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United States Department of Agriculture

Agricultural Research Service

Title: The Change in Quantity of Bacteria of Xanthomonas Axonopodis Pv Citri Dispersed Down Wind from Canker-Infected Grapefruit Trees During a Wind/rain Event

Authors
item Bock, C. H. - UNIV. OF FLORIDA
item Parker, P. E. - USDA-APHIS
item Gottwald, Timothy

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: September 30, 2005
Publication Date: November 7, 2005
Citation: Bock, C., Parker, P., Gottwald, T.R. 2005. The change in quantity of bacteria of xanthomonas axonopodis pv citri dispersed down wind from canker-infected grapefruit trees during a wind/rain event. International Citrus Canker and Huanglongbing Workshop, Orlando, FL, Nov. 2005. P13,p.78.

Interpretive Summary: The yield and marketability of citrus is limited in several tropical wet parts of the world by citrus canker (caused by Xanthomonas axonopodis pv. citri, Xac). The disease can cause severe epidemics and there are few options for control, although eradication has been favored. A thorough knowledge of the epidemiology of Xac can contribute to improving the eradication program and eventual management of citrus canker. There is limited information available on the dispersal of bacteria in the field during rain showers (which are often associated with strong winds, especially in tropical storms and hurricanes). The aim of this work was to investigate the dynamics of dispersal of the bacteria from infected plants during wind-rain events. The quantity of bacteria declined rapidly in the first few h of dispersal, and the relationship between quantity of bacteria dispersed and time was described by a power law model. Most bacteria dispersed were collected within the first 10 min of the wind/rain event . Both short- and long-term storm events occur in Florida and even the latter are often characterized by bands of fast moving, short-lived storms. These results suggest that it is during the first few minutes of a storm that greatest quantities of Xac bacteria are dispersed. Although bacteria continue to be produced beyond the first few minutes of the storm the concentrations are dramatically reduced, so the first minutes of a storm are likely to be a critical period for dispersal of Xac bacteria and infection of surrounding citrus.

Technical Abstract: The yield and marketability of citrus is limited in several tropical wet parts of the world by citrus canker (caused by Xanthomonas axonopodis pv. citri, Xac). The disease can cause severe epidemics and there are few options for control, although eradication has been favored (1). A thorough knowledge of the epidemiology of Xac can contribute to improving the eradication program and eventual management of citrus canker. There is limited information available on the dispersal of bacteria in the field during rain showers (which are often associated with strong winds, especially in tropical storms and hurricanes). The aim of this work was to investigate the dynamics of dispersal of the bacteria from infected plants during wind-rain events. Wind was simulated using yard-blowers (11-27 m/sec, depending on experiment), and spray (4.5 l/min) was generated using sprayers directed horizontally into the canopy of canker-infected plants (2). Panel and funnel samplers collected splash down wind and under the plants, respectively. The volume collected was measured and bacteria colony counts were made on nutrient agar and related to wind duration using regression analysis. Bacteria were collected down wind from trees throughout a 52 h sampling period (Figure 1), however, the quantity of bacteria declined rapidly in the first few h of dispersal. The relationship between quantity of bacteria dispersed and time was described by a power law model. In a second experiment over 4 h and more frequent sampling 50% of the total bacteria dispersed were collected within the first 10 min of the wind/rain event (Table 1). The concentration of bacteria in the splash declined rapidly in the first few minutes of dispersal. Funnel samplers located under the canopy showed a similar trend in bacteria dispersal with time. Both short- and long-term storm events occur in Florida and even the latter are often characterized by bands of fast moving, short-lived storms. These results suggest that it is during the first few minutes of a storm that greatest quantities of Xac bacteria are dispersed. Although bacteria continue to be produced beyond the first few minutes of the storm the concentrations are dramatically reduced, so the first minutes of a storm are likely to be a critical period for dispersal of Xac bacteria and infection of surrounding citrus.

Last Modified: 8/29/2014
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