Brassinosteroids Research May Provide a Way Forward for Citrus

For five years, Dr. Fernando Alferez and his UF/IFAS research group in Immokalee have been working with TreeDefender IPCs, studying how to help newly planted citrus trees in an area of widespread HLB. The results have been clear: Protecting the trees with IPCs from the moment they are planted keeps them free from HLB. IPCs are an effective tool against psyllids and greatly reduce canker. Here is an excerpt of Alferez’s report, which points to another tool — brassinosteroids — in the fight against HLB:

“… Our team has seen greatly improved fruit quality in TreeDefender-protected trees. We planted Valencia trees protected with IPCs in Feb. 2018 and have evidence from the first two crops (Feb. 2021 & 2022), showing significantly more ºBrix and a better ºBrix/acid ratio than non-protected trees. This is relevant because these crops were harvested after IPC removal. In the first crop, about 60% were infected. By the second, all of the trees were HLB-positive. Installing IPCs from the beginning is a beneficial kick-start that lasts at least two seasons even though the trees become infected. 

Next month, we will harvest the third crop that has now been 100% infected for about one year. We are anxious to know the new data on fruit quality.

Our challenge now is to prolong tree health and keep trees producing quality fruit in a sustainable way once IPCs are removed and the trees are exposed. This requires some of the other tools in our toolbox, including the application of brassinosteroids to the trees once the IPCs are removed. 

Brassinosteroids are plant growth regulators that can induce immune responses in some plants, although research about citrus is scarce. Some data shows that brassinosteroids delay HLB infection because the treatment activates the immune machinery in the tree. Trees treated with brassinosteroids have less incidence of psyllids and fewer psyllid eggs and nymphs than non-treated trees. Progression of HLB infection is significantly reduced with brassinosteroid treatment, as is rust mite damage. 

However, we do not know how long the effects of brassinosteroids last. This will dictate how many applications are needed and will determine the cost per acre. Thanks to a USDA-NIFA grant, we are confident that we can answer this question.”

This is exciting work from Alferez, and it appears that brassinosteroids may be a way forward for the Florida citrus industry.

Bio: Scott Thompson is co-founder of Tree Defender, Radical Ag-Tech, and Care Planet Technologies. He is a Central Florida native with a background in agribusiness, food manufacturing, and bioscience.

This column is sponsored by Tree Defender, and the opinions expressed herein may not reflect those of CFAN or of its advertisers.

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