Studie av rottickans S-form i ett röjningsbestånd av gran

Sammanfattning: The aim of this study was to examine if heartwood properties and stump diameter affected the establishment of Heterobasidion parviporum in a Norway spruce stand at the stage of pre-commercial thinning. In addition, the effects of Rotstop® application on the stumps were investigated. A field experiment was created by cutting 90 stumps with a diameter ranging between 2.0 and 13.9 centimeters, and the material was then divided into three diameter classes. Half of the stumps in each diameter class were treated with Rotstop® and the remaining stumps were untreated. The following day a solution containing spores from Heterobasiodion parviporum was applied. After seven weeks, discs were cut from all the stumps and stored in separate plastic bags. After one week of storage, the discs were examined for establishment of conidiophores, fruiting, from the Heterobasidion parviporum. There was no correlation between heartwood content and size or number of infections, while the diameter of the stump was somewhat correlated with the occurrence and extent of infections. The stumps treated with Rotstop® had significantly fewer infections than the untreated stumps. Rotstop® performed best in the mid and the large diameter classes where only 20 percent and 10 percent respectively were infected while 80 percent of the untreated stumps in both classes were infected. The results indicate that an increased stump diameter may increase the risk for an infection but not necessarily the number of infections per stump. The conclusion is that delayed or late pre-commercial thinning in spruce should be avoided during the vegetation period or performed in combination with stump treatment to reduce the risk of infection.