This in from Tim Gaver, Extension Agent II, Citrus, IFAS/St. Lucie County Extension
Subject: Attached is the main body of an e-mail response to a question posed by Doug Bournique to Dr. Tim Gottwald, USDA pathologist in Ft. Pierce. Input was also obtained from Dr. Jim Graham, IFAS Pathologist, CREC in Lake Alfred. This information has been sent to members of the Indian River Citrus League and is being sent to you with permission from Dr. Gottwald…
This note is in response to your call this morning concerning what Indian River growers can expect and what actions they can take relative to citrus canker in the aftermath of Tropical Storm Fay. First I sincerely hope that all growers in the Indian River area sustained no damage to homes and commercial facilities and no structural damage to plantings. I have discussed the situation at length with Dr. Jim Graham, and provide the following for your consideration.
Expected Canker Situation:
We have experienced a highly beneficial three-year hiatus with essentially no tropical storms since Wilma in 2005 and thus have somewhat dodged the canker bullet during this timeframe. However, as we all know and have experienced, TS Fay caused accumulations of 8-10 or more inches of rainfall to date and rains may continue for the remainder of the day or longer. In addition, tropical storm winds of 20-50 mph were common as storm squall lines passed over and the storm has had duration of over 24 hours so far. This has caused a very significant and sustained canker bacterial inoculum dispersal event and prolonged infection period. Wind and rain in excess of 18 mph causes bacteria to be forced through stomata and directly into foliage, stems, and more importantly, fruit surfaces, embedding the bacteria in the fruit. Even fruit with a good coating of copper will likely sustain infections as the relentless pounding of wind and rain probably washed much, if not all, of this covering off. This is concurrent with a highly susceptible stage of fruit development, where fruit are still sizing up and stomata are exposed with only a thin waxy cuticle on the surface. Undoubtedly, heavy infection has occurred in some areas. Infection is dependent on what inoculum sources were preexisting in your area and especially the existing infections in adjacent plantings. Plantings with young, vigorous trees will probably be hardest hit, whereas, those with mature trees that can act to some extent as their own windbreaks, may have somewhat less infection. However, even plantings with tall perimeter windbreaks will still experience considerable infection. In areas where canker is endemic, the edges of plantings are likely to be the most heavily infected.
Possible Remedial Actions:
Unfortunately, infection has already occurred, and there is no known curative spray to reduce infections that are already established. Most importantly, do not enter or work the plantings while moisture is still on the foliar and fruit surfaces or you will spread inoculum further mechanically. Apply and maintain copper-containing bactericides immediately and regularly to reduce further infection this year and keep inoculum down as much as possible for next year. Canker is a yearly phenomenon, and as diseased fruit and foliage abscise, keeping the new foliage and fruit clean for the following season will reduce the epidemic that next season. If canker was in the vicinity prior to the storm, you will undoubtedly experience infection. Have thorough inspections before harvest and prior to taking the fruit to the packinghouse to avoid rejection of loads. Infection is expected to be widespread in plantings as a result of the storm, thus pruning of individual branches is unlikely to be effective. We continue to work toward the day when canker will become a quality issue and some blemishes in packed fruit are allowable.