The role of mechanized harvesting in the development of bluestain in pine

The influence of mechanized harvesting on the development of bluestain was assessed by comparing pine logs felled and trimmed with a chainsaw with tho se felled by a commercial harvesting machine. Corsican pine (Pinus nigra va r maritima (Ait.) Melville) grown in the United Kingdom was cut in June and August, and the logs were assessed for bluestain 3, 6, 9, and 12 weeks aft er felling. Mechanically harvested logs were in two groups: maximum damage (mean amount of bark loss similar to 35% of total cover) and minimum damage (similar to 12% mean bark loss). However, all mechanically harvested logs were much more susceptible to attack by bluestain fungi than chainsaw-proce ssed logs, which typically had <1% bark loss. Mechanically harvested logs h ad bluestain on similar to 10% of the surface area of sample discs compared with <1% in the chainsaw-harvested logs. Little bluestain developed if bar k loss was <10%. The most extensive stainers were Ceratocystis coerulescens Munch) Bakshi and Leptographium wingfieldii Morelet; other frequent bluest ain fungi included Ophiostoma piceae (Munch) H. & P. Sydow, Sphaeropsis sap inea (Fr.) Dyke & Sutton, and a Graphium species. Bluestain bark beetle vec tors were excluded from the logs, but other arthropods apparently acted as vectors. Using data from the study, a model was devised to predict of stain development following a known amount of bark damage.