Effects of pyriproxyfen and imidacloprid on mortality and reproduction of Menochilus sexmaculatus (Coleoptera: Coccinellidae), predator of Agonoscena pistaciae

The effect of two insecticides, imidacloprid and pyriproxyfen, were investigated on some biological parameters of ladybird beetle Menochilus sexmaculatus (F.) (Coleoptera: Coccinellidae) under laboratory condition. Theladybird beetle were exposed to insecticides by ingestion of the common pistachio psylla, Agonoscena pistaciae Burckhardt and Lauterer (Hemiptera: Psyllidae) (prey). For imidacloprid, maximum field recommended concentration (MFRC) (۱/۱ MFRC = ۱۴۰ ppm), ۱/۲ and ۱/۴ MFRC were tested. For pyriproxyfen dilutions of ۱/۱ MFRC (۵۰ ppm), ۲/۱ and ۱/۲ MFRC were used after ۲۴ h. The ۱۰۰% mortality was observed with imidacloprid in all tested concentrations, whereas no mortality was observed by pyriproxyfen even at the highest concentration (۲/۱ MFRC). Because of the high mortality observed with imidacloprid, lower concentrations of ۱/۱۰, ۱/۲۰ and ۱/۴۰ MFRC were tested and all predators were killed ۳, ۷ and ۱۰ days after treatment, respectively. At ۱/۱۰۰ MFRC, no eggs were laid but prey consumption was continued for two weeks. At ۱/۱ and ۲/۱ MFRC of pyriproxyfen, ingestion of prey was reduced by ۱۸% and ۲۳%, respectively. At ۱/۱ and ۱/۲ MFRC of pyriproxyfen, fecundity and fertility of the coccinellid predator was decreased to ۴۳% and ۲۴.۵%, respectively. Imidacloprid at ۱/۱۰۰ MFRC caused significant reduction on fecundity but had no detrimental effect on fertility of the produced eggs. Therefore, unlike the pyriproxyfen that had not acute toxicity, the imidacloprid was extremely toxic to coccinellid at MFRC. However, pyriproxyfen was able to affect on feeding ratio and reproduction of M. sexmaculatus.

کلیدواژه ها:

The common pistachio psylla ، Insecticide ، Menochilus sexmaculatus ، Predator ، Sublethal effects