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Predatory Insects Used for Greenhouse Biological Control

By Kendra Knutson
UWRF University Communications

DEC. 7. 2006--Beware mealybugs, spider mites and thrips! A University of Wisconsin-River Falls senior has introduced predatory insects for biological control into the foliage house at the campus greenhouse complex.

Nicholas Kuehl, a horticulture landscape design major from Kewaunee, Wis., developed his independent study project with the help of UWRF horticulture Professor Terry Ferriss. She thought it would be an excellent project to provide hands-on experimental learning while being "reflective of sustainable approaches," said Ferriss.

Kuehl will investigate the effects of using beneficial insects to control unwanted pests instead of control with chemical sprays. The UWRF foliage greenhouse is home to several different plant species including tropical, desert, and plant cultivars.

Insects have been a problem for years. In the past, the solution was to spray insecticides; however, this can have a negative effect on the environment and may reduce the overall plant quality. So Kuehl, designed a plan to battle the pests by releasing three kinds of commercially available predatory insects: Cryptobugs (a predatory beetle), Spidex (predatory mites), and Thripex (another species of predatory mites).

Cryptobugs, which target the mealybug species, are placed on the infected leaves in the evening at a temperature above 61 degrees Fahrenheit and take action by eating their prey completely. A bottle of Cryptobugs costs $15.70 for a 100ml bottle containing 25 adults. The activity of the Cryptobugs is indicated by the presence of empty egg pouches.  

Spidex can only survive by eating the two-spotted spider mite. In order to introduce Spidex, the bottle must be shaken before opening, and then sprinkled onto the leaves of infected plants. Temperatures should be at 68 degrees Fahrenheit for atleast a couple hours.   Adult predatory mites and nymphs search actively for their prey and suck out their body contents. The spider mites that have been eaten can be identified as tiny black dots on the leaves. A single bottle of Spidex containing 2000 adults mixed with wood chips costs $16.79.

Thripex targets various thrip species but they may also eat spider mites. In the introduction stage the container is shaken gently and sprinkled onto infected leaves much like Spidex. Temperatures must remain above 68 degrees Fahrenheit for some hours of the day.   Thripex also searches for its prey and sucks them dry. A 1000ml bott le contains: 10,000, 25,000 or 50,000 predatory mites (all stages) + some grain mites (all stages) mixed with bran and costs $11.78.

Kuehl said once a week the beneficial insects will be added into the greenhouse for the four week introduction period. During this time, observations and spot checks will be made. Some predators may die or escape through the vents and more will have to be added.

The goal is to try to keep an adequate number of predator insects in the greenhouse at all times in order to control the population of the plant-eating insects. Kuehl will make observations for the rest of this semester and then greenhouse manager Dan Waletzko or another student will have to take over his project as Kuehl will be graduating in December. He is currently seeking a career in interior landscape design, targeting companies in Minneapolis. His ultimate goal is to run his own business.

For more information about predatory insects log on to .  


Last updated: Thursday, 22-Apr-2010 16:07:51 Central Daylight Time


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