Field crops represent one of the largest land uses in the United States – over 320 million acres were planted in 2008. Corn and soybeans, the principal crops grown in Indiana, account for about half of this acreage, with 86 million and 75 million acres, respectively, planted nationwide in 2008. These large acreages also represent substantial inputs for pest management – there are several important insect pests of both crops, and management options for these pests covers a spectrum that includes cultural controls, insect-resistant plants (both transgenic plants (eg. Bt corn) and those developed using traditional breeding), biological control, as well as many insecticidal options.
Many of these pests have affected large areas of cropland for decades, despite a dynamic approach to management that has employed a wide variety of approaches. This underlines the fact that there is still an urgent need for more and better information about elementary aspects of the life histories of these pests and how they may equip the insects to overcome modern management approaches. I am interested in working with students to identify weaknesses in current management approaches using studies of insect biology in the field and laboratory.
Examples of current projects include:
Refuge structure in transgenic corn: The use of mandatory refuges in Bt corn plantings has led to exploration into methods of simplifying refuge planting, including seed mixtures, to increase rates of compliance and ease of implementation. We are interested in how various rates of seed mix affect larval densities, root damage, and adult beetle emergence (timing and sex ratios). Our long-term goal is to develop an understanding of how the biology of the insect may be influenced by the configuration of the refuge, and, subsequently understanding which refuges actually function the most efficiently in minimizing opportunities for sub-lethal larval exposure while promoting random mating among adult beetles.
Quantifying risks of “stacking” herbicide traits in transgenic corn: Herbicide-tolerant corn (primarily glyphosate-tolerance) is becoming increasing popular and currently composes the majority of corn grown in Indiana. It is often combined (“stacked”) with traits for insect resistance (i.e. Bt toxin expression). Glyphosate tolerance results in increased convenience for growers, but causes problems with weed escapes of volunteer corn in the following years’ crop. In addition to expressing herbicide-tolerance traits, these volunteer plants often express some levels of Bt toxins found in the parent as well. Despite this, these plants sustain heavy damage and are able to support development of rootworm larvae to adulthood. We are interested in quantifying the risks of larval exposure to volunteer, herbicide-tolerant, Bt corn in both soybeans and corn. The long-range goal of this work is to determine how to balance herbicide-tolerance with insect resistance management.
Assessing range of corn rootworm variant using digital imagery: The corn rootworm variant has presented a management challenge to growers in the upper Midwest for approximately 20 years. We are attempting to develop a novel method of determining whether female beetles are likely to oviposit in soybeans by using baited traps, combined with digital photography and image analysis software, to develop a color-based screen that will enable us to distinguish soybean-feeding, variant females from those that oviposit primarily in corn. We hope to use this to develop a site-specific, sensitive monitoring tool that will enable us to increase grower confidence in management decisions for first-year corn plantings.