Browsing by Author "Edwards, CA"

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An Economic Comparison of Pesticide Application Regimes for Processing Tomatoes
(Priel Publ, 2003) Yardim, EN; Edwards, CA
In a field experiment aimed at the management of pests, diseases and weeds in tomato agroecosystems using a recommended range of pesticide applications compared with lower chemical input systems, the economics of pesticide use on processing tomatoes in Ohio, USA, was evaluated in 1994 and 1995. The pesticide regimes used included: (i) full-spectrum recommended pesticide use, based on a comprehensive pesticide application schedule including insecticides (carbaryl, endosulfan and esfenvalerate), a fungicide (chlorothalonil) and herbicides (trifluralin and paraquat); (ii) insecticides only, based on applications of the same insecticides and doses used in (i); (iii) fungicides and herbicides only, based on applications of the same fungicides and herbicides used in (i); and (iv) control plots, which received no pesticide applications. All of the costs involved in applying pesticides (chemicals, machinery, labor) were recorded for all treatments for the economic analysis. Overall, the fungicide treatments resulted in higher yields than either the control or the insecticides-only regime, and the profits from the full-spectrum pesticide and fungicide & herbicide regimes were greater than those from the insecticide-only regime and controls in 1994. The yields and profits from all pesticide regimes were substantially less in 1095 than in 1994.
Effects of Organic and Synthetic Fertilizer Sources on Pest and Predatory Insects Associated With Tomatoes
(Priel Publ, 2003) Yardim, EN; Edwards, CA
The effects of organic. (composted cow manure) and synthetic (NPK) fertilizers on pests (aphids and flea beetles) and predatory arthropods (anthocorids, coccinellids and chrysopids) associated with tomatoes were evaluated in a 2-year randomized complete block field experiment. Our data suggested that the application of either organic or synthetic fertilizers could increase pest populations on tomatoes. However, there were lower populations of aphids on tomatoes grown with the organic fertilizer than on those grown with the synthetic fertilizers in the second year of the experiment, indicating that organic fertilizers may have the potential to reduce pest attacks in the long term. Anthocorid populations were larger on tomato plants with high aphid populations in the synthetic than in the organic fertilizers-treated plots.
Effects of Weed Control Practices on Surface-Dwelling Arthropod Predators in Tomato Agroecosystems
(Springer, 2002) Yardim, EN; Edwards, CA
Weed control, an important practice in agroecosystems to protect crop production, is usually achieved with herbicides. However, these pesticides are expensive, pose potential risks to the environment, may affect some beneficial organisms indirectly, and decrease overall arthropod biodiversity, including pests and their natural enemies, by removing weeds that might act as hosts or shelters for many organisms. The activity density response of important surface-dwelling arthropod predators (ground beetles [Coleoptera: Carabidae], ants [Hymenoptera: Formicidae] and spiders [Arachnida: Araneae]) to herbicides (trifiuralin and paraquat), and to two alternative weed management practices (rye straw mulch and mechanical treatment to maintain weeds below threshold levels, in comparison with an untreated check), was assessed using pitfall traps. The mulch treatment had the greatest effect on activity density, reducing the number of predators trapped significantly (P<0.05). Herbicide use resulted in significant (P<0.05) reductions in the activity density of ground beetles. Most predators were trapped in the check plots - which had the highest weed biomass, followed in turn by numbers trapped in the threshold weed control treatment, the full herbicide application and the mulch treatment plots.
