Inhibition of brain acetylcholinesterase activity in songbirds exposed to fenitrothion during aerial spraying of forests.

In 1976, outbreaks of Pine Beauty moth (Panolis flamme&) were recorded on plantations of Lodgepole pine (Pinus contorta) in northern Scotland and by 1977 attacks were so severe that chemical control was urgently required to avoid serious damage to large areas of forest. Aerial spraying of insecticide on the scale required had not been used previously in the United Kingdom and the preferred ULV technique had neither been tested nor approved for forestry use. In 1978 a programme of spraying with fenitrothion (O,O-dimethylO-~-methyZ-4-nitrophenyl) phosphorothioate) was begun urder limited clearance from the U.K. Pesticides Safety Precautions Scheme. A condition of this clearance was that any environmental impact resulting from the spraying programme should be assessed, including effects on forest songbirds. A limited study done in 1978 showed that residues of fenitrothion were present on birds of several species taken within a few days of the spraying (TILBROOK 1978). No major immediate effects on wildlife were observed but population studies by BROAD & DENNIS (1978) suggested some decrease in numbers in two of the seven most abundant songbird species in the period following spraying. However only a limited amount of residue analyses were done and no attempt was made to determine any sub-lethal effects of the spraying. In 1979 and 1980 further areas of forest were sprayed with fenitrothion using the ULV technique and on both occasions sampZes of various avian species were taken to determine any effect on brain acetylcholinesterase (ACHE) activity and provide further information on the distribution of fenitrothion residues in the birds. The results of this work are reported here,