Trissolcus basalis parasitizing
Southern
green stink bug eggs.
PHOTO: Jack Kelly Clark,
courtesy
University of California
Statewide IPM Program. |
Trissolcus basalis
(Hymenoptera: Scelionidae)
The egg parasitoid
Trissolcus basalis has been present in the southern U.S. for
many decades. It is known worldwide because of its importance as a
parasitoid of the southern green stinkbug, Nezara viridula. |
Appearance
Minute black wasp with downward elbowed antennae and flattened
abdomen. Wing veins are not obvious.
Habitat (Crops)
T. basalis most likely occurs in all crops attacked by
southern green stinkbug including cotton, grains, soybeans and other
legumes, tomatoes and other solanaceous crops, sweet corn, sunflower,
cole crops, cucurbits, fruit and nut crops.
Pests Attacked
The primary host of T. basalis is the southern green
stinkbug. T. basalis also attacks the eggs of other species of
stinkbugs.
Life Cycle
T. basalis adults mate immediately after emerging from host
eggs. The female typically inserts one egg into a host egg. Heaviest
parasitoid egg production occurs during the first few days after
emergence, then tapers off. The average number of eggs produced per
female was 230-300 in one laboratory study. Adults emerge from the host
eggs in 9 to 12 days. The life-cycle averages about 23 days at 22°C.
Relative Effectiveness
Southern green stinkbug was accidentally introduced into Australia
in 1916, New Zealand in 1944, and Hawaii in 1961. T. basalis has
long been considered to be effective at controlling southern green
stinkbug in these regions. However, recent studies indicate that
control by T. basalis may not be the success previously thought.
In addition, T. basalis has not provided consistent control of
southern green stinkbug on soybeans in the southern United States.
Strains of T. basalis from Italy, Spain, and France were
introduced into California in 1987 and field research showed that 87% of
the eggs per mass and 80% of all southern green stinkbug egg masses
examined by researchers were parasitized by T. basalis. T.
basalis disperses and reproduces well, it parasitizes other stinkbug
species when its preferred host is not available, and it is not known to
be subject to hyperparasitism or pathogens in North America. T.
basalis has a high female to male ratio (up to 5:1) which increases
its effectiveness as a parasitoid.
Pesticide Susceptibility
In field trials, T. basalis was little affected by
applications of permethrin, but was susceptible to methyl parathion,
especially within the first six hours. The methyl parathion also killed
some wasps as they exited the host eggs, probably from spray residue on
the egg exterior being ingested as they chewed through.
Conservation
Follow the IPM guidelines as outlined in the tutorial of this guide.
A nectar source is helpful to other scelionid wasps and may also
provide nourishment for T. basalis.
Commercial
Availability
T. basalis is not commercially available in North America at
this time.
Acknowledgment
Thanks to Walker A. Jones, USDA Agricultural
Research Service, Weslaco, TX, for reviewing and making suggestions that
have improved this section.
References
Awan, M.S., Wilson, L.T., and Hoffmann, M.P. (1990) Comparative
biology of three geographic populations of Trissolcus basalis
(Hymenoptera: Scelionidae). Environ. Entomol., 19: 387-392.
Clarke, A.R., Walter, G.H. (1990) Trissolcus basalis as a
biological control agent of Nezara viridula in south east Queensland.
Proc. 6th Australian Soybean Res. Workshop: 71-73. Brisbane,
Queensland, Australia.
Clausen, C.P. (Ed.) (1978) Introduced Parasites and Predators of
Arthropod Pests and Weeds: A World Review. (Clausen, C.P., Ed.)
Agriculture Handbook No. 480, USDA Agricultural Research Service,
Washington, D.C.
Habeck, D.H., Bennett, F.D., and Frank, J.H. (eds.) (1990)
Classical Biological Control in the Southern United States. Southern
Cooperative Series Bull. No. 355. University of Florida, Gainesville,
FL. 197 pp.
Hoffmann, M.P., Davidson, N.A., Wilson, L.T., Ehler, L.E., Jones,
W.A., and Zalom, F.G. (1991) Imported wasp helps control southern
green stink bug. California Agric., 45: 20-22. Orr, D.B. (1988)
Scelionid wasps as biological control agents: a review. Fl. Entomol.,
71: 506-528. Orr, D.B., Boethel, D.J., and Layton, M.B. (1989)
Effects of insecticide applications in soybeans on Trissolcus
basalis (Hymenoptera: Scelionidae). J. Econ. Entomol., 82:
1078-1084.
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