Applying insecticides to resistant life stages of insects, such as the eggs of many insects, adults of armored scales or gall insects inside plant tissue, may kill off natural enemies and so result in increased numbers of plant feeding insects. Also, insecticide drift may destroy natural enemies on other plants in the area. In general, the use of pesticides destroys natural enemies and interferes with natural control. Use cultural and biological controls whenever possible to prevent the need for insecticides. Some plants are more susceptible to insect attack than others.
Plants have many mechanisms of defense against insects.
Plant leaves may contain natural chemicals that adversely affect insects feeding on them. Some plants have extremely hairy leaves or thick, waxy cuticles that deter insect feeding. Other plants have developed a tolerance to insect feeding that allows them to sustain substantial defoliation without suffering serious injury. These are all considered host plant resistance. In some cases, certain varieties of a plant are more susceptible than other varieties.