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Plantwise Factsheets for Farmers

Cutworms on Brassica

Agrotis spp.
Kenya

Recognize the problem

Cutworm is a greyish hairless worm of waxy appearance. It curls up into a little ring of C-shape when held in the hand. It is usually found in the surrounding area of the cut plant. The cutworms are actually caterpillars that hide in the soil during the day and only emerge at night to feed on the young plants or plant parts.

Background

They usually attack at night cutting the young parts on the base. Ploughing helps expose the cutworm to natural predators and sunlight which eventually kills them. Fields which are usually weedy, high in organic residue and very wet due to a lot of irrigation are associated with cutworms.

Management

Non-chemical control
  • Prepare fields to be planted earlier and remove weeds.
  • For small infestations, dig out the damaged seedling to find and kill the cutworm.
  • Flooding the field before transplanting helps to kill the young cutworms in the soil.
  • Transplanting can be delayed so that the seedlings can tolerate damage.
  • Physical barriers can be used on small plots to prevent cutworm feeding. Sticks or protective collars, made out of paper towel holders, cups, etc., can be used as barriers. Push the collar a few centimetres into the soil to act as a physical barrier.
  • Use biopesticides, such as Bacillus thuringiensis (Bt).
Chemical control
  • There are many registered and effective chemical products to use against cutworms. These include, Deltamethrin, Lambda cyhalothrin and Bifenthrin. A bait made with host plants mixed with insecticide can help to trap and kill larvae.
  • These chemicals are most effective on small cutworms, less than 2.5cm in length

When using a pesticide, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, and pre-harvest interval.

The recommendations in this factsheet are relevant to many countries where this pest or problem is present

Authors: This factsheet is based on information written for "The Brassica Farming Handbook", first published by KENGAP Horticulture 2011.
Kengap Horticulture Ltd, P.O Box 12898-00400 Nairobi, Kenya
tel: +254 722 575544; +254 723 491549 email: books@kengap.co.ke; www.kengap.co.ke
©CAB International. Published under a CC-BY-SA 4.0 licence.

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