Musk Thistle Suppression Using Weevils for Biological Control

Musk thistle, Carduus thoermeri Weinmann = Carduus nutansL. (Campanulatae: Asteraceae) is an invasive Eurasian weed that has become widespread in the contiguous United States. It reproduces by seed and was first reported in the United States in 1953 in Harrisburg, Pennsylvania. Being a highly competitive weed, it has replaced much of the native vegetation in pastures, rangelands, croplands, and along state highways in many parts of the USA and Canada. Its success is due to its prolific seed production, seed longevity, and lack of natural enemies to suppress it. As it spread rapidly in the absence of any native insects capable of suppressing it, the United States Department of Agriculture started a program in search of its natural enemies in Italy in the early 1960s. The Canada Department of Agriculture provided funds for the Commonwealth Institute of Biological Control (now CABI Bioscience) to extend the search across Europe from western France to Austria. As a result of this search,...