|Phoofolo, Mpho - IOWA STATE UNIVERSITY|
|Obrycki, John - IOWA STATE UNIVERSITY|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 17, 2000
Publication Date: N/A
Interpretive Summary: The European corn borer is a very serious pest of corn in the US causing losses of $12/acre with estimated losses approaching 1 billion dollars per year in the U.S. Researchers are continuously developing environmentally safe ways of managing the corn borer. The use of Trichogramma brassicae, an egg parasitoid, to reduce the number of insects, is very promising. T. brassicae is a small wasp that lays its eggs in corn borer eggs. A wasp egg hatches within the corn borer egg and consumes the contents of the egg killing the corn borer. Research was conducted to determine if these wasps could be released in a corn field to manage this insect. Release of between 100,000 and 2.8 million wasps per acre reduced the number of corn borers per plant by 46% and the inches of corn borer tunnels per plant by 41% over a two year period. These data demonstrate that egg parasitoids are an alternative to conventional insecticides for managing the European corn borer. This research benefits corn growers by providing an environmentally compatible technology for insect management and benefits the general public by reducing the amount of agricultural chemicals loaded into the environment.
Technical Abstract: To assess inundative releases of Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae), a European egg parasitoid of Ostrinia nubilalis (Hubner) (Lepidoptera: Crambidae), against O. nubilalis in Iowa, we examined the relationship between release densities and parasitism levels. The number of wasps released in each 0.25-hectare plot was zero (control), 25,000, 50,000, 100,000, and 200,000 wasps. In 1995 and 1996, levels of egg parasitism were affected by the number of parasitoids released. Although one of the release densities used (200,000 parasitoids) is higher than that recommended in Europe, levels of O. nubilalis egg parasitism we observed were lower (maximum of 54%) compared with those reported in Europe (maximum of 93%). The percentage of O. nubilalis egg masses (parasitized and unparasitized) preyed upon by naturally occurring predators was not influenced by the number of wasps released in 1995. However, in 1996 predation was inversely correlated with T. brassicae release rates, suggesting that T. brassicae release rates influenced egg predation.