Seasonal pattern in production of conidia of Godronia cassandrae f. sp. vaccinii in highbush blueberry in Norway.

摘要

Godronia canker (Godronia cassandrae f. sp. vaccinii) is a severe disease in young plantings of highbush blueberry (Vaccinium corymbosum L.) in Norway. In Europe, only the imperfect stage (Topospora myrtillii) has been reported, and thus conidia produced in pycnidia are assumed to be important for dissemination of the fungus. The seasonal pattern of production of conidia was investigated in a commercial planting of 'Jersey' in 1998 and a research planting of 'Bluecrop' in 1998 to 2000. The disease became apparent in March on shoots infected the preceding growing season, and lesions started to form pycnidia containing conidia in April. Samples of stems with distinct lesions of Godronia canker were collected from the bushes every two to three weeks from early spring to autumn. Stem pieces with lesions were shaken in water to release conidia from the pycnidia, and the numbers of conidia were determined by microscopy. Conidia were present throughout the growing season, but the highest numbers occurred during May, with 106 to more than 107 conidia per lesion. The numbers generally decreased during July to 20% or less of that found in May, and decreased further during September to around 4%. Ability to germinate remained high throughout the period conidia were trapped, from April to November/December. Options to manage the disease are discussed.