Cotton
Cotton Leaf Roller
Syllepte derogata
Insect
In a Nutshell
- Feeding damage on leaf margins.
- Leaves curl up and wilt.
- Premature defoliation.
- Compromised boll formation.
- Dirty pale green, semi-translucent larvae.
Cotton
Symptoms
Initial symptoms appear as leaves rolled in the shape of a trumpet, mainly on the top parts of the plant. Larvae are located inside and chew on the leaf margins. Gradually, the rolled leaves curl and droop, leading to defoliation and the premature ripening of the bolls. Boll formation can be compromised if the attack takes place during bud formation or flowering stage. However, in general, heavy infestations occur only sporadically. This can lead to significant yield loss if the population of insects is not controlled. S. derogata is also a common pest in okra.
Recommendations
Organic Control
Biological control by parasitic species or other predatory insects can be used to reduce the infestation. Two species of larval parasite, Apanteles sp. and Mesochorus sp., and 2 species of pupal parasite, Brachymeria sp. and Xanthopimpla sp. have been used successfully in field trials. If insecticides are needed, spray products containing Bacillus thuringiensis (Bt) to reduce populations.
Chemical Control
Always consider an integrated approach with preventive measures and biological treatments if available. Insecticides containing pyrethroids, cypermethrin and indoxacarb (or a mixture of these active ingredients) have been used with some success in cotton fields to lower infestation levels.
What caused it?
Damage is caused by the feeding activity of the larvae of the cotton leaf roller, Syllepte derogata. The adult moths are medium sized and have a wingspan of 25-30 mm. They are of a yellowish-white color, with distinctive black and brown spots on the head and thorax. Dark-brown wavy lines can be observed on both wings, forming conspicuous patterns. Females lay eggs on the underside of the leaves, more commonly on the younger ones on the top of the plant. Young larvae feed initially on the underside of leaves, but then move to the upper side to build the distinct rolled-leaf cocoon where they also pupate. The larvae can be up to 15 mm long and are of a dirty pale green, semi-translucent color.
Preventive Measures
- Plant resistant varieties if S.
- derogata is a recurrent problem.
- Plant later in the season to avoid population peaks.
- Grow healthy plants with a good fertilization program.
- Check your plants or fields for any sign of disease or pest.
- Handpick leaves infested with eggs, rolled leaves and caterpillars.
- Use traps to attract moths.
- Avoid indiscriminate insecticide use that destroys natural enemies of the pest.Remove or destroy infested plants and your waste by burning it.
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