Heterobasidion annosum infection of Picea abies following manual or mechanized stump treatment

Abstract

Heterobasidion annosum (Fr.) Bref. s. l. colonization following thinning was studied in 1246 stumps of Picea abies (L.) Karst. trees from 14 previously unthinned stands in Sweden. Treatments included mechanized and manual application of (1) 35% urea solution, (2) Phlebiopsis gigantea (Fr.) Jül. spores, and (3) 5% solution of disodium octaborate tetrahydrate (DOT), and untreated stumps, cut in the summer and winter. Compared with untreated stumps cut in the summer, all stump treatments and winter cuttings significantly reduced the colonized stump area 6–7 weeks after thinning by 88–99%. Mechanized stump treatment provided as good protection as manual treatment against H. annosum infections. The probability of spore infection (p _ij ) was reduced by 53–83% in mechanized treatment and 79–98% in manual treatment compared with untreated summer thinning. In terms of p _ij , urea had significantly higher control efficacy than P. gigantea and manual treatment performed better than mechanized treatment.

Keywords:

• Biological control
• chemical control
• disodium octaborate tetrahydrate
• Norway spruce
• Phlebiopsis gigantea
• stump infection
• thinning
• urea

Acknowledgments

The study was financed by Skogforsk's framework programme, The Swedish Forest Research Foundation (SSFf), Rattsjö Foundation and Wingqvist Foundation. The field data were collected by staff at Skogforsk's experimental stations in Ekebo, Brunsberg and Sävar, and by staff at The Swedish University for Agricultural Science's (SLU) experimental stations at Tönnersjöheden and Asa. Staff at SLU, Department of Forest Mycology and Pathology, provided help with the laboratory work. Dr Gunnar Jansson, Skogforsk, made useful comments on the statistical analysis. Dr Iben M. Thomsen, Dr Duncan J. Morrison, one anonymous referee and colleagues at Skogforsk made constructive comments on the manuscript. Mr Nigel Rollison revised the English language. The help of all these people is gratefully acknowledged.