Definition - What does Pest Resurgence mean?
Pest resurgence is observed when pests previously targeted and successfully controlled by pesticide recur, but in higher numbers than they did before. The reason for this is the removal of predators together with pests. They either die from the pesticide, or move away because their food source has disappeared.
Safeopedia explains Pest Resurgence
In nature, pest populations are balanced by the relationship between predators and pests. If predators are removed from or migrate away from a particular environment, opportunistic pest species are able to breed unchecked. It is virtually impossible to annihilate an entire pest population from an area. Survivors may be safe in areas not covered by the pesticide application or survive sub-lethal doses as a result of uneven pesticide application. With predators no longer a factor, they are able to multiply very rapidly causing infestations that are worse than ever before. The problem can be addressed through Integrated Pest Management (IPM) strategies.