Recovering Huanglongbing-affected Young Citrus Trees
Posted August 2025
Researchers: Fernando Alferez, Saoussen Ben Abdallah, Osbaldo Vasquez
Contact: Fernando Alferez, UF/IFAS SWFREC alferez@ufl.edu
Summary:
Adoption of individual protective covers (IPCs) does not occur in all groves, and in some cases, trees are still planted with no protection. Under these circumstances, if trees are left unprotected, they become infected with huanglongbing (HLB) during the first year, and they’ll never enter fruit production. We wondered if these trees could be recovered so they may become productive as they age. We know that treatment with brassinosteroids (Brs) may induce a strong immune response in young trees by activating the salicylic acid pathway. We hypothesized that infected young trees could be recovered by covering them with IPCs, so reinfection would not occur as the psyllids would be excluded, and by treating them with Brs, so an immune response would be induced. We started a trial in February 2023. After one year, all trees tested positive for HLB and were declining. Then, in February 2024, one-third of the trees were covered with IPCs, and another third of the trees were covered with IPCs and received a monthly dose of Brs at a rate of 6.2 fl oz/100 gallons of water. The remaining third of the trees were left unprotected and not treated, so they served as the control trees. After one year, there was a clear recovery of the trees that were covered with IPCs, with better canopy density and larger leaves than the control trees. These effects were maximized in trees that were not only covered with IPCs but also treated with Brs. In this case, bacteria titer has been significantly reduced. We will continue monitoring the trees for at least one more year to determine if these changes are sustained over time.
Take Home Message:
- If unprotected at planting, trees become HLB positive in less than one year.
- Covering young, infected trees with IPCs can recover these trees; the effect is maximized if Brs are also applied.
- The combination of IPCs and Brs treatment reduces bacteria titer in young, infected trees.
