Pest control in OSR
www.adas.uk
Steve Ellis ADAS High Mowthorpe
Oilseed rape (OSR) area in the UK
Defra: Structure of the agricultural industry
OSR yield in the UK
Defra: Structure of the agricultural industry
Crystal ball gazing• Fewer actives
• More expensive actives
• Threat of resistance
• Environmental concerns
Fewer new products
1960
s
1970
s
1980
s
1990
s
2000
s
2010
s0
40
80
120
New active ingredient (AI) registations by decade
No.
of
AI
regi
stra
tions
The days of cheap insurance sprays are over
NB resistance detected in pollen beetle, csfb, pea & bean weevil, grain aphid, peach potato aphid
Source: Pesticide Usage Survey Reports for arable crops in Great Britain
Pyrethroids & their alternatives: Pollen beetle control in UK
Standard treatment
Alternative products
Pymetrozine Indoxacarb Thiacloprid
Lamda-cyhalothrin @ €8.41/ha
€45.91/ha €35.21/ha €21.71/ha
Legislation
• Sustainable Use Directive • Promotes IPM• Implementation of IPM obligatory• National action plan• Priority to non-chemical pest management
The art of doing nothing• Most difficult
decision you can make
• Do you need to treat?
• Requires 100% confidence in information at your disposal
Risk assessment and thresholds
• HGCA Research Review No. 73 A review of invertebrate pest thresholds Ellis, SA, Berry P & Walters KW 2009
• Thresholds valuable in defining need to treat• Lack of confidence in current thresholds?• Improved knowledge of crop physiology • Use crop tolerance to assess pest risk
• Under SUD thresholds will become pivotal component of IPM
How will thresholds evolve?
• User friendly
• Inexpensive to use
• Based on sound science
• Take account of crop tolerance
• Combine pests in feeding groups
Calendar of oilseed rape pests• Slugs
• CSFB
• TuYV
• Pollen beetle
• Seed weevil
• Pod midge
• Turnip sawfly
• Sep-Nov
• Aug-Nov
• Sept - Dec
• Mar-May
• May-Jul
• May-Jul
• May-Aug
Beetle feeding destroys bud
Pollen beetle
Loss of buds means blind stalks
Pollen beetle numbers 1988–2006
Source: Fera survey data
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4
6
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12
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16
1988 1990 1992 1994 1996 1998 2000 2002 2004 2006
Mean
beetl
es/p
lan
t
Winter rape threshold
Backward rape threshold
Old thresholds
Area of oilseed rape treated against pollen beetle
0
20
40
60
2004 2006 2008 2010 2012
% o
f to
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OS
R a
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or
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beetl
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% s
pra
ys w
hen
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Changes in the pyrethroid susceptibility of pollen beetle populations 2007–2013
This bar chart is reproduced with the kind permission of IRAC
Insecticide resistance• Widespread
resistance to pyrethroids
• About 60% of beetles tested resistant
• Alternatives to pyrethroids more costly
Pollen beetle predictor
Tried and tested through HGCA-funded research
Adopted by Bayer
• Start of migration• % migration• New migration
www.hgca.com/pests
Pollen beetle: the story so far
• Rape spray thresholds rarely exceeded
• Around 20% rape area sprayed against pollen beetles (2012 PUS)
• Impact on natural enemies and insecticide resistance
• Are current thresholds out of date in relation to modern varieties/or being used?
• Rape is inherently tolerant of pest attack
• Could the thresholds be re-evaluated in relation to crop tolerance?
Initial hypotheses
• Oilseed rape produces more buds than it needs to achieve potential yield
• ‘Excess’ buds can be sacrificed to pollen beetle
• Loss of ‘excess’ buds has no impact on yield
www.adas.uk
Key questions
• How many buds does a pollen beetle eat?
• How many ‘excess’ buds does a rape crop produce?
• Does excess bud number vary between varieties and season?
