Outbreaks of banks grass mite (Acari: Tetranychidae) in grain sorghum following insecticide applications

Buschman, L.L.; DePew, L.J.

Outbreaks of banks grass mite (Acari: Tetranychidae) in grain sorghum following insecticide applications

1990

Buschman, L.L. | DePew, L.J.

Banks grass mite, Oligonychus pratensis (Banks), abundance was monitored in grain sorghum (Sorghum bicolor (L.) Moench) to determine if applications of insecticides directed at greenbug, Schizaphis graminum (Rondani), induced outbreaks of Banks grass mites. Aerial applications of two commonly used insecticides, chlorpyrifos (0.28 kg [AI]/ha) and parathion (0.67 kg [AI]/ha), and an untreated check were replicated three times and repeated during each of 3 yr. In each test, mite densities were higher in insecticide-treated sorghum than in untreated sorghum. Data subjected to analysis of covariance (with pretreatment mite numbers used as the covariate) indicated that mite densities were significantly higher in insecticide-treated sorghum than in untreated sorghum, but that mite densities in chlorpyrifos- or parathion-treated sorghum, did not differ significantly. Mite predators per 1,000 mites were not significantly, lower in insecticide-treated sorghum than in untreated sorghum. Both insecticides were effective in reducing greenbug densities.

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