Life After Individual Protective Covers: Protecting New Flushes from Huanglongbing
Posted August 2025
Researchers: Ozgur Batuman, Lauren Fessler Mathews, Sanju Kunwar, Ana Redondo, Fernando Alferez
Contact: Ozgur Batuman, UF/IFAS SWFREC obatuman@ufl.edu
Summary:
Individual protective covers (IPCs) are proven effective in protecting young citrus trees from huanglongbing (HLB) by excluding Asian citrus psyllids (ACP). However, IPCs can be used only for 2-3 years after planting, depending on the citrus cultivar’s vigor and other horticultural traits. When IPCs are removed, trees become exposed to rapid ACP colonization and infection of CLas (2-3 months) in the grove. Similarly, the productivity of mature citrus trees unprotected from ACP feeding during the emergence of new flushes is dramatically reduced due to multiple reinfections. Therefore, citrus trees in HLB-endemic Florida conditions must be well protected from ACPs and reinfection after IPC removal, particularly when producing new flushes. To achieve this, we used the application of plant defense inducers, including brassinosteroids (Brs) and systemic acquired resistance inducers (SARs), to shield new growth from reinfection. We evaluated the efficacy of Brs and SARs in protecting young shoots emerging on trees treated with or without OTC-injection in the grove. Brs sprays were applied monthly, whereas SARs were only used once after the major flush cycle in May 2024. Three months after OTC injection and/ or three Brs or one SAR applications, qPCR results indicated significant CLas reduction in Brs- or SAR-treated trees, coupled with OTC injection, but not in non-injected trees. Field studies evaluating these approaches have demonstrated promising results. IPCs effectively block CLas infection, OTC reduces bacterial titers, while Brs and SARs protect new shoots from ACP-mediated reinfections. Ongoing field trials aim to refine and integrate these tools into comprehensive integrated pest management (IPM) programs.
Take Home Message:
- SARs and Brs can protect young flushes from ACP-mediated CLas infection or reinfections.
- The use of SARs and Brs, along with other IPM tools (IPCs and OTC injections), can help sustain productivity.
- SARs tested are not available, but Brs are commercially available for growers for HLB management.
