Growers often use living organisms that are natural agents of a target pest to to control pests and diseases in the greenhouse or growroom. These biological control agents include predators, other insects, mites, fungi or bacteria and these need to be released and get established when pest populations are low. They are not fast acting like pesticides and should be used early as a control to prevent infestations instead of a rescue treatment after the infestation has grown out of hand. Natural controls are best used preventatively, early in the cropping cycle, when plants are small and pest numbers are low and before pest damage occurs. Using natural controls requires a different mindset from traditional pest control where growers wait until damage occurs, then treat with insecticides or miticides.

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Some of the advantages of using biological control agents include:

  • less worker exposure to toxic pesticide residues;

  • safer end products and better consumer acceptance;

  • less chance of damage from excessive spray;

  • improved plant quality;

  • no re-entry intervals (REI) to follow;

  • minimal equipment needed for application;

  • preserving the effective life of pesticides used by decreasing the development of resistance.

While biological control programs have a long history of use and extensive research base for greenhouse vegetable crops, growers often need to experiment to see what works best in their individual situation. in that they rely on living interactions, biological control programs use little extra effort to be successful. However, using natural controls requires time to understand the environmental requirements and interaction history of pest and the control agent, patience to develop an effective strategy for their use and patience to see the program through. It may be best to start in an small area or greenhouse first and expand as your experience expands. The suitable solution depends on the pest, your environment, crop requirements and grower experience.

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Getting Started in Biological Control

  1. Proper Cultural Practices - Start clean and stay clean Biological Controls for Pests in Garden, Greenhouse or Growroom 04Biological control is more likely to be successful if it is integrated with the proper cultural controls to discourage insects and diseases. Practices to help prevent pest infestations include:

    1. Maintain a clean, closely mowed area around the greenhouse to restrict entry of pests from outside – keep areas around greenhouse as weed free as possible and keep cull piles as far as possible from the greenhouses to reduce pests that develop in thick growth.

    2. When possible (at the conclusion of each production cycle), remove all plants and any plant debris, and clean the greenhouse thoroughly and fumigate.

    3. Keep doors, screens and ventilators in good repair. Use double entry doors where possible to insulate the environment from direct entry to the outside.

    4. Use clean or sterile soils or ground media, tools, flats and other equipment.

    5. Inspect new plants thoroughly to prevent insect or disease infested material being introduced into the greenhouse. Disinfect or sterilize new plants before entry is a good practice.

    6. Remove leaks or pooled water that can lead to fungus gnat infestations.

    7. Avoid wearing yellow clothing which is attractive to many insect pests.

    8. Discard or remove heavily infested plants or material.

    9. Over fertilizing crops promotes tender lush growth that is prone to aphids, white flies and other sucking insect pests. It is harder for natural controls to be effective under those conditions without proper planning beforehand.

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  1. Get Educated about the types of Pests and available Natural Controls

Learn the biology and life cycles of the insect and mite pests and their natural control agents. Also become familiar with the specific environmental requirements needed by the different natural control agents. Temperature and humidity levels need to be in the zones required for the natural control agent to flourish.

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  1. Review Past Pest Problems

Know the species of pest that may will cause problems. Natural control agents can be very specific to the host or pest they will control. While some are general predators, many rely the life cycle of the pest to be effective.

  1. Review Pesticide Use

Many insecticide residues can adversely affect natural control agents for some time after their application. Direct contact and pesticide residues on containers, benches, greenhouse plastic etc. may be directly toxic to natural agents or effect how well they survive and reproduce. Make sure all residues are gone before starting biological control.

Be ready to use compatible pesticides, if necessary. Multiple pest complexes affecting ornamental crops make it difficult to control all pests – so sometimes compatible pesticides are needed. However, rarely is a pesticide compatible with all the natural agents released. Adverse effects can be minimized by spot treatments (as compared to cover sprays) and the application method (drenching versus spraying). Effects vary depending upon the type of pesticide used and the natural agent. Some natural agents may be more sensitive to pesticide residues depending upon whether they are a parasitic wasp or predator. Certain species or life stages may be more sensitive, too.

  1. Do Regular Scouting

Check the crop regularly and consistently to anticipate when various pest populations may become a problem. Plan ahead and release natural control agents in sufficient time manage the pest problem before it becomes an infestation. Also, keep good records so you know where potential hot spots of pest activity are, and can evaluate the effectiveness of the natural control agents after release.

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  1. Transition into Biological Control Agents

Start in a small to learn how to use natural control agents. Decide what crops make the most sense for you to trial. If you are propagating, you will want to begin in that growing area. Release natural control agents in your stock plant production or begin as soon as you receive cuttings. If you are growing edible crops such as herbs or vegetables that may be a logical starting point. As your experience and comfort level expands, you can expand your use of biological control agents.

  1. Plan ahead

Plan ahead. Biological control agents, especially parasites, are often specific to a pest or may be shipped in a stage that does not attack the targeted pest. Some insecticide residues can adversely affect natural agents for up to three to four months after their application. Review your pesticide use for the past 3 to 4 months before starting biological control.

  1. Release Rates and Timing

Some of the newer, more selective insecticides and miticides (including some insect growth regulators) are compatible with certain natural agents. For more information on pesticide compatibility with natural agents, consult with your supplier or refer to the Internet resources mentioned above.

Work with your supplier to determine the appropriate release rates and timing based upon the pest activity (determined by regular monitoring), effectiveness of the biological control agents and the crops grown. Are the rates for a preventative or curative treatment?

Patience and commitment is needed.

You need to be able to tolerate some pests in order for the natural agents to work. A proactive approach is needed for natural agents don’t work as quickly as pesticides. However, pests do not develop resistance to the natural agents, so biological control is an important part of resistance management.

Some Suggested References on Biological Control

Cranshaw. W. 2004. Garden Insects of North America. The Ultimate Guide to Backyard Bugs. Princeton University Press. 656 pp.

Flint, M.L. and S. H.Dreistadt. 1998. Natural agents Handbook: The Illustrated Guide to Biological Pest Control. 154 pp. University of California. Publication # 3386.

Gill, S. and J. Sanderson. 1998. Ball Guide to Identification of Greenhouse Pests and Beneficials. Ball Publishing, Batavia, IL. 244 pp.

Lamb, E. and B. Eshenaur. 2014. Greenhouse Biocontrol Workbook.  NYS Integrated Pest Management Program. Cornell University Cooperative Extension.  84 pp.  Available online at:

Malais, M. and W. J. Ravensberg. 2003 The Biology of Glasshouse Pests and Their Natural agents- Knowing and Recognizing. Koppert Biological Systems, PO Box 155, 2650 AD Berkel In Rodenrijs, The Netherlands. 288 pp.

Smith, T. and L. Pundt. 2014. Greenhouse Pest Guide web App.

Stack, Lois Berg. (ed). 2013-2014. New England Greenhouse Floriculture Guide. A Management Guide for Insects, Diseases, Weeds and Growth Regulators. New England Floriculture Inc and the New England State Universities. Available from the Northeast Greenhouse Conference  (

Thomas, C. 2005. Greenhouse IPM with an Emphasis on Biocontrol. Publication No. AGRS-96. 89 pp. Pennsylvania Integrated Pest Management Program. Available from: Publications Distribution Center, The Pennsylvania State University, 112 Agricultural Administration Building, University Park, PA 16802-2602 Tel: 814-865-6713, Fax: 814-863-5560 or Available on line at

S. Rice Mahr, R.A. Cloyd, and C. Sadof. 2001. Biological Control of Insects and Other Pests of Greenhouse Crops. North Central Regional Publication 581

Some helpful websites:

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