Field Crops News

Transgenic Corn Safe for Insect Predators

Transgenic Bacillus thuringinesis (Bt) corn hybrids are now available commercially and have been shown to be highly effective in controlling European corn borer larvae, due to high levels of the Bt protein toxin present in corn tissue. Foliar sprays of Bt are known to be safe to a variety of predators, but the season-long production of higher levels of Bt protein in transgenic corn raises the question of whether there might be an effect on predatory insects. Bt corn from Ciba Seeds (using Event 176) produces Bt protein in both the plant and pollen. Three common predatory insects found in corn, the twelvespotted lady beetle, Coleomegilla maculata, the insidious flower bug, Orius insidiosus, and the common green lacewing, Chrysoperla carnea, were studied in the laboratory and field to determine the effect of Bt corn on their development, survival and abundance in the field. In laboratory studies, there were no differences in immature survival and development rates when these predators were fed pollen from Bt corn. Similarly, in field plots, there were no differences in the abundance on Bt corn, compared to the same hybrid without Bt. These results suggest that use of Bt corn hybrids is compatible with biological control by insect predators.

Source: C. D. Pilcher, J. J. Obrycki, M. E. Rice and L. C. Lewis. 1997. Preimaginal development, survival and field abundance of insect predators on transgenic Bacillus thuringiensis corn. Environ. Entomol. 26: 446-454.

Searching for Natural Enemies of Lygus Bugs

Canadian researchers are in pursuit of exotic parasitoids of mirid bugs (such as tarnished plant bug and other plant bugs) for release in Canada. Over 1550 parasitoid cocoons were collected in Austria, Hungary, southern Germany and Switzerland in the second year of an AAFC (similar to our USDA) project. A culture of the wasp Peristenus stygicus was established from Hungarian collections. Other wasp species, primarily P. digoneutis, are still in storage as overwintering cocoons, and will be cultured as they emerge. Once laboratory rearing methods are devised, they will raise large numbers of these imported parasitoids for release and establishment in Canadian alfalfa fields.

For more information contact Howard Thistlewood at

Agriculture and Agri-Food Canada
Pest Management Research Centre
Vineland, Ontairo
phone (905) 562-4113

Source: Pest Management News 8(4): 6, Winter 1996.

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