Pvoceednuu. of the Ttlt lntei nattouul WOIk/llg Contereuce 01/ Stoved-proiuct Protection - Volumf

Behavioural responses of Sitophilus oryzae (L.) toward intactand damaged cereal kernels

P Tremateira , F Fontana and A SClarrettal

Abstiuci

The behavioural activity of Siioph ilu» oi uzae (L ) towardmtact and damaged kernels at five types of cereals-T,ltICU/)! aestu-um , T dIU 11111, T dICOCCUlII, T

mouococcnn, and T spelia-vez» exammedThe cereals are attractive m different ways, naturally

dehulled and hulled cereals release volatile substances onceai tiftcially dehulled or split However, dehullmg andsplitting the kernels affects the behaviour of 5 all/zoe m adifferent mannerThe substances released from different parts of the kernel

act independently to one another The pencarp layers mayprevent these volatile substances from bemg released, inhulled cereals, the chaff increases the protection agamsttheir release Once removed, volatile substances arereleased but only m small amounts compared to the case mwhich kernels are split The release mechanism wasIdentical for all cereals exammedIn order of decreasing attraction, the followmg SIXfactors

have been recogmzed the germ, the kernel endospermWithout the germ, the kernel pencarp layers, the wholekernel Without the chaff, the whole kernel With the chaff,lastly the chaff

Introduction

Volatile attractants for several beetle species that mfestgrams have been Identified from cereal grams and theirproducts (e g , Nara et al , 1981, SeJfelnasr et al , 1982,Mikolajczak et al , 1984, Pierce et al , 1990, Philhps etal , 1993, Trematerra et al , m press)Researchers have demonstrated close range onentatlon of

adult Sltopllllul>gl'ClIW1'IU1:> (L ) and 5 zeamw,', (Motsch )to the volatIles of wheat. rye, barley and nce as well as tofractIons thereof (Ohsawa et ai, 1970, Nawrot, 1973,Levmson and Levmson, 1978, Levmson and Kanaujla, 1981)Gram weeVils were found to assemble m response to the totaltnglycendes and esters of long-cham fatty aCids recovered from

lJ)plJartment S A V A, UnlveNtv of M"lt,e I-g6100 Campouawl,Italv

wheat (Nawrot and Czaplicki. 1978) Feeding and ovipositionalbehaviour of 5 gI'C(//((/'IU,,, to stored wheat. wheat extracts anddumnues was investigated by Kanaujia and Levinson (1981) andby Levinson and Kanaujia (1982)Susceptibility of cereals to the mfestation of Sitoplu! us

01 usie (L ), and the demography of nee weevil and Itsunphcations for pest management have been reported (Sinha,1971, Longstaff and Evans, 1983, Baker, 1988, Sinha et al ,1988, Baker et al , 1(91) In general, the demography of 5oiuzae ISunsuitable to higher temperatures at lower hurrudrties.but IS favoured above the other species at cooler, more moistconditions (Beckett et al , 19(4)The development penod of the rice weevil on polished rice

was significantly longer (McGaughey, 197"+, Singh. 1(81),the role of nee gram pencarp layers on the development oftlus species was studied by Haryadi and Fleurat-Lessard( 199..+) AnalYSIS of development rates of 5 oi uzae wasalso reported by Trematerra et al (1996)Gram volatiles can have sigmficant effects on host

selection behaviour m gramvores and that these effects maydiffer substantially between species shanng the sameresource (Landolt and Phillips, 1997, Trematerra et al , mpress) Niche partrtionmg m the stored-gram ecosystemmay therefore be facilitated by sermochemicals ongmatmgfrom a heterogeneous food substrate Lipids m kernels maymfluence the movement behaVIOur of stored-product msectstoward the gramMore research IS needed With stored-product msects m

which natural volatile extracts from food sources are studiedand key semlochemlcals that affect vanous species areIsolated StudieS of food volatiles will lead to a betterunderstandmg of mteractions m the stored-productecosystem and could Yield more effectIve apphcatIOns ofsemlochemlcals m pest management (Burkholder, 1990,Phillips, 1997, Trematerra 1997)The objective of our study was to exanune the behaVIOural

activity of 5 OII/zae toward mtact and damaged kernels ofTntlculII ae;,tll'IWI, T dloum, T d'COCCUIII, T

