Canadian Forest Service Publications
Development of a biological control strategy to mitigate hemlock dwarf mistletoe in retention silviculture systems: Colletotrichum gloeosporioides–western hemlock dwarf mistletoe pathosystem. 2006. Askew, S.E.; Shamoun, S.F.; van der Kamp, B.J. BC Journal of Ecosystems and Management 7(1): 23-29.
Issued by: Pacific Forestry Centre
Catalog ID: 26092
Global concern about enhanced habitat diversity and sustainable forests expressed by wood product consumers has resulted in a change from clearcut to variable retention (VR) practices. The change to VR, however, opens stands and exposes western hemlock crowns to light, which can activate latent western hemlock dwarf mistletoe infections. An inundative biological control using the fungus Colletotrichum gloeosporioides may provide another method of control for western hemlock dwarf mistletoe, especially in variable retention areas and riparian and sensitive ecosystems. This study focussed on: determining a lead isolate through pathogenicity screening of PFC C. gloeosporioides for the field study; comparing the efficacy of C. gloeosporioides using a Stabileze and a sucrose and gelatin formulation; and determining the mode of infection of C. gloeosporioides on western hemlock dwarf mistletoe. Stabileze and sucrose-gelatin treatments formulated with C. gloeosporioides were shown to decrease the number of shoots and berries of dwarf mistletoe within a 3-4 month period, although it appeared that this biological control may not have the ability to kill dwarf mistletoe swellings. Colletotrichum gloeosporioides was re-isolated mainly from outer bark (44-71%) compared to living bark and wood (0-32%) for all the PFC 2415 formulation treatments. No re-isolation occurred in any of the dead wood samplings. Additional findings are summarized and discussed, and several research priorities are suggested. Further research in enhancing C. gloeosporioides efficacy and determining the mode of C. gloeosporioides infection on dwarf mistletoe is required.