The ragweed leaf beetle Zygogramma suturalis F. (Coleoptera: Chrysomelidae) in Russia: current distribution, abundance and implication for biological control of common ragweed, Ambrosia artemisiifolia L.

The ragweed leaf beetle, Zygogramma suturalis F. (Coleoptera: Chrysomelidae), was introduced to Russia in 1978 against the common ragweed, Ambrosia artemisiifolia L. By 1985, it successfully acclimated and suppressed ragweed in the original release site and several neighbouring fields. However, because of crop rotation, its population density drastically decreased. In 2005 and 2006, we conducted selective quantitative sampling in Southern Russia. The results showed that the ragweed leaf beetle was distributed over an area of about 50,000 km2 in Krasnodar territory, west of Stavropol’ territory and south of Rostov province, i.e. most of the area heavily infested by ragweed in Russia. However, the average Z. suturalis population density was very low: approximately 0.001 adults per square metre (m2) in crop rotations and approximately 0.1 adults/m2 in more stable habitats, although in a few of the studied plots, up to 2–3 adults/m2 were recorded. As for common ragweed, average percent cover in crop rotations and in stable habitats was approximately 1% and 40%, correspondingly. A detectable level of host plant damage (≥5%) was recorded only in a few plots. The observed spatial variation of the Z. suturalis population density was mostly determined by the host plant abundance. The last was strongly dependent on the stability of the habitat, being much higher in stable habitats. Thus, it is still possible that stable protected field nurseries could be a promising method of Z. suturalis propagation for biological control of ragweed in surrounding locations.