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1 August 2000 Effect of Fungicide Application on Activity of Neozygites fresenii (Entomophthorales: Neozygitacaea) and Cotton Aphid (Homoptera: Aphididae) Suppression
M. Leonard Wells, Robert M. McPherson, John R. Ruberson, Gary A. Herzog
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Abstract

The development of resistance in aphid populations highlights the importance of biological control as a pest management tactic. Four treatments were evaluated to determine the effects of pesticides on the population dynamics of Aphis gossypii Glover and Neozygites fresenii (Nowakowski) Batko: (1) weekly applications of the insecticide imidacloprid (Provado 1.6 F); (2) weekly applications of the fungicide chlorothalonil (Bravo 720); (3) applications of imidacloprid (Provado 1.6 F) when aphid densities exceeded 30 aphids per leaf, and (4) untreated control. Differences in aphid density among the four treatments were shown only to be significant during the 1997 growing season; however, aphid densities were greater in the chlorothalonil treatment than in the other treatments during each growing season. Percentage of N. fresenii-killed aphids was most often highest in the chlorothalonil treatment as well. The fungal epizootic caused by N. fresenii was delayed ≈1 wk in the chlorothalonil treatment when compared with the other treatments. This delay allowed the aphids to temporarily escape suppression by the fungus and to continue to increase in density until the density-dependent effects of the epizootic overwhelmed the aphid population. N. fresenii also appeared to persist in the system when imidacloprid was in use and does appear responsible for initial aphid reductions. Treatment did not appear to have a large influence on yield outcome. Yield was variable from year to year and from location to location.

M. Leonard Wells, Robert M. McPherson, John R. Ruberson, and Gary A. Herzog "Effect of Fungicide Application on Activity of Neozygites fresenii (Entomophthorales: Neozygitacaea) and Cotton Aphid (Homoptera: Aphididae) Suppression," Journal of Economic Entomology 93(4), 1118-1126, (1 August 2000). https://doi.org/10.1603/0022-0493-93.4.1118
Received: 9 November 1999; Accepted: 1 May 2000; Published: 1 August 2000
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