Safer Insect Killing Soap is a good solution for tough insect pest infestations. It works as a contact insecticide and has no residual effect. Gardeners just spray this ready-to-use mixture onto their plants every 7 to 10 days and apply at least three times to break the pests' reproductive cycle. Use on houseplants, ornamental foliage plants, flowering plants, and fruits and vegetables. Does not kill beneficial insects. Can be used up to the day of harvest.