Effects of carbaryl and cyhexatin on survival and reproductive behaviour of Cydia pomonella (Lepidoptera : Tortricidae)

The effects of carbaryl, an insecticide and an abscission agent, and cyhexa tin, an acaricide, on the survival, reproductive behaviour and subsequent e gg hatch and larval migration of the codling moth, Cydia pomonella L., were investigated under laboratory conditions. Dilution series starting with th e concentration recommended for high volume application in the field were e venly sprayed in plastic cups. Depending on the concentration used, both pe sticides resulted in high adult mortality, males being more susceptible. Al though the total number of the eggs laid by C. pomonella females was signif icantly reduced in most treatments, the females exposed to different residu es of carbaryl laid significantly more eggs during the first 24 h of exposu re. This was not the case for cyhexatin. While in all treatments almost 50% of the eggs were laid on the side of the cups, the spatial distribution of the eggs laid under the lid and on the f loor was concentration dependent. With one exception, continuous exposure o f the moths to carbaryl significantly reduced the number of spermatophores per female. Less than one spermatophore per female was transferred at the h ighest four concentrations of carbaryl and the highest three concentrations of cyhexatin; whereas, the number of spermatophores per female amounted to about four per female for the other treatments. In contrast to carbaryl, w hich exhibited a high ovicidal effect at all concentrations, the ovicidal a ctivity of cyhexatin was low. This was manifested in a high rate of egg hat ch and the extent of embryonic development in most of the treatments. Furth ermore, while carbaryl killed the newly-hatched larvae at all concentration s, cyhexatin acted as a larvicide at the highest two concentrations only.