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New approaches to managing cabbage stem flea beetles in oilseed rape
Simon Kightley
NIAB
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 634179.
EMPHASIS Effective Management of Pests and Harmful Alien Species - Integrated Solutions
The background
• ADAS (1984) describe CSFB as a damaging pest in Berkshire, Buckinghamshire, Cambridgeshire, Essex and Northamptonshire, Oxfordshire and parts of Warwickshire
• Subsequently controlled with Gamma HCH seed treatments until banned in 1999
• One season with no effective seed treatment
• Subsequently controlled by neonicotinoid seed treatments until banned in 2014
2014/15, 2015/16 & 2016/17
Three years of contrasting experiences……..
And most of them very unpleasant and
depressing!
2014/15 • Neonic ban coinciding with high CSFB
numbers after increasingly warm winters (3oC is critical for egg laying and larval development)
• Poor conditions for establishment in central East Anglia – cool, dry, early September
• Extensive predation by CSFB adults on later sown crops
• No successful establishment in trials after 27th August in Cambridge area – but no farm survey
Trial losses in Autumn 2014
Key Successful establishment Successful farm crop Partial establishment Complete failure
NIAB, Staughton drilled 17-20 Aug
NIAB, Hardwick Drilled 8 Sept
LSPB, Girton 27-29 Aug
LSPB, Impington 4-8 Sept
Saaten Union, Cowlinge 2-4 Sept
Saaten Union, Wickhambrook 24 Aug
KWS, Barley 29 Aug Re-drilled 17 Sept Failed
NIAB, Bottisham Farm crop 15 Aug, good Early sowing 19 Aug, OK Main sowing 29-31, failed Site written off (4080 plots)
NIAB, Trumpington 2 Sept Effective write off. Site maintained by transplants for disease obs.
NIAB HQ 22 Aug - OK 4 fields 2-7 Sept Fragments only remaining, supplemented by transplants
ADAS Boxworth Drilled 22 Aug; Re-drilled 8 Sept. Failed
Trial losses in Autumn 2014
Key Successful establishment Successful farm crop Partial establishment Complete failure
NIAB, Staughton drilled 17-20 Aug
NIAB, Hardwick Drilled 8 Sept
LSPB, Girton 27-29 Aug
LSPB, Impington 4-8 Sept
Saaten Union, Cowlinge 2-4 Sept
Saaten Union, Wickhambrook 24 Aug
KWS, Barley 29 Aug Re-drilled 17 Sept Failed
NIAB, Bottisham Farm crop 15 Aug, good Early sowing 19 Aug, OK Main sowing 29-31, failed Site written off (4080 plots)
NIAB, Trumpington 2 Sept Effective write off. Site maintained by transplants for disease obs.
NIAB HQ 22 Aug - OK 4 fields 2-7 Sept Fragments only remaining, supplemented by transplants
ADAS Boxworth Drilled 22 Aug; Re-drilled 8 Sept. Failed
Teversham – Autumn 2012
Cruiser treated seed – Further up the field, breeders’ trials, with untreated seed, survived well.
2015/16 • Much better conditions for establishment – good
rainfall, warmer
• High adult beetle numbers
• Losses of commercial crops (see survey)
• Warm winter prolonged egg laying and larval development
• Many larval infested crops branched and stunted
• Backward, pigeon grazed crops affected by late frosts
• Low yielding year
2016/17
• Dry September
• High adult beetle numbers
• Losses of commercial crops (see survey)
• Cool October/November reduced egg laying/larval development
• Few larvae reported in petioles
• Surviving crops developed well in normal April period
• Reduced CSFB pressure for Autumn 2017?
