How can you eradicate small caterpillars that are infesting your canna lilies?

A caterpillar called a leaf roller is a common problem to cannas. Regular applications of an insecticide soap purchased from a garden store can help control, but to truly eradicate the leaf roller, three or four weekly applications of BT, bacillus thuringiensis, will stop this pests life cycle. The leaf roller ingests the product while eating the folded leaf and can no longer eat afterwards, dying from starvation. BT only affects this type of caterpillar while it is harmless to other beneficial insects. Because it has to eat the BT to be effective, you may find evidence of the pest's leavings inside when releasing the caterpillar's webbing from a leaf, but the leaf roller itself will be dead or gone. Application of these two suggestions should be done in late evenings. Both the soap and the BT are much friendlier to the environment than true poisons by selectively controlling this pest. Use one and wait to see results before applying the other.