Influence of yield on coffee tree leaves rust

Abstract

Yield is a definite factor in the development of coffee tree rust. With the objective of learning which processes occur in those plants and affect the susceptibility to rust, trials were conducted at Epamig Experimental Farm, in Machado County, Brazil, from 1989 to 1991. Evaluation of coffee tree rust, leaf nitrogen, potassium and boron were investigated on plants which underwent a total pruning of fruits, in plants with 50% and 100% of berries, at two pruning times, viz December and April, and in three developmental stages of fruit (initial, green and ripe stages). Correlation coefficient among rust indices and contents of leaf compounds (N, K and B) were also determined. The leaf nitrogen contents occurred at normal levels, although an inverse correlation had been observed with the rust indices. The inverse relationships between leaf potassium contents and rust indices denoted that low levels of that element favored the disease. There was no significant correlation between boron and rust index.