Morphological and Molecular Characterization of Lasiodiplodia theobromae Causing Stem Gummosis Disease in Rubber Trees and Its Chemical Control Strategies

Rubber tree (<i>Hevea brasiliensis</i> Muell. Arg.) is a major tropical cash crop in southern China, with Hainan and Yunnan provinces being the main planting areas. In July 2023, bark cracking and gumming were observed on the trunks of mature rubber trees in Haikou City, Hainan Province, leading to xylem rot, which severely impacted the healthy growth of the rubber trees. The present study was conducted to confirm the pathogenicity of the patho-gen associated with stem gummosis disease, characterize it using morphological and mo-lecular tools, and devise field management strategies. Pathogenicity testing showed that this strain induced symptoms similar to those of natural outdoor infestation. Based on morphological study and molecular analyses of internal transcribed spacer (<i>ITS</i>), transla-tion elongation factor 1 alpha (<i>TEF1-α</i>), and β-tubulin 2 (<i>TUB2</i>) sequences, the causal agent was identified as <i>Lasiodiplodia theobromae</i>. Field trials demonstrated that an inte-grated fungicide approach-combining trunk application of Bordeaux mixture with root irrigation using citric acid-copper 6.4% + chelated copper-ammonium 15% at both 0.1% and 0.2% concentration-effectively suppressed stem gummosis disease incidence in rub-ber trees. To the best of our knowledge, this is the first report of <i>L. theobromae</i> causing stem gummosis on rubber tree in China. The findings of this study can provide valuable infor-mation for the management strategies and understanding of this disease.