HOST RANGE OF LEMA CYANELLA (COLEOPTERA: CHRYSOMELIDAE), A CANDIDATE FOR BIOCONTROL OF CANADA THISTLE, AND OF FOUR STENOPHAGOUS, FOREIGN THISTLE INSECTS IN NORTH AMERICA

Abstract

AbstractIn the field in Europe, Lenta cyanella (L.) has been reported to breed only on Canada thistle (Cirsium arvense (L.) Scop.) whereas in the laboratory it breeds on species in the genera Cirsium, Carduus, and Silybum. In one laboratory choice test, L. cyanella preferred Cirsium drummondii T.&G. over Canada thistle. In one field-cage test, it concentrated feeding and oviposition on one C. drummondii which thrived in preference to three other C. drummondii and Canada thistle which grew poorly. In a second field-cage test, Canada thistle predominated and L. cyanella fed and oviposited most on Canada thistle although its intrinsic preference for C. drummondii was still apparent. A review of the field host-plants of three accidentally introduced thistle-feeding insects, Orellia ruficauda (F.), Cleonus piger Scop, and Cassida rubiginosa Müller, and the introduced biocontrol agent Rhinocyllus conicus Froel., showed that these insects, which have a wider range of hosts than has L. cyanella, concentrate breeding on introduced species of Cynareae (Compositae). Based on this evidence, it is extrapolated that L. cyanella will exploit Canada thistle and will not damage populations of native Cirsium species when established in North America.