B. A. Croft

ARTHROPOD RESISTANCE TO INSECTICIDES: A KEY TO PEST CONTROL FAILURES AND SUCCESSES IN NORTH AMERICAN APPLE ORCHARDS

Cases of developed resistance in apple arthropods in North America, including pests and natural enemies, are reviewed with emphasis on the past 20 years since organophosphate (O‐P) insecticides were first widely employed. During this period, no key pest, including the codling moth, Laspeyresia pomonella L., has developed resistance to the O‐P compound, azinphosmethyl, while a variety of secondary pests including mites, aphids, leafhopper and leafminers, have done so as well as several important natural enemies of these species. The extensive features of DDT, O‐P, carbamate and pyrethroid resistance in the predatory mites Tyhplodromus occidentalis Nesbitt and Amblyseius fallacis (Garman) are described. Also discussed is the impact of long‐term O‐P use and resistance in relation to pest problems, insecticide selectivity and IPM, increased biological control, changing requirements for new chemical insecticides and possibilities for “resistance management” within the entire arthropod pest natural enemy complex associated with this crop.

SELECTION FOR PERMETHRIN RESISTANCE IN THE PREDATORY MITE AMBLYSEIUS FALLACIS

In selections of two greenhouse populations of the predatory mite, Amblyseius fallacis, a 64‐fold increase in resistance to permethrin was achieved after about 12 permethrin applications. The initial populations were established by mixing a variety of laboratory colonies, and adding a few individuals from recently collected field colonies. One population was treated alternately with azinphosmethyl and permethrin; it developed permethrin resistance more slowly than did the population receiving only permethrin treatments. A third population, established from the laboratory colony with the highest initial resistance level, showed little increase in resistance. After selection all three populations showed reasonable survivorship in the greenhouse on plants sprayed at recommended field rates of permethrin. All three populations also maintained resistance to azinphosmethyl, whether or not they received selection with this compound. These permethrin‐resistant predatory mites may provide biological control of pest mites on crops where synthetic pyrethroids are used to control other pests.