Modelling the spread of butt rot in a Picea abies stand in Finland to evaluate the profitability of stump protection against Heterobasidion annosum

A simulation model for the spread of butt rot in a Norway spruce (Picea abies (L.) Karst.) plantation was developed for southern Finland. It consisted of submodels for stand growth, infection of stumps with Heterobasidion annosum (Fr.) Bref., stump treatment, harvesting damages, vegetative spread of H. annosum in the root system and decaying of standing trees The simulation model was based on earlier studies conducted in the Nordic countries. Simulations indicated that summer thinnings increase the proportion of decaying trees the more the higher is the infection frequency of the stumps. Early and frequent summer thinnings also increased the proportion of decaying trees. When the stumps were treated, the amount of butt rot stayed near the same level as with winter thinnings. Stump treatment was profitable in most cases when the stump infection frequency was more than 20%. One summer cutting without stump treatment caused the most severe economical losses in the first thinning. If the stand was infected in the first thinning, the profitability of stump treatment in the second thinning was low. (C) 1998 Elsevier Science B.V.