Effects of grasshopper-control insecticides on survival and brain acetylcholinesterase of pheasant (Phasianus colchicus) chicks

Abstract

Ring-necked pheasant ( Phasianus colchicus) chicks were exposed via contact and/or ingestion to formulations of three insecticides (Lorsban 4E, chlorpyrifos; Cygon 480E, dimethoate; and Furadan 480F, carbofuran) applied to pasture plots at one and four times the rate recommended for control of grasshoppers (Orthoptera: Acrididae) in prairie Canada. Chicks (3 d old) were exposed for 48 h in pens with the sprayed vegetation and were fed either unsprayed grasshoppers or grasshoppers sprayed at the same rates as the vegetation. Control groups were exposed to unsprayed vegetation and received unsprayed grasshoppers. Three replicates were conducted throughout June and early July 1992. Although some signs of acetylcholinesterase (AChE) depression were observed in chicks exposed to insecticides, there was no difference in the number of mortalities among treatment and control groups. Chicks that died during the exposure period gained significantly less weight than survivors in all groups. Among surviving chicks, weight gains of those exposed to the high- rate Furadan treatment consuming sprayed food were significantly lower than those of controls (1.8 vs. 6.6 g/d). Brain AChE activity was lower overall in surviving chicks than in those that died; it was not significantly reduced among chicks that died in any treatment group. Overall, survivors of Furadan- exposed treatment regimes had lower AChE activity than those of Cygon and Lorsban treatments; birds in high-spray-rate treatments of all insecticides had lower AChE activity than those in all low-spray-rate treatments; and birds in all treatments consuming sprayed grasshoppers had lower AChE activity than those fed unsprayed grasshoppers. Food consumption was not affected by any treatment.