Cirsium arvense is considered as one of the world’s worst weeds and the third most troublesome weed in Europe. It has become increasingly problematic in ecological areas where conventional control measures are restricted. Thus control that exploits both plant competition and herbivory by specialized native insects, may be an inexpensive and sustainable alternative control measure. To date, augmentation or conservation of native agents has received little attention compared to other approaches but interest is growing. Reasons for this are that future progress in classical biological control of Cirsium arvense will depend on the identification of new, host specific herbivores from the native range, and better predictions and evaluations of non-target impacts. Surveys are being conducted for herbivores on Cirsium arvense in North Khorasan. We are beginning this project but already realize the importance of Cassida rubiginosa, a univoltine shield beetle feeds on foliage of Cirsium arvense. For successful use of this insect as a biological control agent, knowledge is required about (i) the insect densities required to obtain the desired control level, and (ii) the factors preventing this insect from attaining such population levels. This information may lead to the development of strategies to increase population densities of the agents.

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