Dynamics of cotton ramulosis epidemics caused by Colletotrichum gossypii var. cephalosporioides in Colombia

摘要

The main cotton growing regions in South America are affected by Colletotrichum gossypii var. cephalosporioides (Cgc). The most severe epidemics provoke considerable yield reductions linked to meristem necrosis, over-sprouting, branching and stunting. The SinA Valley is the greatest cotton producer in Colombia and is heavily affected by this disease. Using data from field trials conducted in 2012, 2013 and 2014 in a naturally infested area covering 15 planting dates, we attempted to identify weather variables linked to ramulosis epidemics. Cotton planting season in the SinA Valley runs from August to November, with higher rainfall intensity and frequency for crops planted earlier at the season while decreasing as the meridional winter solstice is approached. Rainfall, temperature and RH variables were significantly correlated with disease development (measured as AUDPS for ramulosis infection intensity). Rainfall alone was able to explain the majority of variation in ramulosis development across all the testing planting dates. A linear regression model was fitted for this association between ramulosis development and accumulated rainfall. Disease development is higher in the early planting dates (mid-August to September) while the disease is absent in crops established at October.