Michael J. Weiss

The Present and Future Role of Insect-Resistant Genetically Modified Maize in IPM

Commercial, genetically-modified (GM) maize was first planted in the United States (USA, 1996) and Canada (1997) but now is grown in 13 countries on a total of over 35 million hectares (>24% of area worldwide). The first GM maize plants produced a Cry protein derived from the soil bacterium Bacillus thuringiensis (Bt), which made them resistant to European corn borer and other lepidopteran maize pests. New GM maize hybrids not only have resistance to lepidopteran pests but some have resistance to coleopteran pests and tolerance to specific herbicides. Growers are attracted to the Bt maize hybrids for their convenience and because of yield protection, reduced need for chemical insecticides, and improved grain quality. Yet, most growers worldwide still rely on traditional integrated pest management (IPM) methods to control maize pests. They must weigh the appeal of buying insect protection “in the bag” against questions regarding economics, environmental safety, and insect resistance management (IRM). Traditional management of maize insects and the opportunities and challenges presented by GM maize are considered as they relate to current and future insect-resistant products. Four countries, two that currently have commercialize Bt maize (USA and Spain) and two that do not (China and Kenya), are highlighted. As with other insect management tactics (e.g., insecticide use or tillage), GM maize should not be considered inherently compatible or incompatible with IPM. Rather, the effect of GM insect-resistance on maize IPM likely depends on how the technology is developed and used.

Millet preference, effects of planting date on infestation, and adult and larval use of proso millet by Ostrinia nubilalis (Lepidoptera: Crambidae).

Abstract The interaction between millet and European corn borer, Ostrinia nubilalis (Hübner), was investigated to gain insight into whether millet could serve as a refuge or trap crop for O. nubilalis management. In 1995, 1996, and 1999, millet selection studies were conducted in North Dakota and New York with four millet species. Proso millet, Panicum milliaceum L., had the highest infestation and widest distribution of O. nubilalis developmental stages, indicating the presence of both univoltine and bivoltine ecotypes. Siberian foxtail millet, Setaria italica (L.) Beauvois, harbored the greatest number of adults, followed by German foxtail millet, Setaria italica (L.) Beauvois. These two millets appeared to serve as better aggregation sites than proso millet. In North Dakota in 1997, proso millet planting date studies showed later planting dates were more heavily infested than earlier dates; in 1998, this trend was reversed. The change in trends between years was probably a result of differences in the respective growing seasons and subsequent differences in O. nubilalis flights. Adult sampling showed that both old and young females aggregated in proso millet during the day; however, at night, it appeared that young females moved out of millet to oviposit, whereas old females remained in millet. Egg masses were detected in proso millet over a 7-d period in 1997 and a 4-d period in 1998. Larval sampling showed planting proso millet between late May and mid-June may maximize the presence of individuals from both O. nubilalis ecotypes. Once the optimal combination of planting date, plant density, and millet type is found, millet may serve as an effective refuge or trap crop for O. nubilalis management.