| The overall effects of pesticide use in agroecosystems have received a great deal of attention in recent decades because of the potential undesirable non-target effects of pesticides. By designing and implementing a field experiment comparing the recommended chemical management of pests, diseases and weeds in tomato agroecosystems, I was able to evaluate the effects of a comprehensive pesticide treatment program, individual components and lower chemical inputs on the incidence of pests, predators and nematodes over two seasons. The pesticide treatments used included: (i) full spectrum pesticide use; based on a comprehensive pesticide application schedule including insecticides (carbaryl, endosulfan, and esfenvalerate), a fungicide (chlorothalonil) and herbicides (trifluralin and paraquat); (ii) insecticide only use treatment; based on applications of the same insecticides and doses as in the full spectrum pesticide use treatment; (iii) fungicides and herbicides only treatments; based on applications of the same doses fungicide and herbicides as in the full spectrum pesticide use treatment; (iv) control plots received no pesticide applications. The pest populations studied included: aphids (potato aphid, Macrosiphum euphorbiae and green peach aphids, Myzus persicae, flea beetles (Epitrix spp.), and thrips (Thrips spp.). The predatory arthropods investigated included ground beetles (Carabidae), rove beetles (Staphylinidae), tiger beetles (Cicindellidae), lady beetles (Coccinellidae), spiders (Araneae), ants (Formicidae), and anthocorids (Anhocoridae: Hemiptera).;Insecticide applications provided efficient control of aphids and flea beetles, but they led to reductions in numbers of various groups of predators. In general, foliage-dwelling predators were more sensitive to pesticide applications than ground-dwelling predators. Fungicide and herbicide applications caused decreased populations of anthocorids and foliage-dwelling spiders and consequent increases in the numbers of aphids and flea beetles. Free-living nematode populations were sensitive to pesticide applications in general; in particular insecticide applications consistently led to increase in plant parasitic nematode numbers. Early blight caused by Alternaria solani was a serious disease limiting the yields. An economic comparison of pesticide applications on processing tomatoes showed that fungicide applications were critical to maintain yields and profitability of tomato production in the presence of early blight disease. |
