EVOLUTION OF SECONDARY PESTS IN CALIFORNIA PEAR ORCHARDS UNDER MATING DISRUPTION FOR CODLING MOTH CONTROL

After rapid transition from an organophosphate to a mating disruption-based codling moth, Cydia pomonella, control program from 1996 to 1999, secondary pests previously controlled have become sporadic pests in California pear orchards. Codling moth control is currently achieved using pheromone dispensers (hand-applied or puffers) supplemented with reduced-risk insecticides as determined by monitoring. The reduction in the use of organophosphate insecticides has resulted in the decrease of pear psylla, Cacopsylla pyricola, and twospotted spider mite, Tetranychus urticae, populations through increased activity of beneficial insects. This has led to reductions in pesticide use specific to these two pests. During the transition period, two secondary pests, pear rust mite, Epitrimerus pyri, and oblique-banded leafroller, Choristoneura rosaceana, caused significant damage. By developing monitoring techniques and treatment thresholds these two pests are now controlled with appropriately timed insecticides. Pear sawfly, Caliroa cerasi, lygus bug, Lygus Hesperus, and Western spotted cucumber beetle, Diabrotica undecimpunctata, are very sporadic secondary pests that occasionally need to be controlled with well-timed insecticides. Katydids, previously not considered a pest on pears, were observed feeding on maturing fruit in North Coast orchards. The Mediterranean katydid, Phaneroptera nana, an exotic species present in California since 1940s, was found to be responsible for the feeding damage. This species overwinters as eggs on vines and the nymphs migrate to the edge of pear orchards as the fruit ripens. Presently the secondary pests of major concern, for which studies are still ongoing, are Western boxelder bug, Boisea rubrolineata and consperse stink bug, Euschistus conspersus. Western boxelder bug is also a pest at the edge of orchards adjacent to the riparian corridor where this insect overwinters. Damage from consperse stink bug can be observed throughout the orchard. We will present monitoring techniques developed for these secondary pests and results of insecticide trials for the most effective timing and control.