In the long battle against HLB, there have been no tactics as successful at safeguarding citrus trees as protective screen. Citrus under protective screen (CUPS) structures can exclude the Asian citrus psyllid (ACP) and HLB from entire blocks, while individual protective covers (IPCs) can keep individual trees free of HLB for the critical first few years after planting.
In early October, the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) hosted a CUPS and IPC seminar and field day at the Citrus Research and Education Center (CREC) in Lake Alfred.
Arnold Schumann, UF/IFAS professor of soil, water and ecosystems science, pioneered research into CUPS and gave an overview of what has been learned since he installed his first structure at CREC 12 years ago. Today, there are about 2,000 acres of commercial CUPS in the state of Florida.
“The primary goal of CUPS is to exclude ACP and thereby keep HLB out of the citrus planting,” Schumann said. “That was extremely successful in the first 10 years of our original structure. Then we had Hurricane Ian, which damaged the screen and exposed the trees to ACP and HLB. It took us about 11 months to get the structure repaired because of a delay in getting material. We are at about 11% HLB infection in the structure now — still better off than outside, where 100% infection is the norm.”
Schumann added a few important points: Once a CUPS structure is repaired, trees are not being re-infected because ACP are again excluded. And infected trees can be replaced inside the structure.
According to Schumann, it takes about seven to 10 years to get to profitability after the expensive upfront investment in the CUPS structures. But profit potential is high due to large production of beautiful fresh fruit under the screens. The vast majority of current CUPS acres are planted in grapefruit.
Fernando Alferez, UF/IFAS associate professor of citrus horticulture, has led the research effort to evaluate IPCs. They have been a huge success in protecting young trees from HLB in the grove. More than 1 million trees have been protected by the bags.
Alferez spoke about his ongoing research of utilizing brassinosteroids to enhance tree health and delay HLB infection after the IPCs come off trees. He says this system can be a bridge to trunk-injection therapy to help trees survive and even thrive as they move into fruiting years.
Alferez also discussed new research, which will be evaluating insecticide-infused netting to enhance pest control. These nets could help manage smaller pests like mites and thrips that can get through the material. Another experiment will evaluate the insecticide-infused netting placed around blocks of citrus with a 10-foot-tall wall — similar to a CUPS but with no roof. He will report data from these research projects as it becomes available.
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