| Popis: |
Brunchorstia pinea (Karst.) Hohn [perfect = Ascocalyx abietina (Lagerb.) Morelet] causes shoot dieback in conifers. Damage of Scots pine plantations in Britain was first reported in the late 1970s, previously only Corsican pine was damaged. In both these species initial shoot tissue symptoms of water soaked and necrotic development in the buds and internodes were shown to develop earlier in the winter than they did in Europe and N.America. The milder winter conditons in Britain were thought to be invovled. Internode infections were relatively more frequent compared with bud infections in Scots pine than in Corsican pine. This leads to proportionally more shoot deaths due to internode girdling in Scots pine than in Corsican pine. In both species bud scales, proximal portions of the leaf scales and internode epidermis were proposed as sites of infection. Corsican pine was more susceptible to infection by B.pinea than Scots pine but not to development of necrosis in the tissue. Norway spruce was successfully infected which gives the first record of B.pinea on Norway spruce in Britain. Pyncidial production was greater on diseased Scots pines than Corsican pines and was believed to influence potential epidemic development. Variation in susceptibility within a Scots pine stand was associated with β-phellandrene levels of the cortical monoterpene component. High altitude favoured B.pinea as shoot vigour was low. It was proposed that prolonged periods of high humidity favoured B.pinea survival in shoot tissues as well as dissemination and germination of spores. Winter shading did not influence B.pinea development. Recent attacks of B.pinea in Britain were not due to increased pathogen virulence. Apothecia which are rare in Britain, were found in association with unusual environment conditions. Recent outbreaks of B.pinea were thought to be due to environmental conditions reducing host vigour and favouring B.pinea development. |