IlIOHococucm and T "pelta

Materials and Methods

Cereals supply

T ael>flvulII and T dlml/II (naturally dehulled cereals)

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and T diCOWUlI, T 1J1011oceX'CWJI and T speit« (naturallyhulled cereals) were used m the expenments The cereals weregrown m the Mohse region (Central Italy) For each cereal, 25grams of kernel were preparedT ae"tl1'll/)l and T d 10 utu whole kernel Cmtact

cereal-gram). split kernel (2 pieces).T d I(OCC IUJI, T 1JIOlIOCOCCIWI and T speit« whole

kernel, artrfrcraily dehulled kernels; split kernel (2 pieces)

Experimental insects

Test insects. adults of 5 cn uzae , were collected fromfarm-stored wheat and cultured for two generations at 25 ±I°C temperature and 70 ± 5(,0 relative humidity (I.' h ) pnorto the experiment The food media used were soft springwheat kernels at 12% moisture content

Test conditions

All expenments were conducted usmg established colornes ofmsects m complete darkness at 25 ± IOC and 70 ± 5~t I.' hRelease and recapture of S oryzae adults by 2 - 5 active

devices from Flit- Trak Me traps were carried out m an arena(45 em dram ) In all expenments 100 adults of mixed sexand age were released The number of nce weevils trappedwas checked after 12 hours and the percentage frequency ofde tee non was then computedThe first set of compansons was effected for the followmg

three couples whole naturally dehulled vs whole naturallyhulled cereals. whole naturally dehulled vs wholeartificially dehulled cereals, split naturally dehulled vs splitnaturally hulled cereals To measure the differentattractiveness of each cereal, three sets of expenmentsunder three conditions were performed I1l which five trapswere batted by means of five types of cereals wholenaturally dehulled and whole naturally hulled. together.whole naturally dehulled and whole artificially dehulled,together. split naturally dehulled and split naturally hulledgrams. togetherFor each test matenal or combination of matenals studied

SIX replicates were performed

Termmology and mathematical tools

By "expenmental run' we mean the data obtamed dunngthe test III which 100 mdrviduals were left free to pickamong two or more "choices' The span of each run was setto be long enough so as to leave the expenmental resultsunaffected by the time (further detatls on the expenmentalprocedure are discussed III Trematerra et al • 1996)Several different combmatlons of chOICes were analysed

Results and Discussion

Case study 1

The first set of compansons was made for the three

following couples· whole naturally dehulled vs whole naturally hulled cereals(1 A),

· whole naturally dehulled vs whole artificially dehulledcereals (l B).spht naturally dehulled vs split naturally hulled cereals (1C)In the three cases the same amounts of blends of cereals

were put m the trap to measure the food preference of 5OJ uzaeAccordmg to the results no defimte preference emerges

for the case m which the cereals m their natural state arecompared naturally dehulled or naturally hulled cereals havethe same attractiveness The situation changes. m astatisticallv significant way. when the chaff was removedfrom the naturally hulled cereals In this case, theattractiveness of the artificially dehulled cereals mcreases,thereby demonstrating that some volatile substance IS

releasedMuch more mterestmg IS the test III which two blends of

split kernels of naturally dehulled and naturally hulledcereals respectively are compared Smce 1 C restores thefeatures of 1 A despite the mcreased appeal one ought toexpect for the naturally hulled cereals, one must concludethat both naturally dehulled and naturally hulled cerealsrelease volatile substances once split or dehulled

Case study 2

To measure the different attractiveness of e.u h cereal.three sets of expenments under three different conditionswere performed m which frve traps were baited With thesefrve cereals. m the followmg conditions· whole naturally dehulled and whole naturally hulled.together (2 A) ,whole naturally dehulled and whole artificially dehulled,together (2 B).

