Biological characteristics and control agent screening of the guava twig blight pathogen

Objective This study aims to clarify the biological characteristics of Neopestalotiopsis egyptiaca, the causal agent of guava twig blight, and screen effective fungicides to provide a theoretical basis for disease control.

Method The effects of different culture conditions on fungal growth and conidial germination were determined through single-factor experiments. The inhibitory effects of six common chemical fungicides were evaluated using the mycelial growth rate method.

Result Optimal mycelial growth was observed at 25 ℃, pH 5.0, and under 24 h light exposure. In contrast, sporulation was significantly enhanced at 20 ℃, pH 10.0, and under 12 h light conditions. The optimal conidial germination occurred at 25 ℃ and pH 7.0. Furthermore, both mycelia and conidia exhibited certain salt tolerance. Among the six tested fungicides, thiophanate-methyl and pyraclostrobin showed the strongest inhibitory effects, with half maxmal effective concentration (EC₅₀) of 0.6986 and 1.4054 μg/mL, respectively. Kasugamycin and mancozeb also demonstrated inhibitory activity, with EC₅₀ of 244.4771 and 365.9905 μg/mL, respectively.

Conclusion N. egyptiaca exhibits strong adaptability, thriving across a wide range of temperatures and pH levels. In vitro toxicity tests indicate that thiophanate-methyl and pyraclostrobin are the most effective fungicides and should be prioritized for field control.