Citrus canker continues to impact Florida citrus, increasing premature fruit drop and decreasing yield and fruit quality. While copper sprays have long been relied upon to control this disease, concerns about environmental impact and possible resistance development have led to efforts to find sustainable alternatives.
Previous studies have shown that plant defense inducers alone may have the potential for citrus canker control, but University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researchers wanted to see if they could also be used in rotation with traditional copper sprays at a reduced frequency to effectively manage citrus canker in the grove.
A field trial was conducted on mature Hamlin trees at two commercial sites in Collier and Charlotte counties with known canker pressure. Application of Kocide 2000 at a 21-day interval was used as the standard for canker control. This was compared to reduced frequency of Kocide 2000 and the use of plant defense inducers (Actigard and a proprietary product abbreviated PDI 7), both alone and in rotation with 42-day intervals of Kocide 2000.
In the commercial plot in Collier County, Actigard alone as a spray, and in rotation with Kocide 2000 at 42-day intervals as both a spray and a drench, reduced the incidence of fruit lesions to the same level as the standard 21-day intervals of Kocide 2000. In the Charlotte County plot, all treatments except Actigard drench reduced fruit lesion incidence to levels comparable to the standard 21-day interval of Kocide 2000 (Figure 1)…