Venturia inaequalis, causal agent of apple scab, has lower tolerance than V. nashicola, causal agent of Japanese pear scab, for high temperature

Abstract

The incidence of apple scab, caused by V. inaequalis, has gradually decreased in recent years, while the incidence of Japanese pear scab, caused by V. nashicola, has been high. For that reason, the effects of high temperature on conidial germination and mycelial survival were investigated. Conidial germination of V. inaequalis was strongly inhibted at 35°C and 40°C as compared with that of V. nashicola. Mycelia of V. inaequalis did not survive at 40°C, but mycelia of V. nashicola did. From these results, conidial germination and mycelial survival of V. inaequalis seems to have lower tolerance than V. nashicola to high temperature. Therefore, a primary factor in the recent decrease of apple scab incidence may be due its greater sensitivity to high temperatures compared with Japanese pear scab fungus, even though the two kinds of fungi have almost the same epidemiological traits.