Slug pellet timing and placement in winter wheat and oilseed rape (HGCA Topic Sheet no.88)

Slug pellet timing and placement in winter wheat and oilseed rape

Topic Sheet No. 88
Summer 2005

Action:

  • Assess slug damage risk – see Topic Sheets 84 (wheat) and 85 (oilseed rape).

  • Do not normally apply slug pellets to stubble.

  • If risk is high, broadcast slug pellets as soon as possible after drilling; DO NOT wait until crop emergence.

  • If warranted by slug damage, apply pellets after emergence.

If you are unsure about any of the suggested actions, or want them interpreted for your local conditions, consult a professional agronomist.

Application timing

Consult Topic Sheets 84 (wheat) and 85 (oilseed rape) for methods of integrated control, based on damage risk assessment.

Trials over three years compared the performance of slug pellets broadcast:

  • on stubble up to 6 weeks before drilling

  • soon after drilling and rolling.

Figure 1 shows examples of the data obtained with winter wheat. In the dry weather of 2002 and 2003, there were no significant differences between pellet timings.

In 2004, under wet conditions, pellets applied to stubble were much less effective than those applied just after drilling and rolling.

Pellets kill slugs that are active on the surface but many slugs remain in the soil largely unaffected. In a wet autumn, slugs breed rapidly from this reservoir and grow, so new slugs become surface-active as autumn progresses.

This shows clearly the importance of applying pellets just before damage is expected in a wet autumn.

Other trials with winter wheat showed that waiting to apply pellets at crop emergence gives poorer control (Figure 2).

Similar results on application timing were obtained in studies with oilseed rape.

Risk assessment

Application after drilling and rolling allows proper assessment of damage risk, based on soil and weather conditions at and after drilling.

This risk assessment is not normally possible for pellets applied to stubble (except where oilseed rape has been ‘Autocast’ or when prolonged wet weather has delayed drilling).

Soil from rain splash on pellets does not significantly affect the time taken for slugs to find the pellets and feed.

Slugs start to feed on wheat seeds and oilseed rape seedlings almost immediately, so pellets should be applied as soon as possible after drilling, rather than waiting until after heavy rainfall.

Further treatment with pellets after emergence is justified where slug activity is high and crop growth is slow.

Broadcast or admix

Pellets that are broadcast kill slugs more quickly than pellets that are drilled with seeds. Broadcasting gives more consistent slug control, particularly in combination with fine, firm seedbeds that help protect seeds and seedlings.

Admixed pellets are ineffective in fine seedbeds because both seeds and pellets are unavailable to slugs, which survive to attack emerging seedlings.

Pellet admixtures with wheat seeds can be effective when direct-drilling, or in open cloddy seedbeds.

Summary

Usually, the best time to apply slug pellets, to protect seeds and young seedlings, is just after drilling. Application at this time permits proper assessment of damage risk. Pellet applications to stubble may be made unnecessarily in dry autumns and are less effective than after drilling in wet autumns.

This Topic Sheet, together with numbers 84 and 85, resulted from a Defra sponsored Sustainable Arable LINK Project. Partners are ADAS Consulting, Bayer CropScience, CropTech, De Sangosse UK, Godfrey Farms, HGCA, Rothamsted Research, Lonza and University of Newcastle.

Further information:

Dr David Glen, Styloma
E-mail: davidmglen@btopenworld.com

Ongoing project 2436

Pest management in cereals and oilseeds - a guide, HGCA (2003)

Topic sheets are free

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The Home-Grown Cereals Authority (HGCA) has provided funding for this project but has not conducted the research or written this report.While the authors have worked on the best information available to them, neither the HGCA nor the authors shall in any event be liable for any loss, damage or injury howsoever suffered directly or indirectly in relation to the report or the research on which it is based.

Reference herein to trade names and proprietary products without stating that they are protected does not imply they may be regarded as unprotected and thus free for general use. No endorsement of named products is intended, nor is any criticism implied of other alternative, but unnamed products.


(c) HGCA, Topic Sheet No. 85, Summer 2005

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