Redistribution is accomplished by collecting and releasing adult beetles. In Alberta, redistribution of beetles is about 65% successful. The black dot spurge beetle is more effective on high, dry and exposed sites, on coarse soils. Two insects, the black dot spurge beetle Aphthona nigriscutis, and the copper spurge beetle Aphthona flava can be used as biocontrol agents in leafy spurge. Several years are required for the weevil population to become established so that it can effectively control the thistle. Weevils may be gathered by collecting about 500 infected nodding thistle seed heads in mid-August, and placing them in new stands.
Nodding thistle is attacked by a weevil, Rhinocyllus conicus introduced to Saskatchewan in 1968. Generally, the target weed is a long-lived perennial species that is especially difficult to control by traditional means. Classical biocontrol has had good long-term success in some instances, particularly in rangeland. Classical biological weed control with insects involves introducing host-specific natural enemies from the target weed’s native range. Biocontrol is often separated into two categories: introducing classical biocontrol agents, often insects, and the increase and inundative use of organisms, often disease agents.Ĭlassical biocontrol introduces natural predators to weed populations. Biocontrol of weeds is using living organisms to destroy weeds, or to inhibit their growth and ability to compete with crops.
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