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Good Bug Corner (05/21/15)

This week’s featured group is beneficial wasps (also called parasitoids) that attack and kill eggs and immature stages of many insect pests. Parasitoids are described as tiny wasps in the insect order Hymenoptera and include many different families (Braconidae and Ichneumonidae, for example).

Good Bug Corner

This week’s featured group is beneficial waspsent.jk.6.mp (also called parasitoids) that attack and kill eggs and immature stages of many insect pests. Parasitoids are described as tiny wasps in the insect order Hymenoptera and include many different families (Braconidae and Ichneumonidae, for example). A good example of a successful parasitoid in North Dakota is Macroglenes penetrans that parasitized the eggs and larvae of wheat midge. As part of the annual wheat midge soil survey, we also assess the parasitism rate on wheat midge. The parasitism rate for 2014 ranged from 0 to 100 percent in some fields with an average of 11 percent parasitism. Although the parasitic wasp - wheat midge populations are cyclic, M. penetrans plays an important role in keeping wheat midge controlled naturally. We need to continue to conserve parasitic wasp populations when possible by spraying insecticides only when pest populations are at economic threshold levels, and avoiding any late insecticide applications to minimize the negative impacts on the parasitic wasps that are active at that time.

Many parasitoids are available commercially for release into fields or gardens, and can be obtained from distributors of beneficial insects. A good example of a parasitoid that has been commercially reared and released in sweet/field corn fields for biocontrol of European corn borer is Trichogramma species. This tiny wasp is only 1 mm long! It has been used for biological control of many leaf-feeding caterpillars including armyworms, squash borers, cankerworms, alfalfa caterpillars, cutworms, cabbage loopers, and other pests.

Thanks to the North Dakota Wheat Commission for supporting the wheat midge soil survey.

Janet J. Knodel

Extension Entomologist

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