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An innovative group of growers in southern Washington and Deborah Henderson, a private consultant and researcher in British Columbia, have been investigating the use of Trichogramma a tiny wasp which parasitizes moth eggs, as an alternative to pesticides for the management of raspberry pests. In January, 1995, in Tacoma, Washington, these growers and Dr. Henderson came together to share their experiences at the Rasp berry Farm Improvement Club Forum, sponsored by NCAP. Also attending were other interested raspberry growers, private consultants, Washington State University researchers and extension personnel. The forum, the first of its kind held at the Western Washington Horticultural Society annual meeting allowed farmers to discuss their own experimental projects with participants and included a presentation by Dr. Henderson.

The raspberry growers from the Vancouver area of Washington described their project releasing Trichogramma wasps and green lacewing Chrysopa spp., for the management of orange tortrix, Argyrotaenia citrana Orange tortrix, a tan moth that lays its eggs on the underside of the raspberry leaf, is a major problem in raspberries because its larvae are contaminants of harvested raspberries. If processors find as little as one «worm" (larvae) in the harvested raspberries they can reject the whole batch.

Most populations of orange tortrix in the western parts of Oregon, Washington, California and British Columbia are kept in check by naturel parasites and predators and do not require intensive management. However, in Vancouver, Washington, high populations of orange tortrix have plagued growers for decades.

It is not known whether this unique situation exists because some vital predators or parasites are missing or because farmers have created the perfect breeding "rounds through years of pesticide applications. However, growers are very concerned. As farmer/researcher Jerry Dobbins states, "We do not have a chemical registered for the orange tortrix.» That's just as well because the pesticides typically used are causing more problems for the growers by killing the naturel predators that keep mite pests in check Jerry Dobbins and several of his neighbors are attempting to get off this vicious cycle of pesticide use by incorporating releases of Trichogramma and green lacewing into their pest management program. Their past releases have been so successful that they have designed an experiment this year to refine their release process.

Dobbins first heard about using beneficials to manage pests in Canada. Dobbins and other growers wanted to hear more about the biological control programs in Canada so NCAP invited Henderson to attend the forum. Her presentation was heartily received at the Raspberry Farm Improvement Club Forum.

Henderson began her work with Trichogramma in raspberries in the fields of the Fraser Valley of British Columbia in 1991. She developed an economically feasible program that achieves between 80 and 90 percent control of the cranberry wireworm with innundative releases (the release of large numbers of insects) of Trichogramma. In 1992, Henderson decided to test a surplus number of Trichogramma on raspberries. She released about 1.35 million Trichogramma over 36 raspberry plants to manage cutworms. Control of cutworms with the Trichogramma was equal to control with two diazinon, one malathion, and one azinphos-methyl spray. Henderson repeated the experiment in 1993 with similar results.3

Henderson staunchly believes that using two biological controls is more effective than using one. She described the successful cranberry wireworm management program as an example. The program combines the use of pheromones and Trichogramma When wireworm populations are low pheromones work best. Trichogramma require high populations to be effective.

The success of Henderson's past investigations has spurred her to develop three new research projects using smaller numbers of Trichogramma on raspberry this year. Although Henderson's work is not investigating the same pests as the Vancouver, Washington growers, the information on her experiences and methods using the tiny wasp Trichogramma in the field is quite valuable and inspiring to the Vancouver growers.

In order to increase the efficiency of their beneficial insect releases some of the Vancouver area growers are investigating other biological control methods. One grower will be experimenting with establishing habitat around fields to promote Trichogramma and other beneficial insect populations. The growers will also have the opportunity to test another moth parasite in a lab/office setting. The parasite, a tiny fly, parasitizes the fate larval stages of moths. Researchers have been working with this parasite for codling moth in Washington. The growers have set up a simple experiment to see if the fly will attack orange tortrix larvae Another participating grower will be testing a beneficial mite on her pest mite populations in strawberries.

Another biological option that could also be combined with the release of Trichogramma is mating disruption of the orange tortrix (This involves using a mating pheromone, a chemical produced by an insect to attract the opposite sex, to disrupt the normal mating behavior of a pest.) Research has been clone on this practice by processors and Oregon State University researchers with good results. Unfortunately, the research has not been published and the mating pheromone for orange tortrix is no longer commercially available. It is possible that with researchers, processor, farmers, and industry cooperation, an alternative manufacturer for the orange tortrix mating pheromone could be found. This would add yet another viable option to the array of alternative management practices raspberry growers are developing to reduce their dependency on pesticides.

Gwen Bane

1. Berry, R.E., 1978. Insects and mites of economic importance in the Northwest. Corvallis, OR: Oregon State University Book Stores, Inc. p.75.

2. Rosenstiel, R.G., 1949. Life history and control of the orange tortrix in Oregon. Journal of Economic Entomology 42:37 40.

3. Henderson, D., ES Cropconsult Limited Vancouver, B.C. Personal communication, March 6, 1995.

Citation : Bane, Gwen, 1995, " Using Beneficial wasps for raspberry pest management", Vol 15, No. 1, Spring 1995, pp. 7-8.

Copyright © 1995 Northwest Coalition for Alternatives to Pesticides.

Reprinted with permission.

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