Biological Control: Purchasing Natural Enemies
David Orr and James Baker
Department of Entomology, North Carolina State University
What Is Biological Pest Control?
Biological control can be broadly defined as any activity involving the manipulation of natural enemies such as predators, parasitoids, or pathogens to reduce or suppress pest populations. This covers a great range of activities from simple conservation of natural enemies by careful selection of a pesticide that is least toxic to them to the deliberate release or introduction of natural enemies to augment natural populations and act as a living insecticide.
Some Advantages of Biological Pest Control
Incorporation of biological control into an integrated pest management (IPM) program reduces the legal, environmental, and safety challenges posed by insecticides, and in some cases also reduces costs of pest management.
As an alternative to reducing pest populations with insecticides, biological control methods can be used in agricultural settings to prevent pest populations from reaching damaging levels.
When used properly, a number of commercial biological control products can be very effective in agricultural settings. Unlike broad-spectrum insecticides, which kill a wide range of insects and other animals, natural enemies usually have very specific preferences for certain types of insects. They may do no harm at all to other beneficial insects and are less harm to the environment.
Some Disadvantages of Biological Pest Control
Biological control takes more intensive management and planning. It can take more time, require more record keeping, more patience, and sometimes more education or training. Successful use of biological control requires a greater understanding of the biology of both the pest and its enemies. Many natural enemies are very susceptible to pesticides, and using them successfully in an IPM program takes great care. In some cases, biological control may be more costly than pesticides. Often, the results of using biological control are not as dramatic or quick as the results of pesticide use. Most natural enemies attack only specific types of insects - unlike broad-spectrum insecticides, which may kill a wide range of insects.
Develop a Plan
Before attempting to use natural enemies in a pest management program, you should have a very good understanding of the pest complex you are dealing with, and of your overall crop management system. This should include a positive identification of the pests. Because so many management decisions must be made when using natural enemies, the chances for failure are greater when they are used incorrectly. Careful planning is critical to ensure that the product selected for use is correct for your specific situation and specific pest, that the quality is adequate, and that the timing and rate of application are correct. Help in these areas can be obtained through the North Carolina State University Cooperative Extension Service.
Purchase With Care
"Buyer beware" is a good concept to remember in making any purchase. Buying biological control agents is no exception. There are dozens of suppliers in the marketplace. Some may want to sell you products that you do not want or need. Some may not be able to provide the technical help that successful use of biological control requires. Just as you would not buy insecticides from someone who just mixes chemicals in the back yard as a hobby, you should expect professional standards from suppliers of biological control. A thorough scientific analysis should be required for any product you are trusting to protect your crop.
Names, addresses, and telephone numbers of suppliers can be obtained from the sources listed at the end of this publication. When selecting a supplier, asking the kinds of questions listed here may help you to find the best supplier for your needs.
1 -
Does the company provide you with professional consulting services to set up an IPM program prior to selling you natural enemies? This should include a thorough determination of your pest situation and current crop management practices.
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Does the company provide you with detailed instructions on how to handle and apply natural enemies prior to their arrival?
3 -
Does the product arrive by overnight delivery in an insulated container that may contain a coldpack? This will protect natural enemies from temperature extremes, and prevent some natural enemies from emerging prior to arrival.
4 - Does the company provide any measure of the quality of the natural enemies you received? For example:
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Does the company tell you exactly what species you will receive and who made the species determination? This determination should have been made by a recognized taxonomic expert, not neccessarily someone at the company. The species name should be a double Latin name, for example: Encarsia formosa. If the name appeared as Encarsia sp. you would not know what species you had, and both you and the supplier would be unsure of whether the product would work for your specific pest problem.
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How many did you receive? This should be presented as an average plus or minus a range. Be aware that with some natural enemies only the female actually attacks the target pest. You should find out if this is the case for control agents you are purchasing and, if appropriate, expect to see the number of females shipped to you.
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How vigorous is the material sent to you? For the batch of natural enemies from which your shipment came, it is fair to ask for measures of the average fecundity (reproductive capacity), lifespan, and sex ratio (% females). In some cases it may be important to have specific information such as the percentage of natural enemies with wings (as in the case of some parasitic wasps such as Trichogramma, which can lose the ability to fly in insectary cultures), or the percentage that are parasitized (some ladybeetles are simply scooped from overwintering sites, and a substantial portion may be parasitized and die before they do any good in the field). In order to know whether these numbers are adequate, standard values taken from an independent article in a scientific journal should also be provided so that you can make comparisons.
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How many natural enemies actually emerged alive in your crop? The supplier should provide you with some method for determining how many natural enemies actually emerged in your crop. This can be very important since it is the only way you can determine the actual rate of product that you applied to your crop.
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Does the company offer reasonable solutions for any difficulties you may encounter? Does it follow up to determine the success or failure of your program?
Evaluate Your Biological Control Program
To determine how successful your biological control program is you should develop a strict set of conditions in the planning stage before the program actually starts. The success of your program will be easier to determine if:
1 - You have at least one pair of "treated" versus "untreated" plot areas. Use natural enemies only in the "treated" plot(s). The untreated plot(s) may be handled in the usual way with an existing pesticide program, but should not receive natural enemies. The treated and untreated plots should be far enough apart to avoid the drift of pesticide into the treated plot(s) and dispersion of natural enemies from the treated to untreated plot(s). Your supplier can help you with this information.
2 - Define what measurements to take in the plot areas. Some examples of the type of information that would be helpful are as follows:
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the rate of natural enemies that actually went into your plot(s) (see "Purchase With Care," condition 4)
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the percentage of the target pest population that is parasitized (if applicable)
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the density (determined as number per plant or feet of row) of the damaging stage of the pest before as well as after treatment (Remember that natural enemies usually require more time than pesticides to have an effect on populations)
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the level of pest damage
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yield.
Information About Suppliers of Natural Enemies
There are many companies that sell natural enemies, and several reference sources that provide general information about both the companies and natural enemies. Two reference sources are listed below:
Directory of Producers of Natural Enemies of Common Pests. Bio-Integral Resource Center, P.O. Box 7414, Berkeley, CA 94707. Annual. Cost: approximately $10.00
Biological Control Virtual Information Center
Members of the Association of Natural Bio-control Producers