PRODUCTIVE FLOWS DETERMINE THE FROSTY POD ROT EPIDEMIC STRUCTURE OF CACAO IN SOUTHEASTERN MEXICO

Abstract

Cocoa (Theobroma cacao L.) production in Southeastern Mexico is affected by frosty pod rot (Moniliophthora roreri), with losses exceeding 75 %. Currently, there are no comprehensive studies analyzing the inoculum-fruiting relationship on the epidemic structure to improve the effective control of the disease. This study aimed to evaluate the effect of climatic conditions and the involvement of different fruiting flows on the increase of the epidemic intensity during a productive cycle in the state of Tabasco and Northern Chiapas, Mexico. In six plantations, 10,621 fruits 8 to 10 cm in size, associated with six fruiting courses were labeled during the 2011-2012 productive cycle. The disease incidence was assessed. The cumulative incidence progress curves of the total production cycle and the partial epidemics per fruit course were adjusted to temporal models. In addition, the area under the disease progression curve (AUDPC) and Yf were estimated. The relationship of incidence with temperature, relative humidity, and fruit quantity was analyzed. The disease occurred for 10 months, with an average incidence of 75.8 %. The absolute weekly incidence was positively related to the number of fruits (r = 0.55-0.82), number of hours/week of temperature in the range of 20-26 °C (r = 0.41-0.87), and relative humidity greater than 60 % (r = 0.40-0.67). AUDPC (14,132-8186), Y_f (54.5-88.7 %) and Weibull rates (0.003-0.005) of annual epidemics indicated polycyclic epidemics. The partial epidemic analysis by fruiting courses showed contrasting rates (P = 0.05) between a monocyclic epidemic (R² = 0.92 - 0.99) of the first and second fruit sets and polycyclic epidemics of the subsequent fruit settings (R² = 0.93 - 0.99), indicative of the effect of the primary inoculum, followed by a combination of this with the secondary inoculum, with significant increases through the production cycle. Results suggests that an effective disease control should consider both inoculum sources, as well as the use of predictive climatic warnings and subregional fruiting dynamics.