Field efficacy of wintertime insecticide applications against greenbugs, Schizaphis graminum (Rondani) (Hemiptera: Aphididae), on winter wheat (Triticum aestivum L.)

Authors: ROYER, TOM - Oklahoma State University; Elliott, Norman - Norm; GILES, KRISTOPHER - Oklahoma State University; KINDLER, S - Retired ARS Employee

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2011
Publication Date: 5/1/2011
Citation: Royer, T.A., Elliott, N.C., Giles, K.L., Kindler, S.D. 2011. Field efficacy of wintertime insecticide applications against greenbugs, Schizaphis graminum (Rondani) (Hemiptera: Aphididae), on winter wheat (Triticum aestivum L.). Crop Protection. 30(7):826-832.

Interpretive Summary: Winter wheat producers in Oklahoma often combine an insecticide treatment with a top-dress application of nitrogen during late fall or winter to control existing greenbug populations. We evaluated the efficacy of insecticides applied in cold weather conditions typical of winter in Oklahoma to determine weather factors that affect the efficacy of insecticide treatment. Insecticides provided control ranging from 0% to 98%, but generally responded similarly to temperature. Maximum, minimum and average daily temperatures that during the two days post treatment affected the efficacy of all the insecticides tested. While each insecticide had a unique response, a combined regression of percent control on average daily temperature predicted that a 95% level of control would be achieved when post treatment temperatures exceeded 13.6 degrees C. Rainfall that occurred post-treatment affected the efficacy of dimethoate but did not affect the other insecticides. Cooler temperatures preserved insecticide persistence, allowing good control 14 days post treatment if temperatures warmed. Generally, winter wheat producers can expect reasonable control of greenbugs from insecticides applied during the late fall and winter, as long as post-treatment temperatures exceed 13 degrees C within the following 14 days. The decision to apply insecticides should be made based on existing treatment thresholds for greenbug.

Technical Abstract: Winter wheat producers in Oklahoma often combine an insecticide with a top-dress application of nitrogen during late fall or winter to control existing greenbug populations. We evaluated the efficacy of three classes of insecticides applied in cold weather conditions ranging from -13.3 degrees to 28.9 degrees C from 2002-2004 for greenbug control in winter wheat in replicated small plots. Insecticides provided control ranging from 0% to 98%, but generally responded similarly to temperature. Response of dimethoate, chlorpyrifos and lambda-cyhalothrin was correlated with maximum, minimum and average daily temperatures that occurred two-day post treatment. While each insecticide had a unique response, a combined regression of percent control regressed on average daily temperature predicted that a 95% level of control would be achieved when post treatment temperatures exceeded 13.6 degrees C. Rainfall that occurred post-treatment affected the efficacy of dimethoate but did not affect the other insecticides. Cooler temperatures preserved insecticide persistence, allowing good control 14 days post treatment if temperatures warmed. Generally, winter wheat producers can expect reasonable control of greenbugs from insecticides applied during the winter, as long as post-treatment temperatures exceed 13 degrees C within the following 14 days. The decision to apply insecticides should be made based on existing treatment thresholds for greenbug.