Conifer plantations are thinned to maximise production of high quality timber for lumber, fire wood, and hydro poles. However, thinning increases susceptibility to fungal diseases such as Armillaria root disease and Annosus root rot. Fungal pathogens and root diseases are detrimental to the forestry industry as they are responsible for lost revenue due to tree mortality in establishing, and mature stands. Recently thinned white pine (Pinus strobus) and red pine (Pinus resinosa) plantations in Simcoe County, Ontario, Canada were surveyed to document the presence/absence and spatial distribution of Armillaria spp. and Heterobasidion spp., two important fungal pathogens found in our region. Fifteen pine plantations (1:0, 1:1, or 0:1 red to white pine ratios) established between 1928 and 1980 were surveyed using band transects. Symptomology expressed by the trees was characterised (e.g., needle colour, crown needle density, branch dieback, ± fruiting bodies) and documented along with dbh (at 1.3 m), height, tree density, and decay class to examine their relationship to disease presence.
Results/Conclusions
Both red and white pine were found to be suitable hosts for Armillaria and Heterobasidion spp. Plantation type did not influence presence/absence of Armillaria and Heterobasidion (F2,14 =1.00, p=0.39, F2,14 =0.969, p=0.40). Armillaria and Heterobasidion infected 1.0 ±0.8SE % and 0.1 ±0.04SE % of plantation trees, respectively. Our study suggests that the presence of fruiting bodies was the most effective indicator of Armillaria and/or Heterobasidion establishment within plantations. Early detection of root disease symptoms after thinning will help forest managers develop and adopt effective control measures. Bio-control treatments, for example, could be applied immediately after thinning to prevent the establishment of root diseases. Further investigation is required to understand the rate at which root diseases spread within red pine and white pine plantations.