Survey, characterization and management of leaf blight of Chrysanthemum caused by Alternaria alternata (Fries) Keissler

Abstract

Leaf blight caused by Alternaria alternata is one of the most important foliar diseases hindering the cultivation of chrysanthemum as it infects both leaves and flowers. The survey conducted in eastern dry zone of Karnataka, India revealed highest disease severity at Chikkanahalli in Tumakuru district and the least disease severity (8%) at Mavahalli in Kolar district. The pathogen produced conidia which are typically muriform, dark brown, thick walled. The conidium was up to 33.93 – 57.42 μm long and 10.44 – 18.27 μm wide with 6 - 7 transverse septa and 1 - 3 longitudinal septa. (Majority of conidia are non-beaked few with short rudimentary dark brown beaks, with a range of 13.05 - 26.10 μm length). Molecular confirmation of the causal organism was done through PCR amplification and
sequencing of ITS region. In-vitro evaluation of fungicides revealed, among contact, systemic and combi-products tested copper oxy chloride 50%WP, hexaconazole 5% SC and Zineb 68% + hexaconazole 4% WP and tricyclazole 18% + mancozeb 62% WP respectively were effectively inhibited the pathogen. In-vivo evaluation of fungicides revealed, foliar application of copper oxy chloride 50% WP @ 0.3 per cent proved to be highly effective in arresting spread of the disease.