Florida citrus producers have long used copper as a way to protect against citrus canker. However, it’s time for growers to have other options.
That’s a message shared by Ozgur Batuman, University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) associate professor and citrus pathologist at the Southwest Florida Research and Education Center in Immokalee. He spoke on this topic at the recent Citrus Health Forum in Quincy, Florida.
“Currently, the main strategy to manage citrus canker is through copper sprays. It’s costly and requires repeated applications,” said Batuman. “It’s tedious work for growers. Also, you are putting out a toxic chemical, which accumulates in the soil and harms the trees and the environment. It’s a really toxic material that we are spraying every 21 days.”
Batuman said citrus canker is among the most devastating diseases that Florida farmers must contend with every year, second only to citrus greening disease.
According to UF/IFAS, citrus canker is spread by wind-driven rain, overhead irrigation, flooding, insects, birds and animals. Leaf symptoms can appear as small, round blister-like lesions with water-soaked margins and yellow halos. Severe infection can cause defoliation or worse.
“If the citrus canker disease outbreak occurs early in the season while the small fruits are developing, that can be detrimental, because citrus canker can cause fruit drop,” Batuman said. “However you look at it, citrus canker is really a serious disease of citrus and has to be managed before the disease starts.”
Copper has long been used in protecting citrus from canker because it protects the growing tissue, whether it be on the fruit, leaves or twigs. It provides protective film so that bacteria cannot penetrate through wounds or the natural openings of the tree’s stomata.
But copper’s toxicity and potential for eventual disease resistance leave its long-term viability in doubt.
“Because of this reason, some growers are worried about using copper, and thereby the groves become inoculum sources for nearby growers because they are not taking care of the canker disease in their groves,” Batuman said. “The bacterium we are trying to manage through copper sprays is known to develop resistance to copper. Copper-resistant bacterium in Florida will make the situation even worse.
“We are always interested in copper alternatives,” Batuman concluded.
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