Simulated Heterobasidion disease development in Picea abies stands following precommercial thinning and the economic justification for control measures

The development of Heterobasidion infection following one precommercial thinning (PCT) in a Norway spruce stand was simulated in the root disease model RotStand, adjusted with a specific growth model for young trees. The effects of stand age at PCT, spore infection probability on PCT stumps, intensity of PCT and efficacy of control measures on disease development were simulated for different management alternatives and the percentage of decayed stems at final felling was compared. Economic outcomes during a rotation were calculated in the decision support system, Heureka. Stand age and the probability of spore infection at PCT did not significantly influence decay frequency at final felling. The percentage of decayed stems at final felling increased with increasing PCT intensity. PCT at stand age of 20 years with stump treatment reduced disease impact, and summer PCT with stump treatment resulted in higher economic outcome compared to PCT without stump treatment during summer or winter. Infection of PCT stumps can negatively impact timber production. If economic gain from stump treatment during PCT is sought, new cost efficient application techniques should be developed. Because results and conclusions are based on simulated disease development and treatment, more field research is needed to validate some findings.