Semi-field study
Pollen beetles introduced at green bud
A single beetle can destroy nine buds (On average)
y = 9.5766e-0.0397x
R2 = 0.9823
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Inoculated beetles
Po
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Excess flower number is dependent on variety in winter rape
Variety Excess flowers/m2
2008/09 2009/10
Castille (OP) 3747 8816
Excalibur (Hybrid) 7019 10760
PR54D03 (Semi dwarf hybrid)
7107 9505
Mean 5958 9694
Excess flower number is inversely related to plant number
0
100
200
300
400
0 20 40 60 80 100 120
Plants/m2
Exc
ess
flow
ers
per
plan
tCastille 2009
Excalibur 2009
PR45D03 2009
Castille 2010
Excalibur 2010
PR45D03 2010
WOSR: Threshold calculation
• Assuming crop with 40 plants/m2
• Excess flower number would be on average about 200 /plant
• Single beetle can destroy about 9 buds
• Need about 22 beetles/plant to destroy all excess flowers
Pollen beetle threshold varies with plant number
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5
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0 20 40 60 80 100
Plants/m2
Polle
n b
eetle
thre
shold
per
pla
nt
Winter OSR
Spring OSR
Pollen beetle control thresholds
Plants in lower plant populations produce more branches and, therefore, more flowers
Plants/m2 can be estimated by counting the number of plants within a square foot and multiplying by 11
Further questions
• Is a crop less tolerant of pollen beetle damage if it has been pigeon damaged?
• Is a crop less tolerant of pollen beetle damage if the pest attack is concentrated on the main raceme?
WOSR pruning experiments
• 2 sites: ADAS Rosemaund and High Mowthorpe.
• 2 seed rates (30 and 120 seeds/m2 ADAS Rosemaund only)
• 2 defoliation treatments: defoliated and non defoliated.
• Defoliation carried out on 19/2 (RM) and 11/3 (HM)
• 3 pruning treatments: removal of all buds on the terminal raceme from 0, 50 or 100% of the plants at green bud.
Pruning Treat 3
DISCARD
DISCARD
DISCARD
DISCARD
0% 0% 100% 0% 100% 0% 100% 50% 100% 0% 100% 50% 100% 50% 100% 50%
DISCARD
Pruning Treat 2 100% 50% 0% 50% 50% 100% 50% 100% 0% 50% 0% 100% 50% 0% 0% 0%
Pruning Treat 1 50% 100% 50% 100% 0% 50% 0% 0% 50% 100% 50% 0% 0% 100% 50% 100%
Defoliation no yes no yes no yes no yes no yes no yes yes no no yes
Seed rate 30 30 120 120 30 120 120 30 120 30 30 120 120 120 30 30
Plot 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Defoliation (Rosemaund)
30 seeds/m2 Non defoliation 30 seeds/m2 Defoliated
Pruning photos (Rosemaund)
No pruning D Pruned D No pruning ND Pruned ND
Pruning experiment Rosemaund(Plot yield data)
Seed rate (seeds/m2) DefoliationNo
DefoliationGrand Mean
30 (21 plants/m2) 3.22 3.73 3.48
120 (50 plants/m2) 3.10 3.66 3.38
Grand Mean 3.16 3.70 3.43
P SED LSDSeed rate 0.331 0.094 0.213
Defoliation mean <.001 0.094 0.213Seed rate*defoliation 0.813 0.133 0.302
Yield loss of 0.54t/ha in response to defoliation
Pruning experiment Rosemaund(Quadrat yield data)
Treatment Pruning treatmentGrand MeanSeed rate
(seeds/m2)Defoliation treatment 0% 50% 100%
30Defoliation 4.22 3.64 3.32 3.73No Defoliation 5.05 4.10 4.74 4.63
120Defoliation 3.74 3.64 3.90 3.76No Defoliation 5.04 4.76 4.69 4.83
Grand Mean 4.51 4.04 4.16 4.24
P df SED LSD Seed rate 0.407 3 0.122 0.389 Defoliation <.001 6 0.127 0.311 Pruning 0.167 24 0.25 0.517 Seed rate*Defoliation 0.519 8.19 0.176 0.405
Seed rate* Pruning 0.463 26.56 0.314 0.645 Defoliation* Pruning 0.789 29.72 0.316 0.645
Seedrate* Defoliation* Pruning
0.393 30.65 0.445 0.909
Pruning experiment High Mowthorpe (Quadrat yield and plot yield data)
Defoliation treatment
Pruning treatment Grand Mean0% 50% 100%
