Prolong the Health of Young Citrus Trees

By Fernando Alferez, Ute Albrecht, Ozgur Batuman, Jawwad Qureshi and Saoussen Ben Abdallah

Individual protective covers (IPCs), which are psyllid-exclusion mesh bags, are increasingly being adopted to efficiently protect newly planted citrus trees from huanglongbing (HLB) infection. However, IPCs typically must be removed after two to three years due to tree growth.

Early evidence indicates that brassinosteroids (Brs), a relatively new class of plant hormones, delay HLB progression. With the aim of prolonging tree health after IPC removal, University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) researchers are investigating the efficacy of Brs in protecting and/or preventing trees from Asian citrus psyllids (ACP) and Candidatus Liberibacter asiaticus (CLas) infection once they are left exposed.

Brs have been approved for commercial use in Florida citrus. Although the project is in its first months, researchers have already found that treatment with Brs prevented CLas infection four months after IPC removal. In contrast, 60% of the trees grown in IPCs without subsequent Brs treatments were HLB-affected at this time. After Brs treatment, trees are flushing more profusely and setting more fruit. In addition, less psyllids per flush were found. Long-term efficacy of treatments still must be assessed.

Take-home messages of the research are as follows:

• Brassinosteroids delay HLB progression after IPC removal.
• Citrus trees flush more profusely after Brs treatment once IPCs are removed.
• Psyllid population is affected by Brs treatment.

This project is funded by the U.S. Department of Agriculture National Institute of Food and Agriculture.

Fernando Alferez is an assistant professor; Ute Albrecht, Ozgur Batuman and Jawwad Qureshi are associate professors; and Saoussen Ben Abdallah is a post-doctoral associate — all at the UF/IFAS Southwest Florida Research and Education Center in Immokalee.