Evaluation of some selective insecticides and their combinations with summer oil for the control of the pear psylla Cacopsylla pyri

A field trial was carried out to evaluate the efficacy of several selective insecticides for the control of pear psylla Cacopsylla pyri (L.) (Hemiptera: Psyllidae) in two successive years. Three insect growth regulators (lGRs) - diflubenzuron, pyriproxyfen and teflubenzuron, and an amin-hydrazine derivative - amitraz, were evaluated singly and in combination with summer oil (1%). All insecticides were applied at recommended label rates in both years. When compared with the untreated control, all insecticides alone and their combinations with summer oil, except for pyriproxyfen alone, provided control of young (1st and 2nd instars) nymphs. However, combined applications of these insecticides and summer oil were more effective than either insecticide alone for controlling the egg and young nymph stages of the pest. The products were less effective against older (3rd-5th instars) nymphs, even in combination with summer oil, and failed to suppress the population of older nymphs. Adding oil to sprays also delayed oviposition by winterform and summerform females. With the exception of oil with amitraz, combinations of insecticides with summer oil did not cause any phytotoxicity during the study.