RNA citrus greening treatment approaches commercialization

Citrus greening, also called Huanglongbing, is a bacterial infection of citrus plants. It is one of the most serious citrus diseases in the world. Once infected, most trees die within a few years. There is no cure. While the disease poses no health threat to people or animals, it has devastated millions of acres of citrus crops throughout the United States and abroad.

In the United States, citrus greening is spread by a tiny insect called the Asian citrus psyllid (Diaphorina citri Kuwayama). Infected trees produce fruits that are poorly colored, possibly lopsided, and bitter. This fruit can only be sold for juicing.

Citrus greening is currently found throughout Georgia, Florida, Puerto Rico, and the U.S. Virgin Islands. It is also found in portions of Alabama, California, Louisiana, South Carolina, and Texas. This devastating and incurable disease has significantly reduced global citrus production, with Florida experiencing an 80 percent drop from its pre-disease peak by 2023.

Silvec Biologics, a Maryland-based agtech company specializing in RNA-based plant protection products, has announced that its groundbreaking RNA vector delivery product has advanced to the Full Science Review Phase of the EPA Pesticide Regulation Improvement Act registration process.

This milestone follows the successful completion of Milestone #4 — Technical Screen in July 2024. The product, developed in collaboration with Southern Gardens Citrus (a U.S. Sugar subsidiary), the University of Florida, and Texas A&M AgriLife Research, is designed to combat citrus greening. 

Silvec holds the exclusive sublicense for U.S. Sugar’s novel delivery vector, created with the University of Florida, and antimicrobial peptide technologies from Texas A&M AgriLife Research. The product utilizes a mild, non-transmissible virus found in most citrus trees, reprogrammed to express a natural antimicrobial peptide from spinach. Field trials have shown that a single application can provide long-term reduction in yield declines caused by the citrus greening bacteria. This product is the first to use a viral vector to mitigate pathogen damage without genetically modifying the tree or its fruit and is compatible with all commercial citrus varieties.

“As U.S. Sugar shifts its focus to increasing Florida sugarcane production, we are confident in passing our citrus vector technology to Silvec for commercialization. This technology is poised to play a vital role in combating citrus greening,” said Mike Irey, Director of Research and Special Projects at U.S. Sugar.

Rick Dantzler, Executive Director of the Citrus Research and Development Foundation, a partnership between Florida citrus growers and government agencies, added, “CRDF fully supports Silvec in the regulatory approval process, as we believe this citrus vector technology will be instrumental in reducing the devastating effects of citrus greening on Florida’s citrus industry.”

The citrus vector product received USDA approval for commercial use in all Florida counties following a positive Environmental Impact Statement in June 2020. Silvec and its regulatory partner, the IR-4 Project, submitted an EPA registration application in January 2024, initiating an 18-month review process. “We are eager to build on the pioneering work by U.S. Sugar, the University of Florida, and Texas A&M AgriLife Research over the past 15 years and look forward to commercializing the citrus vector product once regulatory approvals are secured,” said Silvec CEO, Dr. Rafael Simon.

Kranthi Mandadi, Ph.D., a professor of plant pathology and microbiology at Texas A&M AgriLife Research, commented, “After years of research and development, we are thrilled to see the citrus vector and spinach defensin technology advance to the EPA registration phase. This project exemplifies the critical public-private partnerships necessary to develop innovative solutions to complex challenges like citrus greening.”