2019 Citrus canker trial results
In this report, we focused on the 2019 citrus canker trial results. The citrus canker trial was performed in a 7-year old `Ray Ruby’ grapefruit block with windbreaks (Vero Beach, FL). The multi-metal materials were applied at 0.5 lb. metallic Cu per acre on April 2, April 23, May 13, June 3, June 24, July 15, August 5, August 26, September 16, October 7, and October 28. Disease ratings were performed on July 15, August 26, October 7, and November 11 based on incidence of fruit lesions for 100 fruit per treatment from the middle 3 trees in each plot (0.17 acres/plot). Harvest was done on November 11 and the yield was measured as lb. fruit per tree in each plot. A subset of fruit from each tree was sized and tested for juice quality at CREC packing house/pilot plant facility (Lake Alfred, FL). MM25C75M, MM25C75Z, and MM10C45M45Z treated grapefruits showed 0% of fruit with canker lesion present throughout this trial, which was significantly better than the untreated control (0.8%, 1.2%, 4.6%, and 8.2% at successive disease ratings). Monthly rainfall in 2019 was below average, so early season leaf inoculum and subsequently fruit lesions were low throughout the trial making it difficult to differentiate between moderate and strong efficacy. The yield of MM25C75M, MM25C75Z, and MM10C45M45Z treated grapefruits was 50.6, 60.5, and 49 lb/tree respectively. The yield of MM25C75Z treated grapefruits showed a statistic difference compare with untreated grapefruits (43.8 lb/tree). The mean fruit diameter for MM25C75M, MM25C75Z, and MM10C45M45Z treated grapefruits of 86.9, 83.6, and 85 mm, respectively, was not significantly different from the untreated controls (85.8 mm). No significant differences were found in internal fruit quality based on brix acid ratio or total soluble solids. Greenhouse results of the most recent formulations are not available because the inoculation occurred too late in the fall to get clear results even with the Blockade positive control. A new trial will be initiated around spring flush when day length has increased to provide robust greenhouse flush.