Prolong Tree Health by Combining Covers and Brassinosteroids

As every Florida citrus grower knows, it has been difficult to grow trees and fruit profitably since huanglongbing (HLB) disease was discovered in the state in 2005. Soon after the disease was discovered, officials determined it couldn’t be eradicated largely because the Asian citrus psyllids (ACP) that spread it showed up years earlier and were in virtually all citrus-producing regions.

In an Oct. 16 presentation, University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Associate Professor Fernando Alferez reported that most newly planted trees test positive for HLB in less than six months. The horticulturist suggested that ACP-excluding individual protective covers (IPCs) and brassinosteroids (BRs) can be combined to prolong young citrus tree health.

Alferez’ key points regarding IPCs and BRs included:

• IPCs are currently the best management practice for keeping young trees free from HLB in Florida’s endemic areas.
• IPCs improve tree growth, fruit yield and quality.
• IPCs reduce canker incidence.
• IPCs do not exclude all pests. This means that regular scouting is still necessary. Controlling secondary pests remains important.
• Not all varieties perform equally under IPCs. Those that perform well include Valencia and Hamlin oranges, Tango mandarins, grapefruit and pummelo. 
• BRs induce several coordinated defense responses in young citrus trees and improve tree growth.
• If no HLB reinfection occurs (if IPCs are used), BRs may recover young trees (up to 3 years old) already affected by HLB and in decline. These trees in recovery are producing fruit.

Alferez reported that approximately 17,000 acres of newly planted citrus trees in Florida have adopted IPCs as a management tool. He also noted that plants treated with BRs are less attractive to ACPs.

Alferez works at the UF/IFAS Southwest Florida Research and Education Center in Immokalee. Multi-county citrus Extension agent Mongi Zekri hosted his presentation.