Methods for efficient estimation of rust incidence in coffee plantations

Abstract

Two systematic patterns were evaluated for efficiency in estimating coffee rust incidence in lots of Caturra and Bourbon. True disease incidence was determined in the middle third of each tree in the selected lot. The different sampling patterns were compared on the basis of the bias and standard error of the estimated incidences obtained with computer simulations of different combinations of sample sizes, average incidence and patterns of spatial dispersion for the disease. The parallel row pattern was at least as efficient as the traditionally recommended W pattern. In order to attain better estimates of coffee rust incidence, it seems more important to sample more leaves per tree than more trees per field. The recommended protocol for estimating rust incidence in coffee plantations is described.