Identification and Fungicide Sensitivity of Lasiodiplodia Species Causing Postharvest Fruit Rot of Durian in Hainan, China

Durian (Durio zibethinus Murr.), a renowned tropical fruit crop, is increasingly cultivated in the Hainan Province of China. In June 2025, symptoms of postharvest fruit rot were observed on durian fruits from a commercial orchard in Sanya City, Hainan Province, with a disease incidence of approximately 5.2%. Three fungal isolates were obtained and identified as Lasiodiplodia pseudotheobromae and L. lignicola based on morphological characterization and multi-locus phylogenetic analysis (combining ITS, TUB2, and EF1-α gene sequences). Pathogenicity assays confirmed both species as causal agents of durian postharvest rot, with rapid lesion expansion and eight tropical fruit hosts, including banana and mango, posing a threat to postharvest storage. Fungicide sensitivity tests showed imazalil and imazalil sulfate with mean EC50 values of 0.07 µg/mL and 0.08 µg/mL as most effective, followed by prochloraz, iprodione, and prochloraz-Mn. L. lignicola was more sensitive to most fungicides than L. pseudotheobromae. These findings underscore the need for species-specific fungicide strategies in disease management. This is the first report of L. pseudotheobromae and L. lignicola causing durian postharvest rot in this preliminary study from Hainan. With Hainan emerging as a key production region, further research is essential to develop effective control measures against this economically significant disease.