Now that bloom has arrived, it is time to start thinking about canker management. As the fruitlets develop, they will become susceptible around the end of March to the beginning of April. The spring fruit lesions are particularly concerning because they cause fruit drop. Without proper management, early-season canker can cause 90 to 100% crop loss with favorable spring weather (frequent rain).
Susceptible varieties include grapefruit, Hamlin, and other early sweet oranges, navels, and lemons. Susceptibility in new varieties is not well documented, but severe outbreaks have been observed on OLL-8.
Foliar applications of copper provide the best management on bearing trees with the main aim of protecting fruit. Copper sprays on a 21-day interval provide the best protection currently available. The 21-day interval maintains a protective layer, replenishing the copper layer that slowly degrades from rainfall and fruit.
For Valencia fruit, three sprays in spring should be sufficient. Hamlins will …..
Learn more about how to Prepare for Citrus Canker Season on the Citrus Industry website.