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United States Department of Agriculture

Agricultural Research Service

Research Project: PECAN CULTIVATION AND DISEASE MANAGEMENT Title: Wind speed and wind-associated leaf injury affect severity of citrus canker on Swingle citrumelo

Authors
item Bock, Clive
item Graham, Jim -
item Gottwald, Timothy
item Cook, Amanda -
item Parker, Paul -

Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 19, 2010
Publication Date: January 15, 2010
Citation: Bock, C.H., Graham, J.H., Gottwald, T.R., Cook, A.Z., Parker, P.E. 2010. Wind speed and wind-associated leaf injury affect severity of citrus canker on Swingle citrumelo. European Journal of Plant Pathology. 128:21-38.

Interpretive Summary: Citrus canker can cause severe damage to citrus. It is endemic in Florida. The bacterium is dispersed in rain splash, particularly in strong wind. Simulated wind/rain events on young plants of Swingle citrumelo in the presence of inoculum showed higher wind speeds (>10 m sec-1) consistently resulted in higher incidence and severity of citrus canker developing. At 15 ms-1, there was a dramatic increase in disease. Visible injury to leaves of Swingle citrumelo due to wind was evident at wind speeds = 13 m sec-1. The relationship between wind speed and disease, and wind speed and injury was described by a logistic model. More disease was associated with visible injury as the wind speed increased. Disease not associated with visible injury also increased with wind speed. The petiole-leaflet junction was more often infected at higher wind speeds (=17 m sec-1). Concentration of the inoculum increased disease. Reducing wind speed in citrus groves with the aid of wind breaks may contribute to a reduction in the severity of an epidemic by reducing dispersal and infection events.

Technical Abstract: Citrus canker (caused by the bacterial pathogen Xanthomonas citri subsp. citri, Xcc) can cause severe damage to citrus. It is endemic in Florida, and occurs in other citrus growing regions. The bacterium is dispersed predominantly in rain splash. To simulate dispersal in splash, and to investigate the effect of wind speed on infection, young plants of Swingle citrumelo were exposed to sprayed inoculum at different wind speeds. Wind was generated using an axial fan, and a pressurized sprayer delivered the inoculum spray. In the five experiments higher wind speeds (>10 m sec-1) consistently resulted in higher incidence and severity of citrus canker developing. By 15 ms-1, there was a dramatic increase in disease. Visible injury to leaves of Swingle citrumelo due to wind was evident at wind speeds = 13 m sec-1. The relationship between wind speed and disease, and wind speed and injury was described by a logistic model. More disease was associated with visible injury as the wind speed increased, and disease not associated with visible injury also increased with wind speed. The petiole-leaflet junction was more often infected at higher wind speeds (=17 m sec-1). The concentration of the Xcc inoculum increased the incidence and severity of citrus canker in all experiments. Reducing wind speed in citrus groves with the aid of wind breaks may contribute to a reduction in the severity of an epidemic by reducing dispersal and infection events.

Last Modified: 11/26/2014