Effects of Temperature on Growth, Pathogenicity, and Fungicide Sensitivity of Two Coniella Species Causing Grape White Rot

Grape white rot, primarily caused by Coniella diplodiella and Coniella vitis, is a major fungal disease threatening grape production worldwide, with C. vitis more prevalent in China. Temperature is a critical environmental factor influencing pathogen development and disease outbreaks, but how temperature influences the biological characteristics, pathogenicity, and fungicide sensitivity of these two pathogens remains limited. This study aimed to evaluate the effects of temperature on mycelial growth, conidial germination, extracellular enzyme activity, pathogenicity, and fungicide sensitivity of C. diplodiella 2019 and C. vitis GP1. The growth, conidial germination, extracellular enzyme production, pathogenicity, and fungicide control efficacy against the two pathogens were systematically evaluated under different temperature conditions (5, 15, 25, 35, and 45 °C). Results showed temperature significantly affected all investigated traits in both species. Optimal mycelial growth, conidial germination, and pathogenicity occurred at moderate temperatures (25 °C), whereas extreme temperatures (5 °C and 45 °C) significantly markedly inhibited fungal development and disease severity. C. vitis GP1 showed greater adaptability and consistently higher pathogenicity than C. diplodiella 2019 across the tested temperature range. Fungicide sensitivity also differed between the two species, and the inhibitory activity of difenoconazole was significantly reduced under temperature extremes, indicating that fungicide performance is influenced by environmental temperature. These findings demonstrate that temperature regulates both fungal development and fungicide efficacy, providing new insights into the temperature-dependent epidemiology of grape white rot and a scientific basis for optimizing disease management under changing environmental conditions.