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Flowers, Sweets and a Nice Place to Stay: Courting Beneficials to Your Nursery

"Farmscaping" or "nurseryscaping" is an approach to crop production with a focus on enhancing the activity of beneficial organisms. This emphasis on biological control, sometimes called bio-intensive pest management, is gaining attention for its potential to reduce pesticide use. It is thought that by providing food and habitat resources for beneficial agents, growers can attract and retain these allies. Encouraging natural enemy activity might reduce the oscillations in pest populations and regulate insects and mites below damage thresholds. The benefits of catering a feast for natural enemies may be many, including reduced pesticide costs, mitigating negative pesticide effects, improving worker safety, and increased plant quality. Complicating successful implementation in ornamental systems is the diverse range of plants, pests, natural enemies, and production systems existing and the limited research available directly from nursery production systems. One strategy to increase utilization of this ecological approach is to encourage more on-farm trials in nurseries and increased information dispersal to and amongst growers.

This article has been developed to provide resources for those considering a more biologically oriented pest management system.

Where to Begin . . .
Attracting and conserving natural enemies requires an understanding of their basic requirements for food, behavior and housing. Many biological control agents need supplies of nectar, pollen, and host prey to sustain and increase their populations. By providing an extended season of floral resources, growers may increase the number and diversity of predators and parasitoids (insect parasites) within their systems. There are studies that show that trend. In a review of 209 intercropping studies in 1991, Andow found that 52% of the 130 natural enemy species studied increased in density in mixed plantings with only 9% having lower densities. Predatory species seemed to benefit from intercropping slightly more than parasitoids. Coll in a review of literature on parasitoids in field crops found parasitoids were more abundant in 72% of intercropping case studies. In 54% of those studies, the parasitism rate was higher in intercrops (Quarles and Grossman, 2002).

Dufour in Farmscaping to Enhance Biological Control (Dufour, 2000) suggests the following considerations in farmscaping design:
1) Examine the ecology of the pests and beneficials.

Determine the most important pests requiring management, important predators and parasites of the pest, and the primary food sources, habitat, and other ecological requirements of both pests and beneficials. Details are useful. How is the pest attracted to the crop? From where does the pest move into the crop? What is its behavior and life cycle? Similar information about the beneficials is important.

It is extremely useful to inventory key pests and beneficials in and around the crop or production system. Correct identification is critical and useful to shape the selection of plant resources. How does one determine which natural enemies attack which pests on which plants and when? There are many varied resources for identification of regional pests and beneficials (Ambrosino, 2005b; Bragg et al, 2004; Dreistadt, 2001; Flint, and Driestadt, 1998; Rosetta, 2001; Rosetta, 2005).

2) System Phenology
When do the pests and beneficials appear? [Noting flowering times on alternate plants can be helpful. These are sometimes called phenological indicators]. What are the economic damage and action levels on the crop? When and how long are food resources (nectar, pollen, alternate hosts or prey) available for beneficials? Where do pests and beneficials overwinter?
Suggestions for planning and evaluating insectary plantings can be found at the website by Ambrosino 2005a.

3) Strategic planning
Growers might consider a reduction in pest habitat (e.g. eliminating overwinter habitat); augmentation of beneficial habitat; or planting of trap crops. They should also consider economic costs (e.g. ground preparation, planting, and maintenance).

Planting systems
There are a variety of approaches to incorporating insectary plants into production systems. Insectary plantings can be added within the crop by interplanting strips or individual plants throughout the nursery. This concept has been utilized in some greenhouse and nursery systems by the use of banker plants which host non-problematic pests. The alternative prey provide for the early establishment and consistent buildup of predators or parasitoids.

Planting strips or hedge rows can be incorporated along the perimeter of the nursery or crop. Many retail and container nurseries already display plants in strips along the edge and entryway to their production sites. The addition of specific insectary plants to these existing plantings may be relatively easy to integrate.

Insectary plantings can also involve the introduction of a cover crop between or throughout rows of plants. Some bareroot and ball and burlap plant production systems already utilize cover crops and this might be expanded. An example of this is the use of buckwheat to act as a sink or trap crop for lygus pests in shade trees and the use of slow growing fescue species between plant rows to suppress weeds and reduce soil erosion and dust.

There are many factors that influence the choice and suitability of an intercropping or planting system. There are several good resources with information; pros and cons; and examples of these planting systems (Ambrosino 2005a; Dufour, 2000; Earnshaw, 2004; Quarles and Grossman, 2002).

Specific plants
It is suggested that growers provide an extended season of floral resources. This can be accomplished by selecting plants that flower from the early season through the late season. Cranshaw (1996) reported good attraction of beneficials to the parsley family, Apiaceae; mustard family, Cruciferae (such as the early flowering basket-of-gold, Aurinia saxatilis), the mint family, Lamiaceae; and some members of Compositae (such as Achillea). Many local growers have a good idea of plants in flower at various times of the season in this region.

