Journal of Taiwan Agricultural Research

Author:Chao-Jung Wu, Chiao-Wen Huang, Jer-Way Chang, and Hui-Fang Ni*

Abstract:

    The causal agent of lychee pepper spot disease is Colletotrichum siamense. The symptom shows black needle-like spots on leaf, fruit, petiole and pedicle. In this study, many isolates of Colletotrichum spp. were isolated from needle-like spots on lychee ‘Gue Wei’ and ‘No Mi Ci’ and all of them were identified as C. siamense based on morphology and molecular phylogenetic analysis. In our previous study, the pathogenicity of C. siamense on lychee has been validated on lychee ‘No Mi Ci’. In this study, pathogenicity test was conducted on lychee ‘TN 7’ to confirm that the pathogen causes symptoms on other variety in addition to ‘No Mi Ci’. The temperature effect on C. siamense mycelial growth and spore germination was investigated. It was found that the optimal temperature for mycelial growth was 25−30℃, and mycelia growth of C. siamense kept viable under 15℃. In addition, spores germinated and produced appressoria on lychee leaves under 20–30℃. The result of fungicide sensitivity test indicated that thiabendazole + oxine-copper and thiophanate–methyl are the most suppressive on mycelial growth of C. siamense, followed by iminoctadine triacetate and tebuconazole. In addition, thiabendazole + oxine-copper, dithianon and pyraclostrobin had best suppression on spore germination, followed by azoxystrobin + difenoconazole and tebuconazole. The results of this study provide information for fungicide selection and control strategy on lychee pepper spot disease in the field.

Key words:Lychee, Pepper spot disease, Fungicide sensitivity

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