The effect of benomyl and thiophanate‐methyl on earthworm populations in apple orchards

The use of the fungicides benomyl and thiophanate‐methyl on experimental orchard plots for 3 years and of benomyl on a commercial orchard for 1 year resulted in a drastic reduction of earthworm populations. The species of earthworms affected were Lumbricus terrestris, L. castaneus, L. festivus, L. rubellus, Allolobophora caliginosa, A. chlorotica, A., longa, A. rosea, A. tuberculata and Octolasium cyaneum. L. terrestris and A. chlorotica were more affected than the other species, both being virtually eliminated after 2 years' spraying. The depleted populations of species other than L. terrestris and A. chlorotica recovered to normal levels after a 2‐year rest period following a single year's treatment with benomyl (1.40 kg/ha). The role of the surface‐feeding L. terrestris is discussed in relation to the spray fall‐out on the sward and to grass management.