Releasing Trichogramma Wasps from Commercial Insectaries

Quick facts
Natural enemy: Various Trichogramma species

Common names: None

Class:, Order:, Family: Insecta, Hymenoptera; Trichogrammatidae

Pest: Trichogrammaattack the eggs of many moth and butterfly species in various crops.

Almost microscopic, stingless wasps that are generally sold as immatures inside moth eggs, often glued to small cards. May also be sold loose for mechanical application.
Biocontrol significance Trichogramma wasps can successfully suppress moth and butterfly pests under appropriate conditions and when appropriate release methodologies are used. Some species are present naturally, but numbers are usually too low to satisfactorily control pests.
Life history Female Trichogramma wasps lay one or more eggs within recently laid host eggs. Immatures develop within the egg, killing it before the caterpillar can hatch. Eggs typically turn black before adult wasps emerge.
for use

When they arrive in the mail:
1. Prepare a series of canning jars (1/2 pint, pint, or quart). Plan on using 1 jar for every 10 square feet (this may vary depending on the crop; consult the supplier for details), with approximately 3,000 wasps per jar. The supplier will specify the number of wasps per card.

2. Place about 5 very small daubs of honey along the inside of the top 1/4 of the jar using the tip of a toothpick. It is important that the honey does not drip because wasps can get stuck in the honey.

3. Place the Trichogramma card(s) into the bottom of the jar.

4. Cover the jar with fine mesh, such as window screening. The holes need to be large enough to allow the wasps to escape but small enough to exclude ants. Place a sheet of paper over the mesh, and screw the band onto the jar.

5. Place the jars indoors out of direct sunlight at room temperature. Check daily for wasp emergence. Look for dark, pin-prick size spots moving along the inside of the jar.

Releasing the wasps:
1. As soon as wasps are visible, put jars amongst the plants in the field. In most annual crops, jars can be placed upright directly on the ground.

2. Tear off the paper covering the top of the jar without removing the band.

3. Create a rain and sun shield by positioning 4 or more stakes around the jar and tape or otherwise affix a styrofoam plate on top of the stakes. We have had good success by placing 3 plastic forks (handle down) firmly into the soil and spearing inverted styrofoam bowls through the tines of the forks. Construct the shelter to be positioned approximately one inch above the top of the jar.

Suggestions for enhancing impacts Avoid making releases under extremely hot, cold, rainy or windy conditions. The wasps can live for approximately 5 days in the jars, so that releases can be delayed until weather conditions improve. Several weekly releases may be more effective than a single larger release.
Sources of natural enemies See Suppliers of Beneficial Organisms in North America
More information and selected references

Andow, D.A. 1997. Integrating biological control in IPM systems. In: Andow, D.A., D.W. Ragsdale and R.F. Nyall (eds.) Ecological Interactions and Biological Control. Westview Press, Boulder, CO.

Andow, D.A. and D.R. Prokrym. 1991. Release density, efficiency and disappearance of Trichogramma nubilale for control of European corn borer. Entomophaga 36: 105-113.

Kanour, W.W., Jr. and P. P. Burbutis. 1984. Trichogramma nubilale (Hymenoptera: Trichogrammatidae) field releases in corn and a hypothetical model for control of European corn borer (Lepidoptera: Pyralidae). Journal of Economic Entomology 77: 103-107.

Knutson, A. 1998. The Trichogramma manual. Texas Agricultural Extension Service, The Texas A&M University System.

Mahr, S. Know your friends, Vol. 1, number 4 (Midwest Biological Control News).

Prokrym, D.R., D.A. Andow, J.A. Ciborowski and D.D. Sreenivasam. 1992. Suppression of Ostrinia nubilalis by Trichogramma nubilale in sweet corn. Entomologia Experimentalis et Applicata 64: 73-85.

Wajnberg, E. and S.A. Hassan (editors) 1994. Biological Control with Egg Parasitoids. CAB International, Wallingford.

Prepared by George E. Heimpel, David A. Andow, and Jonathan G. Lundgren, University of Minnesota; and Susan Mahr, University of Wisconsin. Copyright and reprint information. (Last update October 18, 2000)
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