Infection and growth of Heterobasidion spp. in Picea abies

• Main Author: Berglund, Mattias
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2005
• Subjects: Not in use; please see Agris categories; Korhonen; Niemelä; Norway; Stump; Northern Sweden
• Online Access: https://pub.epsilon.slu.se/809/; https://pub.epsilon.slu.se/809/2/MattiasBerglund.pdf

In economical terms, species of Heterobasidion are among the most severe fungal pests in coniferous forests of the northern hemisphere. The fungi cause interior decay in the stem of trees and trees may also die as a cause of infection. Two species of Heterobasidion have been identified in Sweden, Heterobasidion annosum s.s. (Fr.) Bref. and Heterobasidion parviporum Niemelä & Korhonen. The former has been identified from southern to central Sweden whereas the latter is present throughout the whole country. Stump treatment, using chemical or biological treatment agents, is the most widely used silvicultural method to prevent infection by Heterobasidion. This thesis mainly focuses on different aspects of biological stump treatment using Phlebiopsis gigantea (Fr.) Jül. The effectiveness of stump treatment against air-borne Heterobasidion spores with P. gigantea, when applied at different rates of stump coverage was investigated in southern Sweden. The results showed that, in order to achieve the best control, the aim should be to cover the complete stump surface with the treatment agent. In another field experiment in southern Sweden the effectiveness of Finish and Swedish strains of P. gigantea was compared. Two formulations containing two species of Trichoderma were also included in the study. Two of the Swedish P. gigantea strains showed the best control against air-borne Heterobasidion spores. None of the Trichoderma formulations significantly reduced Heterobasidion infection. The effect of stump treatment using P. gigantea on stumps from trees that were already infected by H. parviporum at the time of felling was studied in south-western Sweden. It was hypothesized that P. gigantea may restrict the growth of Heterobasidion in the root system of treated stumps. However, no such effect was observed and treatment of stumps from already infected trees can, based on this study, not be recommended as a means of restricting the spread of the pathogen. In the last study, the ability of inoculated H. annosum s.s. to establish and grow in trees and stumps in northern Sweden (outside its natural range of distribution) was compared with the ability to establish and grow in southern Sweden. In the trees, H. annosum s.s. established in almost as many trees in the north as in the south of Sweden. However, spores of H. annosum s.s. showed an inability to establish on stumps, in both parts of the country. This indicates that routes of infection, other than through fresh stump surfaces may be involved in the disease cycle of H. annosum s.s. in Norway spruce.