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Integrated Pest Management Program

Department of Plant Science and Landscape Architecture, Department of Extension

Fact Sheets > Greenhouse > Insect and Mite Pests,Fact Sheets > Greenhouse > Biological Controls

Biological Controls for Greenhouse Pests

Introduction

Biological control is the using of living organisms (natural enemies) such as insects, mites, fungi or bacteria to control pests and diseases.  Natural enemies are living organisms that need to be released when pest populations are low.  They do not act as quickly as pesticides, so cannot be used as a rescue treatment. Natural enemies are best used preventatively, early in the cropping cycle, when plants are small, pest numbers are low and pest damage has not yet occurred. This is a completely different mindset compared to the traditional pest control that growers generally do – waiting until they see damage and then treating with insecticides or miticides.

 Biological control programs have a long history of use and extensive research base for greenhouse vegetable crops. Greenhouse vegetable crops are generally longer term crops, have a higher threshold for pest damage (only the fruit needs to be blemish free and not the foliage), and are often grown in monocultures. The laws controlling the use of pesticides are also stricter for food crops than for ornamentals. The use of bumble bees for pollination makes it very difficult to use pesticides when growing greenhouse vegetables.  Many Connecticut growers produce a diverse mix of spring crops, so there is less of a research base. Growers often need to experiment to see what works best in their individual situation.

Some of the advantages of using biological control agents include:

  • less worker exposure to toxic pesticide residues,
  • less chance of spray damage,
  • improved plant quality,
  • no re-entry intervals (REI) to follow
  • minimum equipment needed for application
  • part of “green” marketing    
  • preserving the effective life of pesticides used by the greenhouse industry by removing the selection pressure for development of resistance

However, biological control programs use living organisms – so extra effort is needed to make these programs work.  Commitment, patience (natural enemies don’t work as quickly as pesticides), and a desire to learn about the life history and environmental requirements of pest and its natural enemy are all needed. It’s also often best to start in an isolated, small area or greenhouse first. Starting in propagation houses or stock plant production, or houses with edible crops may be a logical first step.  As you gain experience, biological control programs can be expanded.

Types of Natural Enemies

Different types of natural enemies may include parasitic wasps or flies, predators, pathogens and entomopathogenic i.e. (insect-killing) nematodes.

Parasitic wasps lay eggs inside the host, and kill the host as the newly hatched larvae begin to feed. They are are very host specific compared to more generalist predators. Parasitic wasps require one host to complete their development as they kill the host in this process. Correct species identification of the host prey is needed to determine the specific parasitic wasp needed. Different species of parasitic wasps are available for use against aphids, whiteflies, leafminers, scale insects and mealybugs.  These parasitic wasps do not have a stinger so are not harmful to humans. They are also very small, so will not be noticed by your customers. 

Predators feed on pests but reproduce independent of the pests. They may deposit eggs or larvae on plant leaves. Predators tend to be more generalist feeders and are less host specific than parasitic wasps. For example, different species of predatory mites feed upon pest mites and thrips.

Entomopathogenic (insect killing) nematodes are microscopic roundworms that enter the insect's body through openings in the exoskeleton. The nematodes multiply inside the host insect and release a bacterium that is toxic to the host.  Nematodes complete their life cycle within a few days. Large numbers of infective nematodes are produced that will search for new hosts. Steinernema feltaie is commercially available for use against fungus gnat larvae and thrips pupae in the growing media.

Pathogens such as insect-killing fungi (Beauveria bassiana) and Paecilomyces fumosoroseus or bacteria (Bacillus) can be sprayed on the foliage. Beauveria and Paecilomyces are used against whiteflies, aphids, and thrips. These fungi use enzymes to dissolve the insect’s cuticle and then use the insect as a food source. 

Bacillus is a microbial product that acts as a stomach poison. Once inside the pest’s digestive system, a protein toxin attacks the gut, so the targeted pest stops feeding and dies.  Different strains are available for different pests including caterpillars and fungus gnat larvae.

 

Steps to Getting Started in Biological Control

1) Gather resources – educate yourself

It takes time and commitment to learn the biology and life cycles of the insect and mite pests and their natural enemies.  Become familiar with the specific environmental requirements needed by the different natural enemies. If your greenhouse environment doesn’t provide the appropriate temperatures and humidity levels, it may be difficult for the natural enemies to survive. For example, Encarsia formosa (a parasitic wasp used against greenhouse whiteflies), adults rarely fly at temperatures below 64°F. At temperatures above 86°F, their adult life span is shortened. If you are dealing with warmer summer temperatures, the parasitic wasp Eretmocerus may be a better choice.  The mealybug destroyer (Cryptolamus montrouzieri) prefers warmer temperatures – between 72 to 77°F. Is this compatible with the temperature requirements of the crops being grown?  The predatory mite, Phytoseiulus persmilis, does best at a humidity range above 60% RH. (Predatory mite eggs do not survive as well at lower humidity levels).

