ETIOLOGY AND MANAGEMENT OF ALTERNARIA LEAF SPOT (Alternaria cucumerina (Ellis and Everh.) Elliott) AND ANTHRACNOSE (Colletotrichum lagenarium (Pass.) Ellis and Halsted) DISEASES IN BOTTLE GOURD (Lagenaria siceraria (Mol.) Standl.)
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Date
2019-11
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University of Horticultural Sciences, Bagalkot
Abstract
Bottle gourd [Lagenaria siceraria (Mol.) Standl.] is one of commonly grown vegetable crop in India. Anthracnose and leaf spot are major diseases affecting the crop, hence a study was conducted on etiology and management of diseases. The causal agents of Alternaria leaf spot and anthracnose were confirmed through pathogenicity test, cultural, morphological and molecular identification as Alternaria cucumerina and Colletotrichum lagenarium respectively. Among eight solid media tested, potato dextrose agar supported maximum (85.26 mm) growth of A. cucumerina at 12 days of incubation and temperature of 30oC and pH of 6 were optimum for the growth of the pathogen. Colletotrichum lagenarium maximum myceial growth (86.66 mm) was observed in PDA, temperature of 25o C and pH 6 were found favourable for the growth of the pathogen.
In vitro evaluation of fungicides against A. cucumerina revealed that at 500 ppm concentration the fungicide propiconazole gave maximum inhibition (100.00 %) of radial mycelial growth and lowest inhibition was recorded in thiophenate methyl (24.81 %) followed by carbendazim (25.55 %). Among bioagents Trichoderma harzianum was most effective in inhibiting the mycelia growth of A. cucumerina with 75.30 per cent inhibition. In case of C. lagenarium, carbendazim+ mancozeb and propiconazole gave maximum inhibition (100.00 %) of radial mycelial growth at all three concentrations tested. Trichoderma harzianum was most effective in inhibiting the mycelia growth of C. lagenarium with 88.80 per cent inhibition.
Field evaluation of fungicides and bio agents against Alternaria leaf spot disease indicated that, two foliar sprays of hexaconazole @ 0.1 per cent recorded least PDI (23.60). Treatment propiconozole@ 0.05 % gave least per cent disease incidence (13.87) on fruits with highest reduction of anthracnose disease with highest yield 15.78 t/ha and net returns 88,883 Rs/ha.
Among thirteen genotypes screened against Alternaria leaf spot disease under natural epiphytotic conditions the genotype Arka Bahar registered lowest PDI (24.87). In case of anthracnose disease genotypes BL-9 and Arka Bahar showed moderately resistant reaction with lowest Per cent Disease Incidence of 28.20 and 26.50 respectively.