CEUTORHYNCHUS LITURA (F.) (COL. CURCULIONIDAE), A POTENTIAL INSECT FOR THE BIOLOGICAL CONTROL OF THISTLE, CIRSIUM ARVENSE (L.) SCOP., IN CANADA

Abstract

The suitability of Ceutorhynchus litura for the biological control of Cirsium arvense in Canada was evaluated. It is concluded that introduction of C. litura is justified on the grounds that its feeding is restricted to a group of three systematically related genera, Cirsium–Silybum–Carduus. This host pattern is highly stable, and probably prepleistocene in origin, and does not include any economic plant species. C. litura is compatible with phytophagous insects already present on C. arvense in Canada and its establishment should not prejudice the introduction of other European insects against the weed. C. litura is, however, subject to a number of ecological restrictions and is only likely to be an effective control agent in cultivated fields where it can build up a high density over several years.