Browsing by Author "Yardim, E.N."

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A Comparison of Recommended and Reduced Insecticide Regimes in Alfalfa
(2001) Yardim, E.N.; Ozgen, I.; Kulaz, H.
The objective of this study was to evaluate the effects of the recommended rates of insecticides applied at two different population levels of the alfalfa weevil, Hypera variabilis Hbst. (Coleoptera: Curculionidae) and the reduced levels of insecticides on alfalfa weevil, predators and yield in 1998 and 1999. More specific objective was to search for options to reduce insecticide usage while implementing an effective pest control, thereby developing more economically and environmentally sound alfalfa production systems. The treatments used included: i) recommended rate insecticide (malathion) at population level of 5 weevils/sweep, ii) recommended rate at population level of 10 weevils/sweep, iii) 50% of recommended rate at population level of 10 weevils/sweep, iv) stripe spray of 50% rate at population level of 10 weevils/sweep, where insecticides were applied only on 0.5 m stripes in plots while the next 0.5 m stripes were not treated and v) control. The results indicated that the recommended rate insecticide application at 5 weevils/sweep level provided the highest reduction in the weevil densities in both years. No significant differences occurred among the weevil densities in the plots received the recommended rate, the 50% rate and the stripe spray insecticide treatments at 10 weevils/sweep level. Predators were in general more abundant in the insecticide treated plots compared to the control. The insecticide applications, except the stripe spray in 1999, led to increases in yields.
Diversity of Arthropod Communities in Transgenic Bt Cotton and Nontransgenic Cotton Agroecosystems
(Entomological Society of America, 2003) Men, X.; Ge, F.; Liu, X.; Yardim, E.N.
In a 3-yr field experiment, possible effects of Bt transgenic cotton plants expressing cry1A (c) gene from Bacillus thrungiensis Berliner variety kurstaki on diversities of arthropod communities and pest and natural enemy sub-communities were assessed in insecticide treated and untreated cotton fields, as measured by the Shannon-Weaver diversity index. The treatments included: 1) nontransgenic cotton with no insecticide treatment (nontransgenic), 2) nontransgenic cotton with insecticide treatments (nontransgenic+insecticide), 3) transgenic Bt-cotton with no insecticide treatment (Bt-cotton), and 4) transgenic Bt-cotton with insecticide treatments (Bt-cotton+insecticide). The results indicated that Bt-cotton increased the diversity of arthropod communities and pest sub-communities; however, it decreased the diversities of natural enemy sub-communities. Insecticide treatments increased diversities of communities and sub-communities of arthropods in both transgenic Bt-cotton and nontransgenic cotton agroecosystems, but the increase may be an artifact of increased evenness through mortality of insecticide-targeted species.
The Effects of Chemical Pest, Disease and Weed Management Practices on the Trophic Structure of Nematode Populations in Tomato Agroecosystems
(Elsevier, 1998) Yardim, E.N.; Edwards, C.A.
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. © 1998 Elsevier Science B.V.
Effects of Neem-Based and Chemical Insecticides on Some Arthropods in Alfalfa
(2001) Yardim, E.N.; Ozgen, I.; Kulaz, H.
In this study, we tested the effects of two different doses of neem (azadirachtin) on the alfalfa weevil, Hypera variabilis Hbst. (Coleoptera: Curculionidae), aphids and predators (Coccinellids, anthocorids, chrysopids and spiders) and compared the effects with those of a broad spectrum insecticide (malathion) in a controlled experiment in 1998 and 1999. Malathion treatments reduced alfalfa weevil densities significantly (p < 0.01) by 77.9 and 87.4% in 1998 and 1999, respectively. Alfalfa weevil numbers in the low dose neem-treated plots were lower by 45.2% in 1998 and 50.2% in 1999. There were 45.3% fewer alfalfa weevils in the high dose neem-treated plots in 1999. In 1998, aphid numbers were reduced by 11.1, 25.3 and 41% in the low dose neem-treated plots, the malathion-treated plots and the high dose neem-treated plots, respectively. Aphids were more abundant in the malathion-treated plots, whereas they were fewer in the neem-treated plots compared to the control in 1999. The treatments did not have any significant effects on the total numbers of predators.
Populations of Alfalfa Weevils (Coleoptera: Curculionidae) and Aphids (Homoptera: Aphididae) on Different Alfalfa Cultivars
(Asian Network for Scientific Information, 2006) Yardim, E.N.; Yilmaz, I.H.; Arvas, Ö.; Candan, C.
Populations of alfalfa weevil, Hypera variabilis (Gyllenhal) (Coleoptera: Curculionidae) and aphids were evaluated on 12 alfalfa, Medicago sativa L. cultivars in 2002 and 2003. The cultivars used included MA-324, MA-414, MA-525, P-5693, Gara, Desica, Kayseri, Hemedan, Prosementi, Bilensoy, Prista and Elci. There were no significant differences among the weevil populations on different alfalfa cultivars in any of the years. Aphids were more abundant (p<0.05) on Kayseri cultivar in both years, on Bilensoy only in 2002 and on MA-324, Hemedan and Elci in 2003. Under the current pest pressure and ecological conditions, MA-324, MA-414, MA-525, Desica and Elci cultivars that provided higher (p<0.05) yields than most of the cultivars seemed more promising in forage production. © 2006 Academic Journals Inc.