Since 1989, the Pennsylvania State University and the PA Dept of Agriculture have supported the development of IPM programs in both field greenhouse vegetables. These programs maximize the use of natural enemies and pest resistant varieties to control the major pests such as whiteflies, aphids, two-spotted spider mite, western flower thrips, powdery mildew, early blight, alternaria, etc. in conjunction with soft compounds to treat "hot spots" and maintain good sanitation. Having a pesticide-free environment allows for the use of bumble bees to pollinate crops, replacing the mechanical vibration method. Many growers generate greater profits by marketing their vegetables as "pesticide free".
To many greenhouse vegetable growers, the possibility of using biocontrols sounds great, however making the transition from using traditional pesticides to a biological control program may seem too difficult for them. Managing pests with biological controls requires thought, careful planning and the realization that every crop cycle may prevent a unique situation. Results are not instantaneous so patience is a must.
Consider these steps when you develop an Integrated Pest Management (IPM) program in your operation
- Start small - As with any new technology, start small. Learn the system in one greenhouse or field and expand as you gain confidence and knowledge.
- Pesticide Residues - Discontinue using insecticides with residual activity at least one to three months prior to introducing biocontrols. Pesticide residues on plants, and greenhouse coverings can be deadly to biocontrol agents. Consult suppliers for information on specific products if you want to be certain about the compatibility of a compound that has been applied.
- Soft Pesticides - Consider the use of "soft" or "reduced risk" compounds (i.e. insecticidal soap, ultra-fine horticulture oil, neem compounds) for treating hot spots or pests that are not being controlled biologically. Have products on hand before outbreaks occur. Some biocontrol suppliers sell these products, and can give you compatibility information. Always consult your supplier before spraying. Some growers find it beneficial to have a sprayer designated for soft pesticides only, avoiding contamination with toxic insecticides.
- Good Sanitation - Weed management is critical to the success of a biocontrol program both before and during crop production. Weeds serve as reservoirs for pests and diseases and may upset the predator-prey balance you are trying to establish in the crop. It is also critical to maintain a weed free zone around the outside perimeter of the field or greenhouse for the same reason. Using a herbicide will have pests scrambling for another food supply, which will probably be your crop - remove weeds and destroy!
- Clean Transplants - In many cases, serious pest and disease problems that plague growers throughout the growing season result from the purchase of infested transplants. Selection of a reputable transplant grower ensures a quality transplant. Inspect what you are buying!If you are growing your own transplants, the area used for transplant production should follow strict sanitation procedures.
- Sticky Cards - Begin monitoring with sticky cards when the crop is planted in the field or placed in the production house. Yellow sticky cards are effective in trapping whiteflies, fungus gnats, shore flies, thrips, winged aphids and leafminer flies. Blue cards are used to monitor for thrips, however, they are easier to see on yellow cards. Place one card per 1,000 square feet in a grid pattern, and near vents and doors to catch migrating insects. Record insect pests caught on cards and change them on a weekly basis.
- Start Early - Begin introductions of biocontrol agents when pest populations are at low levels. This can be determined by weekly crop inspection. For example, high populations of pests such as whiteflies reduce the effectiveness of the natural enemy Encarsia formosa through honeydew secretions. The sticky honeydew will interfere with the parasite's walking and searching speed and may even cause them to become trapped and die.
Source for Biological ControlsThe biocontrols discussed in this article are commercially available from biocontrol distributors. For a complete list of suppliers, visit this website: www.cdpr.ca.gov/docs/dprdocs/goodbug/benefic.htm Or request a written copy:
California Environmental Protection Agency Department of Pesticide Regulation Environmental Monitoring and Pest Management Branch 1020 N. Street, Room 161 Sacramento, California 95814-5604
California Environmental Protection Agency DEPARTMENT OF PESTICIDE REGULATION Environmental Monitoring and Pest Management Branch 1997 Edition Charles D. Hunter