Kraft pulping of jack pine killed by the Swaine sawfly

Kraft pulping studies were done on jack pine (Pinusbanksiana Lamb.) defoliated by Swaine jack pine sawfly (Neodiprionswainei Midd.). Trees dead as long as 7 years, dead and living trees sprayed with Lindane insecticide, and dead trees wrapped in cotton to prevent secondary insect attacks were tested. There was a statistically significant decrease in unscreened pulp yield (adjusted to screened pulp permanganate No. 20) with length of time since death, e.g., 44.6% (1 year) to 43.4% (7 years); but sufficient variation exists between the trees in any category such that, from a practical viewpoint, all trees tested could be used for pulp manufacture. There were no apparent differences in pulp yield between treated and untreated trees dead for the same length of time. Pulp strength decreased approximately linearly with length of time since death. A decrease in the chip thickness range of −6 mm to +2 mm (total laboratory accepts) and an increase in the −2 mm (pan) thickness range with length of time since death were observed.