Combining IPCs and Brassinosteroids to Protect Young Citrus Trees

Research studies show that about 60% of Florida citrus trees are infected by HLB disease within six months of planting. By one year, 100% of citrus trees are infected.

For that reason, the use of individual protective covers (IPCs) has become very popular to protect young citrus trees from the Asian citrus psyllid (ACP). The covers have proven to be effective in excluding the ACP from feeding on tree foliage and therefore stopping the spread of HLB.

Fernando Alferez, assistant professor of citrus horticulture with the University of Florida Institute of Food and Agricultural Sciences, has studied the use of IPCs extensively. He presented his findings during the recent Florida Citrus Industry Annual Conference. His IPC research began in 2018 on newly planted trees. The covered trees were compared to a control planting where no covers were used.

“After two years, we found trees with IPCs were able to bloom and set fruit, and they also remained HLB-free,” Alferez said. “The fruit size was improved by the IPCs. About 70% of fruit coming from covered trees were normal size. In the uncovered trees that were infected by HLB from the very beginning, the numbers were opposite with only about 30% of fruit being normal size. Fruit quality also was improved with IPCs.”

Alferez said the goal of keeping trees HLB-free until they begin fruiting was achieved using IPCs. But soon after their removal and HLB infection begins, fruit production and quality will fall. So, he began experimenting with the use of brassinosteroids to slow the rate of HLB infection in trees that have had IPCs removed.

The early research shows that brassinosteroid applications will slow the rate of HLB infection in newly uncovered trees, although Alferez said it is not clear what exactly is causing the effect. Applications also appear to improve fruit quality.

Alferez said he will continue research for as long as possible on how the use of IPCs in combination with brassinosteroids can slow down HLB and improve fruit production and quality in young citrus.   

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