Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 9/30/2005
Publication Date: 11/7/2005
Citation: Gottwald, T.R., Graham, J., Riley, T., Sun, X., Hughes, G., Ferrandino, F., Taylor, E.L., Bock, C., Irey, M.S., Gilligan, C., Seem, B. 2005. Estimating the increase and spread of citrus canker caused by the interaction of pedestrian versus catastrophic weather events, humans, and bad luck. Second International Citrus Canker and Huanglongbing Workshop, Orlando, FL, November 7-11, 2005. C3, p. 13.
Technical Abstract: The bacteria, Xanthomonas axonopodis pv. citri (Xac), that causes Asiatic Citrus Canker (ACC) can move in any of a variety of modes in the presence of free moisture. From a meteorological point of view, gentle rain, rain with wind, rain storms, tropical storms, and hurricanes can all disperse Xac inoculum. The preceding series of meteorological events are increasingly more effective at dispersing inoculum over greater distances. If inoculum is maintained in a moist condition, mechanical spread and subsequent infection can occur also over a range from within tree to very long distance dispersal via human transport. Human assisted dispersal can also occur by movement of infected plant material, which can range from very short distance (local) to extremely long range (global = among countries and continents). From an epidemiological point of view, epidemics of ACC are composed of a series of discontinuous pulses of inoculum that first introduce Xac to the host population, then a combination of multiple meteorological and mechanical events further dispersing inoculum and exacerbating the epidemic. However, dispersal events vary greatly in distance and quantity of inoculum dispersed. As a result, the temporal dynamics of citrus canker within individual trees, within individual plantings, and regionally is essentially a stair-step function with the ‘rise’ of the step directly related to the intensity of the event and the ‘run’ directly related to the time between events. Another complicating factor is the incidence and severity of Asian leafminer. This insect has greatly exacerbated ACC epidemics in both Florida and Brazil by causing prodigious production of inoculum and increasing the number of infection courts that greatly enhance and prolong host susceptibility and when infected, result in further increases in inoculum production. The interaction between leafminer, Xac, and meteorological events results in greatly increased bacterial dispersal and subsequent bacterial infection gradients. Numerous storm and mechanical events have contributed to the spatial distribution and patterns of spread of ACC in Florida. The three hurricanes and one tropical storm that crossed the Florida peninsula during 2004 exacerbated preexisting ACC infections and established numerous new infections. The various affects of rain intensity, weather frontal boundaries, tornados, and other meteorological events will be discussed.