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Eteobalea intermediella Riedl
(Lepidoptera: Cosmopterygidae)

by Rich Hansen, USDA-APHIS-PPQ, Forestry Sciences Lab, Montana State University, Bozeman, MT 59717-0278.

Eteobalea intermediella was approved for release in the US in 1995. A few field releases have been made in western Canada and the western US, but no established populations have yet been confirmed. (Background information about Dalmation toadflax and yellow toadflax is available.)

Appearance

Eteobalea intermediella adults are slender moths about 8-9 mm long, with a wingspan of 16-18 mm. Wings are dark brown with black and white spots. Adults are generally active in the evening and before dawn.

Larvae are cream-colored caterpillars with brown head capsules, and reach a maximum length of about 12 mm. They are found in tunnels within toadflax roots.

E. intermediella adults and larvae are very similar to those of E. serratella; the two species may be separated only by examining male genitalia or the egg chorion.

Habitat

Grasslands, pastures, agricultural fields, and roadsides infested with yellow or Dalmatian toadflax.

Pests attacked

Eteobalea intermediella attacks both Dalmatian and yellow toadflax. Host specificity tests indicate that this species utilizes a small number of perennial Eurasian species in the family Scrophulariaceae; no North American plants so far tested were attacked.

Life cycle

Adults appear in late spring and again in late summer or early fall. Moths live for several weeks but apparently do not feed. After mating, females lay eggs, in loose strings of 3-8, in leaf axils on the lower portion of a toadflax stem. Each female may lay up to 180 eggs. Newly-hatched larvae enter the stem and mine down into toadflax roots.

Larvae feed within the root cortex, constructing silk-lined tunnels. Generally, 3-7 larvae may be found within the root system of a toadflax plant, depending on the size of the roots. Mature larvae tunnel back to the root crown area or up into the base of a stem and construct a chamber in which pupation occurs.

There are two, and possibly three, generations per year in Europe. Winter is spent as larvae within toadflax roots.

Relative effectiveness

Larval root boring by Eteobalea spp. does not usually kill toadflax plants directly, but does decrease flowering and seed production and reduce plant vigor. There is not yet sufficient information available to predict the efficacy of this agent under North American field conditions.

Pesticide susceptibility

Unknown.

Conservation

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

Commercial availability

Eteobalea intermediella is not yet generally available in North America.

References

Saner, M.A. and H. Müller-Schärer. 1994. Impact of root mining by Eteobalea spp. on clonal growth and sexual reproduction of common toadflax, Linaria vulgaris Mill. Weed Res. 34: 199-204.

Saner, M.A., P. Jeanneret, and H. Müller-Schärer. 1994. Interaction among two biological control agents and the developmental stage of their target weed, Dalmatian toadflax, Linaria dalmatica (L.) Mill. (Scrophulariaceae). Biocontrol Sci. & Technol. 4: 215-222.

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