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Thesis

Epidemiology and Management of Turcicum leaf Blight of Maize Caused by Exserohilum turcicum (Pass.) Leonard and Suggs

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2005
M.S.Kulkarni
UAS Dharwad
Ph.D

Turcicum leaf blight disease of maize caused by Exserohilum turcicum symptoms were recognized by long spindle shaped necrotic lesions with grey colour centre, immature and chaffy ears. The disease appeared in severe form in most of the maize growing areas of Karnataka. Crop loss estimation studies revealed that, avoidable grain and stover yield losses in susceptible genotype were to the extent of 52 and 40 per cent, respectively. Linear regression crop loss models were developed. Arabhavi isolate recorded high virulence. Sixty-five days old plants found vlnerability to infection. An incubation period of 28 hours was found ideal for more than 90 per cent spore germination. Saccharum arundinaceum Retz. was identified as a potential alternate host to E. turcicum and plays an important role in the epidemiology of TLB in Karnataka. Significantly maximum disease severity was noticed in crop sown on 16th September. Crop sown between February and April found least affected. The weather factors viz., minimum temperature (11.3-21.40C), maximum temperature (26.3-29.40C), relative humidity (58.7-84.5%) and rainfall (47.104 mm) were highly favourable for disease epidemic. The locations viz., Arabhavi, Dharwad, Devihosur, Sankeshwar and Nagenahalli were identified as ‘hot spots’ in Karnataka. Significant ad positive correlation existed between rainfall and relative humidity with spore load. The genotypes viz., Allrounder, IB-8501, Cargill 900M, Hi-Shell, NAC-6004, C-111, KH-517, Kaveri 235 and NK-6240 were identified as slow blighters. The disease was responsible for photosynthesis loss to the extent of 89.40 per cent in susceptible genotype. Fourteen inbred lines registered as resistant sources. The QPM genotypes HQPM-4 and HQPM-5 found highly resistant. Integration of tolerant hybrid DMH-2 and seed treatment with carboxin power (2 g/kg) or combined seed treatment with Azospirillum sp. (25 g/kg) and Trichoderma harzianum (6 g/kg) followed by three sprays with mancozeb ( 0.25%) was found to be the most effective IDM package.

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