In addition to flowering time, one must consider the floral structure of the plant. The design of the nectary, recessed and hidden, or shallow and easily available also influences the beneficial fauna that utilize the flower for nectar and pollen. Readily accessible pollen and nectaries such as found in umbels of plants in the Apiaceae family or sunflowers or plants with extrafloral nectaries such as vetch are very attractive to many tiny parasitic wasps and predatory flies.

Some plants act as a sink or source of pest species of concern as well as natural enemies. Shade trees nurseries are familiar with the migration of thrips and lygus from nearby grass fields as they dry down or are harvested. Grasses might favor predatory beetles but might also allow food and cover for voles. One can also utilize a preferred host as a trap crop such as the example of buckwheat for lygus.

The dispersal of the natural enemies away from the insectary plantings into the crop is desirable but specific insect and mite immigration information can be difficult to obtain. Chaney found that effects from sweet alyssum flowers were noted 30 - 40 ft (9 - 12.2 m) away from the plantings near lettuce fields. Sweet alyssum has a good reputation for attracting beneficials with a ratio of 204 beneficials per pest, nor does it attract lygus bugs or aphids (Quarles and Grossman, 2002). Research in several planting systems in California indicated the rubidium (Rb) marked insects which fed in borders around farms, including lady beetles, lacewings, syrphid flies, and parasitic wasps, moved 250 feet into adjacent crops (Long, 1998).

Conservation of habitat
How would you feel if your home was constantly plowed under every three weeks? A stable habitat is beneficial for some natural enemies such as ground beetles and many spiders. An example of this is shown in the impact of strip harvesting versus clear-cutting entire fields of alfalfa. Quantitative differences between the two harvesting methods show dramatic differences in the numbers of spiders per acre (1 million vs 105,000); 287,000 parasitic wasps versus 70,000; 205,000 lady beetle adults versus 46,000 and a roughly equivalent impact on their larvae, 232,000 versus 11,000 (Quarles and Grossman, 2002). Beetle banks and uncultivated areas are two strategies designed to create a more favorable habitat for these types of allies.

Farmscaping or nurseryscaping involves the study of a dynamic and complex system, made particularly difficult given the diversity in much of greenhouse and nursery production. This presents challenges requiring additional knowledge or management skills for growers. A systematic, research-oriented approach in planning habitat enhancement will improve the chances of a desirable outcome and reduce potential mistakes. Such efforts, implemented with a spirit of experimentation, determination, and a good sense of humor, will likely benefit the grower in a better understanding of the ecology of pest management, no matter what the outcome of the experiment. Hopefully, the following resources will encourage growers to explore the option of insectary plants.

Written Resources:
Cranshaw, W. 1996. Home-grown Pest Control. American Nurseryman September 15, 1996.

Gurr G. M. and Wratten, S. D. (eds). (2000). Biological Control:Measures of Success. Kluwer: Dordrecht. 448 pp. (ISBN 0-412-84280-7)

Gurr G. M., Wratten, S. D. and Altieri M. A. (eds). (2004) Ecological Engineering: Advances in Habitat Manipulation for Arthropods . CSIRO Publishing, Melbourne (Australasian publisher)/ CABI International, Wallingford (European Publisher)/ Cornell University Press, Ithaca ( Americas publisher). 244 pp. ( ISBN 0643090223)

King, S. and W. Olkowski. 1991. Farmscaping and IPM. The IPM Practitioner 13(10):1-12.

Picket, C. and Bugg, R.L. eds. 1998. Enhancing Biological Control: Habitat Enhance to Promote Natural Enemies of Agricultural Pests. University of California Press. Berkeley, CA.

Quarles, W. and J. Grossman. 2002. Insectary Plants, Intercropping and Biological Control. The IPM Practitioner 24(3):1-11.



Ambrosino, M. A. Practical Guidelines for establishing, maintaining and assessing the usefulness of insectary plantings on your farm. IPPC, Oregon State University.

Dufour, R. 2000. Farmscaping to enhance biological control. ATTRA, Fayetteville, AK. [Note: download fee].

Dufour, R. 2001. Biointensive Integrated Pest Management (IPM). ATTRA, Fayetteville, AK. [downloadable PDF].

Earnshaw, S. 2004. Hedgerows for California Agriculture: A Resource Guide. Community Alliance with Family Farmers (CAFF), Davis, CA

Edwards, Clive. ed. 2007. Enhancing Arable Biodiversity: Six practical solutions for farmers. SAFFIE. HGCA. London.

Holland, J. and Ellis, S. 2008. Beneficials on farmland: Identification and management guidelines.HGCA. London.

