Biological control of WBC promising
However, Mike Hoffmann, Ph.D., a researcher at Cornell University, found that a few species of moth, including the western bean cutworm, are susceptible in the laboratory and asked Bradshaw about testing the wasp’s effect on cutworms.
Trichogramma ostrinae lay eggs inside western bean cutworm eggs that have been deposited in sacs on field crops. Their larva develop inside and feed on the contents of the egg. If the host egg is large enough, it may even support the development of more than one trichogramma.
UNL Panhandle REC Adds Research for Dry Bean and Corn
The Scottsbluff project was carried out in 2011 by Fernanda Pelegrinotti, an intern from Brazil (UNESP, Universidade Estadual Paulista), under Bradshaw’s supervision. Cages were set up around corn and dry bean plots at two separate locations at the Panhandle Research and Extension Center at Scottsbluff. Four of the cages (two on corn and two on beans) were infested with both female western bean cutworm moths and parasitoids. Another two cages were infested with moths, but no parasitoids, as controls. After about 10 days of exposure, the western bean cutworm egg masses were evaluated.
Pelegrinotti found that the wasp will parasitize western bean cutworm, and in fact the parasitism rate was higher in dry beans than in corn. In addition, some of the cutworm eggs were victims of other mortality factors. The conclusion is that an augmentative release could significantly increase the mortality rate of western bean cutworm in dry beans, Bradshaw said.
Bradshaw said research conducted in eastern sweet corn fields on European corn borers showed that the parasitoids worked well as part of an integrated pest management (IPM) strategy in combination with chemicals.The overlaid insecticide did not kill off the trichogramma wasps.
Parasitized eggs also are noticeably darker than non-parasitized, so a field scout would be able to distinguish between the two and, in the future may be able to make a recommendation for treatment based on the rate of parasitism, he said.
Further Research Needed
The next step depends on money. So far, funding has not been secured to continue research, but there are more opportunities to present the project to funding agencies, he said.
Bradshaw said there are a lot of questions to answer: How does this treatment work in upright bean plants compared to viney? How large is the effective area of control — how far the parasitoids would spread from the release point? How long does it take for parasitoid eggs to emerge from cutworm eggs after they’ve been laid into the eggs, and how does that match up with the cutworm life cycle?