Effects on the native plant community of Persicaria perfoliata biological control by the Asian weevil Rhinoncomimus latipes

The response of the native plant community to biological control of Mile-a-minute weed, Persicaria perfoliata (L.) Gross (Polygonaceae) by the Asian weevil Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae) was investigated over the three-year period 2011-2013. Persicaria perfoliata (MAM) is an annual vine from Asia that has invaded the eastern US, where it can form dense monocultures and outcompete other vegetation. MAM was discovered in several disturbed habitats in Alleghany County, North Carolina in 2010. Rhinoncomimus latipes was released in May 2011 as part of a classical biological control program. Each year MAM cover, weevil abundance and plant community diversity and cover were quantified to ascertain what if any changes occurred in the native plant community due to potential biological control of MAM. Two release and two control (no weevil release) transects were established. At the end of year one (2011) MAM cover was lower in both release plots compared to the control, with percent cover of native plant taxa higher than the control in one of the two transects where weevils were released. In year two a late spring frost resulted in severe damage to MAM in the control and one release plot. Analysis of one release transect showed a 10-20% increase in native plant diversity compared to the previous year. In the third year after weevil release there was a trend for increased native plant cover in the presence of the weevil, though no significant differences between the control and release transects was observed. Species riches was higher early in the season in one transect with weevils but this did not continue throughout the growing season. Based on our data there appears to be no wide-scale and consistent benefit to the native plant community after release of Rhinoncomimus latipes to control MAM.