· splrt naturally dehulled and spht naturally hulled grams.together (2 C)In the first case 5 01 uzae has clear preferences. m

decreasmgorder T nlOIlOcoccnm (35%). T aesu cu m(27%). T duruni (l90/<). T dicoccuni (11%) and Tspeli« (80/<) Statistical errors do not significantly affectthe results Thus. mostly due to their volatiles, the vanouscereals attract Sitophtlus to different degreesThe dlstnbutlOn of the msects drastically changes as the

chaff IS removed (2 B) Wlthm the statistical error. four ofthe ftve cereals have the same degree of attractiveness Tac"'flvnm. T rllcoccum, T nWIIOCOCCU!H and T :;,peltarange from 18% to 25% With errors of ± 10% • T durum.With 100/<. IS deflmtely the least attractive Thus.removmg the chaff frees volatile substances which mask thetrue nature of the cereal The naturally hulled cereals. oncedehulled. reveal the same degree of attractiveness and as a

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Pl'Oceedwgl> of tile Tt]: Iutemauoua! WOIkulg Couieieuce 011 Stol'ed-pJ'(x!u(t Protection - VO/lillie 1

consequence, the random factor mfluence increases and sothe statrstical errors double with respect to the previouscase This could imply that either the released substancesare smular for the different cereals or that they are so strongas to overlay umformly the expenrnental arenasThe situation m which split cereals are compared produces

quite different results (2 C) In this case, the differencesamong the cereals are restored even If the degree ofattractiveness IS changed from the case m which the naturalkernels are present T ((e"tl1'IUI/ and T d,CU(UIIJI arethe most attractive (30 C;c ). followed by T il 10 Ii III and Tspelt« (169c ), then T monococcum (SSb )From the results obtained (m 2 Band 2 C), It IS possible

to argue that dehullmg and splittmg the kernel havedifferent effects on the behaviour of S!tOp/1Illll> , in both theexperiments. attractive volatile substances are released, fordehulled kernels the same substances seem to prev allwhereas, for split kernels. substances typical of each cerealare present

Case study 3

For each given naturally hulled cereal, traps baited bvnaturally hulled and artifICIally dehulled kernels werecompared (3 A, 3 B. and 3 C) and a blend of naturallvhulled kernels was compared to a blend of artifICIallydehulled kernels of the same cereals (3 D)Wlthm the statistical error, the percentage of chOICe IS

the same m all the cases naturally hulled kernels arepreferred at about 20%, artifICIally dehulled kernels arepreferred at about 809c ThIS result makes clear thatremovmg the chaff releases attractive substances and thatthe release mechamsm appears to be the same for all thecereals testedFor each gIven cereal, traps baIted by whole and spht

kernels were compared (4 A - E) and a blend of wholekernels was compared to a blend of spht kernels of the samecereals (4 F) Wlthm the statistIcal error the percentage ofchOIce IS the same m all the cases whole kernels arepreferred at about 20%. spht kernels are preferred at about80% ThIS result makes It clear that breakmg the kernelsreleases volatile attractive substances and that the releasemechamsm appears to be SImIlar for all fIve cereals. elthelnaturally dehulled or hulledCompanng the results reported m 3 A - D and 4 A - F

WIth 2 A - C suggests the followmg sphttmg the kernelsreleases odours otherWIse trapped mSlde whether they arenaturally dehulled or hulled ThIS means that the pencarplayers prevent these substances from bemg released As falas naturally hulled grams are concerned, the chaff mcreasesthe protectIOn agamst thIS type of release Removmg thatprotectIOn. the substances are released but only m smallamounts compared to the case m whIch kernels are sphtRemonng the chaff releases dIfferent quantities of volatJie

attractant substances of the endosperm of the kernel andsubstances m the true germ The latter seem to be moreappealmg than the torrner and seem to be the same tor thedifferent cereals

