Date of Graduation

5-2017

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Jason K. Norsworthy

Committee Member

Gus M. Lorenz

Second Committee Member

Robert C. Scott

Third Committee Member

Trenton L. Roberts

Fourth Committee Member

Edward E. Gbur

Keywords

Biological sciences, Herbicides, Insecticides, Safening, Weed science

Abstract

Interactions between herbicides and insecticides in crop production have been documented for a number of years. Research has shown that applications of some organophosphate insecticides at planting can reduce cotton injury following applications of the soil-applied herbicide clomazone. Additionally, recent research has shown that, when applied as seed treatments prior to planting, some neonicotinoid insecticides can safen rice to drift from both glyphosate and imazethapyr. Since insecticide seed treatments are commonly used in many crop production systems throughout the Midsouth, exploring their ability to reduce injury from herbicides in other crops besides rice is of great interest. Presently no research exists examining the potential for insecticide seed treatments to reduce herbicide injury in soybean or grain sorghum, important rotational crops in Arkansas. Research contained herein investigates the possibility for commonly-used neonicotinoid insecticide seed treatments to reduce injury from herbicides via drift and soil application in both crops, in addition to applications of postemergence herbicides in soybean that typically cause injury. Results from these studies indicate that injury from herbicide drift may be reduced through the use of insecticide seed treatments in both crops. Injury from seven of the eight herbicides evaluated in soybean, and three of three herbicides in grain sorghum, was reduced in at least one of four site years. Additionally, safening to soil-applied herbicides was seen in five of nine herbicides evaluated in soybean in one or more site years. Injury from soil-applied herbicides in grain sorghum was not reduced in any of the four herbicides evaluated, nor was a safening effect seen in applications of postemergence herbicides in soybean. The amount of injury reduction varied substantially among site years, indicating a strong environmental effect on level of safening. However, based on the fact that insecticide seed treatments are incorporated across a wide array of environmental conditions each spring, it seems likely that some growers will see the benefits of reduced injury following herbicide exposure.

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