The accumulation and loss of organochlorine insecticide residues by beetles, worms and slugs in sprayed fields

Abstract

Analyses of samples of ground-beetles, worms and slugs at four sites showed large differences in uptake, retention and metabolism by these groups. Live beetles caught in pitfall traps after field applications of DDT did not contain more than about 4 ppm pp′-DDT, but beetles artificially exposed during spraying acquired up to 70 ppm on their body surfaces. Metabolism to pp′-DDE was rapid and in one species resulted in residues of 58–75 ppm which declined to about 5 ppm after four months. Worms and slugs acquired much higher levels of DDT and these were more persistent. Breakdown in worms was chiefly to DDE and in slugs to TDE. Worms from an aldrin-treated site contained both dieldrin and aldrin, the proportions of each changing with time. The aldrin was probably from the soil within their guts. It was concluded that higher residues were picked up by invertebrates which fed at the soil surface after a foliage application of pesticide than by subterranean species after a soil application followed by rotovation. Acute poisoning of birds could result from the consumption of insects exposed to DDT spraying.