Establishment, Dispersal, and Influence ofCeutorhynchus lituraon Canada Thistle (Cirsium arvense) in the Gallatin Valley of Montana

Abstract

Ceutorhynchus lituradispersed 9 km in 15 yr from its point of release in 1972 with incident of infestation of Canada thistle plants at one study site reaching 92% in 1987. Plants generally survived larval feeding in the spring, but holes created by departing larvae provided entrances for arthropods, nematodes, and diseases. Subsequent mortality rates were high for belowground Canada thistle shoots. However, the number of new shoots from underground roots the following spring usually offset the mortality that had been indirectly caused by C.litura.