The identification of native phytophagus insects associated with Canada thistle (Circium arvens (L.) Scop) and their biological control potential

In order to achieve a non-chemical way based on ecological approach for controlling of C. arvense and the possibility of using insects as biological control agents, a series of tasks including collecting, identification and basic evaluation of herbivore insects is being used to control Canada thistle were conducted in North Khorasan province. Three different climatic sites of C. arvense with 6 km. distance from each other were chosen in the province. Each site was regularly visited during spring and summer. In each screen, parasites on host plants were collected by using umbrella and aspirator. Then 10 sample plants – each of which from one site – and their roots were taken to laboratory. In the lab, all parts of the host plants were inspected for any possible insect. Then the insects were collected and identified. The result of the study was to identify 12 species of herbivor insects on Canada thistle plants which Cleonis pigra and Lixus scolopax caused 22% mortality in the stalk of C. arvense. Among the collected phytophagous insects, an species belong to order coleopteran (Cassida rubiginosa) caused a biomass reduction up to 76%. It was found that a curculionid species (Larinus planus) reduced the seed production of Canada thistle to 17%.