Combining Landscape and Augmentative Biological Control to Suppress European Corn Borer Populations in Sustainable Low-Input Systems
The ultimate goal of this study is to provide corn producers with practical, easily implemented pest management strategies that can be adapted throughout the Corn Belt. Our objectives are to determine which agronomic crops and erosion-control plants best stimulate European corn borer (ECB) oviposition and to assess ECB control in corn when egg parasitoids are inoculated into moth aggregation sites.
Over the past 150 years, prairies of the North Central region have been replaced by an agrarian landscape. In Iowa, more than 70 percent of the land is farmed with 13 million acres in corn, 8.8 million acres in soybeans and 3.6 million acres in oats, alfalfa and hay.
Improved plant genetics and high-chemical input unquestionably have resulted in remarkable production. Most scientists agree, however, that high-input agriculture is not sustainable. Public concerns about environmental problems such as surface and groundwater contamination, pesticide residues in food, soil erosion and wildlife habitat destruction have challenged all agricultural scientists to address sustainable agriculture.
We intend to contribute to the goal of sustainable agriculture by using landscape and crop diversity as low-input methods to localize European corn borer (ECB) Ostrinia nubilalis (Hubner) Lepidoptera: Pyralidae) populations, enhance natural enemies of ECB, and reduce the need for chemical insecticides.
Annual yield loss to ECB costs farmers in the Midwest anywhere from $15 to $50 for every acre of corn. Scouting and properly timed applications of chemical insecticide or Bacillus thuringiensis (Berliner), a biological insecticide, can be effectively used to manage first generation ECB larvae (Moffat 1991, Showers et al. 1989). There are no economically effective means, however, for managing the second generation of this pest; insecticide applications are difficult to time because of a prolonged oviposition period.
Three millet varieties (proso, pearly and Siberian millet) were compared for their attractiveness to ECB as potential trap crops. Trap crops are plants which may be planted as barrier rows around a target crop, and to which pests are attracted, thus reducing pest numbers on the crop.
Field and cage trials were conducted. Field trails assessed preferences between the three types of millet and three growth stages of each. The cage trials compared egg-laying by corn borer moths on the three types of millet and corn.
Field studies showed that the moths aggregated in Siberian millet, avoided pearly millet and attacked (measured as damage caused by larvae) proso millet most severely. A general tendency to prefer taller plants was observed. Cage trials showed little difference between the millets and sweet corn under hot, dry conditions (with a non-significant majority of egg masses laid on corn). Under more optimal conditions, corn and pearly millet plants received the highest numbers of egg masses. Most of the corn borer egg masses laid on the millets were parasitized by released parasitic wasps, but most of the parasitization in corn only occurred within 15 feet of the millet plots.
For more information:
102 Genetics Lab c/o Insectary
USDA-ARS Corn Insects & Crop Genetics Research Unit
Iowa State University
Ames, IA 50011