacia J. 2005. Effect of nitrogenfertilizer on the intrinsic rate of increase of the rustyplum aphid, Hysteroneura setariae (Thomas) (Homo-ptera: Aphididae) on rice (Oryza sativa L.). EnvironEntomol. 34:938–943.

Jahn GC, Litsinger JA, Chen Y, Barrion AT. 2007.Integrated pest management of rice: ecological con-cepts. p. 315–366. In: Koul O, Cuperus GW, editors.Ecologically based integrated pest management. Wall-ingford (UK): CAB International. p. 462.

Katanyukul W, Chandaratat C. 1981. Insect pests ofupland rice and their control. Report first FAO/UNDP/Thailand training course on improved culturalpractices for upland rice, Chiang Mai, Thailand, 5–23October 1981. Food and Agriclture Organization,Rome, Italy, p. 22.

Litsinger JA. 1993. A farming systems approach to insectpest management for upland and lowland rice farmersin tropical Asia. p. 45–101. In: Altieri MA, editor. Cropprotection strategies for subsistence farmers. Westviewstudies in insect biology. Boulder (CO): Westview Press.p. 197.

Litsinger JA. 1994. Cultural, mechanical, and physicalcontrol of rice insects. p. 549–584. In: Heinrichs EA,editor. Biology and management of rice insects. NewDelhi: Wiley Eastern Ltd. p. 779.

Litsinger JA. 2008. Areawide rice insect pest management: aperspective of experiences in Asia. p. 351–440. In: KoulO, Cuperus G, Elliott N, editors. Areawide IPM: theoryto implementation. UK: CABI. p. 590.

Litsinger JA, Entomology Department. 1979. An inexpen-sive kerosene light trap to monitor rice insects. Int RiceRes Newslett. 4(2):17.

Litsinger JA, Lumaban MD, Bandong JP, Pantua PC,Barrion AT, Apostol RF, Ruhendi. 1980. A methodol-ogy for determining insect control recommendations.IRRI Research Paper Series No. 46. p. 31.

Litsinger JA, Apostol RF, Serrano OT, Barrion AT. 1981.Acid fuchsin technique to stain stylet sheaths of the ricebug Leptocorisa spp. feeding on rice grains. Int Rice ResNewslett. 6(1):19–20.

Litsinger JA, Apostol RF, Obusan MB. 1983. White grub,Leucopholis irrorata (Coleoptera: Scarabaeidae): peststatus, population dynamics, and chemical control in arice-maize cropping pattern in the Philippines. J EconEntomol. 76:1133–1138.

Litsinger JA, Barrion AT, Dandi Soekarna. 1987a. Uplandrice insect pests: their ecology, importance, and control.IRRI Research Paper Series No. 123:1–41.

Litsinger JA, Canapi BL, Bandong JP, dela Cruz CG,Apostol RF, Pantua PC, Lumaban MD, Alviola ALIII, Raymundo F, Libetario EM, et al. 1987b. Rice croploss from insect pests in wetland and dryland environ-ments of Asia with emphasis on the Philippines. InsectSci Appl. 8:677–692.

Litsinger JA, Barrion AT, Bumroongsri V, Morrill WL,Sarnthoy O. 1997. Natural enemies of the rice green-horned caterpillar Melanities leda ismene Cramer(Lepidoptera: Satyridae) and rice skipper Pelopidasmathias Fabricius (Lepidoptera: Hesperiidae) in thePhilippines. Philippine Entomologist. 11:151–181.

Litsinger JA, Libetario EM, Barrion AT. 2002. Populationdynamics of white grubs in the upland rice and maizeenvironment of Northern Mindanao, Philippines. Int JPest Manag. 48:239–260.

Litsinger JA, Libetario EM, Barrion AT. 2003. Earlyplanting and overseeding in the cultural control of riceseedling maggot Atherigona oryzae Malloch in thePhilippines. Int J Pest Manag. 49:57–69.

Litsinger JA, Bandong JP, Canapi BL, dela Cruz CG,Pantua PC, Alviola AL, III, Batay-an E. 2005.Evaluation of action thresholds against chronic insectpests of rice in the Philippines: I. Less frequentlyoccurring pests and overall assessment. Int J PestManag. 51:45–61.

