EPIDEMIOLOGY AND INTEGRATED MANAGEMENT OF COLOCASIA BLIGHT

Abstract

newlineABSTRACT newline newlineRepeated microscopic examination of diseased Colocasia plant parts and infested soil revealed the presence of mycelium, chlamydospores and oospores of Phytophthora Colocasiae, the blight pathogen. The pathogen was found to survive as chlamydospores and oospores in infected left over corms in the field and seed corms which constituted the primary source of inoculum under Himachal Pradesh conditions. Twenty four lines of Colocasia were field evaluated for two years against blight but none was disease free. However, two lines CE-7 and JC with disease severity in the range of 10.1-25.0% were categorized as moderately resistant. There was less sporangial germination of P. colocasiae being maximum at 250C. Maximum zoospore germination (82.6%) occurred at 150C. Twelve hours leaf wetness period was found essential to initiate disease and with an increase in leaf wetness period, there was corresponding decrease in incubation and latent periods. Earlier sown crop (May) gave higher crop yield inspite of more disease incidence than late sown crop. The appearance of disease was delayed by one week in mulched over unmulched crop and eupatorium leaves and twigs was the best mulch. Intercropping with maize reduced blight severity. Higher doses of nitrogen increased disease severity however, higher doses of phosphorus and potassium decreased it. Among different botanicals tested, dried powder of eupatorium inhibited mycelial growth of pathogen. Systemic fungicides Ridomil MZ, Matco-8-64, Unilax and Curzate M8 were effective in inhibiting mycelial growth of pathogen. Corm dip in Ridomil MZ at 0.3% for one hour before sowing and three fortnightly foliar sprays of Ridomil MZ at 0.25% controlled the disease. Combinations of systemic fungicides with protectants were better than individual fungicides in managing disease. Integration of corm dip in Indofil M-45 for one hour, eupatorium mulch and three fortnightly foliar sprays of Ridomil MZ were highly effective in reducing the Colocasia blight severity with 76.9% disease control. newline newline