HOST SPECIFICITY AND SUITABILITY OF LEMA CYANELLA (COLEOPTERA: CHRYSOMELIDAE), A CANDIDATE FOR THE BIOLOGICAL CONTROL OF CANADA THISTLE (CIRSIUM ARVENSE)

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Abstract
The host specificity of Lema cyanella (L.) (Coleoptera: Chrysomelidae) and its suitability as a biological control agent were investigated. The females lay an average of 1564 eggs and development from egg to adult takes 17.6 days at 25°C during the day and 20°C during the night (average about 23°C). Feeding of adults and larvae is confined to Cirsium, Carduus, and Silybum species, and according to literature records, Cirsium arvense (L.) Scop. is the main host. No economic plants are attacked. A colony of field collected beetles imported from Germany was infected with a Nosema disease. It is recommended that disease free L. cyanella should be released against the weed C. arvense in North America.