A La Niña weather pattern is most likely this spring, with higher-than-average temperatures and below-average rain predicted in Florida, researcher Megan Dewdney reported in a Feb. 24 presentation about postbloom fruit drop (PFD). That could have some influence on the severity of PFD, since its preferred climate is humid and subtropical, and the fungus moves with rain splash and wind-borne rain.
Dewdney, a plant pathologist with the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS), said human activities such as equipment movement can also move the fungus that causes PFD. She added that the disease is more severe in areas with multiple blooms, which can be promoted by HLB and other diseases.
A primary symptom of PFD is orange-colored lesions on petals. The lesions can blight the entire blossom or cluster when the disease is severe. Fruit and petals fall, leaving a button that can last up to 18 months on the tree. Leaves around the infected flowers are often twisted and small, Dewdney said.
Control options include removing declining trees to reduce the inoculum. It might be prudent to prune out HLB-affected branches if there are only one or two per tree. Dewdney suggested using strobilurin-containing fungicides, including Abound, Gem, Headline, Amistar Top, Pristine and Priaxor. They work best when combined with Ferbam fungicide.
Dewdney works at the UF/IFAS Citrus Research and Education Center in Lake Alfred. She made her presentation to numerous growers and others virtually, via Zoom. In the same presentation, she also discussed scouting and management for citrus black spot and citrus canker. Her presentation was hosted by Mongi Zekri, UF/IFAS citrus Extension agent for several southwest Florida counties.
Learn more about PFD in Dewdney’s recent Tip of the Week article.
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