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

Abstract

Summary The effects of carbaryl, an insecticide and an abscission agent, and cyhexatin, an acaricide, on the survival, reproductive behaviour and subsequent egg hatch and larval migration of the codling moth, Cydia pomonella L., were investigated under laboratory conditions. Dilution series starting with the concentration recommended for high volume application in the field were evenly sprayed in plastic cups. Depending on the concentration used, both pesticides resulted in high adult mortality, males being more susceptible. Although the total number of the eggs laid by C. pomonella females was significantly reduced in most treatments, the females exposed to different residues of carbaryl laid significantly more eggs during the first 24 h of exposure. 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 floor was concentration dependent. With one exception, continuous exposure of the moths to carbaryl significantly reduced the number of spermatophores per female. Less than one spermatophore per female was transferred at the highest 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, which exhibited a high ovicidal effect at all concentrations, the ovicidal activity of cyhexatin was low. This was manifested in a high rate of egg hatch and the extent of embryonic development in most of the treatments. Furthermore, while carbaryl killed the newly‐hatched larvae at all concentrations, cyhexatin acted as a larvicide at the highest two concentrations only.

Pesticide contamination of milkweeds across the agricultural, urban, and open spaces of low elevation Northern California

“…It is not clear how an LD 50 of one compound over 36 hours compares with an LD 50 of a different compound over 48 hours, and what either of these can tell us about risk in the field. A larval monarch will consume a plant for much longer than 48 hours, and generally longer exposure times will decrease survival (Abivardi et al, 1999; Yue et al, 2003; Wang et al, 2009, 2013; Nasr et al, 2010; Rehan and Freed, 2015; Ahmed et al, 2016; Liu et al, 2018b). Thus, considering shorter exposure times is likely to be a conservative approach which underestimates risk.…”