Biocontrol of Common St. Johnswort (Hypericum perforatum) with Chrysolina hyperici and a Host-Specific Colletotrichum gloeosporioides

摘要

Common St. Johnswort is widespread in eastern Canada but it seldom constitutes a serious weed problem. A demographic study conducted in 1993 and 1994 at four typical undisturbed sites indicated that 36 to 96/100 of establishedl St. Johnswort shoots died during the growing season. Mor- tality was always associated with infection by a host-specific Colletotrichum gloeosporioides. The leaf-feeding beetle Chrysolina hyperici occurred at all sites and caused maximum midsummer de- foliation of 27/100 in 1993 and 51/100 in 1994.