Effects of Temperature and Moisture Duration on Spore Germination of Four Fungi that Cause Grapevine Trunk Diseases.

Grapevine trunk diseases (GTDs) are serious threats worldwide and are difficult to control, in part because the environmental requirements for epidemiological processes of the causal fungi are poorly understood. We therefore investigated the effects of temperature and moisture duration on spore germination of four fungi associated with two GTDs (Esca complex and Eutypa dieback): Phaeomoniella chlamydospora (Pch), Phaeoacremonium minimum (Pm), Cadophora luteo-olivacea (Cl), and Eutypa lata (El). Conidia of Pch, Pm, and Cl were similar: conidia of these fungi germinated profusely (>90%) between 20 and 30°C; Pch and Pm tended to germinate at higher temperatures (up to 40°C for Pm), and Cl at lower temperatures (as low as 5°C). El ascospores germinated between 10 and 30°C. The required duration of moist periods for germination was shortest for Cl (about 6 h), followed by Pm and El (about 12 h), and Pch (about 24 h). Further research on the environmental requirements of GTD fungi may increase our ability to predict infection periods and to thereby improve disease control.