Etiology and chemical control of fungal gummosis disease in flowering cherry trees in Taiwan

Flowering cherries (<i>Prunus</i> subgenus <i>Cerasus</i>) are important street and ornamental trees in Taiwan. Gummosis disease is commonly observed on their trunks and branches, yet the causal agents remain poorly defined. In this study, fungal pathogens were isolated from diseased trees in northern Taiwan and identified through multilocus phylogenetic analysis and pathogenicity assays. Phylogenetic analysis based on internal transcribed spacer, <i>elongation factor 1-α</i>, and <i>β-tubulin</i> sequences revealed three associated species: <i>Botryosphaeria dothidea</i>, <i>Lasiodiplodia thailandica</i>, and <i>L. theobromae</i>. Artificial inoculation confirmed that all three species caused gummosis and internal wood discoloration and produced abundant pycnidia on stems of <i>Prunus campanulata</i> seedlings. To explore chemical control options, eight fungicides representing six modes of action were tested for inhibitory effect and systemic activity. Carbendazim, tebuconazole, propiconazole, and pyraclostrobin strongly inhibited mycelial growth of <i>Lasiodiplodia</i> spp. and <i>B. dothidea</i> (EC₅₀ < 1 mg kg^-1); while fluxapyroxad was highly effective against <i>Lasiodiplodia</i> spp. but not <i>B. dothidea</i>. Root tip-immersion and stem-injection translocation assays indicated good acropetal mobility of carbendazim, tebuconazole, propiconazole, isoprothiolane, and fluxapyroxad, and basipetal transport of tebuconazole, propiconazole, and pyraclostrobin. In greenhouse trials with tebuconazole by five different application methods, preventive stem injection consistently provided the best protection, markedly reducing disease severity, internal discoloration, and pathogen colonization. Topical application (stem painting) required the lowest fungicide input and was effective in suppressing external symptoms. Overall, this study clarifies the etiology of fungal gummosis disease in flowering cherries in Taiwan and demonstrates fungicide application strategies with potential for broader management of fungal trunk diseases in urban landscapes.