Ramularia leaf spot: an emergent disease of cotton in Brazil

Originated from the semi-arid highlands of Mexico, upland cotton (Gossypium hirsutum L.) accounts for more than 90% of world cotton fiber production. Intensively cultivated in Brazilian Cerrado since the early 1980s, the wet and warm environment of the region favors epidemics of fungal diseases such a Ramularia leaf spot, which emerged as the main disease of cotton cultivated in an area as large as one million hectares. Fungicides remain as the only resort to effectively control the disease and up to eight sequential sprays may be needed during the season. Research to improve disease management has been conducted during the last two decades including cultural, genetic, chemical and biological control methods. In this review we summarize current knowledge of the disease and the main findings and gaps on disease epidemiology and management and discuss on future direction towards a more sustainable management of a disease of greatest concern to cotton farmers in Brazil.