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Trissolcus euschisti
(Hymenoptera: Scelionidae)

By Kristin Deroshia, Michigan State University

Last updated March 05, 2015

Introduction

Trissolcus euschisti (Ashmead) is an egg parasitoid of the superfamily Pentatomoidea (Heteroptera) and is the most common member of the flavipes species group in the Nearctic range. Many of the hosts of this parasitoid are of economic importance due to damages caused to agricultural crops; because of this, there is potential for using this species as a biological control agent against various stink bug pests. T. euschisti is native to North America, with a geographically widespread native range; it can be found as far south as Costa Rica and as far north as Canada. This parasitoid will attack host eggs during the growing season, starting in May and going through September.

Appearance

T. euschisti is a minute wasp with adults averaging 1-2 mm in length. The body form appears humped-backed and is black with yellow or orange appendages. The antennae are slender, elbowed, and differ slightly by sex. Female wasp antennae have 11 segments and are club-like in shape at the end. Males have 12-segmented antennae which lack a club. The forewings have reduced venation (Figure 1).

Habitat

T. euschisti prefers egg masses that are found on woody plants such as hackberry, black cherry, redbud, and white mulberry. This parasitoid will also attack pentatomid egg masses in agricultural crops such as soybeans.

Pests Attacked

The host range of T. euschisti is fairly narrow, as it will predominantly attack stink bug species in the Pentatomoidea superfamily. T. euschisti will attack 19-20 different pentatomid species in the Nearctic range. The most commonly attacked species include the following: the brown stink bug (Euschistus servus, Say), the one-spotted stink bug (Euschistus variolarius, Palisot de Beauvois), the green stink bug (Chinavia hilaris, Say), and the predatory spined soldier bug (Podisus maculiventris, Say).

Life Cycle

The average lifespan of T. euschisti is 36.5 days and the average number of progeny produced by a female in her lifetime is 63.7. The maximum production of progeny by a female was found to be on day 2 of her adult life and she can produce eggs for up to 49 days. In temperate climate zones, T. euschisti can have up to five generations per year.

Adult female T. euschisti locate an egg mass host through chemical cues that are found by drumming the antennae over the host eggs (Figure 2). One wasp egg is deposited into each host egg. The adult female will then remain on or near the egg mass to defend it against other parasitoids. The immature wasp hatches out of its egg, eats the developing embryo of the host, and pupates inside the host egg. The number of days it takes for T. euschisti to develop inside the host egg is 25 days for males and 30 days for females at a mean temperature of 27°C. If temperature falls to 15°C, or exceeds 33°C, T. euschisti may develop but fail to emerge from the host egg (Figure 3). Males will emerge approximately one day before females and will wait for their female siblings to hatch out so they can mate with them before dispersing.

Relative Effectiveness

It can take a female parasitoid more than one day to parasitize all of the eggs in one host mass, and she will therefore remain on the mass for an extended period of time. In one study, T. euschisti was able to parasitize all host eggs in an egg mass over a period of seven days. However, eggs deposited by an older female are less likely to develop and emerge than eggs deposited by a newly emerged female. In one observation, successful parasitism occurred on up to the seventh day of host embryo development.

T. euschisti will avoid host egg masses that have been previously parasitized by other parasitoids. This strategy allows the female to conserve her eggs for a suitable host and she will not waste her time on unprofitable host eggs. The offspring of a female with this strategy may also benefit by not having to compete with conspecifics for resources. The egg production time for T. euschisti is longer than that of other parasitoids in the family Scelionidae. This could suggest that T. euschisti is better adapted to seasons or habitats where host eggs can be relatively scarce..

Pesticide Susceptibility

Parasitoid wasps in the Trissolcus genus can be negatively affected by the application of pesticides. Successful emergence of adult wasps from treated host eggs can decrease, depending on the stage of development of the wasp when the pesticide is applied; the pupal stage of the wasp can be particularly susceptible. If a pesticide is applied immediately before adult emergence, the adult may consume the pesticide when chewing out of the host egg, causing death. However, if adults emerged successfully from eggs treated with a synthetic pyrethroid, female fecundity and longevity did not seem to be affected.

If an adult parasitoid comes into direct contact with a pesticide, functions of the nervous system can deteriorate. The ability to walk, and therefore disperse to find suitable host eggs, can be diminished. Similarly, the ability to reproduce and to respond to chemical cues can decrease.

Commercial Availability

T. euschisti is currently not available for commercial use in the United States.

Acknowledgment

Thank you to Dr. Ernest Delfosse, Michigan State University, Department of Entomology, for reviewing and providing feedback that improved this profile.

References

Braman, K. S., and K. V. Yeargan. 1989. Reproductive strategy of Trissolcus euschisti (Hymenoptera: Scelionidae) under conditions of partially used host resources. Ann. Entomol. Soc. Am. 82(2): 172-176.

Johnson, N. F. 1984. Revision of the Nearctic species of the Trissolcus flavipes group (Hymenoptera: Scelionidae). Proc. Entomol. Soc. Wash. 86: 797-807.

Okuda, M. S., and K. V. Yeargan. 1988a. Habitat partitioning by Telenomus podisi andTrissolcus euschisti (Hymenoptera: Scelionidae) between herbaceous woody host plants. Environ. Entomol. 17(5): 795-798.

Okuda, M. S., and K. V. Yeargan. 1988b. Intra- and interspecific host discrimination inTelenomus podisi and Trissolcus euschisti (Hymenoptera: Scelionidae). Ann. Entomol. Soc. Am. 81(6): 1017-1020.

Saber, M., M. J. Hejazi, K. Kamali, and S. Moharramipour. 2005. Lethal and sublethal effects of fenitrothian and deltamethrin residues on egg parasitoid Trissolcus grandis (Hymenoptera: Scelionidae). J. Econ. Entomol. 98(1): 35-40.

Salerno, G., S. Colazza, and E. Conti. 2002. Sub-lethal effects of deltamethrin on walking behaviour and response to host kairomone of the egg parasitoid Trissolcus basalis. Pest. Manag. Sci. 58: 663-668.

Yeargan, K. V. 1979. Parasitism and predation of stink bug eggs in soybean and alfalfa fields. Environ. Entomol. 8: 715-719.

Yeargan, K. V. 1982. Reproductive capability and longevity of the parasitic wasps Telenomus podisi and Trissolcus euschisti. Ann. Entomol. Soc. Am. 75: 181-183.

Yeargan, K.  V. 1983. Effects of temperature on developmental rate of Trissolcus euschisti (Hymenoptera: Scelionidae), a parasite of stink bug eggs. Ann.Entomol. Soc. Am. 76: 757-760.

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