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Plantwise Factsheets for Farmers

Cutworm management in outdoor tomatoes

Agrotis spp.
Tanzania

Recognize the problem

Cutworms (“sota” in Swahili) are 2 to 4 cm long, c-shaped larvae. They are pencil-thick, soft and dark brownish-grey, like the soil. The older, bigger larvae can cut and chew young tomato stems quickly. Under a freshly cut seedling, you can often find a cutworm larva under the soil surface.

Background

Cutworm larvae live in and on the soil surface. During the night and early mornings they search for stems of tomato seedlings, particularly after transplanting. They eat the stems at ground level and cut them. Serious problems occur in the dry season. Chemical control of larvae is possible, but often it is too late to prevent the cutting. Later, cutworms become moths.

Management

If you have experienced cutworm damage the previous season, then preventive measures must be taken:
  • Deeply plough before and after cropping to expose cutworms to natural enemies
  • A day after transplanting, push protective collars made of plastic bottles into soil around seedlings to protect them from cutworms
  • Alternatively, insert two dry wooden sticks next to the seedling stems. Sticks should be the same thickness as an adult finger and about a hand to two hands long. The sticks will confuse the arriving cutworm larvae.
During mass outbreaks (uncountable numbers of larvae) more action might be taken:
  • Hand pick larvae from the soil at night or early in the morning
  • Apply ash around the seedlings
  • Chop 30-40 hot peppers or 1/2 litre of hot pepper powder into a 10 litre big bucket of warm (not boiling) water. Let the liquid steep (infuse) for 1 day. Remove the pepper and dilute with another 10 litres of cold water in the knapsack sprayer. Add 20 drops of dishwashing soap. Spray in the evening directly on to the soil around the stem of seedlings or young plants until soil is wet.
  • If possible, avoid spraying pesticides because the ones used for cutworm larvae (e.g. carbaryl, bifenthrin, WHO toxicity class II moderately hazardous) are toxic. If pesticides must be used, spray in the evening directly on to the soil around stems of seedlings and young plantings. Apply 1 spray per early season only, and do not enter field for 1 day because sprays are toxic. Do not spray 14 days or less before harvest.

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: Tanzania

Authors: Ezekiel Lyimo, Adeltruda Massawe, Martin Kimani, Joyce Bakengi, Richard Musebe, Mwangi Jubilant, Mansuet Tilya
Plantwise
©CAB International. Published under a CC-BY-SA 4.0 licence.

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