Final answer:
Pesticides typically kill only the insects present at the time of application and should be used as a last resort, as per the IPM approach. Plants produce compounds that help them recover from damage and also manage insect populations. Overuse of pesticides can lead to insect resistance.
Step-by-step explanation:
In most cases, pesticides kill only the insects present in the air during the time of treatment. Plants benefit from producing compounds that deter or kill insects year-round because these compounds enhance the plant's ability to recover from various types of damage. Additionally, these compounds can be crucial when other biological control tools are unable to keep insect populations and resistance in check, thus protecting the environment and lowering costs. However, reliance on pesticides should be minimized, as insects can develop resistance to them, rendering them ineffective. Hence, pesticides are typically considered a last resort, following the Integrated Pest Management (IPM) approach which favors more ecologically friendly options.