The effects of chemical pest, disease and weed management practices on the trophic structure of nematode populations in tomato agroecosystems

We assessed the responses of nematode communities to mixtures of insecticides, fungicides and herbicides in a tomato (Lycopersicon esculentum L.) field experiment. The treatments were: (i) full spectrum of recommended pesticides; including insecticides (carbaryl, endosulfan and esfenvalerate) a fungicide (chlorothalonil) and herbicides (trifluralin and paraquat); (ii) only insecticides; based on applications of the same insecticides and similar doses to the full spectrum treatment; (iii) only fungicides and herbicides; based on similar fungicide and herbicide applications and doses to the full spectrum pesticide use treatment; (iv) control plots which received no pesticide applications. Nematode populations were separated into plant parasites. bacterivores, fungivores, omnivores and predators. The temporal community dynamics of different nematode trophic groups differed with the pesticide applications. Plant-parasitic nematode populations were much higher in the full spectrum pesticide-treated and in the insecticide-treated plots than in control plots. Fungivorous nematode populations were affected adversely by all treatments. Bacterivorous nematode populations were lowest in the full spectrum pesticide-treated plots and the fungicide-and herbicide-treated plots. Predatory nematode populations were lower in the full spectrum pesticide-treated plots than in the control plots. (C) 1998 Elsevier Science B.V.