Epidemiologia da ferrugem e da cercosporiose em cafeeiro irrigado sob pivô central

Abstract

Plant disease can be influenced by irrigation method if the microclimate is modified specially at the aerial part of plants, contributing to leaf disease intensity. This research aimed to evaluate the occurrence and severity of rust and just the occurrence of brown eye spot at coffee leaves, in coffee plants irrigated by center pivot, with different water depths. The experiment was carried out at the experimental area of Engineering Department at Federal University of Lavras, at coffee plants, Rubi cultivar (MG 1192) planted on March 1999 spaced 3,5 meters between rows and 0,8 meters between plants susceptible to rust and brown eye spot. The experimental design was randomized blocks with three replicates and six water depths at plots, corresponding to 60%, 80%, 100%, 120% e 140% of water depth evaporated from a Class A pan, including the non irrigated control plot. The disease was evaluated on coffee leaves, at an average 23 days interval, from April 2004 through June 2006. Each plot was made up of 8 effective plants, being inspected 8 leaves per plant, with four at north face and four at south face, all inspected at the medium third vertical part of plant, on third our fourth pair of leaves of lateral branches. The area up to the disease progress curve (AACPD) was calculated and the analysis of variance tested, including regression analysis for those cases when the probability level was less than 5%. At 2004/2005 harvest, a significant difference was observed among irrigation water depths and the side of plant (North or South) for both 2004/2005 and 2005/2006 harvests. A larger incidence of rust at the non irrigated plot was observed while the smallest was observed at the largest water depth (140% ECA), with larger disease progress observed at the south face. The severity of rust was larger at 80% ECA and the smallest at 140% ECA, with largest disease progress at south face of plant. Occurrence and severity peaks for rust were observed in August for both years. In relation to brown eye spot, no significant interaction was detected among water depths and plant face. It could be verified that, for brown eye spot occurrence, significant effects were detected among water depths on both harvests and in plant face only for harvest 2004/2005. Larger occurrence at 140% ECA and smallest occurrence at non irrigated plot, with larger disease progress at north face of plant. Two brown eye spot peaks were observed, one in March and another in June, with larger occurrence in June for both harvests. Larger occurrence of brown eye spot was observed from May to July.