Epsilon Archive for Student Projects

Abstract

Each year, Heterobasidion spp. is a major cause of economic losses to forestry in the northern hemisphere, including Sweden. New results indicate that pre‐commercial thinnings could be at risk for Heterobasidion spp. infections. Since no wood usually is used from pre‐commercial thinnings, there would not be any timber losses from leaving high stumps instead of low stumps when carrying out this measure. It could therefore be of a great interest if the stump height, of both Norway spruce (Picea abies (L.) Karst.) and birch (Betula spp.), affects the susceptibility to Heterobasidion spp. after a pre‐commercial thinning is performed.

The objective of this study was to investigate if there were any differences in infection frequency from airborne Heterobasidion spp. spores depending on whether the stump height is high (1 m) or low (15 cm) in pre‐commercial thinnings in the southern Sweden. The efficacy of stump treatment by Plebiopsis gigantea (Fr.) Jül. and the infection frequency of birch were also investigated for the two stump heights in five different sites.

There was a significant difference in infection frequency between treated spruce, untreated spruce and birch when samples from both high and low stumps were included.

The efficacy is a measure of the reduced mean relative infected area of the infections related to a control. High untreated spruce did not show a difference in efficacy compare to low untreated spruce, nor did treated spruce and birch.

The infection frequency of birch stumps was significant higher on high stumps (17.3 %) and hence they were more susceptible to Heterobasidion spp. than low (12.2 %).

No significant effect of the susceptibility depending on the stump height was observed for untreated spruce nor treated spruce.

Other reasons than risk of infection could be a reason to create high treaded spruce stumps. One reason could be the more ergonomic treatment height compared to perform stump treatment on low height.

A five year long‐term research study was established with the objective to investigate if a known Heterobasidion spp. infection spreads into surrounding trees or if it dies out in inoculated high and low spruce stumps.

It is possible that the stump height is of importance for the spreading of Heterobasidion spp. infections in the long‐run, which is the purpose of the long‐term study to find out.