Things You'll Need
Liquid dish soap
Caterpillars are destructive little creatures that feed on leafy vegetation, eating their way through plants and trees. They turn into butterflies that can lay up to 1,000 eggs, which will hatch more hungry caterpillars. If not dealt with, the caterpillar infestation will ruin plants, trees and crops. Fortunately, you have several ways to kill black caterpillars without harming your garden or yard.
Purchase an insecticidal soap at a local garden center or home improvement store. Made from naturally derived fatty acids, insecticidal soaps are safer than traditional insecticides. Read and follow all warnings and directions printed on the label. Each type and brand of insecticidal soap has its own set of specific instructions.
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Spray the soap directly on the caterpillars. Look on the tops as well as the bottoms of leaves and on the plants' stems.
Repeat the process 7 to 10 days after the initial treatment.
Mix 1 gallon of warm water with 1/4 cup of dish soap. Pour the mixture carefully into a garden sprayer.
Spray the soapy water on caterpillars on house siding, outdoor furniture and other nonliving items. Soak the insects completely.
Repeat the process whenever you see caterpillars. Alternatively, pick the caterpillars off the surfaces and place them in a bucket filled with warm, soapy water.
Install birdhouses near the infested area. If birds move in, they will eat the caterpillars.