Host range study of green thistle beetle (Cassida rubiginisa) as a biological control agent for Canada thistle (Cirsium arvense)

Canada thistle Cirsium arvense (L) Scop is one of the most important of world weed and third important weed in Europe. Weed Biological control is a safe، environmental friendly and practical method for weed management in agroecosystems. After finding an appropriate insect biocontrol agent of weed، the first necessary stage is doing host range tests. Host range studies on green thistle beetle (Cassida rubiginosa)، in which feeds actively on this weed as larva and Adult، were studied in 20 crops with two methods of no-choice and multiple-choice، and in 22 weeds through field surveys. The results showed that plant feeding and female ovipositor by green Thistle was observed in Russian knapweed، Common Russian thistle، Bull thistle and Canada thistle. Green Thistle beetle fed on safflower but only about 5% of plant shoots only in no choice treatments; however this beetle did not deposit any eggs on sunflower. Green thistle beetle could be a promissing classical biocontrol agent for Canada thistle in grasses، natural grasslands، agricultural fields and pastures.