Pesticides and the soil fauna: effects of aldrin and DDT in an arable field

Aldrin dust (3 cwt. of 1¼% per acre) or DDT dust (2 cwt. of 5 % per acre) was applied to small plots replicated four times and four plots were untreated. All plots were kept fallow for one year. Soil samples were taken at 2 to 3-monthly intervals and the fauna extracted by a notation method. The insecticides did not affect Lumbricidae, Enchytraeidae or Nematoda. Nearly 100 species of arthropods were found, and the greatest effects were those of DDT on mesostigmatid mites and of aldrin on entomobryid or isotomid Collembola and on Pauropoda. Most species of Collembola increased in DDT-treated plots, apparently because mesostigmatid mites were reduced. In terms of biomass Coleoptera and Diptera were most affected. Both insecticides killed more pests than predators or beneficial animals. The effects of the insecticides were greatest during late summer or autumn.