pestmanagement


Beating ’em with biology


A look at how insects can be an effective alternative tomanual labour and chemical warfare against invasive plants.


By Jeanne Hughes T


here are a number of ways to control invasive plants. Manual control is probably the one home gardeners are most familiar with. This is just plain labour and includes digging, hand-pulling, and clipping. If you have Himalayan blackberry on your property, perhaps you hired a large machine to dig it up – this is mechanical control.


Chemical control with herbicide is another common method of controlling invasive plants. To reduce non-target damage to native plants we administer herbicides with a stem injector, backpack sprayer, or we cut the stem of woody shrubs (such as scotch broom or butterfly bush) and paint it with herbicide to reduce the likelihood it will resprout.


Probably one of the most interesting methods of controlling invasive plants, however, is biological control. As you know, invasive plants arrived in our region without the natural pests and predators that keep their population in check in their native land. The idea behind biological control is that you track down one of these pests, release it here, and let it do its damage. There are definitely instances where this approach has gone seriously awry. Two of the most famous of these are the introduction of the mongoose to Hawaii for rat control resulting in the decimation of endemic Hawaiian birds, and the introduction of cane toads to Australia to control the cane beetle resulting in a dramatic change to the


British Columbia’s first biological control agent was released in 1951. The leaf- feeding Chrysolina beetle was used to attack the toxic agricultural weed, St. Johns-wort.


Australian landscape, and a worse problem than the cane beetle posed. So it should go without saying that biological control agents are introduced with the greatest care. The process in Canada is indeed a long and careful one, and is conducted in cooperation with the International Institute of Biological Control (Switzerland), Agriculture and Agri-Food Canada, the provincial ministries of Agriculture, Fisheries and Food, and Forests, Lands, and Natural Resources Operations, and through the support of private sector groups such as the B.C. Cattlemen's Association.


The first step is studying potential insects that feed on targeted weeds in their native habitat. Meticulous research is then conducted to ensure that the insect will attack only the targeted weed and not other vegetation. Long-term results are reviewed by North American Biocontrol agencies and if the biological control agent is proven to damage the weed without


14 British Columbia Berry Grower • Fall 2011


attacking other vegetation, it is approved for release at the federal level. The B.C. Plant Protection Advisory Council then approves or rejects the release of these federally approved weed control agents to British Columbia.


Initial releases are made under controlled conditions to enable the bugs to become established and to increase populations for redistribution in the province. These steps take upwards of 10 years to complete, and are costly to undertake; however, I have read that in the long run it is worth it. Researchers suggest that the overall return over costs is generally at least 50:1 and often up to 100:1. While biological control agents do not eradicate an invasive plant, successful biocontrol will reduce the vigour, abundance, and economic losses caused by it.


In British Columbia, the very first biological control agent was released in 1951 — the Chrysolina beetle, a leaf-


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