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United States Department of Agriculture

Agricultural Research Service


Location: Subtropical Plant Pathology Research

Title: The Effect of Irrigation on the Temporal Increase of Citrus Variegated Chlorosis

item Goncalves, Fabricio -
item Stuchi, Eduardo -
item Lourenco, Silvia -
item Kriss, Alissa
item Gottwald, Timothy
item Amorim, Lilian -

Submitted to: International Research Conference on Huanglongbing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 2013
Publication Date: N/A

Interpretive Summary: The effect that various levels of irrigation had on incidence and severity of citrus variegated chlorosis (CVC), caused by Xylella fastidiosa, on fruit and leaves was evaluated over three years. Irrigation reduced both symptoms on leaves and the number of symptomatic fruit per tree, indicating higher disease levels were found on water-stressed plants. Both disease incidence and severity increased over time regardless of the level of irrigation used, and higher incidence was found on the upper branches of the tree compared to the lower branches.

Technical Abstract: The incidence and severity of citrus variegated chlorosis (CVC) caused by Xylella fastidiosa is higher in the northern region than in the southern region of Sao Paulo, Brazil. This is in part due to differences in the climate and especially rainfall, as the northern region tends to be drier than the southern region. The progress of CVC under three levels of irrigation was assessed in a grove located in the northern region of Sao Paulo. Trees (10-yr-old Natal sweet orange) were arranged in a randomized complete block with a 3x2 factorial scheme, with three levels of irrigation and two methods of infection of X. fastidiosa. Disease incidence in branches and number of symptomatic fruit per tree were evaluated for three years. A monomolecular model was used to describe the progress of CVC incidence for all treatments. Irrigation reduced CVC symptoms in trees, especially the number of symptomatic fruit per tree. Based on significant reduction of symptomatic fruit, irrigation in citrus can be used also to reduce the main negative effect of CVC, which is fruit size. Our results also explain the higher intensity of CVC in the northern region of Sao Paulo state where a dry season occurs.

Last Modified: 4/19/2014
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