Jepson, P. and M. Vaughn. 2007. Farming for Pest Management. Xerces Society and IPPC.

Long, R.F., A. Corbett, C. Lamb, C. Reberg-Horton, J. Chandler, M. Stimmann. 1998. Beneficial insects move from flowering plants to nearby crops. California Agriculture, September-October. P. 23-26.

Morandin, L. et al. 2011. Hedgerows enhance beneficial insects on farms in California's Central Valley. California Agriculture 65(4):197-201.

Pendergrass, K. et al. 2008. Plants for Pollinators in Oregon. USDA-NRCS. Plant Materials no. 13.

Powell, W. et al. 2004. Managing biodiversity in field margins to enhance integrated pest control in arable crops (3-D Farming Project). Can download each separate section (Parts 1-6). HGCA. London.

Rosetta, R. 2001. Selected Bibliography: IPM for Ornamental Plants. Department of Horticulture Oregon State University.

Scott, A. 2004. Beneficial Insects Resource Guide.



Colley, M.R. and J.M. Luna. 2000. Relative Attractiveness of Potential Beneficial Insectary Plants to Aphidophagous Hoverflies (Diptera: Syrphidae). Environmental Entomology 29(5):1054-1059.

Greer, L. 2000. Greenhouse Management: Sustainable Aphid Control. ATTRA, Fayetteville, AK.[Downloadable PDF].


Fungus Gnat Management

UC IPM Online. 2001. Fungus Gnats, Shore Flies, Moth Flies, and March Flies.

Scale insects

Benefits of insectary plants. Various insectary plants evaluated for impact on armored scale insects (Pine needle scale - Chionaspis pinifoliae and Euonymous scale - Enaspis euonymi) on Scotch pine (Pinus sylvestris) and wintergreens (Euonymous fortunei ‘Colorata’)

Spider Mite Management

P. D. Pratt, R. Rosetta, B. A. Croft . 2002. Plant-Related Factors Influence the Effectiveness of Neoseiulus fallacis (Acari: Phytoseiidae), a Biological Control Agent of Spider Mites on Landscape Ornamental Plants. Journal of Economic Entomology 95(6):1135-1141.

Rosetta, R. 2010. When Mites Make Right. Digger July 2010 pp. 41-46.

Thrips Management
Van Driesche, Roy. 1998. Western Flower Thrips in Greenhouses: A Review of its Biological Control and Other Methods.

Greer. L and S. Diver. 2009. Greenhouse IPM: Sustainable Thrips Control. [Downloadable PDF].

Whitefly Management

Greer, L. 2000. Greenhouse Management: Sustainable Whitefly Control. ATTRA, Fayetteville, AK.[Downloadable PDF].

Additional Biological Control Resources:
Written Resources:
Dreistadt, S.H. 2004. Integrated Pest Management for Floriculture and Nurseries. Publication #3405, ANR Publications, University of California, 6701 San Pablo Avenue, Oakland, CA 94608-1239. 422 pp.

Flint, M.L. and S. H. Driestadt. 1998. Natural Enemies Handbook: The Illustrated Guide to Biological Pest Control. # 3386. ANR Publications, University of California, 6701 San Pablo Avenue, Oakland, CA 94608-1239. 154 pp.

Additional Biological Control Websites:

Ambrosino, M. A Pocket Guide to Common Natural Enemies of Crop and Garden Pests in the Pacific Northwest. IPPC, Oregon State University. This PDF has lots of color images of natural enemies and a nice little section with each family of commonly confused and similar insects.

Applied Bionomics. 2010. IPM and Biological Control for Ornamental Nursery Pests.

Association of Natural Biocontrol Producers

Biological Control Virtual Information Center. North Carolina State University. This site has a very good overall explanation of biological control. It also has specific recommendations for augmentation in greenhouses and interiorscapes.

Hollingsworth. 2012. PNW Insect Management Handbook. Oregon State University, University of Idaho and Washington State University.

Mahr, D., Whitaker, P., and N. Ridgway. 2008. Biological Control of Insects and Mites: An Introduction to Beneficial Natural Enemies and Their Use in Pest Management.

Mahr, S. et al. 2001. Biological Control of Insects and Other Pests in Greenhouse Crops.

Rosetta, R. 2001. Selected Bibliography: IPM for Ornamental Plants. Department of Horticulture, Oregon State University.

Shrewsbury, P. M. Patt, J. M. 2003. Flowering Plants to Enhance Biological Control of insect pests in Nurseries.

Suppliers of Beneficial Organisms in North America. A great resource from the California Department of Pesticide Regulation. Both a PDF and html version available.

Weeden et al. June 12, 2005. Biological Control: A Guide to Natural Enemies in North America. Cornell's site with nice coverage of the basics of biological control.


Website editor:
Robin Rosetta
Page last modified 11/15/12

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