Case study 4

The analysis at the appeal of each single part wasundertaken (figure 1 A - D) In those hgui es are shown theresults of the experimental runs m which naps are baited bywhole kernels. chaff, artmcially dehulled kernels, spht

kernelsThe figures reter to the three naturally hulled cereals and

to the blends of all of them Chaff and whole kernels attractat the same statistical level and this value IS very low Ifcompai ed to that ot split kernels ThIS IS an expected result.as the chaft covers the kernel and the only substances. or atleast the pnncipal ones, released are those at the chaff It ISlikelv that the chaff traps the volatile substances at thekernel to a high level of effu iencv Furthermore, the chaffhas a verv low amount of atti actrve substances, or producesrepellent volatilesFrom the same ngure I A-D. furthemore , split kernels

are more appealing than dehulled kernels ThIS substantIatesthe hypotheSIS that a kernel IS made up of an external sheet(the pencarp layers) and the true body (endosperm andgerm) Both of these contam volatile attractIVe substancesbut those of the pencarp layers are less etflclent than thoseof the bodyThe msets of the figure 1 A - D show the compansons

between blends made up by whole kernels + chaff +dehulled kernels (mdlcated as 'all parts' ) and spht kernelsIt should be noted that 'all parts' has a statistIcal valuewhIch IS the SImple sum of the components as they are Itcould be that the substances released from dIfferent parts ofthe gram act mdependentlv

Case study 5

The last step was the analYSIS of the attractIveness of thetrue germ (figure 2 A - E) For the naturallv hulledcereals, thIS analySIS underwent two steps FIrst. hulledkernels were carefully spht. the spht kernels were dIVIdedmto two groups pIeces beanng the germ and the chatf onone Side and pIeces WIthout germ but WIth the chaff, on theother The results of these runs are m hgure 2 C 2 - E 2Lastly. the kernels, once dehulled, were dtvtded as tn theprevIOus case The results of these runs are m fIgure 2 A-El ObvIOusly, the naturally dehulled cereals underwentonly the second stepObservmg the fIgures 2 A - E 2, It IS clear that the germ

has some speCIal appeal for S 011/:::((1', but not With Tuel>fll'ul1l, and the kernel part beanng the germ IS moreattracttve than the remamder Once agam, It IS eVIdent thatchaff prevents the dIffUSIOn of volattle substances, or

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Proceediuqs or the Tih International Workillg Conference on Stored-product Protection - Volwme 1

depresses their attractiveness. In fact, within the standarderrors, the comparisons made with the hulled cereals are notstatistically significant (figure 2 C. 1- E. 2).

Conclusions

Mostly due to their odour, the various cereals are differentlyattractive. Naturally dehulled and hulled cereals releasevolatile substances once artificially dehulled or split.However, dehulling and splitting the kernels differentlyaffects the behaviour of the S. oruzae adults. By comparingsuitably devised experimental runs it turns out that thesubstances released from different parts of the kernel actindependently to one another.

100===== --,A

75

5025

0whole chaff dehul. split

100C

75

50

250whole chaff dehul. split

Splitting the kernels releases volatiles, typical of eachcereal, otherwise trapped inside it whether they arenaturally dehulled or hulled. This means that the pericarplayers may prevent these volatile substances from beingreleased. In hulled cereals, the chaff decreases the release.Once removed, those volatile substances are released but insmall amounts compared to the case in which kernels aresplit. Such a release mechanism is the same for all cerealsconsidered.Removing the chaff releases different quantities of volatile

compounds of the body of the grain: pericarp layers,endosperm and the true germ. The latter seems to be moreattractive than the first two and it masks the true nature ofthe kernels.

10075

50251----------1

whole chaff dehul. split

100I~~III

0

1 T~

f..-----

.'3Pm

TI 1 I

75

5025owhole chaff dehul. split

Fig. 1 A-D. Comparison of traps baited by the three naturally hulled cereals: whole kernels, chaff, artificially dehulledkernels, split kernels (T. dicoccum , figure 1 A: T. monococcum, figure 1 B: T. spelta, figure 1 C) and tothe blends of the three cereals (figure 1 D). The insets of the figures show the comparisons between blendsmade up by whole kernels + chaff + artificially dehulled kernels (indicated as all parts) and split kernels.