Cabbage stem flea beetle (Psylliodes chrysocephala) (Dr Sam Cook – Rothamsted Research)
Life cycle : univoltine
Late Aug- Oct
Adults move into new crop, mate feed on leaves causing ‘shot-
holing Aug - Feb
Eggs laid at base of plant when warm & humid
Late Aug – March
Larvae feed in leaf petioles, 3rd instars feed in
stem Dec – May
Larvae drop to the ground ; Pupate in
the soil for c. 3 months
May-July
Adults emerge, feed on leaves,
pods
July – Sept
Aestivate in sheltered areas
Larval feeding damage
• Has really only come to the fore in spring 2016
• High levels of infestation widely reported • Apparently healthy crops failing to grow
away, in cool, grey, early spring conditions
Larval damage to growing point
Short, highly branched plants Delayed flowering Increased vulnerability to other pests (pigeons, pollen beetles)
Larval feeding damage
• Larvae are pretty well immune to sprays once they are feeding inside the plant
• Assessing yield loss is highly speculative • Yield loss likely to be worse in low
populations – just a numbers game
What we don’t know
• Dispersal distance of the adults
• Whether a couple of hard winters might knock the population right back
• What sort of rape-growing moratorium and over what sort of area would be needed to do any good: County? Region?
Encouraging news from Sweden?
Harvest year – 1975-2014
CSFB population cycles in Skåne (Southern Sweden)
Larv
ae p
er p
lant
Source: Jordbruks verket - Sweden
Update from Skåne
Harvest year – 1983-2015
Larv
ae p
er p
lant
CSFB population cycles in Skåne (Southern Sweden)
Source : Jordbruks verket - Sweden
Improved strategies for Autumn 2015
For trials: • Early-sown neonicotinoid seed-treated surround
crops (Experimental Licence) • Treated seed in pathways (tramlines) and in strips
through trials • Fine seedbed preparation • Starter fertiliser • Early use of neonic insecticide spray (Insyst) • Regular and frequent pyrethroid insecticide
sprays (Not good for beneficial insects!!!) • Irrigation (where available) • Insect netting
Help from the UK Government!
Acknowledgement of the serious threat to the oilseed rape crop:
• A derogation for limited use of neonic seed treatment in worst affected counties
• A derogation for use of neonic insecticide crop sprays
Better establishment
• Better soil moisture and warmer temperatures than autumn 2014.
• Better luck with establishment locally.
BUT
• More widespread reports of farm crop failures
• More reports of neonicotinoid seed treatments failing to control CSFB
• Observations of pre-emergence herbicides holding crop back
• Huge problem with larvae
Pre-emergence herbicide effect
• Observations that our Clearfield trial at Hinxton, grown without pre-ems, got away better than the rest of our trials
• We used:
– BANASTAR (dimethenamid-p, metazachlor, quinmerac)
– CIRRUS (clomazone)
NIAB TAG Crowd Sourcing Survey
Using farmer on-line responses to map the range and severity of the flea beetle problem:
• Is it spreading?
• Is it date dependent?
• Is it weather dependent?
• Is it affected by establishment method?
• Do ‘neonic’ seed treatments still work?
• East Anglia/Bucks./Herts. is the main area affected by cabbage stem flea beetles. • Later sowings most at risk.
• Neonicotinoid seed treatments were no guarantee of protection. • Regret not asking for reduced or zero plantings.
Survey responses
Data summary
0
2
4
6
8
10
Nu
mb
er o
f re
spo
nse
s/d
ay
Sowing date
Crop damage intensityInsignificant Low Moderate Severe Very Severe
Combined damage score No. of obs.
Variety typeMixed 25.3 30Conventional 25.4 78Hybrid 27.7 73Establishment methodAutocast 15.4 7Plough 21.4 33Non-inversion 24.1 63Subcast 27.7 32Direct drill 33.5 46Seed treatmentOther 22.3 65None 26.3 95Neonicotinoid 36.2 21
A summary of other data
Combined damage score No. of obs.
Variety typeMixed 25.3 30Conventional 25.4 78Hybrid 27.7 73Establishment methodAutocast 15.4 7Plough 21.4 33Non-inversion 24.1 63Subcast 27.7 32Direct drill 33.5 46Seed treatmentOther 22.3 65None 26.3 95Neonicotinoid 36.2 21
A summary of other data
Combined damage score No. of obs.
Variety typeMixed 25.3 30Conventional 25.4 78Hybrid 27.7 73Establishment methodAutocast 15.4 7Plough 21.4 33Non-inversion 24.1 63Subcast 27.7 32Direct drill 33.5 46Seed treatmentOther 22.3 65None 26.3 95Neonicotinoid 36.2 21
A summary of other data
Combined damage score No. of obs.
