The effect of coffee production systems on potential vectors of Xylella fastidiosa in Puerto Rico
Puerto Rico was once a major exporter of coffee; coffee continues to have a major impact on Puerto Rican culture. In recent years, coffee production has greatly declined as United States labour regulations place Puerto Rico at a disadvantage compared to other Caribbean nations. Since the 1960s the government has used incentives to promote intensively farmed monocultures of 'sun coffee'. Ecological concerns have recently energized a movement to re-establish environmentally friendly 'shade coffee' where coffee is grown in the understory intercropped with trees that contribute to renewable soil quality and offer alternative crops for human consumption. We examined how the contrasting production systems impact the abundance and diversity of insect pest species. Specifically, we examined the distribution of sharpshooter leafhoppers (Cicadellidae: Cicadellinae) that are potential vectors of the pathogen Xylella fastidiosa that may impact two of Puerto Rico's main crops (coffee and citrus). Insect distribution was contrasted between sun coffee monocultures, low-diversity shade coffee (one predominant shade species) and high-diversity shade coffee (mixes of shade species). Results suggest that sun coffee and high-diversity shade coffee support comparatively low populations of Cicadellinae. Cicadellinae populations varied greatly in low-diversity shade coffee and were dependent on shade species utilized. Many shade species did not result in high pest numbers, but one of the most common shade species utilized in Puerto Rico, Inga vera, resulted in very much higher Cicadellinae populations when planted as the sole shade species. These results suggest that pest species assemblages need to be considered in developing the new shade coffee industry.