Effect of windbreaks on wind speed and canker incidence on grapefruit

Authors: GRAHAM, JH - University Of Florida; MEYERS, ME - University Of Florida; Gottwald, Timothy; Bock, Clive

Submitted to: International Citrus Congress Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2017
Publication Date: 1/18/2018
Citation: Graham, J., Meyers, M., Gottwald, T.R., Bock, C.H. 2018. Effect of windbreaks on wind speed and canker incidence on grapefruit. International Citrus Congress Proceedings. 37:item 2.

Interpretive Summary: Citrus canker is a severe disease of citrus that can effect stems, leaves and fruit with unsightly lesions 'cankers' that diminish fruit quality and marketability. The disease also has international trade implications for exporting/importing countries who have trade restrictions/quarantines to keep infected fruit from establishing in uninfected areas. Disease control is a difficult but exceeding important to ensure importing countries that steps are being taken by exporters to ensure that only diseased free fruit enter the marketplace. The bacterial disease is spread from lesions to uninfected trees by wind-blown rain. As wind speed increases so does the probability of infection. This paper describes the use of windbreaks composed of large evergreen tree species surrounding citrus plantings to reduce wind speed during rainstorms and thereby reduce the chance of new infections. Results from our studies confirm that windbreaks are a highly effective method for protection of fruit from infection by the citrus canker bacteria. The research is advantageous to citrus growers who are attempting to control citrus canker and improve market access.

Technical Abstract: For fresh grapefruit, the goal is to maximize pack-out by minimizing canker lesions on fruit. The objective of these trials was to determine the relationship between wind speed and incidence and severity of citrus canker on 5 to 7 yr-old Ruby Red grapefruit trees located in two trial blocks (~4.5 ha) surrounded on all sides by a 6 to 10 m tall Corymbia torelliana windbreak. The experiment was conducted from 2013 to 2015. A series of weather stations were deployed in east-west and north-south directions across the orchards to measure the effect of proximity of citrus trees to the windbreak on wind speed expressed as the number of wind gusts =5 m s-1, and to determine the relationship with incidence of fruit lesions on grapefruit. The number of wind gusts =5 m s-1 increased with distance from the windbreak. The highest fruit canker incidence occurred in approximately the central zone of the block and the lowest incidence was found nearest windbreaks. Number of wind gusts and canker were linearly related, i.e., the greater the number of gusts, the higher the fruit disease. As the number of wind gusts increased with distance from the windbreak, incidence of unsightly wind scar also increased. These results confirm that windbreaks are a highly effective method for protection of fruit from infection by Xanthomonas citri subsp. citri, as well as physical damage from wind buffeting.