Variety typeMixed 25.3 30Conventional 25.4 78Hybrid 27.7 73Establishment methodAutocast 15.4 7Plough 21.4 33Non-inversion 24.1 63Subcast 27.7 32Direct drill 33.5 46Seed treatmentOther 22.3 65None 26.3 95Neonicotinoid 36.2 21
A summary of other data
Seed rate x companion crop experiment
Companion crop
OSR seed rate/m2 60 80 100 120
No companion crop N60 N80 N100 N120 Mixture A A60 A80 A100 A120 Mixture B B60 B80 B100 B120 Mixture C C60 C80 C100 C120
OSR variety: CHARGER A = Insect deterrent: Fenugreek B = Insect attractant: Pak choi/Chinese cabbage/salad rocket/linseed C = Insect neutral: Berseem clover/crimson clover/Persian clover/common vetch Replicates: 4 Sites: 3 – Cambridge (Hinxton), Morley, Sutton Scotney
Companion cropping
Generalised plot layout
12 m
2 m
The aim was to achieve well defined rows of oilseed rape in a carpet of non-hardy, companion species plants.
Separate sowings of: 12 rows companions, 4 rows oilseed rape
Companion cropping (Sutton Scotney)
Fenugreek Rocket, Pak Choi,
Chinese cabbage, Linseed
Common vetch Crimson clover Berseem clover Persian clover
Damage observations (1 good; 5 bad)
29/09 15/10 29/09 15/10OSR 60 3.8 4.3OSR 80 3.5 3.8OSR 100 3.3 3.5OSR 120 3.8 3.3 3.6 3.7A OSR 60 4.0 3.3A OSR 80 3.5 2.8A OSR 100 3.5 3.3A OSR 120 3.5 3.0 3.6 3.1B OSR 60 2.3 1.0B OSR 80 2.0 1.0B OSR 100 2.3 1.0B OSR 120 2.5 1.0 2.3 1.0C OSR 60 3.5 2.8C OSR 80 3.3 2.5C OSR 100 3.0 2.5C OSR 120 3.3 2.5 3.3 2.6
Trt x sdrt Trt meansCambridge obs.
Treatment name
Treatments:
OSR only
OSR and Fenugreek
OSR and exotic brassica/ linseed mix
OSR and legume mix
Damage observations (1 good; 5 bad)
29/09 15/10 29/09 15/10OSR 60 3.8 4.3OSR 80 3.5 3.8OSR 100 3.3 3.5OSR 120 3.8 3.3 3.6 3.7A OSR 60 4.0 3.3A OSR 80 3.5 2.8A OSR 100 3.5 3.3A OSR 120 3.5 3.0 3.6 3.1B OSR 60 2.3 1.0B OSR 80 2.0 1.0B OSR 100 2.3 1.0B OSR 120 2.5 1.0 2.3 1.0C OSR 60 3.5 2.8C OSR 80 3.3 2.5C OSR 100 3.0 2.5C OSR 120 3.3 2.5 3.3 2.6
Trt x sdrt Trt meansCambridge obs.
Treatment name
TreatmentName 12/1 26/1 12/1 26/1OSR 60 3.5 3.5OSR 80 3.3 3.3OSR 100 3.5 3.5OSR 120 3.5 3.3 3.5 3.4A OSR 60 3.3 3.0A OSR 80 3.3 2.8A OSR 100 3.5 3.0A OSR 120 3.3 3.0 3.4 3.0B OSR 60 3.0 3.0B OSR 80 3.0 2.8B OSR 100 3.0 3.0B OSR 120 3.0 2.3 3.0 2.8C OSR 60 3.3 3.0C OSR 80 3.3 2.8C OSR 100 3.3 2.5C OSR 120 3.3 2.8 3.3 2.8
Morley obs.Trt x sdrt Trt means
-5
0
5
10
15
20
25
30
35
40
45
Pe
rce
nta
ge
da
ma
ge
(n
ea
rest
5%
)
Percentage CSFB damage
Fenugreek Brassica and linseed mix Legume mix OSR
Working with Reading University and Rothamsted Research (Duncan Coston)
Control of companion species
• No killing frosts in 2015/16 winter
• Several herbicide applications were tried but were rather ineffective post-Christmas and limited by label regulations
• Brassica/linseed mix was particularly resilient – crowded-out the OSR
Back to beetle biology
• New attempts to monitor beetle dispersal and migration in the approach to harvest 2016
• We favour yellow stick traps
Conclusions from 2016
• Establishment is helped by early sowing, good seedbeds, warmth and rain.
