California Agriculture

Conventional almond growers in Merced and Stanislaus counties who use organophosphate, carb-amate and pyrethroid insecticides were compared with participants in the Biologically Integrated Orchard Systems (BIOS) program, who do not use these broad-spectrum insecticides. The results demonstrated consistent but not significantly lower infestation by navel orangeworm and peach twig borer for growers who used broad-spectrum sprays. Infestation by ants resulted in the most consistent difference between the two management practices, with significantly less damage when broad-spectrum sprays were used. The differences in overall pest damage were relatively minor, but the variation was greatest among those not using broad-spectrum sprays. Winter survival of the navel orangeworm parasitoid, Goniozus legneri, and parasitism by this beneficial insect were low in all orchards, sprayed or unsprayed. Winter removal of unharvested almonds to fewer than two per tree reduced navel orangeworm infestations in both treatments. Although many of the almond growers not using organo-phosphate, carbamate or pyrethroid sprays had less damage than some who used these materials, the greater range of damage experienced by these growers may explain why more almond growers prefer to use them annually to combat insect pests.