Effects of temperature, and water stress in sycamore, on growth of Cryptostroma corticale

Conidial germination, germ-tube growth and mycelial extension of Cryptostroma corticale on 3% malt agar were all optimal at 25 °C. Dry conidia lost their viability more rapidly at 25° or 30° than those at 20° or below. The fungus grew more extensively in young sycamores (Acer pseudoplatanus) at 25° than at 15° and, at 25°, its growth was greater in trees subjected to water stress. In all inoculation experiments the extent of the stain induced by the fungus was correlated significantly (P ≤ 0.001) with the recovery of C. corticale from the tissues and might thus be used to monitor its progress in sycamore. The results are discussed in relation to the hypothesis that sooty bark disease caused by this fungus is associated with high summer temperatures.