No Defoliation 3.39 3.11 3.33 3.27
Defoliated 2.90 2.99 3.43 3.11Grand Mean 3.15 3.05 3.38 3.11
P SED LSDDefoliation 0.231 0.134 0.286Pruning 0.147 0.164 0.351Defoliation* Pruning 0.225 0.234 0.496
Defoliation treatment Yield (t/ha)
Defoliation 3.76No Defoliation 3.93
Grand Mean 3.85
P 0.006 SED 0.055 LSD 0.116
Yield loss of 0.17t/ha in response to defoliation63 plants/m2
Conclusions
• Defoliation decreased yield but plots were mown late
• Pruning had no impact on yield at either site
• No interaction between defoliation and pruning
Grey field slug – Deroceras reticulatum
Monitoring slug activity & thresholds
• Use of refuge traps (approx. 25cm diameter, 2 teaspoons chicken layers mash)
• Set pre-cultivation when soil moist & weather mild (>5oC) • Nine traps per field (‘W pattern)• Leave overnight, examine next morning• Threshold:
• Standing cereals – 4 or more slugs/trap• Cereal stubble - 1 or more slugs per trap
Metaldehyde stewardship group
• Max application rate 210g as/ha• Max dose 1 August – 31 December 210g as/ha• Max dose rate/annum – 700g as/ha• No pellets within 6m of watercourse• Do not apply when heavy rain forecast • Do not apply metaldehyde if drains flowing
Treatment timing & application method
• Broadcast pellets more effective than ad-mixing with seed
• Broadcast ASAP after drilling
• Only treat up until 4 true leaf stage
• NB Metaldehyde Stewardship group
Slug pellet use, applications/crop
Source: Defra report PS2803
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1.6
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2
1998 2000 2002 2004 2006 2008
Year
Avera
ge n
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ber
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ap
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s
Wheat
Oilseed rape
Effect of slug damage on yield
• 22 ADAS wheat trials have compared the effects of methiocarb & metaldehyde on slug damage
• Between 30% & 96% plants grazed• Only 2 sites (9%) showed +ve yield response to treatment• No comparable data for OSR• Can we equate damage with yield effects?
Trial treatments• Seed rates:
• 10, 20, 40, 80 and 160 seeds/sq.m.
• Leaf damage:• None• Remove 1 cotyledon (OSR only)• Remove leaf 1 as leaf 2 is emerging• Remove leaf 1 as leaf 2 is emerging, and leaf 2 as leaf 3 is
emerging• Remove leaves 1,2,3 and 4 as each successive leaf is emerging
Impact of leaf pruning on oilseed rape yield (2011/12)
Effect of slugs on OSR: Conclusions
• In four of six experiments leaf pruning decreased yield• Removal of one cotyledon and the first true leaf never reduced
yield• No evidence that crops with low plant populations were less
tolerant than those with high populations• Little difference between conventional & hybrid varieties to
tolerate pest attack• Compensatory growth is determined by environmental
conditions
Objective
“Can higher seed rates be used to reduce the requirement for slug pellets?”
Funded by the Chemical Regulatory Directive (CRD)
Pros () & Cons (Χ) of increasing seed rate
Oilseed rape
Cost Χ Χ Χ
Lodging Χ Χ Χ
Early/even ripening
Disease =
Pests
Weeds Direct effect on yield from too many plants (no lodging)
Χ Χ
OSR - Yield responses to seed rate
What did we do?
• Fitted a curve describing each yield response to seed rate for in the 20 experiments
• Start with a seed rate of 60 seeds/m2
• Assess the effect of different slug pressures on the gross margin over seed costs, without slug pellets
• Seed cost: Hybrid £32/kg, Conventional 12/kg• OSR price: £350/t
• Assessed effect of single dose of slug pellets• £13.50/ha, 63% efficacy
Should I increase seed rate to combat slugs?
