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Praying mantis on Sunflower

Many field crop and greenhouse vegetable producers inquire about the best use of natural enemies and commercial biological control agents. Biological control agents (BCA) include small parasitic wasps, as well as predators.

Successfully Using BCAs

Lacewing larvae for biological control.

Lacewing larvae for biological control.

Producers should always start by conserving natural enemies and knowing the major species in order to include them in their integrated pest management (IPM) plans. In general, closed farming systems, such as greenhouses and netted high tunnels, see more success with biological control agents compared to open field production systems. The following are additional tips for successfully using BCAs:

Use the Correct Species at the Right Time and Dosage

Producers should choose species that are easy to handle and are effective. This step takes time to learn. Many farmers have their favorite species of predators, which include lacewing and lady beetle larvae. The trick is to release them at the right time, synchronized with the life cycle of the pest and in the right numbers using the best methods. Don’t scatter lacewings that come in bottles like spreading fertilizer. Hang small cups in the foliage and gently pour out the larvae.

Producers should also use an adequate amount of larvae at the right time. Use biocontrol agents ahead of a pest outbreak after full identification. Parasitic wasps can be very specific for aphid and whitefly species. Do not buy them in a rush. Also, purchase them early during the week, not late in the week to avoid beneficial insects dying in shipment.


Extension professionals have purchased and tested natural enemies from many different online vendors including Arbico Organics, Gardens Alive, Kopert, and Rincon-Vitova Insectaries, among others. Growers can purchase many different species of BCAs in certain numbers. These are packaged in bottles (predators) or strips (parasitic wasps). They all seem to provide good products and customer services in case of a problem.

If you have concerns, give the vendor a call and discuss with a technical service representative. Before calling, make sure you know the pest species you are trying to manage and approximate area where you want to implement a biological control plan. Vendors can then stagger the mailing of BCAs on a weekly basis and not ship all at once.

High Tunnel Pest Exclusion Systems

High tunnel pest exclusion (HTPE) systems that use shade cloth have added benefits in terms of integration with natural enemies. For example, the use of a 50 percent shade-cloth based exclusion system can help contain adult lacewings, which are voracious feeders of small insects like aphids, whiteflies, and thrips under high tunnels. When using an insect barrier fabric or row cover, gardeners can also introduce natural enemies under the fabric and close tight to let the natural enemies feed on small insects.

Trap Crops

Trap crops can increase plant biodiversity and reduce pest infestations on the main crop. This can result in an overall reduced need for overhead spray applications. In large IPM research plots and field demonstrations, professionals have experienced an increase in parasitic tachinid flies and predators – such as syrphid flies, lady beetles, and spiders – on trap crops that actively feed on leaffooted bugs and other large pests.

More Information

A true IPM approach integrates various pest prevention, control, and biocontrol tactics into an environmental-friendly solution. Contact Alabama Extension professionals for details about IPM tactics and design a plan that suits your farm. The new Organic Vegetable IPM Slide Chart has many trap crop, pest exclusion, and bioinsecticide use recommendations that can help protect natural enemies. Visit the www.alabamabeginningfarmer.com for various learning materials and videos on IPM.


Trade and brand names used in this publication are given for information purposes only. No guarantee, endorsement, or discrimination among comparable products is intended or implied by the Alabama Cooperative Extension System.

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