Bacillus thuringiensis, better known as Bt powder, is a type of natural bacteria that kills caterpillars on plants. Bt powder does not harm other types of beneficial insects.
Most pesticides kill caterpillars, but the chemicals found in these pesticides kill other insects, such as predatory wasps, earthworms and ladybugs. In addition, the stems and leaves absorb these chemicals, making pesticides unsuitable for plants grown for the purpose of eating. Neem oil can be used to control caterpillars along with other pests such as thrips, leaf miners and whiteflies; however, neem oil can kill beneficial insects, such as earthworms and bees.