Hybrid
Conventional
Should I increase seed rate to combat slugs? – financial implications
Plants lost to slugs (%)
20 40 60 80
Hybrid
40 seeds/m2 No change +20% (+£1/ha) +20% (+£4/ha) +60% (+£20/ha)
60 seeds/m2 No change No change No change +20% (+£1/ha)
100 seeds/m2 No change No change No change No change
OP commercial
40 seeds/m2
+80% (+£18/ha)+100%
(+£27/ha)+100%
(+£46/ha)+100% (+£95/ha)
60 seeds/m2 +20% (+£3/ha) +40% (+£7/ha) +60% (+£16/ha) +100% (+£53/ha)
100 seeds/m2 No change +20% (+£1/ha) +40% (+£6/ha) +80% (+£24/ha)
Is it worth applying slug pellets?
Hybrid
Conventional
Should I increase seed rate or apply slug pellets?
OSR: seed rate vs pellets
• For hybrid oilseed rape sown at 40-100 seeds/m2
• increasing seed rate never gave a greater gross margin than either slug pellets or leaving the crop untreated.
• For OP commercial oilseed rape sown at 40 seeds/m2
• increasing seed rate by 80-100% was as, or more, cost effective than using slug pellets for low to moderate slug pressure (20 to 50% plants lost to slugs). There was no benefit at 60 seeds/m2 or more.
• For OP home-saved oilseed rape sown at 40 - 60 seeds/m2 • increasing seed rate was as, or more, cost effective than to use slug
pellets for low to moderate slug pressure (20 to 60% plants lost to slugs).
• There was no benefit of increasing seed rate at 100 seeds/m2 or more
Cabbage stem flea beetle
SeptAdults move to new crop, mate and feed on leaves
causing ‘shot holing’
Sept-OctEggs laid at base of
plants if mild
Oct-FebEggs hatch when mild and larvae feed in leaf
petioles
March-AprilLarvae feed on main stem behind growing
point
MayLarvae pupate in soil
June-JulyAdults emerge and
feed on foliage
Life cycle
Courtesy of Caroline Nicholls, HGCA
CSFB resistance to pyrethroids
No. of samples No. beetles Resistant beetles (%)
Hertfordshire 1 31 55
Essex 1 7 14
Cambridgeshire 4 100 60
Suffolk 2 57 54
Norfolk 2 45 27
Yorkshire 2 49 100
Total 12 289 59
CSFB control thresholds
Adult beetles• >25% leaf area eaten at the cotyledon–2 true leaf growth
stage• >50% the leaf area eaten at the 3–4 true leaf stage• The crop is growing more slowly than it is being destroyed
Larvae• >35 beetles/water trap in total over the monitoring period
(emergence – end Oct)• >2 larvae/plant or 50% petioles damaged
Artificial cabbage stem flea beetle
• Does what it’s asked
• Can be relied upon to cause consistent leaf damage
Tolerance of OSR to loss of leaf area
Creating cabbage stem flea beetle adult damage
Treatment Both cotyledons Leaf 1 Leaf 2
1 None N/A N/A
2 Slight N/A N/A
3 Moderate N/A N/A
4 Severe N/A N/A
5 Moderate Slight N/A
6 Moderate Moderate N/A
7 Moderate Severe N/A
8 Moderate Slight Slight
9 Moderate Slight Moderate
10 Moderate Slight Severe
11 Moderate Moderate Slight
12 Moderate Moderate Moderate
13 Moderate Moderate Severe
14 Moderate Severe Slight
15 Moderate Severe Moderate16 Moderate Severe Severe
Tolerance of OSR to loss of leaf area – Green leaf area (LSD P<0.05 = 81.4)
Tolerance of OSR to loss of leaf area – Dry matter (LSD P<0.05 = 0.63)
Csfb – cultural control? (Number of larvae in stem or petiole, February 2015)
Low risk sites
High risk sites
Aphids & turnip yellows
• Reddening, purpling of leaf margins and interveinal discoloration
• Not readily recognisable
• Confused with physiological/nutritional deficiencies
• Usually not expressed
before stem extension
Turnip yellows facts & figures
• Yield reduction in UK by up to 26%
• Greatest yield loss with early infection
• Persistent, circulative, non-propagative virus
• Differences between varieties, virus titre, symptom expression
• Various weeds provide reservoir for virus
• Source of information AHDB Cereals and Oilseeds
Aphid migration
TuYV Transmission
Winter OSR
Aphid migration datawww.rothamsted.ac.uk/insect-survey
AHDB Aphid News
Weekly reports
Suction traps: Winged aphids
Yellow water traps: Winged aphids
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% s
ampl
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ant a
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MACE
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Year
kdr super-kdrne
2012 2013
AHDB Resistance (Peach–potato aphid)
TuYV: available products
Product Active ingredient
Plenum Pymetrozine
Teppeki Flonicamid
Biscaya Thiacloprid
TuYV – timing insecticide sprays• Sprays are expensive
• Generally only apply one spray
• Spray early or late?