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Proceeduup, oi the Ttli Iutei uatiouo! WOI hilli] Couieieuce 011 Stol'ed-pl'oc/ud Pmtedwl/ - Volume

A

-e-

f-

100

75

50

25

oend.ger

100CI

t--

75

50

25

oend ger end

100C2

..- -T --,1

I__ -1-_

t--

75

50

25

oend gercha end cha

DI

T-'

~

I--

D2

- -~ -- T.L

- -1---

end

100

75

50

25

oend ger

100

75

50

25

oend gercha

B

I--

100

75

50

25

oend ger

end

end cha

end

100E1

T.L

-J:

I--

75

5025

oend ger end

100 [ 2

75

50 --'---.L --~--

25 >--

aend gercha end cha

Fig. 2 A - E2 Comparison of trap-, baited by <plit kemel-, endo-perm + germ VI> endosperm (r ae-nvum , figure 2 A, Tdurum , figure 2 B, T dicoccum, figure 2 C I, T monococcum , figure 2 D I, T spelta. hgine 2 E 1) andof trap- baited by -plit kernels endo-perm + germ + chaff V~ endosperm (T dicoccum, figure 2 C 2, Trnonococcum, figure 2 D 2, T <pelta, figure 2 E 2)

Smce chaff and whole grams have the same. low.statistical level of attractiveness one must conclude that thechaff traps the volatile substances of the gram body at a highlevel of efficiency, given that the chaff has a VE'l y lowamount of attractive substances Spht kernels are moreappealmg than dehulled kernels, pencarp layers and the truebody (endosperm) both contam attractive compounds butthose of the external layers are less active than those of theendosperm Both m the case of naturally dehulled andnaturally hulled cereals, It IS clear that the germ has somespecial appeal and. but for T oestn-um , the kernel partbeanng the germ IS definitely more attractive than theremamderThus. m order of decreasmg attraction, the followmg

have been recognized the germ part. the kernel inside(endosperm) WIthout the germ. the kernel pencarp layers.the whole kernel WIthout the chaff, the whole kernel WIththe chaff. the chaff

References

Baker. J E 1988 Development of four strains of Sitophilusoryzae (L ) (Coleoptera Curcuhorudae ) on barley. corn(maize), nee and wheat Journal of Stored ProductsResearch, 24. 193~ 198Baker. J E . Arthur. F H . and Bruckner, P L 1991Susceptibility of Twelve Genotypes of Triticale to the RIceWeevil (Coleoptera Curcuhonidae ) and the Lesser Gram

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Pmceedllly" of ilie Ttli lntei uauouat Wadel/III Couterence Oil Stin el-proiuct Protection - Vol wile 1

Borel (Coleoptera Bostnchldae) Journal ofEntomological SCIences, 26, 339 - 3.+.+Bur kholder, W E 1490 Practical use of pheromones andother attractants tor stored-product insects In Ridgway,R L , Silverstem , R M , and Inscoe, M N , ed ,Behaviour-Modrfymg Chemicals for Insect ManagementApplications of Pheromones and Other Attractants NewYork, Mallei Dekker Inc, '+97-516Haryadl, Y and Fleurat-Lessard , F 199.+ Factorsaffectmg survival and development of Sitophilus oryzae(L ) m nee gram pencarp layers In Highley, E ,Wnght, B J ' Banks, H J , and Champ, B R , ed ,Proceedings of the 6th International Working Conferenceon Stoi ed- product Protection. Canberra, Australia. Apnl19l)'+ I, 525 - 527

Kanaujia , K Rand Levinson. H Z 1981Phagostimulatory responses and ovipositional behaviour ofSrtophilus grananus L to newly harvested and storedwheat gram Zertschnft fur angewandte Entomologie , 91,.+17-'+2'+

