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United States Department of Agriculture

Agricultural Research Service

Title: Influence of Herbicide Tolerant Soybean Production Systems on Insect Pest Populations and Pest-Induced Crop Damage

Authors
item Mcpherson, R - UNIV. OF GEORGIA
item Johnson, Wiley
item Mullinix, JR., B - UNIV. OF GEORGIA
item Mills, Iii, W - UNIV. OF GEORGIA
item Peebles, F - UNIV. OF GEORGIA

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 16, 2002
Publication Date: June 1, 2003
Citation: McPherson, R.M., Johnson, III, W.C., Mullnix, Jr., B.G., Mills, III, W.A., Peebles, F.S. 2003. Influence of herbicide tolerant soybean production systems on insect pest populations and pest-induced crop damage. Journal of Economic Entomology. 96(3):690-698.

Interpretive Summary: Weed management in soybean has radically changed in recent years due to the widespread adoption of transgenic cultivars with resistance to herbicides such as glyphosate and glufosinate. Weed management in transgenic cultivars is less costly and much simpler than in conventional cultivars without herbicide resistance. The dynamics of insect pests in herbicide resistant transgenic soybean are unknown. Trials were conducted in Georgia to study the effects of weed management in conventional cultivars and transgenic herbicide-tolerant cultivars on insect pest populations. Soybean cultivar had very little impact on the insect species observed. Soybean looper, three-cornered alfalfa hopper, and whitefringed beetles demonstrated no varietal preference in this study. Insect pest numbers were higher in plots where weed densities were reduced by either postemergence herbicides or preplant herbicide plus postemergence herbicide. In the postemergence herbicide plots, there were no differences in insect pest densities between the conventional soybean cultivars (treated with chlorimuron, clethodim, lactofen and acifluorfen plus bentazon) compared to transgenic herbicide-tolerant cultivars (treated with glyphosate or glufosinate). Defoliation from velvetbean caterpillar feeding differed between soybean varieties at some locations but not between herbicide treatments. It appears that the newly developed transgenic soybean cultivars and their specific herbicide treatments do not adversely affect the seasonal abundance of insect pests and pest-induced crop injury. Weed management systems can influence certain insect pests periodically during the growing season, but this is due to the system being utilized and not the genetic modification for herbicide resistance.

Technical Abstract: The effects of weed management in conventional cultivars and transgenic herbicide-tolerant cultivars were examined in soybean to assess their impact on insect pest populations. Soybean cultivar had very little impact on the insect species observed, except that maturity group effects were observed for stink bug population densities on some sampling dates. Stink bugs were more abundant on the early-maturing varieties in mid-season. Soybean looper, three-cornered alfalfa hopper, and whitefringed beetles demonstrated no varietal preference in this study. Insect pest numbers were higher in plots where weed densities were reduced by either postemergence herbicides or preplant herbicide plus postemergence herbicide. The exception to this weed treatment effect were grasshoppers, which were more numerous in weedy plots. In the postemergence herbicide plots, there were no differences in insect pest densities between the conventional herbicides (chlorimuron, clethodim, lactofen and acifluorfen plus bentazon) compared to transgenic herbicide-tolerant cultivars (treated with glyphosate or glufosinate). Defoliation from velvetbean caterpillar feeding differed between soybean varieties at some locations but not between herbicide treatments. Some defoliation levels were <40% where velvetbean caterpillar populations exceeded the current economic threshold of 40 caterpillars/25 sweeps. It appears that the newly developed transgenic soybean cultivars and their specific herbicide treatments do not adversely affect the seasonal abundance of insect pests and pest-induced crop injury. Weed management systems can influence certain insect pests periodically during the growing season, but this is due to the system being utilized and not the genetic modification for herbicide resistance.

Last Modified: 9/10/2014
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