Litsinger JA, Alviola AL, dela Cruz CG, Canapi BL,Batay-an EH III, Barrion AT. 2006a. Rice whitestemborer Scirpophaga innotata (Walker) in southernMindanao, Philippines. I. Supplantation of yellowstemborer S. incertulas (Walker) and pest status. Int JPest Manag. 52:11–21.

Litsinger JA, Bandong JP, Canapi BL, dela Cruz CG,Pantua PC, Alviola AL III, Batay-an E. 2006b.Evaluation of action thresholds against chronic insectpests of rice in the Philippines: IV. Stemborers. Int JPest Manag. 52:194–207.

Loevinsohn ME. 1994. Rice pests and agricultural environ-ments. p. 487–513. In: Heinrichs EA, editor. Biologyand management of rice insects. New Delhi: WileyEastern Ltd. p. 779.

Loevinsohn ME, Litsinger JA, Heinrichs EA. 1988. Riceinsect pests and agricultural change. In: Harris MK,Rogers CE, editors. The entomology of indigenous andnaturalized systems in agriculture. Boulder (CO):Westview Press. p. 161–182.



MacLean RH, Litsinger JA, Moody K, Watson A,Libetario EM. 2003. Impact of Gliricidia sepium andCassia spectabilis hedgerows on weeds and insectpests of upland rice. Agri Ecosyst Environ. 94:275–288.

Mochida OM, Joshi RC, Litsinger JA. 1987. Climaticfactors affecting the occurrence of insect pests. Weatherand rice. Philippines: IRRI. p. 149–164.

Morris RA. 1986. Upland rice farming systems. p. 119–131.Progress in upland rice research. Los Banos (Philip-pines): IRRI. p. 567.

Ooi PAC, Shepard BM. 1994. Predators and parasitoids ofrice insect pests. p. 584–612. In: Heinrichs EA, editor.Biology and management of rice insects. New Delhi:Wiley Eastern Ltd. p. 779.

Pathak MD, Dyck VA. 1975. Studies on insect pests ofupland rice. p. 186–97. Major research in upland rice.Los Banos (Philippines): IRRI.

Plowright RA, Prot JC, Aung T, Mew TW. 1990. The effectof Pratylenchus zeae on upland rice. Rev Nematol.13:283–291.

Prot JC, Villanueva LM, Gergon EB. 1994. The potential ofincreased nitrogen supply to mitigate growth and yieldreduction of upland rice cultivar UPLRi5 caused byMeliodogyne graminicola. Fund Appl Nematol. 7:445–454.

Rothschild GHL. 1970. Observations on the ecology of therice-ear bug Leptocorisa oratorius (F.) (Hemiptera:Alydidae) in Sarawak (Malaysian Borneo). J ApplEcol. 7:147–167.

Rothschild GHL. 1971. The biology and ecology of rice-stem borers in Sarawak (Malaysian Borneo). J ApplEcol. 8:287–322.

Smith J, Litsinger JA, Bandong JP, Lumaban MD, delaCruz CG. 1988. Economic thresholds for insecticideapplication to rice: profitability and risk analysis toFilipino farmers. J Plant Protect Trop. 6:67–87.

Venugopal MS, Litsinger JA. 1984. Effect of carbofuran onrice growth. Protect Ecol. 7:313–317.

Villanueva LM, Prot JC, Matias DM. 1992. Plant parasiticnematodes associated with upland rice in the Philip-pines. J Plant Protect Trop. 9:143–149.

Way MJ, Islam Z, Heong KL, Joshi RC. 1998. Ants intropical irrigated rice: distribution and abundance,especially of Solenopsis geminata (Hymenoptera: For-micidae). Bull Entomol Res. 88:467–476.

Way MJ, Javier G, Heong KL. 2002. The role of ants,especially the fire ant, Solenopsis geminata (Hyme-noptera: Formicidae), in the biological control oftropical upland rice pests. Bull Entomol Res. 92:431–437.

Williams DJ. 1970. The mealybugs (Homoptera, Coccoi-dea, Pseudococcidae) of sugar-cane, rice, and sorghum.Bull Entomol Res. 60:109–188.

Yoshida S. 1981. Fundamentals of rice crop science. LosBanos (Philippines): IRRI. p. 269.

Zhang Z, Li D. 1999. A possible relationship betweenoutbreaks of the oriental migratory locust (Locustamigratoria manilensis Meyen) in China and the El Ninoepisodes. Ecol Res. 14:267–270.



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