Levinson, H Z and Kanaujia. K R 1981Phagostimulatory responses of male and female Sitoplulusgrananus L to newly harvested and stored wheat gramNaturwissenshaften , 68, .+.+Levinson, H Z and Kanaujia , K R 1982 Feedmg andoVipoSitIOnal behavIour of the granary weevtl (Sltophllusgranallus L ) mduced by stored wheat, wheat extracts anddummies Zeltschnft fur angewandte Entomologle, 93,242 - 305Longstaff, B C and Evans, D E 1983 The demographyof the nce weeVil, Sitophilus oryzae (L ) (ColeopteraCurcultomdae), submodels of age-speclftc survivorship andfecundity Bulletm of EntomoloClcal Researchs, 73, 333-3.+-tMcGa ughey , W H 197.+ Insect de\ elopmen t m nullednce effect of vanety, degree of nulltng, parbOllmg andspltt kernels Journal of Stored Products ProtectIOn, 10,81 -88Mikolajczak, K L , Zllkowskl, B W , SmIth, C RandBurhholder, W E 198.+ Volattle food attractants forOryzaephllus sunnamenSlS (L ) from Oats Journal ofChemical Ecology, 10, 301 - 309Nara, J M , Lmsday, R C and Burkholder. W E 1981AnalysIs of volatile compounds m wheat germ 011lesponslble for an aggregatIOn response 111 Trogodermaglabrum larvae Agncultural Food Chenustry, 29, 68-72Nawrot, J and Czaplicki, E 1978 BehaViour of granarywee\ tl beetle (Sltophtius grananus L ) toward" somesubstances extracted from natural products Zeszyty

Problemowe Postepow Nauk Rolmczych, 202, 183 -191Nawrot, J , Wiruecki , Z , Szatranek , J , Malmski , Eand Harmatha , J 1995 Search for natural antifeedantsand attractants for stored product pests Prooceedings ofInternational forum, Stored product protection and post-harvest treatment of plant products, Strasbourg , France,November 1495, 1.+9- 16.+Ohsawa, K , Osluma , K , Yamamoto, I and Yamamoto,R 1970 Attracta tn t for the nee weevil, SItoplul uszeamais Motschulsky (Coleoptera Rhynchophondae) fromnce grams III A new type olfactometer for nee weevilsApplied Entomology and Zoology, 5, 1.21-125Philhps, T W 1997 Sermochenucals of Stored-productInsects Research and Applications Journal of StoredProducts Research, 33, 17 - 30Phillips T W , Jiang, XL, Burkholder, WE, Plulhps ,J K and Tran, H Q 1993 Behavioural responses to toodvolatiles by two species of stored-product Coleoptera,Sitophilus oryzae (Curcuhorudae ) and Tnbohum castaneum(Tenebnorndae) Journal of Chemical Ecology, 19, 723-73.+Singh, K 1981 Influence of nulled nce on msectmfestanon II Developmental penod and productrvity ofSrtophilus oryzae Lmn and Tnbolium castaneum Herbst 111

nulled nee Zeltschnft fur angewandte Entomologle, 9.2,.+7.2-'+77Smha, R N 1990 Role of odor volatiles m the stored-gramecosystem In Fleurat-Lessard, F , and Ducom, P ,ed, Proceedmgs of the 5th InternatIOnal WorkmgConference on Stored-product ProtectIOn, Bordeaux,Fiance, September 1990 I, 3-13Smha, R N , Demlanyk, C J and McKenzie, R I H1988 Vulnerablhty of common wheat cultlvars to majorstored-product beetles CanadIan Journal of Plant SCIences,68, 337 - 3'+3Trematerra, P 1997 Integrated Pest Management ofstored-product msects practical utlhzatlOn of pheromonesAnzelger tur Schaedhngskunde, Pflanzenschutz,Umweltschutz, 70, '+1--t'+Trematerra, P , Fontana, F and Mancml, M 1996AnalYSISof Development Rates of Sitophilus oryzae (L ) mFive Cereals of the Genus Tntlcum Journal of StoredProducts Research, 32, 315 - 322Trematerra, P , Fontana, F , ManClm, M and Scmrretta,A In pless Influence of Intact and Damaged CerealKernels on the BehaVIOur of Rice WeevI!' Sitophilus oryzae(L ) (Coleoptera Curcuhomdae) Journal ot StoredProducts Research

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