Spatial distribution of coffee trees (Coffea arabica L.) potentially diseased with coffee leaf scorch caused by Xylella fastidiosa in Puerto Rico

Abstract

Coffee (Coffea arabica L.) is an economically and socially important crop. In Puerto Rico, the harvest of 2012 was the lowest in the history of the island, mainly because of the economic crisis and phytosanitary problems. The main production problems are of biotic origin. Coffee Leaf Scorch (CLS) also known as 'crespera' caused by the bacterium Xylella fastidiosa (Xf), results in significant economic losses in many countries. In the Caribbean Basin, Xf causes disease in coffee trees in Costa Rica, and in South America it causes epidemics in Brazil. To determine the presence of Xf in Puerto Rico, coffee trees showing CLS disease symptoms were tested with a double antibody sandwich enzyme linked immune absorbent assay (DAS-ELISA) specific for Xf. Spatial cluster analysis using SAT Scan was carried out on data from potentially symptomatic trees. Few trees (< 5%) had absorbance levels within the range of positive values (a 0.7) for Xf. There were significant differences (p<0.0001, x2) in the percentage of trees suspected of infection with Xf in the dry versus the rainy season. Also, the percentage of suspected trees was variable among localities (p<0.05, x2). Spatial clustering showed more than 14 times greater relative risk of encountering infected coffee trees with Xf at higher altitudes such as in Adjuntas, Jayuya and Yauco (p<0.001), which was related to higher numbers of potential vectors at those localities.