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BEN # 51

Adolf Ceska aceska at CUE.BC.CA
Sat Mar 6 13:14:00 EST 1993

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No. 51                            March 6, 1993

Address: aceska at cue.bc.ca         Victoria, B.C.

From: Roy Cranston, B.C. Ministry of Agriculture 
                    <rcranston at galaxy.gov.bc>

British Columbia is heavily committed to the use of natural
agents  to control noxious grassland and pasture weeds. From
modest  beginnings in 1951 with the introduction of a beetle to
control  the poisonous weed St. Johnswort, 50 agents have been
released  against 17 weed species to over 2,000 sites in B.C.  

Significant progress has been achieved in biocontrol development
through the cooperative efforts of the International Institute
of  Biological Control (Switzerland), Agriculture Canada, the 
Ministries of Agriculture, Fisheries and Food and Forests and 
through support of private sector groups such as the B.C. 
Cattlemen's Association.

* Candidate natural agents that feed on a targeted weed and show
  promise for control are studied in their native habitat. 

* Exhaustive studies are carried out to ensure the insect will   
  attack only the targeted weed and not other vegetation.

* Long term results are reviewed by North American Biocontrol 
  agencies. If the natural agent is proven to damage the weed 
  without attacking other vegetation it is approved for release
  in Canada and the United States.

* The B.C. Plant Protection Advisory Council approves or rejects
  release of federally approved natural weed control agents to   
  British Columbia.

* Initial B.C. releases are made under controlled conditions for 
  the purpose of gaining establishment and to increase
  populations for provincial redistribution.

Usually several species are released to improve the chances of 
long-term control of the weed. The B.C. Ministry of Forests,
Range  Branch, maintains bioagent propagation facilities at
Kamloops and  Castlegar. When populations warrant, the insects
are then  redistributed throughout the province.  The Ministry
of  Agriculture, Fisheries and Food maintains computer and map
records  of all weed bioagent releases and redistributions.

Reductions in density, seed production and spread potential are 
realities for some weeds now and the possibility for success 
against other species is encouraging. St. Johnswort, nodding 
thistle and Bull thistle are under effective biocontrol in the 
province and no longer require herbicide treatment. Knapweed 
densities are beginning to decline dramatically at a number of 

Use of natural agents will continue to play an integral and 
expanding role in integrated vegetation management systems in 
British Columbia and will result in less need for chemical, 
cultural and mechanical control programs.

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