Date of Award
Master of Science
Matthew E. O'neal
I conducted a series of field experiments during the 2009 and 2010 field seasons. The purpose of these experiments was to determine if selective insecticides provide adequate control of the soybean pest Aphis glycines, when compared to a broad-spectrum insecticide. I was also interested in finding if selective insecticides reduced soybean exposure to A. glycines. To test for this I collected population data that would allow us to calculate cumulative aphid days (CAD). I also gathered yield data at the end of each field season, which was then compared among treatments to determine if there was a difference in yields based on the treatments. I was also interested in determining if the residual activity of the broad-spectrum and selective insecticides differed. To test for this I compared the populations of A. glycines on caged plants for each of the treatments. I also conducted a cage study to determine if biological control was occurring in the field. To determine if biological control was occurring I compared the populations of soybean aphids on caged and uncaged plants for each treatment at two different time periods after the application of the insecticides. To test for evidence of a bioresidual in either 2009 or 2010, I calculated a Biocontrol Services Index (BSI) for each of the treatments. My findings indicate that selective insecticides are a viable control option for A. glycines. I also was able to determine that biological control was present in 2010, and that a bioresidual occurred in the imidacloprid treatment in 2010 during the first sampling period after insecticides were applied. I also collected natural enemy data for 2009 and 2010. I compared the populations of natural enemies between the two years to determine if the natural enemy community differed between years. I also compared a pre- and post-application date for each of the treatments for all of the natural enemies, as well as the two most abundant species for 2009 and 2010. My findings indicated that the natural enemy community differed between 2009 and 2010, and that selective insecticides have a reduced impact on natural enemies when compared to a broad-spectrum insecticide.
Adam Jerry Varenhorst
Varenhorst, Adam Jerry, "Selective insecticides: the potential for improved control of the soybean aphid as a result of a bioresidual" (2011). Graduate Theses and Dissertations. 12036.