The costs of young stand management keep increasing and labor continues to shrink. Young stand management rely on mechanical cutting as use of chemical herbicides are restricted by forest certification. Alternative – effective and environmentally friendly – biocontrol methods have been studied to prevent vigorous regrowth of stump sprouts. By effective sprout control second pre-commercial thinning (PCT) is not needed which improves cost-efficiency of young stand management.
New methods to young stand management
Pioneering deciduous species cause a need for young stand management (= early cleaning). In early cleaning unwanted trees are removed in order to assure growth of commercially valuable conifers and decrease competition between conifers and faster growing deciduous species. However, cutting deciduous trees is only a temporary solution as it causes vigorous regrowth of stump sprouts. Also, the use of chemical herbicides in young stand management is quite restricted in Finland.
Search for effective and environmentally neutral alternative has been ongoing. The use of white-rot fungus (Chondrostereum purpureum (Pers. Ex Fr.) Pouzar) as a biocontrol agent has been studied. C. purpureum is naturally occurring decaying fungus penetrating freshly wounded wood tissue. C. purpureum has been shown not to cause disease for non-targeted hosts, such as healthy conifers, so its use as biocontrol agent does not pose a risk of the epidemic.
Towards biocontrol
Results have been promising as applying C. purpureum inoculum manually on freshly cut birch stumps has been reported to result mortality of >75%. However, there have been difficulties in motor-manual applying of C. purpureum inoculum in practice because of required additional operations and the weight of the equipment. Mechanized PCT combined with C. purpureum treatment could solve the problem and increase cost-efficiency by preventing sprouting and therefore need for later PCT. Initial experiments of mechanized PCT together with C. purpureum treatment indicated that implementation into practice requires more testing on accuracy and reliability of applying method. Also, the use of C. purpureum inoculum in practice needs license and right of use.
Latest results of C. purpureum treatment by Tehojätkä can befound of EFFORTE Deliverable 2.3: Silvicultural feasibility of new early PCT methods – Prevention of hardwood sprouting with mechanical methods in early PCT.
Decaying fungus C. purpureum was applied to freshly cut stumps by Tehojätkä to prevent sprouting. Photos: Veli-Matti Saarinen (Tehojätkä), www.usewood.fi (UW40-cleaning), Andreas Salmi (C. purpureum).
Text: Tiina Laine & Timo Saksa, Natural Resources Institute Finland