Freeze events in Florida could increase disease pressure in citrus blocks, according to Megan Dewdney, University of Florida Institute of Food and Agricultural Sciences associate professor in plant pathology and Extension specialist.
"Our big concern in terms of foliar problems is going to be melanose. Just as a reminder, melanose produces all of its spores that are really important for the disease, year to year, on dead wood thinner than a pencil," Dewdney said during a post-freeze seminar hosted by the UF/IFAS Citrus Team. "This is a fungus that knows its environment and saves up its spores if there's no rain. It's capable of storing those spores for over a month in dry conditions."
UF/IFAS indicates that grapefruit is the variety most vulnerable to melanose. Disease pressure is elevated in seasons when freezes generate higher volumes of dead wood in the canopy, as fungal structures on dead twigs serve as the primary source of inoculum. That situation has developed following the freezes in late January and early February.
"When we get rain, we're going to have significant melanose. If it's poorly timed, in terms of you've got young fruit on the tree, then all of that inoculum has the potential to hit your fruit," Dewdney explained. "As those poor fruit try to grow, with the amount of melanose, you'll see mudcake symptoms where the whole surface is scarred. Fruit will crack and be lost.
"We don't want to see that. We want to try to get those fruits protected. However, we don't want to do it too far out in advance, because as the fruit grows, that protection gets cracked with the copper. It's a balance of keeping an eye on the weather and making sure you can get your equipment into the grove at an appropriate time."
Monitoring canopy condition, rainfall timing, and spray access remains central to disease management following freeze damage.
Source: Citrus Industry
