The tests in Michigan compare the effectiveness of Trichogramma with insecticides that are currently used against European corn borer in the United States. In addition, the researchers are looking at whether Trichogramma applications can be adapted to the North American agricultural system. Experiments have been conducted in both field corn and seed corn fields.

Results for 1993 field corn plots are typical of the results obtained to date (see table below). Both control of European corn borer and damage prevention was at least as good with the wasps as with insecticides in these tests. By killing European corn borer eggs before they hatch, there is no need to spray insecticides to control the larvae that cause damage to corn plants.

Suppression of second generation European Corn borer in field corn plots treated with bilogical and chemical crop protectants, Centreville, MI, 1993.
Treatment	Rate	% Reduction of European corn borer larvae	% Reduction of cavities	% Reduction of cavity length
Trichogramma	(243,000/acre = 486 capsules)	78.3	74.2	77.1
Dipel 10G	10 lb/acre	33.7	34.8	43.7
Pounce 1.5G	6 lb/acre	64.9	60.8	65.2
Lorsban 15G	6.3 lb/acre	66.2	50.2	63.8

In addition to experiments in field corn, there is a regional project, funded by Pioneer Hi-Bred International, to test Trichogramma for control of European corn borer in seed corn fields in Illinois, Indiana, Iowa, Michigan, Nebraska, and Ontario, Canada. Results at the end of this three year study will show whether Trichogramma applications are a practical method of European corn borer control in seed corn production.

The cost of the wasps is one of the main limitations to using Trichogramma for European corn borer control in corn fields. They cost two to three times that of a single insecticide application. However, if only 1/3 to 1/2 of the currently recommended rate could be released with equal results, the cost would also be reduced by the same proportion. Reduced rates of Trichogramma gave excellent results in preliminary field trials in Michigan in 1994. Over 72% parasitism of European corn borer eggs was achieved with wasp releases of 2/3 the recommended rate. Even the 1/2 rate was acceptable, achieving 55% parasitism. There was no significant difference in yield between either Trichogramma rate and standard chemical treatments. This experiment needs to be repeated to verify the results before recommendations for reduced rates of Trichogramma can be made.

If cost limitations can be removed, Trichogramma applications should be adaptable to United States agricultural systems. Adoption of this method appears to be most likely in seed corn production at first, where insecticide applications and worker safety concerns are greatest.

- David Orr and Doug Landis, Michigan State University