How can I control fall webworms?
A tree is normally very tolerant of some defoliation and control efforts are unnecessary when only a few caterpillars are present. If a citizen is concerned they can control them with the use of biological products or chemical pesticides. Biological products like Safer's BTK™ Biological Larvicide contain the active ingredient Bacillus thuringiensis var. kurstaki (Btk) to control caterpillars. Btk is a selective biological insecticide which controls lepidopterous larvae (caterpillars). Btk crystals release a toxic protein when dissolved in the alkaline digestive system of the insect. Btk has to be applied when caterpillars are actively feeding, and applied so that all foliage is thoroughly covered. The caterpillar stops feeding soon after, and dies within five days. Other insects, mammals, birds and fish are not affected by Btk. These products can be found at most local hardware stores. All Pest Control products purchased and used must be registered with Health Canada and contain a Pest Control Product (P.C.P. or PCP) Number on their label.