The New Zealand Committee on Pesticide Resistance (NZCPR)

INTRODUCTION New Zealand’s primary production relies on pesticides to protect crops against diseases, invertebrate pests and weeds so that our agricultural systems continue to be competitive in world markets. Unfortunately, the repeated use of some pesticides can lead to the development of resistance in some pest species. Pests here include fungi and bacteria (plant diseases), insects and mites (invertebrate pests) and weeds. Resistance is the loss of field control of a pest when a pesticide that would normally give control at recommended application rates is used. It is not a change in the pesticide active ingredient, but rather is a genetic change in the pest that allows individuals in the population to survive in the presence of the pesticide. Resistant individuals are selected by repeated use of the pesticide until they become dominant, possibly leading to pest control failure. Modern selective pesticides, which target specific single sites in pest biochemical pathways, are more likely to select for resistance than older multi-site, broad spectrum pesticides. Consequently, the resistance risk that accompanies new pesticide chemistry is usually well researched and specific resistance management recommendations are generally released along with new pesticides. The main strategies for combating resistance to atrisk pesticides are to limit the number of applications, restrict use to certain crop growth stages and to alternate or mix them with other effective pesticides with a different mode of action.