The Influence of Chemical Management of Pests, Diseases and Weeds on Pest and Predatory Arthropods Associated With Tomatoes
(Elsevier Science Bv, 1998) Yardim, EN; Edwards, CA
The effects of selected pesticide application regimes on pest predator populations as well as pests were investigated in tomato (Lycopersicon esculentum L.) agroecosystems. The treatments included: (i) the full spectrum of recommended pesticides, including insecticides (carbaryl, endosulfan, and esfenvalerate), a fungicide (chlorothalonil), and herbicides (trifluralin and paraquat); (ii) only insecticides, using the same insecticides and doses as in the full-spectrum pesticide treatment; (iii) only fungicides and herbicides; using the same fungicides and herbicides and doses as in the full-spectrum pesticide use treatment; (iv) control plots which received no pesticide applications. In 1994, the insecticides controlled aphids and flea beetles and reduced their populations by 85% and 72%, respectively. However, aphid populations were 125% greater in the insecticide-treated plots than in the control plots in 1995. The fungicides and herbicides caused increases in the numbers of aphids by 33% in 1994 and by 39.8% in 1995 and those of flea beetles by 55% in 1994 and 17% in 1995. All the full-spectrum pesticide treatments had some degree of detrimental effects on populations of predatory arthropods. The different pesticide applications reduced coccinellid beetle Coleomegilla maculata (Col: Coccinellidae), populations by 6.6% to 35.5% in 1994 but only slightly in 1995; Anthocoridae (Heteroptera) numbers by 26.2% to 55.8% in 1994 and 13.5% to 38.8% in 1995; spider (Araneae) populations by 44.6% to 70.9% in 1994 and 37.0% to 91.4% in 1995. Five hypotheses are proposed to explain these results: (1) the fungicide and herbicide applications reduced the populations of predatory arthropods which in turn resulted in higher pest populations; (2) the fungicide and herbicide applications suppressed the fungal parasites of the pests; (3) the applications increased the fecundity of the pests and resulted in more offspring of the pests and hence higher populations, (4) the applications caused some physiological changes in the tomato plants that attracted more pests or stimulated their reproduction and; (5) the fungicide applications provided more nutritious and suitable habitats for the pests by suppressing the disease of the tomatoes, (C) 1998 Elsevier Science B.V. All rights reserved.
The Influence of Pesticide Applications on Helicoverpa Armigera Hubner and Sucking Pests in Transgenic Bt Cotton and Non-Transgenic Cotton in China
(Elsevier Sci Ltd, 2005) Men, X; Ge, F; Edwards, CA; Yardim, EN
Effects of pesticide applications, based on an IPM program on cotton bollworm, Helicoverpa armigera Hubner, cotton mirids and cotton leafhoppers, were evaluated in transgenic Bt-cotton and non-transgenic cotton agroecosystems between 1999 and 2001 in China. Differences in pest populations between cotton varieties were also compared. In 1999 and 2000, bollworm populations on non-transgenic cotton were larger than those on transgenic Bt-cotton. In Bt-cotton fields, the numbers of fourth-generation bollworms were greater than those of in the second and the third generations over all 3 years of study. Leafhopper populations on Bt-cotton were consistently larger than those on non-transgenic cotton during the 3 years of study. Although the use of transgenic Bt-cotton decreased the need for insecticide applications against cotton bollworm, this relaxation from pesticide applications could cause increased populations of sucking insects, which could require additional insecticide applications. (C) 2004 Elsevier Ltd. All rights reserved.
Influence of Pesticide Applications on Pest and Predatory Arthropods Associated With Transgenic Bt Cotton and Nontransgenic Cotton Plants
(Springer, 2004) Men, XY; Ge, F; Edwards, CA; Yardim, EN
The effects of pesticide applications on pests (aphids and acarid mites) and predators (ladybeetles and spiders) were investigated in transgenic Bt cotton and nontransgenic cotton agroecosystems in 1999, 2000 and 2001. Transgenic cotton did not cause changes in populations of acarids and did not reduce numbers of predators considerably; its effects on aphids were inconsistent. Although insecticides were not applied against the main pest cotton bollworm - on transgenic cotton, the total number of insecticide applications in 3 years was no less than the total applied on nontransgenic cotton, because additional applications were required against sucking pests on transgenic Bt cotton. Pesticide applications decreased numbers of aphids, acarids and predatory spiders significantly on both transgenic and nontransgenic cottons. The results suggest that the use of Bt cotton should be evaluated carefully in China.