CHARACTERIZATION AND MANAGEMENT OF BLACK LEAF SPOT OF PAPAYA CAUSED BY Asperisporium caricae (Speg.) Maubl.
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Date
2015-06
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University of Horticultural Sciences, Bagalkot. (College of Horticulture, Bengaluru).
Abstract
Papaya is one of the important fruit crop and known to be infected by several diseases. Among the fungal diseases, black leaf spot caused by Asperisporium caricae is a serious disease of papaya in most of the papaya growing areas. The survey conducted in major papaya growing areas in Southern Karnataka revealed that the highest disease severity of 80.80 per cent on leaves was observed at Gopalapura village in Srinivaspura taluk in Kolar district, followed by 70.80 at Talagunda village in Kolar district and the lowest of 31.15 per cent in Nayanahalli village at Chikkaballapura district. Symptoms of the disease were irregular dark brown to black spots on the lower surface of the leaves and slightly tan colored spots on the corresponding upper surface. The pathogen failed to grow on any of the media tested. The pathogen known to produce conidiophores, which were olivaceous brown, geniculate, smooth in dense fascicle with prominent conidial scars at the tip and measured up to 50-52 µm long × 6-9 µm wide. Conidia were elliptic ovoid, rounded at the top, hyaline to brown in colour, size of the conidia varied from 14-30 × 5-10 μm in length. Spore germination of A. caricae was maximum (60.00 per cent) in two per cent dextrose at 15ºC. The nucleotide sequence of the pathogen had 97 per cent homology with Asperisporium caricae accession number NR119970. The fungicides, hexaconazole @ 0.1 per cent (PDI 46.87 per cent), followed by mancozeb @ 0.25 per cent (PDI 49.68 per cent) and difenconazole @ 0.1 per cent (PDI 50.31 per cent) were found to be highly effective against the pathogen under field conditions.