Jean-François Durand, and
First author and eighth authors: Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), UPR Bioagresseurs de pérennes, Avenue Agropolis-TAA-31, Montpellier, F-34398 France; second author: Institut National de la Recherche Agronomique (INRA), UMR729 Analyse des Systèmes et Biométrie, Montpellier, F-34060 France; third, fourth, fifth, and sixth authors: Instituto del Café de Costa Rica (ICAFE), AP 37-1000, San José, Costa Rica; seventh author: Université de Montpellier II (UMII), Département de Mathématiques, Montpellier, F-34095 France.
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Accepted for publication 15 May 2007.
We monitored the development of American leaf spot of coffee, a disease caused by the gemmiferous fungus Mycena citricolor, in 57 plots in Costa Rica for 1 or 2 years in order to gain a clearer understanding of conditions conducive to the disease and improve its control. During the investigation, characteristics of the coffee trees, crop management, and the environment were recorded. For the analyses, we used partial least-squares regression via the spline functions (PLSS), which is a nonlinear extension to partial least-squares regression (PLS). The fungus developed well in areas located between ≈1,100 and 1,550 m above sea level. Slopes were conducive to its development, but eastern-facing slopes were less affected than the others, probably because they were more exposed to sunlight, especially in the rainy season. The distance between planting rows, the shade percentage, coffee tree height, the type of shade, and the pruning system explained disease intensity due to their effects on coffee tree shading and, possibly, on the humidity conditions in the plot. Forest trees and fruit trees intercropped with coffee provided particularly propitious conditions. Apparently, fertilization was unfavorable for the disease, probably due to dilution phenomena associated with faster coffee tree growth. Finally, series of wet spells interspersed with dry spells, which were frequent in the middle of the rainy season, were critical for the disease, probably because they affected the production and release of gemmae and their viability. These results could be used to draw up a map of epidemic risks taking topographical factors into account. To reduce those risks and improve chemical control, our results suggested that farmers should space planting rows further apart, maintain light shading in the plantation, and prune their coffee trees.
Additional keywords:altitude, climate, cropping practices, Coffea arabica.
© 2007 The American Phytopathological Society