Resurgence: when pesticides kill off natural pest enemies and populations rebound.

Secondary pest outbreak: when natural enemies of potential pests are killed bringing them to pest status

Residues: the number of pesticides remaining in or on plants after a pesticide spray. The residue can also be in or on soil and in water – these move up the food chain.

Resistance: the genetically-acquired ability of an organism to tolerate the toxic effects of the pesticide. This was first noted in flies and mosquitoes in the 1950s. Pests became genetically able to detoxify pesticides through the survival of few from the population even after spraying.

Deciduous: trees/shrubs which lose their leaves seasonally, typically in autumn.