Put together a list of resources plus personal contacts (biological control suppliers, other growers, extension educators etc.) that can help you. See reference list at the end of the fact sheet for some additional articles, web sites and reference books to help you get started.

2) Review past pest problems

                  Review your past pest problems. Know the species of pest you are dealing with. This is especially important if you are considering releasing host specific parasitic wasps for aphids, whiteflies, scales or mealybugs.  For example, if you have foxglove aphid, but mistakenly think you have green peach aphid, if you release the parasitic wasp recommended against the smaller, green peach aphid, the releases will not be effective.  If you are unsure of the aphid species, purchase a mix of different species, to work against both the foxglove and green peach aphids.

3) Review pesticide use

Many insecticide residues, such as pyrethrins or organophosphates can adversely affect natural enemies 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. 

Direct contact and pesticide residues on containers, benches, greenhouse plastic etc. may be directly toxic to natural enemies or effect how well they survive and reproduce. Some of the newer, more selective insecticides and miticides (including some insect growth regulators) are compatible with certain but not necessarily all, natural enemies. For more information on pesticide compatibility with natural enemies, consult with your supplier, or refer to the following Internet resources.

4)  Have a Regular Scouting Program in Place

  Before beginning biological control, you need to have a regular, consistent scouting program established. This helps you anticipate when the various pest populations are of concern, so you can plan ahead and release the natural enemies in sufficient time. You will also know where potential hot spots of pest activity are, and can evaluate the effectiveness of the natural enemies (just like you evaluate the effectiveness of any method of control). Good recordkeeping is essential.

However, yellow sticky cards will attract many parasitic wasps, so you may either want to reduce the number of sticky cards used or the length of time they are in use.  If releasing parasitic wasps, such as Eretmocerus for sweet potato whiteflies, look for parasitism and host feeding on poinsettia indicator plants. If you are releasing parasitic wasps against aphids, the parasitized aphids or aphid mummies are easily seen. Spider mites fed upon by predatory mites will be dried up and shriveled .

5) Transition into biological controls

Start in a small isolated area or separate greenhouse to have a trial area to learn how to use natural enemies. Decide what crops make the most sense for you to trial. If you grow longer term crops, such as poinsettias, that may be a logical starting point. University of Massachusetts research Biological Control: A Growers Guide to using Biological Control for Silverleaf Whitefly in Poinsettias in the Northeast United States (http://extension.umass.edu/floriculture/fact-sheets/growers-guide-using-biological-control-silverleaf-whitefly-poinsettias-northeast-united-) and grower experience on biological control for poinsettias is available to provide you with the necessary background information. It is also a less hectic time of year to learn a new way of managing pests than in the spring. Working with monoculture crops (like poinsettias) is also less complex than the multiple crops and their associated pests in spring bedding plant production.

If you are propagating, you will want to begin in that growing area. Release natural enemies in your stock plant production or begin as soon as you receive cuttings.

However, because of the “zero tolerance” approach with pests in the ornamental industry, cuttings may have been treated with long residual pesticides that are not compatible with the release of biological control agents. These long residual pesticides can adversely affect the establishment and success of your biological control program. In addition, you may receive pests that are highly resistant to a number of pesticides (i.e the Q-biotype of the sweet potato whitefly).  Consult with your supplier to determine what pesticide residues are on the cuttings. Using pesticides compatible with biological control agents or products with shorter residuals helps insure the success of your biological control program.

 If you are growing edible crops such as herbs or vegetables that may be a logical starting point. If there are areas where it is difficult for you to spray (due to re-entry requirements) such as retail houses that may be a logical area to begin your trials. As your experience and comfort level expands, you can expand your use of biological control agents. 

6) Integrate cultural controls

Start clean and stay clean. Remove pet plants and weeds. Pressure wash the greenhouse with a disinfectant. If feasible, use fallow periods to reduce pest pressure.

 Biological control is more likely to be successful if it is integrated with the proper cultural controls to discourage insects and diseases and to grow healthy crops. If you are over fertilizing your crops, the tender lush growth is prone to aphids, whiteflies and other sucking insect pests. It is harder for natural enemies to be successful under those conditions.  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.  

7) 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.  Careful planning is needed before starting a biological control program.  Many insecticide residues, such as pyrethrins or organophosphates can adversely affect natural enemies 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. 

Direct contact and pesticide residues on containers, benches, greenhouse plastic etc. may be directly toxic to natural enemies or effect how well they survive and reproduce.  Pesticide residues on incoming plants or cuttings will also adversely affect the natural enemies.

