I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
Those pests are better prevented than treated because once in the rolled up leaves you can't get pesticide to them. In severe cases it is best to cut the affected stalks to the ground and remove them from the garden. Bury or destroy them as there will be larvae and/or pupae in the plant material. Then spray the remaining stalks and periodically treat the new growth to protect it from the leaf rollers that might be hatching from eggs laid on the plants. Any insecticide effective against caterpillars should work against leaf rollers. Products containing B.t. are very low in toxicity and yet effective against caterpillars if applied to foliage on which the pest are feeding. Keep in mind that B.t. although very low toxicity doesn't last long after spraying and would not provide protection for more than a day or maybe two. Such sprays would need to be applied weekly during times of leaf roller infestation to maintain effective control and to break the life cycle of this pest. Make sure and spray all the leaves including lower leaf surfaces and also inside the top opening of rolled up newly emerging leaves if possible. Products containing carbaryl (Sevin) or acephate (Orthene) are more toxic than B.t. but last longer and are also effective against the leaf roller caterpillars.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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