EFFECTS OF SOME ORGANIC TREATMENTS ON PREDATORS (COLEOPTERA, CARABIDAE) OF CABBAGE ROOT FLY, DELIA-RADICUM (L) (DIPTERA, ANTHOMYIIDAE), ANDON ALTERNATIVE PREY SPECIES

The egg predator, Bembidion lampros, and carabids in total, were more numerous in brassica plots to which organic materials had been applied . The difference persisted into the year following the last applicatio n and was at least partly due to increased breeding in organically-tre ated plots. The difference was immediately detectable in plots treated with manure but was delayed in plots to which straw had been applied. Predation on eggs of Cabbage Root Fly was not significantly increased , probably because egg numbers were low and formed a relatively small part of the predator diet. Alternative prey for carabids was also more abundant in organically-treated plots. The presence of straw on the s oil surface reduced Cabbage Root Fly oviposition. The level of parasit ism was reduced by straw and slurry treatments.