- Institutionen för sydsvensk skogsvetenskap, Sveriges lantbruksuniversitet
Blomquist, Mimmi; Herrera, Sebastian Larsson; Hofmann, Johan; Beram, Refika Ceyda; Cleary, Michelle; Ronnberg, Jonas
Heterobasidion is a severe threat to coniferous forests in the northern hemisphere. Accurate forest management is needed to safeguard the economic values at stake. In this paper we investigate the efficacy of stump treatment with urea and Phlebiopsis gigantea as control treatment in Norway spruce against airborne Heterobasidion infections. The aim of this study was to examine the infection frequency, i.e. frequency of stumps infected by airborne spores, and efficacy of the stump treatments after performing precommercial thinning and final felling, representing highly variable stump diameters. Today treatment after these cuttings are not standard practice across the world.From a total of 27 Norway spruce stands in the southern and mid-regions of Sweden, five precommercial thinning stands and five final felling stands with infection frequencies higher than an economical threshold for treatment, 20%, were selected. In these stands, the efficacy of stump treatment using urea and P. gigantea against Heterobasidion spp. was assessed on stumps of variable diameter. Wooden discs from stumps were analyzed for airborne infections of Heterobasidion spp. 7-8 weeks after treatment. To evaluate the efficacy of treatments, we used the following three different measurements; infection frequency (proportion of infected stumps), relative infected stump area and number of Heterobasidion colonies per square dm, which were tested using three different statistical models each represented by an efficacy value. Overall, untreated stumps were infected to a higher extent than treated stumps, and most infections were found in untreated stumps from final fellings. Treatment with P. gigantea was more efficient for larger sized stumps than small. In precommercial thinnings, urea performed better and had higher mean efficacy values (92-94%) compared to P. gigantea (59%-72%). In final fellings there were no significant differences between the treatments, both had high efficacy values (urea 95.5-99.8% vs P. gigantea 90-98%).Our findings point at the need for accurate stump treatment after precommercial thinning and final felling, when infection rates are likely to be high. Urea seems to be more effective than the biological control agent P. gigantea in controlling Heterobasidion infections in stumps created in precommercial thinnings. We therefore recommend to use urea in precommercial thinnings if possible. In final fellings either urea or P. gigantea can be used.
Forest Ecology and Management
2020, Volym: 462, artikelnummer: 117998
SLU Plant Protection Network