FACT SHEETS>PEST MANAGEMENT>BUYING AND USING NATURAL ENEMIES IN GREENHOUSE FLORAL CROPS

Natural Enemies for Suppression of Greenhouse Pests

III. Buying and Using Natural Enemies in Greenhouse Floral Crops

Pests and Natural Enemies

Introduction
Growers who choose to use biological control agents for pest control in greenhouse floral crops need to follow a series of steps to succeed. Not all pests are amenable to control with biological control, but for those that are, careful attention to the steps discussed in this article is important.

Diagnosing the Problem
Correct diagnosis of the pest problem is essential. Growers must identify the insect they are trying to control. It is not enough to merely know the broad category of pest. Rather than "whitefly", it is necessary to know that an infestation is silverleaf whitefly or greenhouse whitefly. Rather than "aphid", it is necessary to know if it is green peach aphid, chrysanthemum aphid, or any of 30 or so other aphids commonly found in greenhouses. For help contact an Extension representative or an entomologist at a state land grant university. Fact sheets on particular pest groups should be consulted (if available) and attendance at a training meeting is useful.

Selecting Natural Enemy Species
Once the pest has been identified, catalogues from suppliers of natural enemies must be checked to see if any natural enemies being sold will control the pest. Natural enemies will not be available for all pests. To obtain catalogues from suppliers, start by obtaining the pamphlet by Hunter (1997) entitled Suppliers of Beneficial Organisms in North America. This pamphlet can be obtained free from California Environmental Protection Agency, Department of Pesticide Regulation, Environmental Monitoring and Pest Management Branch, 1020 N Street, Room 161, Sacramento, CA, 95814-5624, (phone 916-324-4100). At the end of this article the names of the natural enemies offered by the various suppliers are given, together with a brief note on what kind of pests each natural enemy attacks and which of the North American suppliers offers a given species for sale.

To be successful, you need to learn more about the particular natural enemies used in greenhouses. This information can be obtained from a variety of sources, written at distinctly different levels of detail. Sources include:

• The Green Methods Manual, The Original Bio-control Primer (Cherim 1998) provides 238 pages of information, with about 1-2 pages on each natural enemy it discusses, including information on the appearance of the natural enemy, its life cycle, benefits, drawbacks, application rates, and use precautions. You can obtain this manual from The Green Spot, Ltd., Publishing Division, 93 Priest Rd., Nottingham, NH, 03290-6204.
• Knowing and Recognizing: the Biology of Glasshouse Pests and Their Natural Enemies by Koppert Biological Systems, Inc., which is available locally through IPM Laboratories, Main St., Locke, New York 13092-0300 (call 315-497-2063).
• Biological Pest Management for Interior Plantscapes (Steiner and Elliott 1983) is available from the Alberta Environmental Centre, Vegreville, Alberta, T0B 4L0, Canada. This pamphlet provides color photographs of pests and natural enemies and information on natural enemy/pesticide compatibility.
• The book Biological Pest Control: the Glasshouse Experience (Hussey and Scopes, 1985), available through book dealers, or Cornell University Press in Ithaca, New York).

Using information from these sources, conversations with extension and University entomologists, and insectary representatives, you can choose the natural enemies you want to purchase.

Choosing a Supplier
To choose a supplier, consider the following:
1. Does the supplier sell what you need?
2. Is the supplier a member of the of the Association of Natural Biocontrol Producers?
3. Have you or other growers you know dealt with the supplier before and been pleased with the service?
4. Does the producer provide information about its products?
5. Do packages arrive quickly (1-3 days), on time and in good condition?
6. Is the supplier a primary producer of the agent, or a distributor?
7. Is the producer a large firm that has been around for some years, or a small start up company?

All of these factors must be weighed, along with cost and satisfaction with the product, in selecting your supplier.

Placing your Order
Most natural enemies must be ordered on an as needed basis and used immediately on receipt. Only a few kinds of natural enemies (Bacillus thuringiensis, nematodes) can be stored for more than a few days. Keep track of what you order, the date of the order, and the date it arrives. You can use this information to evaluate the quality of the service from a particular supplier. You need to find a supplier that can consistently supply quality product, when needed, with fast delivery (1-3 days).

Shipping Methods
Natural enemies must be shipped rapidly to the grower. This may be via parcel post or some kind of fast courier service. Speed will increase quality (more will arrive alive) but will also increase cost of the product. Shipping containers should be durable enough that material is not physically damaged in shipment and the temperature during shipment should be controlled by use of artificial ice packs in the summer. Keep records of the order and receipt dates to compute the average shipping times from your suppliers.

Receipt and Inspection for Quality
Once you have received a package of natural enemies, you need to inspect your purchase to see if you have received what your ordered and that is it alive. To confirm the number of natural enemies received may be difficult, especially for small species or ones mixed with a filler material for easy application, such as mites mixed in bran. For other species, such as aphid parasitoids or lady bird beetles, direct inspection may readily show if the animals are alive and how many there are. It is important that you use a hand lens to inspect what you receive and try to relate what you see to the number that is supposed to be in the package. The whitefly parasitoid Encarsia formosa, for example, is sold as sets of 100 pupae glued in tiny wells on cards. With a hand lens you can directly count the number of pupae present, and later, after 2 weeks have been allowed for emergence, pupae can be examined to determine how many actually emerged as adult wasps. Keep records on the results of these counts and inspections so you will know what level of quality you have received for particular natural enemies from particular suppliers.

