Effects of Some Fungicide Treatments on Earthworm Populations and Leaf Removal in Apple Orchards

Abstract

Summary The persistence of leaf litter in apple orchards sprayed with benomyl prompted surveys to examine the effect of fungicide programmes on earthworm populations and leaf removal. Earthworm populations were unaffected by captan with bina- pacryl sprays, but under trees sprayed with benomyl they were significantly lower than under unsprayed trees. The effect of benomyl increased with the number of sprays. Populations recovered when benomyl sprays were discontinued but some residual effects were apparent after three years. Thiophanate-methyl was also found to reduce earthworm populations. Thiophanate-methyl and carbendazim retarded leaf removal and there was a similar but less marked effect with ditalimfos and captan with binapacryl sprays. Leaves sprayed with carbendazim were slow to disappear when over wintered on untreated soils. This result, and those with captan with binapacryl, suggest that fungicides may influence the rate of leaf removal independently of any effects they may have on earthworm populations.