Potential Leafhopper Vectors in Puerto Rico
Plant diseases caused by the xylem-limited bacterium, Xylella fastidiosa, are rapidly increasing in range and severity through the Americas. The strain responsible for citrus variegated chlorosis (CVC) has spread throughout South America causing multi-million dollar losses to the citrus industry. Recent outbreaks of Pierce’s Disease of grapes have caused similar economic losses to viticulture in California and preclude establishment of a wine industry in the southeastern United States. Other strains of X. fastidiosa have long been problematic for the peach and plum industry in the southeastern United States. Losses due to coffee leaf scorch (CLS) are increasing throughout Central America. New strains of X. fastidiosa are continually being discovered and threatening new crop species such as blueberries and ornamentals.
Despite the spread of X. fastidiosa throughout the Americas, this bacterium has yet to be identified in the Caribbean Basin. Many pest species have entered the US by moving in stepping stone fashion through islands in the Caribbean; citrus greening is a recent devastating example. The rapid spread of CVC through South America suggests that Florida citrus may also be at risk from expansion of X. fastidiosa diseases. Two of the major crop species within the Caribbean, citrus and coffee, have been shown to be highly susceptible to X. fastidiosa diseases. For these reasons we view monitoring the incidence of X. fastidiosa in the Caribbean as imperative.
Coffee planting in Adjuntas |
Checking sticky traps |
We recently concluded a 4-year study concluding that X. fastidiosa diseases are not yet present in detectable quantities in Puerto Rico. This study was a joint research effort between scientists from the University of Florida (Brent Brodbeck, Peter Andersen, and Russell Mizell), the USDA (John Hartung and Stuart McKamey) and the University of Puerto Rico (Mildred Zapata and Yobana Mariño-Cárdenas). Over 5,000 plant and insect samples were collected from the coffee/citrus growing regions of Puerto Rico; all samples proved negative for the presence of X. fastidiosa. However, we also concluded that Puerto Rico has an abundance of potential insect vectors so that X. fastidiosa strains will be difficult to control if they reach the islands. X. fastidiosa is only transmitted by sharpshooters (Cicadellidae:Cicadellinae) and froghoppers (Cercopidae) that feed on xylem fluid. In areas where X. fastidiosa diseases are abundant, species of sharpshooters are invariably the primary vectors. Only six sharpshooters have been recorded in Puerto Rico, and we found that four of these species were frequently abundant in coffee and citrus plantings. We view the sharpshooter species Caribovia coffeacola as most likely to be problematic as coffee is a primary host of this species; we also collected it feeding on citrus.
Our findings may have implications for the developing shade coffee industry in Puerto Rico. Shade coffee plantings are more environmentally friendly and sustainable as they are low input and offer habitat diversity that benefits bird and animal populations. Shade coffee also has a higher market value as it arguably has superior flavor. While habitat diversity offers ecological advantages, our previous research established that some hosts used in shade coffee plantings may increase populations of potential vector species. The highest populations of C. coffeacola recorded were in areas where the common leguminous tree, Inga vera, was mixed with coffee plantings. Caging experiments confirmed that this sharpshooter uses Inga vera as an ovipositional and developmental host; coffee serves primarily for feeding of adult Caribovia. Thus, combined plantings of I. vera and coffee allow the sharpshooter to complete its life cycle with a much higher frequency.
Caribova feeding on coffee |
Caging experiments in Adjuntas |
Proper selection of shade species may be important for development of Puerto Rico’s shade coffee industry, particularly if X. fastidiosa reaches the island. We are currently conducting a two year study examining vector utilization of commonly used shade plants to determine shade species that will result in sustainable shade coffee plantings. This is a joint effort between scientists from UF (Brent Brodbeck, Peter Andersen), the USDA (John Hartung), and the University of Puerto Rico (Mildred Zapata and Eduardo Schroder).
More Information
For more information contact Pete Andersen.