Abstract: When insect pests were fed with different host plants, the susceptibility to insecticides would decrease, increase or be unchanged. These changes were related to the activation or inhibition of insect detoxifying enzymes induced by plant allelochemicals, while the induction levels were influenced by some factors such as plant nutrients, structures and distributions of allelochemicals, species and development stages of insects as well as the temperature. The metabolic abilities of induced detoxifying enzymes for the insecticides varied with the types of insecticides, resulting in the variations of insect susceptibility to different insecticides. It was recognized that the induced activation of insect detoxifying enzymes would enhance the frequency of the recessive resistance gene, and would promote the development of insecticide resistance at the early stages. Finally, the effects of host plant on insecticide susceptibility applied in pest management were discussed.

Key words: host plant, allelochemicals, insecticide resistance, detoxifying enzymes, induction