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United States Department of Agriculture

Agricultural Research Service

Title: Post-Establishment Movement of Western Corn Rootworm Larvae: the Role of Egg Density and Cry3bb

Authors
item Hibbard, Bruce
item Vaughn, Ty - MONSANTO CORPORATION

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 21, 2003
Publication Date: N/A

Technical Abstract: The western corn rootworm is one of the most economically important pests of corn with no viable alternative to insecticide in continuous corn. If registered, transgenic corn with resistance to this pest may offer an additional management option. Resistance management is in the interest of growers and industry, but depends upon knowledge of corn rootworm biology. We have conducted a series of experiments to evaluate larval movement after initial establishment. In each experiment, a single plant was infested, which was surrounded by noninfested plants. Originally, two row spacings and two plant spacings were evaluated with a single infestation level to determine if movement occurred. In the summers of 2000, 2001, and 2002, infestation levels of 100, 200, 400, 800, 1,600, and 3,200 viable eggs on a central plant were evaluated to determine the effect of egg density and subsequent plant damage on movement after establishment. In 2001 and 2002, the effect of transgenic Cry3Bb plants was evaluated. Overall, movement up to three plants down the row and across a 0.46 m row was clearly documented after initial establishment. Those larvae that moved weighed significantly more than those larvae that did not move. No significant post-establishment larval movement occurred at lower infestations levels. Larvae apparently move when plants are highly damaged and/or when competition for food exists. In 2001, the transgenic Cry3Bb protein appeared not to be repellent to neonates (at least before a lethal dose was received), but may be somewhat repellent to later instar larvae (or was more toxic under our conditions than expected). This information will be important to seed companies, the Environmental Protection Agency, and modelers in their attempts to develop resistance management plans for transgenic corn by providing more realistic assumptions in current mathematical models.

Last Modified: 10/25/2014
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