Evaluating Aphis Resistance To Pyrethroids In Western Kentucky's Wheat

Two episodes of a potential aphid resistance in wheat and barley were registered in the 2016-17 growing season in Logan and Christian Co. Both fields were treated with 4 applications of pyrethroids: 2 application of Warrior® in the fall (October-November 2016), and 2 in the spring (February-March 2017). These applications did not control aphid populations, in the contrary, aphid numbers were well above (>400/plant) the threshold levels. The reasons for these unsuccessful control events might be due to a lack of an adequate application of the insecticide (low rates, poor coverage, etc.), or the development of resistance. We believe that the presence of these two aphid outbreaks was an indication that the pyrethroids might been ineffective. A rapid bioassay in the laboratory was run but the results were inconclusive due to the presence of an unknown fungus that affected aphids in both fields. This study is a complement to the proposal submitted by Villanueva and Bradley’s titled Timed Insecticide Spray to Control Aphids and Reduce BYDV Infections. These two initiatives coordinate the progress of aphid resistance pests of small grains, and the status of BYDV. Hopefully the KSGPC support both proposals. The objectives of these proposal are: A. To evaluate resistance levels of two aphid species - the bird cherry-oat aphis and English grain aphid) affecting small grains in Kentucky. B. To disseminate findings (using printed, web based media or field days) that will benefit growers, and the small grain industry of KY.