Post-Hurricane Disease Concerns

Phytophthora, citrus black spot and HLB are among diseases that could be spread in Florida groves as a direct or indirect result of Hurricane Milton, researcher Megan Dewdney cautioned. Dewdney, a University of Florida Institute of Food and Agricultural Sciences associate professor of plant pathology, offered suggestions for dealing with those diseases during a recent hurricane recovery webinar.

PHYTOPHTHORA

Phytophthora can be problematic in flooded groves or saturated soils if blocks have a history of the disease. Many groves were flooded or saturated by Milton.  

Root deterioration is acute after trees are in standing water for more than 72 hours, Dewdney said. She noted phytophthora lesions aren’t uncommon on limbs and trunks of toppled trees.

Brown rot is potentially a problem on early-season fruit where dropped fruit attracts zoospores and increases inoculum, the researcher said.

If a grove is already on a phytophthora treatment program, it should be continued on planned rotations, Dewdney advised.

For foot rot or collar rot, she suggested using phosphite salts labeled as fungicides, Aliette, mefenoxam products, fluopicolide or oxathiapiproline. Some of these products require irrigation following application.

Brown rot treatments may be made if sufficient fruit is still on trees. It’s not too late for phosphite salts or Aliette, Dewdney said. Copper can help with active infections and is a good choice for late-season applications, she added. Newer products recommended for brown rot are Revus and Orondis Ultra.

CITRUS BLACK SPOT

Growers with groves near citrus black spot quarantine areas should scout for the disease for the next four years, Dewdney suggested. She noted that the disease possibly moves with hurricanes.

HLB

Dewdney’s concerns about HLB following the hurricane are for trees inside citrus under protective screen (CUPS) and individual protective covers (IPCs).

Rips in CUPS screens could allow HLB-spreading psyllids to enter. Provided rips are repaired quickly, HLB may be isolated. Watch carefully for symptoms and eliminate psyllids, Dewdney suggested.

Growers should inspect IPCs for tears. She noted that some trees in IPCs were infected following Hurricane Ian in 2022 because psyllids entered through tears.

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