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

8) Establish a Good Releationshiop with your supplier 

 Establishing a good relationship with your supplier is critical. They want you to succeed, so should be able to supply you with technical information and advice to set up a biological control program that is specific to your operation.

    • Insure quality of natural enemies

Because natural enemies are living organisms, they require special handling when they are reared, delivered and released in your greenhouses.

    • Fast Shipment  

Be sure that the natural enemies are received quickly (2 to 4 days) and kept cool during shipment. The supplier can ship the natural enemies in a polystyrene box with freeze packs added to keep them cool. When they are received, check to see how warm or cool the freeze packs are. If the biological control agents are not received in a timely matter, they can die, desiccate, and starve. Or they may simply become stressed and age faster so the biological control agents does not perform as well as expected.  Be sure that the shipment will arrive when a responsible party is there to receive it and that it is handled as recommended by the supplier. 

    • Product Quality

Check the natural enemies to see if they are alive before you release them. The natural enemies need to be alive to work. For example, you can place a small sample of adult predatory mites on a white sheet of paper and check to see that the tan colored mites are alive. When using whitefly parasites (Encarsia), you can place the cards inside a small glass jar, and keep it in a shaded, unsprayed area for a few days (2 or 3) to look for the emerging adults.   Some growers use the quality control guidelines developed by the International Organization for Biological Control (IOBC).  See this website for link to a pdf file containing guidelines for 18 different natural enemies.

http://users.ugent.be/~padclerc/AMRQC/guidelines.htm

    • Proper Storage

Consult with your supplier for maximum storage times. In general, many natural enemies should be released immediately upon arrival.  Release in the early morning or early evening.

10) Release Rates and Timing

                  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?

11) Make use of compatible pesticides, if necessary.

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 enemies 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 enemies so check the Pesticide Side Effects Databases on the Internet and talk to your supplier. Some natural enemies 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.

12) Patience and commitment is needed. 

You need to be able to tolerate some pests in order for the natural enemies to work. A proactive approach is needed for natural enemies don’t work as quickly as pesticides. However, pests do not develop resistance to the natural enemies, 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 Enemies 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. http://www.nysipm.cornell.edu/  Available online at:  http://www.nysipm.cornell.edu/nursery_ghouse/biocontrol_wkbk_10-31-13.pdf

Malais, M. and W. J. Ravensberg. 2003 The Biology of Glasshouse Pests and Their Natural Enemies- 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.  http://tiny.cc/greenhousepestguide.

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  (www.negreenhouse.org).

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 http://extension.psu.edu/ipm/resources/pestproblemsolver/greenhouse/greenhouseipm/view

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

http://learningstore.uwex.edu/Biological-Control-of-Insects-and-Other-Pests-of-Greenhouse-Crops-P386.aspx

Some helpful websites:

 

References:

Casey, C. 2005. A Biological Approach. Greenhouse Product News. 15(2): 4 pp.

Cloyd, R. 2006. Biological Control: “Quality Makes All the Difference”. OFA Bulletin. March/ April 2006. 895:25-26.

Cloyd, R. 2005. Insect Growth Regulators: Are they Compatible with Biological Control Agents? OFA Bulletin. January/February 2005. 888: 26-28.

Cloyd, R. 2005. Biorational Pest Control Materials and Natural Enemies: Are They Compatible? OFA Bulletin. May/June 2005. 890: 12-15.

Cloyd, R. 1999. Making Friends with Enemies. Greenhouse Grower. July 1999. 140-144.

Heinz, K. M., R.G. Van Driesche and M.P. Parella. 2004. BioControl in Protected Culture. Ball Publishing.  522 pp.

Hoddle, M. S., R.G. Van Driesche, and J. P. Sanderson. 2002. A Growers Guide for Using Biological Control for Silverleaf Whitefly on Poinsettias in the NE United States. Available on line at http://www.umass.edu/umext/floriculture/

Murphy, G. 2002. Biological and integrated control in ornamentals in North America: successes and challenges. IOBC/Wprs Bulletin 25(1): 197-200.

Orr, D. B. and J. R. Baker. 1997. Biocontrol in Greenhouses. NC Flower Growers Bulletin 42(4) 5-14.

Steward, V. B., J.L. Kintz and T. A Horner. 1996. Evaluation of Biological Control Agent Shipments from Three United States Suppliers. HortTechnology. 6(3): 233-237.

Valentin, R. 2011. Getting off to a clean start. GREENHOUSE Canada. April 2011. 22-32.

Wawrzynski, R. P. and M. E. Ascerno. 1996. Understanding Biological Control in Greenhouses. University of Minnesota Extension Service Fact Sheet. FO-06682

 

Pundt, L. November 2007. Updated  8/2011, 2014