EFFECTS OF GRASSHOPPER-CONTROL INSECTICIDES ON SURVIVAL AND BRAIN ACETYLCHOLINESTERASE OF PHEASANT (PHASIANUS-COLCHICUS) CHICKS

Ring-necked pheasant (Phasianus colchicus) chicks were exposed via con tact and/or ingestion to formulations of three insecticides (Lorsban 4 E, chlorpyrifos; Cygon 480E, dimethoate; and Furadan 480F, carbofuran) applied to pasture plots at one and four times the rate recommended f or control of grasshoppers (Orthoptera: Acrididae) in prairie Canada. Chicks (3 d old) were exposed for 48 h in pens with the sprayed vegeta tion and were fed either unsprayed grasshoppers or grasshoppers spraye d at the same rates as the vegetation. Control groups were exposed to unsprayed vegetation and received unsprayed grasshoppers. Three replic ates were conducted throughout June and early July 1992. Although some signs of acetylcholinesterase (AChE) depression were observed in chic ks exposed to insecticides, there was no difference in the number of m ortalities among treatment and control groups. Chicks that died during the exposure period gained significantly less weight than survivors i n all groups. Among surviving chicks, weight gains of those exposed to the high- rate Furadan treatment consuming sprayed food were signific antly lower than those of controls (1.8 vs. 6.6 gld). Brain AChE activ ity 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 lo wer AChE activity than those of Cygon and Lorsban treatments; birds in high-spray-rate treatments of all insecticides had lower AChE activit y than those in all low-spray-rate treatments; and birds in all treatm ents consuming sprayed grasshoppers had lower AChE activity than those fed unsprayed grasshoppers. Food consumption was not affected by any treatment.