Leaf-roller caterpillars are feasting on my cannas. I hate spraying insecticides because of the other living creatures. Can you suggest any other control methods? —Nina Salazar, North Augusta, South Carolina
Melinda: I am with you on the pesticides. Though I do suggest them as a last resort to fellow gardeners, I personally prefer to tolerate the damage and handpick, trap or use the most environmentally friendly control method.
If handpicking is not an option, try Bacillus thuringiensis (B.t.). It's sold under various names, such as Dipel or Bio-Worm Killer, These bacteria kill only true caterpillars but will not harm other insects, wildlife or people. You will need to make several applications, since these leaf rollers have several hungry generations each season. Apply B.t. to both leaf surfaces. Once the leaf roller eats the treated leaf, it will stop feeding immediately, though death of the insect takes several days.