A Review of Resurgence and Replacement Causing Pest Outbreaks in IPM
Insect and mite pest resurgence occurs when an insecticide or acaricide treatment destroys the pest population and kills, repels, irritates or otherwise deters the natural enemies of the pest. The residual activity of the insecticide then expires and the pest population is able to increase more rapidly and to a higher abundance when natural enemies are absent or in low abundance. Replacement of a primary pest with a secondary pest occurs when an insecticide or acaricide treatment controls the primary pest and also destroys natural enemies of an injurious insect or mite that was regulated below an economic injury level by the natural enemies, thus, elevating the secondary pest to primary pest status. Disruption of natural controls is not always the cause of resurgence or replacement events. A dose-response phenomenon called hormesis can occur in pest populations exposed to sublethal doses of pesticides. This can cause an increase in fecundity (physiological hormoligosis) or oviposition behaviour (behavioural hormoligosis of the pest leading to a significant increase in its abundance. Selective insecticides and acaricides coupled with natural enemies and host plant resistance have become the alternative methods more commonly used by growers that encounter these problems. The purpose of this chapter is to review pesticide-induced resurgence and replacement in modern cropping systems and methods for measuring and resolving these problems.