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SUMMER PRUNING RESTRICTIONS ON OAK TREES
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View the fact sheet on Oak Wilt (pdf/2 pgs/146KB) ...
The City of Toronto, Urban Forestry Services, would like to remind you of the restrictions on pruning oak trees for the period of April 30 to August 1, 2003. This is a renewal of a similar notice issued during the last two years.
Oak wilt is a quarantine pest not yet reported in Canada. The proximity of oak wilt in forests of Central North U.S.A. shows that this devastating disease of oaks can easily spread to Southern Ontario. If the disease is reported and confirmed by Canadian Food Inspection Agency (CFIA), an eradication program will be initiated by CFIA in co-operation with provincial and municipal authorities.
The fungus Ceraticystis fagacearum responsible for oak wilt disease spreads locally from infected to healthy trees through root grafts. The same fungus is spread over long distances by two groups of sap and bark feeding beetles (Scolytidae and Nitidulidae). These insects become active in early May and feed on infected, declining oak trees. The beetles are attracted to fresh wounds on oaks. Live-wood pruning cuts are therefore important sites of infection and pruning of live branches should be restricted on oak trees during the period when these beetles are active. It is very important that we restrict pruning of oak trees from early May to late July. This practice is recommended to prevent the introduction and spread of oak wilt disease in Toronto.
This practice should be easy to follow because oaks usually do not require pruning. When pruning is unavoidable during this period, wound paint should be applied immediately on fresh wounds. Please note that this is not a generally recommended practice and it is just applied in specific cases. Pruning deadwood is excluded from the restriction. Since it does not create fresh wounds on trees, it would not attract the vectors of the fungus.
For more information, please view the fact sheet on oak wilt (PDF/2 pgs/146KB) or call Forest Health Care Inspectors, Alex Bykov (392-1898) and Jozef Ric (392-1436).
Last Modified: Friday, November 5, 2004
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