• This does not guard against subsequent larval infestation.
• Neonics were a tool but no longer the answer. • Early sown, treated/sprayed trap cropping can
help. • Companion cropping can play a part. • Pre-emergence herbicides can hold crop back • And yes, back to higher seed rates!
And so to 2016/17
• Some breeders moving their nurseries away from the Cambridge area
• We maintained a large presence of research and commercial breeders’ and agrochemical trials at Hinxton (Cambs) – 34 ha
• Weather : DRY. A few showers to germinate the seed but not enough for good growth
• The drought affected much of south-east England and has complicated the flea beetle story
Government help withdrawn!
• No derogation for neonic seed treatments
• No derogation for neonic insecticide sprays
2016/17 • Dry September
• High adult beetle numbers
• More losses of commercial crops (see survey)
• BUT:
• Cool October/November reduced egg laying/larval development
• Fewer larvae reported in petioles
• Surviving crops developed well in normal April flowering period
• Reduced CSFB pressure for Autumn 2017?
Monitoring the migration
05
101520253035
5 6 8 9 12 13 15 16 19 20 23 26 27
Ave
rag
e C
SF
B p
er t
rap
Date in September
CSFB trapping - Brooms Barn, 2016
Companions for 2016/17
CropMix
code
1000 seed
weightseeds/m2
seed wt/m2
Plot size
Packet size
OSR 4.5 60 0.27 20 5.4OSR 4.5 90 0.41 20 8.1OSR 4.5 120 0.54 20 10.8CompanionsFenugreek A 12.0 250 3.00 20 60.0Pak choi B 1.9 80 0.15 20 3.0Chinese kale B 4.0 80 0.32 20 6.4Choi sum B 2.4 80 0.19 20 3.8Rocket C 1.4 125 0.18 20 3.5White mustard C 7.4 125 0.93 20 18.5Buck wheat D 33.4 250 8.35 20 167.0
Autumn 2016 – Morley - damage Trt. No.
WOR sdrt Companion mix 09/09 14/09 19/09 26/09 07/10 12/10
1 60 - 1.0 2.7 2.7 3.3 2.0 1.02 90 - 1.0 3.0 2.7 3.7 2.3 1.33 120 - 1.0 3.0 3.0 3.3 2.3 1.04 60 Fenugreek 1.0 2.7 2.7 2.7 2.0 1.05 90 Fenugreek 1.0 2.7 2.3 2.7 2.0 1.06 120 Fenugreek 1.0 2.0 2.3 3.0 2.0 1.07 60 Chinese brassicas 1.0 2.7 3.0 3.3 2.7 2.38 90 Chinese brassicas 1.0 2.3 3.0 3.3 2.7 2.09 120 Chinese brassicas 1.0 2.7 3.0 3.7 3.0 1.710 60 Mustard & Rocket 1.0 1.7 1.7 2.0 2.3 1.011 90 Mustard & Rocket 1.0 1.7 2.0 2.0 2.3 1.312 120 Mustard& Rocket 1.0 2.0 2.0 2.0 2.0 1.313 60 Buck wheat 1.0 1.7 2.0 3.0 3.0 1.014 90 Buck wheat 1.0 2.7 3.0 3.0 2.7 1.015 120 Buck wheat 1.0 2.7 2.7 3.0 3.0 1.0
1.0 2.4 2.5 2.9 2.4 1.3Averaged over treatments
Observations on the 2017 companions
• All except Rocket (Eruca sativa) proved susceptible to the frost
• The white mustard/rocket mix appeared to have potential for protecting the crop
• But:
• If controlled after the winter, will stunt the OSR and reduce yield potential
• Much work still to do
Overall conclusions
• Cabbage stem flea beetles remain a huge threat to the oilseed rape crop
• Threat is greater for later sowings
• Attention to improved conditions for rapid germination is important
• No immediate promise of chemical control
• Successive cold winters may help
• Companion crops have potential and white mustard seems to be the best candidate
• More work needed