Aulacidea acroptilonica Tyurebaev, 1972

Feeds on: Induces galls on Acroptilon repens (L.) DC.

Distribution: United States: Colorado, Montana, Wyoming

Aulacidea acroptilonica
Russian knapweed stem gall wasp

Host: Russian knapweed (Rhaponticum repens).

Gall location: On the stems and branches, often with many galls on the same plant. They seem to most commonly form along leaf nodes.

Description: Irregular swellings, typically 1-3 centimeter in length. Sometimes short and oval-shaped to greatly elongate and spindle-shaped. Occasionally solitary but more often clustered, often with multiple galls or clusters in rows along the entire length of a stem and its branches. Green and fleshy when fresh to brown and rough when old.

Range: The exact range of this species in North America is unknown, but it has thus far been found in several Western and Northwestern states (see below).

The Russian knapweed stem gall wasp was introduced to North America as part of a biological control effort for its host plant, which is considered noxious and a highly-detrimental weed with regard to its impacts on native ecosystems. The extent of this wasp’s release and its current distribution are largely unknown, but it has thus far been encountered in Colorado, Montana, Washington, and Wyoming. Additional populations of Russian knapweed will likely be found to host galls of this species. Biological control documents indicate that at least eight states have established populations, but additional information is unknown at this time.

Aulacidea acroptilonica Tyurebaev, 1972

Gall. Spindle-like, lignified formations on the stem, 25-50 mm long and 20 mm in diameter. The gall size depends on the number of larval chambers (from 1 to 30). A single larval chamber nearly rounded, 3.0 mm in diameter, with smooth surface. Galls develop on all parts of the stem, from the ground-surface up to the flower (Kovalev & Diakontschuk 1986).

Host plant. Acroptilon repens (L.) DC. (Asteraceae) is the only known host plant; probably can induce galls on a closely related species, A. australe Iljin. (Kovalev & Diakontschuk 1986).

Biology. Majority of larvae overwintering in the gall, pupate in March-April; adults emerge by the end of April (Middle Asia) – beginning of May (Kazakhstan and Ukraine) (Zerova, Diakontschuk & Ermolenko 1988); part of adults in Iran emerge in early summer.

Distribution. Iran, Azerbaijan-e Gharbi province (vicinities of Urmia) (Melika & Karimpour 2008), Lorestan (Zalian) (Karimpour et al. 2008). Ukraine (southern part only), European part of Russia, Kazakhstan, Kyrgyzstan, Turkmenistan, Tajikistan, Uzbekistan (Zerova, Diakontschuk & Ermolenko 1988, Kovalev & Diakontschuk 1986).

smooth fusiform lignified swellings of the stem, generally 2.5 cm long and 2 cm thick, with 1-30 gall chambers. The larvae hibernate in the gall, next pupate there.