Host specificity of Euops chinesis, a potential biological control agent of Fallopia japonica, an invasive plant in Europe and North America

Fallopia japonica (Houttuyn) Ronse Decraene (Polygonaceae) is a serious invasive weed in North American and Europe. In its native China, a leaf-rolling weevil, Euops chinesis (Coleoptera: Attelabidae) was found attacking F. japonica in the field. No-choice tests, multiple-choice tests, open field tests and field surveys were conducted as a measure of its host specificity. Forty-six plant species were selected from 17 families for host range testing, among which, six species, F. multiflora, F. japonica, Persicaria perfoliata, Rumex acetosa, R. japonicus and R. aquaticus, were exposed to adults in no-choice tests. However, larvae could only develop successfully on F. japonica, and this plant appeared to be the only host in the field, suggesting the weevil is host-specific. As larval development appears to depend on a fungus in the leaf rolls, the insect–fungus mutualism and risks including host specificity of the fungus should be evaluated before the insect’s introduction.