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PDA Greenhouses Pesticide-Free - April 2006
April 18, 2006
UNIVERSITY PARK, PA – Eight greenhouses at the Pennsylvania Department of Agriculture have remained pesticide-free for two years, thanks to a biological control program of using good bugs to fight the bad ones.
Biological control, also known as biocontrol, uses beneficial organisms to control pests. Since most pests have various parasites, diseases and predators that can kill them, beneficial organisms can be purchased and released into greenhouses as a means of control. This results in improved crop yield and quality. It also can greatly reduce and sometimes eliminate the need for pesticides. This practice is part of a grower’s integrated pest management (IPM) program. IPM aims to manage pests -- such as insects, diseases, weeds and animals -- by combining physical, biological and chemical tactics that are safe, profitable and environmentally compatible.
PDA Plant Pathologist Earl Flack says they started the biocontrol program two years ago so they could continue their research on plant parasitic nematodes. “We were running several bioassays, or studies, with plant parasitic nematodes in soil. Nematodes are microscopic worms that live in the soil and feed on plants and microorganisms. They are very susceptible to the pesticides routinely used in greenhouse management, so we needed to find a way of controlling pests in the greenhouse without affecting the nematodes,” says Flack.
With the help of Cathy Thomas, PDA IPM coordinator and biocontrol specialist, Flack began purchasing and releasing predatory mites, wasps and beetles about once every two weeks. “Before we started the program, if you shook a tomato plant, big clouds of whiteflies would come off the plant. Now, these and other pests like thrips, two-spotted spider mites, mealybugs and scales have been all but eradicated from the four isolation houses, one screen greenhouse, one clean greenhouse and two other greenhouses located in our three buildings.”
The greenhouses contain a variety of plants, including soybeans, wheat, tomatoes, peppers, kudzu, and invasive weeds used in demonstrations, such as purple loosestrife and giant hogweed. Plants that are brought into the greenhouses for study and evaluation are often harboring pests, so containing the problem before it can spread to the rest of the greenhouse is key, says Flack. Another area of concern was infested native plants and ornamentals that grow outside one of the isolation greenhouses. “Pests were making their way in before we trimmed some of the foliage back and made regular releases of beneficial organisms in that area.” says Flack.
The program is working so well that from November through April, Flack doesn’t apply biocontrols at all. During the growing season, three types of predatory mites, two types of parasitic wasps and one type of predatory beetle are released. Flack alternates the applications, advising to release the biocontrols early in the pests’ life cycle, not to wait until you see populations exploding in the greenhouse.
Flack says they are very pleased with how biocontrol has been keeping pests at bay in all the greenhouses. “You’ll have a hard time finding an aphid, whitefly or thrips in our greenhouses. Spider mites are still somewhat of a problem, so we use three different controls to head them off,” Flack explains. He says he was a little skeptical about using biocontrol at first, and advises you must be patient, because control is not immediate. “It took us about six months to obtain control, but we couldn’t be more pleased with the results.”
For more information on the greenhouse biocontrol program, contact Earl Flack at 717-705-4343 or e-mail eflack@state.pa.us. You may also contact Cathy Thomas at 717-772-5204 or e-mail caththomas@state.pa.us.
The PA IPM Program has supported the greenhouse industry in Pennsylvania for over 15 years. The program has helped to develop many resources for greenhouse growers, including the manual, “Greenhouse IPM with an Emphasis on Biocontrol”. The manual was developed to help greenhouse growers implement biocontrol and IPM. The full-color publication (number AGRS-96) containing almost 100 photos is available as a free downloadable PDF file from Web site http://paipm.cas.psu.edu/63.htm. To order a hard copy, contact Penn State’s Publications Distribution Center toll free at 1-877-345-0691. For additional greenhouse IPM resources, see the PA IPM Program’s Greenhouse IPM Web site at http://paipm.cas.psu.edu/13.htm.
The Pennsylvania IPM program is a collaboration between the Pennsylvania State University and the Pennsylvania Department of Agriculture aimed at promoting integrated pest management in both agricultural and nonagricultural situations. For more information, contact the program at (814) 865-2839, or Web site http://www.paipm.org/. To view our archived news releases, see Web site http://paipm.cas.psu.edu/10.htm.