Análise espaço temporal do patossistema colletotrichum em cafeeiro e sua relação com os nutrientes minerais magnésio, cálcio e potássio

Abstract

The aim of this work was to evaluate the effect of mineral nutrition on coffee plants (Coffea arabica L.) susceptibility to Colletotrichum Complex diseases. Part of this work was carried out in nutrient solution, under controlled conditions in a growth chamber. In this part, were set up two assays to evaluate coffee leaves susceptibility to anthracnose, in the first one, coffee plants were submitted to different levels of magnesium, in the second one, plants were submitted to interaction between 5 different levels of both calcium and potassium. It was observed that as excess as deficiency of magnesium increase the susceptibility of coffee plants to anthracnose in leaves, it was observed the minimum critical level (0,5 mmol.L -1 ) and optimal level (1,5 mmol.L -1 ) for anthracnose resistance in leaves. In relation to calcium and potassium interaction, only for the different levels of potassium ther e were significant differences, the increase of the intensity of the disease increased by the addition of potassium. In the second part, analysis of temporal distribution of fruit necrosis in a coffee plantation with conventional management was carried out in Carmo do Rio Claro, MG, Brazil. Geostatistics were used as a tool for analysis. Were proposed and compared two evaluation methods for necrotic fruits in coffee trees. The first one evaluated the number of mummified fruits in one predetermined productive node, the second one evaluate the average incidence of productive node with mummified fruits in the same branch used in the first one method. Maps of different methods of disease evaluation were compared with each other, with leaf nutrient contents (Mg, Ca and K), production, and leafiness maps. Spatial analysis as used in this study allowed evaluate the spatial correlation between two evaluation methods to coffee necrotic fruits, foliar nutrient content (Mg, Ca and K), leafiness and distribution of disease during the time. Both methods used to evaluate necrotic fruits showed correspondent results for the detection of disease foci. Fruit necrosis presented an aggregate pattern of distribution with progress over time. Kriging maps make possible identify a region in which the initial focus of the disease was likely caused by Mg deficiency in leaf tissues.