Impact and control of Vinca minor L. in an Illinois forest preserve (USA)

Vinca minor L., a woody evergreen vine of Eurasian origin, is a sporadic in vader of forest understories in Illinois. We studied understory composition in a mature southwestern Illinois Quercus-Carya forest to evaluate the eff ect of V. minor invasion and test the efficacy of a combined cutting and he rbicide (glyphosate) control treatment. Vinca minor presence did not reduce species richness, evenness, or combined diversity compared to the referenc e area in either spring or summer. One to two years after treatment, V. min or was still prominent in the understory at its original location. In the t reated area, V. minor frequency was approximately 50% less than in the untr eated invaded area. The treated area had a higher proportion of nonvegetate d surface and higher species diversity during summer. Understory species co mposition differed among the invaded, reference, and treated areas. Underst ory composition in the treated area more closely resembled the reference ar ea than the invaded area. This pattern was present with and without the inc lusion of V. minor in the data set. Use of a combined cutting/herbicide tre atment is moderately effective, and an aggressive follow-up program will be required to achieve control of Vinca minor.