• Use T-sum?
• Relationship between virus & yield
TuYV – alternative control options• Amalie – resistant variety
• Produced by Limagrain
• Conventional, open pollinated variety
Amalie – agronomic charactersAmalie DK Cabernet Excalibur
Lodging resistance 9 9 8
Stem stiffness 8 9 7
Height (cm) 137 141 138
Earliness of flowering 5 4 7
Earliness of maturity 6 5 6
Disease resistance
Light leaf spot 7 6 6
Stem canker 8 7 6
Oil content (9% moisture) 45.0 45.2 44.5
TuYV – Varietal tolerance (varieties from 2009/10, mean ELISA reading of TuYV infected plots * Varieties in which TuYV significantly decreased yield
**
*
*
TuYV – future work• Screen varieties for tolerance
• Scale of tolerance
• Annual variation in virus infected aphids
• Cut-off point for treatment
Seed weevil Ceutorynchus assimilis• Rarely problem in winter OSR
• Consumes 25% of seed
• Allows entry of brassica pod midge
• Threshold in northern Britain 0.5 weevils per plant, 1per plant elsewhere
• Apply pyrethroid during flowering if threshold exceeded
Seed weevil (Ceutorhynchus assimilis)
Seed weevil larva
Brassica pod midge Dasineura brassicae
• Lays eggs through seed weevil holes
• Damage worst on headlands
• Causes pod burst and loss of seed
• Seed weevil sprays reduce pod midge
• Can be major problem in spring rape
Pod midge larvae
Turnip sawfly Athalia rosae
Medium size
Yellow body
Black joints on all legs
Two black patches on
thorax
Life history• Hibernate as mature larvae in soil
• 3 generations per year
• First flies May – June, migrates large distances
• Lay eggs locally if host available
• Egg laying starts a few days after hatching
• Females lay 50 - 300 eggs each
• Eggs hatch in 6 - 8 days
• Larvae feed for 10 - 13 days
Eggs laid at edge of leaf
The females lay their eggs singly in small chambers.
Fully grown larvae after 13 days
Larvae hibernate in soil
Rape winter stem weevil (Ceutorhynchus pictarsis)
Rape winter stem weevil damage
Cabbage stem weevil (Ceutorhynchus quadridens)
Comparison of weevil pests of OSR
Latin name Common name
Pest in UK Threshold Comments
Ceutorhynchus assimilis
Cabbage seed weevil
Yes North UK 0.5/plantSouth UK 1.0/plant
Allows entry of pod midge, spring migration
C quadridens Cabbage stem weevil
No None Spring migration
C pictarsis Rape winter stem weevil
No None Occasional pest in northern England, autumn migration
HGCA e-NewslettersUseful for monitoring why?
• Remind you to monitor
• Remind you of thresholds
• Remind you of legislation
• Warn you of outbreaks
• Warn you of new issues
Pest-specific information
Thank you