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

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New active ingredient (AI) registations by decade

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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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Winter rape threshold

Backward rape threshold

Old thresholds

Area of oilseed rape treated against pollen beetle

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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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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

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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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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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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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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