Combat Diseases Appearing in Groves After the Hurricane
November 6, 2024
If there’s one thing Florida growers know, it’s that hurricanes leave more than the initial devastation in their wake. The storms make conditions ripe for diseases in citrus groves and transport pests, viruses, and other pathogens. In addition, the high winds and rain of a hurricane can also cause damage that allows existing pathogens to enter and infect citrus trees. UF/IFAS has been holding Hurricane Recovery Webinars to warn Florida citrus growers to be on the lookout and how to treat any diseases they come across.
Diseases on the Rise in Milton’s Wake
Phytophthora: Watch out for brown rot, foot rot, collar rot, or any other phytophthora-caused issues if your grove has a history of the disease and there was flooding or overly saturated soils in the grove. Roots will deteriorate if they are in standing water for more than 72 hours, and downed trees can develop phytophthora lesions on trunks or limbs that make contact with standing water.
UF/IFAS recommends continuing planned phytophthora treatments. Additionally, phosphite salts labeled as fungicides, such as Aliette, mefenoxam products, fluopicolide, and oxathiapiprolin, can be used to treat foot or collar rot. Revus and Orondis Ultra are newer products that can be used to treat brown rot. Copper is also another option for late-season applications.
Citrus Black Spot: UF/IFAS researchers maintain that citrus black spot is likely transported by hurricanes, and that Florida citrus growers near citrus black spot quarantine areas need to scout for the disease for four years following a hurricane. The most identifiable and diagnostic symptom, according to UF/IFAS, is hard spot lesions on ripe fruit; the lesions are small — 3/16 inch and smaller; round; slightly depressed; have edges that are brick red to dark chocolate brown; and may have a center that is tan with little pinpoint dots. If you suspect citrus black spot in your grove, contact your Extension agent for testing and treatment options.
Citrus Greening (HLB): Growers using Citrus Under Protective Screens (CUPS) or Individual Protective Covers (IPCs) should inspect the screening for rips that could allow in Asian citrus psyllids (ACPs); ACPs enter through the rips and then infect the citrus trees. Growers should repair rips as soon as possible and scout for and treat for ACPs.
Citrus Canker: The bacteria that causes canker is also believed to be moved around by the high winds and rain of hurricanes. UF/IFAS researchers maintain that winds greater than 18 mph will push the canker bacteria past protective coatings, such as copper. It is recommended that Florida citrus growers reapply any protections originally applied to combat canker and scout intensely for the disease. Additionally, citrus canker bacteria have been found in the past to have entered CUPS and IPCs from being blown in by hurricane winds or through rips.