Severe Red Rot Epidemics in Sugarcane in Sub-tropical India: Role of Aerial Spread of the Pathogen

Abstract

Colletotrichum falcatum Went causing red rot in sugarcane has gained a very high virulence in the sub-tropical India by evolving into a virulent pathotype CF13. The disease spread has reached 100% in several thousand hectares during the past few seasons. Reasons for such massive spread of the disease in the states of Uttar Pradesh and Bihar were investigated under field conditions. Observations on disease development in the affected canes revealed infections from soil, sett, water and air. However, more than 58% of the affected canes exhibited infections from aerial route as midrib lesions and the disease progressed from spindle to canes. Although sett and soil borne infections are known to cause rapid spread of disease in sugarcane, bountiful of aerial infections resulted in rapid spread of the disease or aids in large-scale disease build-up, supplementing primary sources of infections. Summer showers, continuous humid weather during grand growth phase and waterlogging during maturity phase along with continuous monocropping of the popular cv Co 0238 in the command area were attributed to the large-scale disease outbreaks. Hence, disease management strategy has to be revised to tackle aerial spread of the disease.