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Centella asiatica is an important medicinal herb that is widely used as leafy vegetable in several Asian countries including Sri Lanka. C. asiatica production has been severely affected by leaf spot disease; even a minor leaf spot can result in a significant loss in yield. The present study aimed to identify the pathogen which causing leaf spot disease in C. asiatica in Jaffna peninsula and to control the pathogen using natural extracts. Diseased leaf samples were collected from Valikamam, Vadamarachchi and Thenmarachchi regions, in each region three sites were selected where C. asiatica is cultivated for commercial purpose. Symptoms were characterized and pathogen was isolated on potato dextrose agar (PDA) medium. Culture characters and morphological characters were studied for each isolates. Koch’s postulates were carried out to confirm the pathogenicity of the isolates. Furthermore, in vitro assays were carried out to control the pathogen with natural plant extracts. Leaf lesions were irregular or angular, pale brown to grayish white in the center, and surrounded by dark purplish halo. The lesion had pycnidia, scattered, dark brown to rusty brown, globose and immersed in host tissue. In PDA medium, young cultures were white in colour, with fluffy and aerial mycelia and mature cultures were whitish grey to black with pycnidia. Hyaline young hyphae turned to pigmented when mature. Chlamydospores were observed in mycelium. Conidia were formed in the pycnidia. The conidia were initially unicellular, hyaline ellipsoid to sub-ovoid. Mature conidia were dark brown, bi-celled, thick walled and ellipsoid. Based on the morphological features the fungal isolates were identified as Lasiodiplodia sp. There was no variation among the isolates collected from different region in Jaffna peninsula. Koch’s postulates confirmed the pathogenicity of Lasiodiplodia sp. Turmeric water extract significantly reduced mycelial growth and spore germination in in-vitro. Association of Lasiodiplodia sp. with C. asiatica has not reported earlier in Sri Lanka, therefore, this is the first report for leaf spot disease caused by Lasiodiplodia sp. on C. asiatica. Further studies are being carried out to identify the pathogen based on molecular techniques.

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