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Eriborus terebrans
(Hymenoptera: Ichneumonidae)

The ichneumonid wasp, Eriborus terebrans, was introduced into the United States as part of a classical biological control project to control the European corn borer. Approximately 140,000 wasps collected from both Asia and Europe were released from 1927 through 1940 in 13 states from Vermont to Virginia and as far west as Indiana and Michigan.

E. terebrans is one of 6 of these introduced species to become established and is one of 3 considered to be important in controlling European corn borer. (Macrocentrus grandii, a braconid wasp, and Lydella thompsoni, a tachinid fly, are the others.) It is currently the most frequently recovered parasitoid of European corn borer in the north central region of the United States.

Appearance

A medium-sized wasp, female E. terebrans are approximately 6-10 mm in body length. Males are slightly smaller. Females have a curving ovipositor (about 3 mm) protruding beyond the abdomen, and both sexes have long antennae (5-7 mm) and are black with reddish-brown legs. The smooth abdomen is slightly more shiny than the head and thorax.

Habitat

Corn fields and surrounding habitats.

Pests Attacked

Ostriana nubilalis, the European corn borer.

Life Cycle

E. terebrans overwinters as a larva inside overwintering corn borers and emergence occurs from 22 to 37 days after resumption of development in the spring. First generation emergence of wasps is in synchrony with the first larval generation of European corn borers. Females mate soon (sometimes within an hour) after emergence and can lay eggs within one day. They prefer to lay their eggs in 2nd-4th stage corn borers.

Adult wasps may live 7-10 days under ideal conditions (75-80°F, and with access to water and sugar). However, lifespan is greatly reduced and is only 3-4 days when temperatures are above 90°F and there are no sugar sources such as flower nectar or aphid honeydew available.

Females are highly attracted to chemicals in corn borer frass and webbing, and to corn borer cuticle, larvae, oral secretions, and feces. When exposed to corn borers, they exhibit ovipositing behavior. E. terebrans is also attracted to corn plants, the host of the European corn borer.

Relative Effectiveness

One of the most widely distributed parasitoids of the corn borer North America, E. terebrans parasitized an average 4.9% and 18.7% of first generation corn borers, and 10.2% and 9.1% of second generation corn borers in Michigan in 1989 and 1990, respectively. Although the activity peak of first generation E. terebrans adults is well synchronized with the population peak of first generation corn borers, second generation wasp emergence peaks about 4 weeks earlier than the 2nd generation corn borer population.

The highest level of parasitism by E. terebrans observed in individual fields in the Michigan study was 37.4%, occurring during the first generation in 1990. In 1938 near Boston, reported parasitism was 55.8%, but long term averages of parasitism in the north central region of the U.S. are 2.4%-7.8%. It should be noted, however, that these figures are from second generation parasitism.

Previous research has suggested that first generation corn borers were more likely to be parasitized by E. terebrans than second generation larvae, but this may vary from year to year. Landis and Haas reported that in most fields during 1989 and 1990, E. terebrans parasitized more first generation corn borers on field edges where fields bordered wooded areas. This relationship was only seen in fields bordering wooded areas, and it was not seen at all with second generation corn borers regardless of bordering vegetation.

Additional studies showed that adult wasps die rapidly when temperatures exceed 90°F and that wasps require some type of sugar on a daily basis or they will die. During the first corn borer generation, prior to corn canopy closure, maximum temperatures in corn fields may often exceed 90°F, and sources of nectar or honeydew may be scarce in the middle of corn fields. Wasps are able to survive better in wooded field borders, where there is more shade and often flowering plants or sources of aphid honeydew. First generation European corn borer larvae near wooded edges were parasitized at two to three times the rate of those in field interiors. Adults are not known to feed on hosts.

If corn is planted in rotation with other crops, E. terebrans adults must disperse from their overwintering sites to the current corn fields before they can become a factor in corn borer control.

Conservation

Wooded areas adjacent to corn fields where E. terebrans can find nectar and/or aphid honeydew and a refuge from the heat will help adult wasps endure high temperatures.

For general information about conservation of natural enemies, see Conservation in the Tutorial section of this site, or the Volume II, No. 1, Feature Article in Midwest Biological Control News.

Pesticide Susceptibility

Unknown.

Commercial Availability

Not available commercially.

Acknowledgement

Thanks to Doug Landis for supplying photographs and information that greatly improved this page.

Taken from:

Bob Wright (1996) Know Your Friends: Eriborus terebrans, Midwest Biological Control News. Vol.III, No.11.

Additional References

Landis, D. A. and M. J. Haas. 1992. Influence of landscape structure on abundance and within-field distribution of European corn borer larval parasitoids in Michigan. Environ. Ent. 21: 409-416.

Ma, R.Z., Swedenborg, P.D. and Jones, R.L. 1992 Host-seeking behavior of Eriborus terebrans (Hymenoptera: Ichneumonidae) toward the European corn borer and the role of chemical stimuli. Ann. Ent. Soc. Am. 85: 72-79.

Winnie, W. V. and H. C. Chiang. 1982. Seasonal history of Macrocentrus grandii and Eriborus terebrans, two parasitoids of the European corn borer, Ostrinia nubilalis. Entomophaga 27: 183-188.

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