Effects of biological control of the invasive weed Persicaria perfoliata by the Asian weevil Rhinoncomimus latipes

Mile-a-minute weed (MAM), Persicaria perfoliata (L.) H. Gross (Polygonaceae), is an annual vine from Asia that has invaded the eastern US where it can form dense monocultures and outcompete other vegetation in a variety of habitats. P. perfoliata was discovered in several disturbed habitats in Alleghany County, North Carolina in 2010. The Asian weevil Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae) was released in May 2011 as part of a classical biological control program. The weevil and plant community were monitored for two growing seasons in 2011 and 2012 to determine what effect insect control had on MAM performance and phenology and to ascertain if any changes occurred in the extant plant community. Two release and two control (no weevil release) transects were established. Rhinoncomimus latipes successfully established in 17 of 20 release quadrats. For the plant community, 97 plant taxa were identified within study quadrats, with 8 taxa showing an ability to compete with MAM. In the release transects MAM plants had a significantly lower fecundity than those in control transects. Transects with weevils also had earlier time of MAM senescence than controls. Within the release treatment, the two transects were located at different elevations. The higher elevation transect showed earlier time of MAM senescence and weevil diapause in 2011 and temperature and light intensity differences have been recorded in 2012. The ability of the weevil to affect MAM performance suggests that biological control effects of MAM are emerging, and that microclimate may have an effect on plant and insect phenology.