Storage
Once you have received a shipment of natural enemies, you must either use them immediately or store them under favorable conditions. There is a range of abilities among natural enemies to tolerate storage. The most durable natural enemy is the bacterium Bacillus thuringiensis, which has storage properties equivalent to most pesticides. It can be stored without refrigeration for months to years. Fungi such as Beauveria bassiana that are formulated for use as insecticides can be stored for a few months if kept refrigerated. Nematodes (various species of Steinernema and Heterorhabditis) can be stored for about 8-10 weeks if keep refrigerated or in a cool room (at about 40-60F, do not freeze). Most parasitoids and predators can only be stored for a few days once they emerge as adults. Keep pupae or adults at about 60F.

Release Methods
Each type of natural enemy will have its own release method. Bacillus thuringiensis, fungi, and nematodes are formulated to be applied as high volume water sprays, using conventional pesticide application equipment. Nematodes must be allowed some time (5-10 minutes) to stand in warm water before application to become active and disperse in the water.

Some kinds of parasitoids (such as Encarsia formosa) are released as pupae glued on cards, which are hung on the foliage of the crop. Others parasitoids (e.g., Eretmocerus eremicus) are released as pupae mixed with sawdust that is sprinkled into the pots. Still others (such as the aphid parasitoids in the genus Aphidius) are released as adults.

Mites are either released mixed with bran, which is sprinkled into pots (as is the case for Hypoaspis miles) or on infested leaves that are placed in the crop canopy (such as Amblyseius spp.).

Most larger predators (Orius bugs, coccinellids, lacewings) are released as active stages (larvae or adults) that are dispersed by hand over the crop canopy. A mechanical applicator has been developed to apply green lacewing eggs.

Evaluation of Results
To tell if released natural enemies are providing control you need to take the following observations:

1. Observe the foliage (or pot surface) to look for the natural enemies themselves. This will confirm their presence at various times after release.

2. Tag plants with aphids, whiteflies, or scales and check the marked leaves weekly to see if the pests are being eaten or parasitized.

3. Count pests weekly on a fixed set of samples (for example, count whitefly nymphs and pupae per leaf on 30 randomly selected leaves) to see what the trend in total pest numbers is. If control is being achieved, the trend in pest numbers should be either be flat or declining, or if rising, doing so only very slowly. If pest thresholds exist for the crop, compare your pest levels to the thresholds.

Calculating the Costs
To compare costs, keep records on the numbers of natural enemies you purchase and release in specific greenhouses. Tabulate total price paid for natural enemies and calculate a pest control price per plant per season for the crop. Compare to costs in chemically treated houses. Compare costs for biological control to the value of the product. Make some allowances for the indirect costs of using pesticides (costs of training workers, keeping records, complying with regulations) in addition to cost of purchasing and applying the materials.

R. G. Van Driesche¹, M.Hoddle², S.Lyon¹, T.Smith³ and P.Lopes⁴
University of Massachusetts, Amherst, MA, 01003

For More Help
For further information contact:
(1) Roy Van Driesche, Dept. of Entomology, Fernald Hall, University of Massachusetts, Amherst, MA, 01003, phone number (413) 545-1061, email vandries@fnr.umass.edu
(2) Tina Smith, UMASS Extension, French Hall, University of Massachusetts, Amherst, MA, 01003, phone number (413) 545-5306, email tsmith@umext.umass.edu, or (3) Paul Lopes, Cranberry Exp. Station, Glen Charlie Rd., E. Wareham, MA 02538-0569, phone number (508) 295- 2212, email lopes@umext.umass.edu.

Acknowledgments
Support for this work was provided by the University of Massachusetts IPM Program and the MA Department of Food and Agriculture, through its Agro-Environmental Technology Grants Program.

Hoddle, M., R. G. Van Driesche, and J. S. Sanderson. 1997. A grower's guide to using biological control for silverleaf whitefly on poinsettias in the northeast United States. Floral Facts. UMASS Extension, University of Massachusetts, Amherst, MA, 01003.

Hunter, C. D. 1997. Suppliers of Beneficial Organisms in North America. CEPA, Sacramento, CA

Hussey, N. W. and N. Scopes. 1985. Biological Pest Control: The Glasshouse Experience. Cornell University Press, Ithaca, New York.

Malais, M. and W. J. Ravensberg. 1992. Knowing and Recognizing: the Biology of Glasshouse Pests and Their Natural Enemies. Koppert Biological Systems, Inc.

Steiner, M. Y. and D. P. Elliott. 1983. Biological Pest Management for Interior Plantscapes. Alberta Environmental Centre, Vegreville, AB, T0B 4L0.

Van Driesche, R. G. and T. S. Bellows, Jr. 1996. Biological Control. Chapman and Hall, New York.

² Current address: Dept. Entomology, University of California, Riverside, CA, 92521

³ Massachusetts Extension, University of Massachusetts, Amherst, MA, 01003

⁴ Massachusetts Extension, University of Massachusetts, Cranberry Exp. Station, E. Wareham, MA, 02538