The product, registered by Maryland-based Silvec Biologics Inc., relies on science pioneered at the Texas A&M AgriLife Research and Extension Center at Weslaco by Kranthi Mandadi, Ph.D., center director and professor in the Texas A&M Department of Plant Pathology and Microbiology. Mandadi worked with Bill Dawson, Ph.D., emeritus professor at the University of Florida, and Choaa El-Mohtar, Ph.D., research scientist at the Citrus Research and Education Center.

Mandadi and his research team demonstrated that naturally occurring antimicrobial peptides from spinach, known as defensins, can protect citrus trees from Huanglongbing, known as citrus greening, one of the most destructive diseases in modern agriculture.

The EPA registration is issued under the Federal Insecticide, Fungicide and Rodenticide Act and allows the spinach defensin-based therapy product to be sold commercially without a tolerance limit — a designation reflecting years of safety data gathered through the research partnership.

From lab discovery to field-ready product

“After years of collaborative research and development with the citrus industry and private sector, we are pleased to see the spinach defensin therapeutic technology achieve EPA registration with no tolerance limit, which is a testament to the product’s safety,” Mandadi said.

He said the EPA registration marks a turning point for the U.S. citrus industry, which has struggled to prevent citrus greening losses.

“This is the result of research that started right here at our center in Weslaco, but it carries impacts nationwide,” said G. Cliff Lamb, Ph.D., director of AgriLife Research. “Seeing our research-enabled development of a fully registered commercial product for producers shows what long-term investment and technology commercialization support in agricultural science can accomplish.”

Mandadi’s work builds on research that began as a collaboration with Erik Mirkov, Ph.D., an AgriLife Research professor and plant pathologist at the Texas A&M AgriLife center at Weslaco. Together, the two discovered the spinach defensin peptides as a possible treatment.

Early studies supported by AgriLife Research, the Foundation for Food and Agricultural Research, and Southern Gardens Citrus – a subsidiary of U.S. Sugar – laid the groundwork for advanced testing, peptide screening and field trials.

“The technology uses a naturally non-transmissible strain of CTV (citrus tristeza virus) already common in Florida citrus trees, reprogrammed to prompt the trees to produce the spinach-derived defensin peptide therapy,” said Mike Irey, director of research at Southern Gardens Citrus, Clewiston, Florida.

The CTV technology, pioneered by Dawson and team at the Citrus Research and Education Center, is a therapy delivery approach that does not alter the tree’s genome. It functions like an immunization for citrus trees. A small piece of plant material from a specially developed source tree is grafted onto an existing citrus tree. This introduces a benign CTV that carries the spinach defensin peptide. Once established in the tree, the CTV continues producing the defensin peptide, which helps fight the bacteria associated with citrus greening disease.

The combined research efforts resulted in patents of the defensin by The Texas A&M University System and the CTV technology by the University of Florida. Patent rights to both technologies are licensed to Southern Gardens Citrus, which championed the technology through sponsored research and development leading up to the EPA registration. Patent rights were sublicensed to Silvec to obtain EPA registration, commercialize the treatment and bring it to market.

A multi-institutional effort

“The progress Dr. Mandadi and collaborators have made makes me hopeful for the future of our citrus industry,” Dale Murden, president of Texas Citrus Mutual, said. “We will have new, sustainable treatments that could keep citrus trees productive under disease pressure. They aren’t just answering research questions but are developing field products to support growers so we can farm profitably.”

The research and development effort spanned multiple public and private institutions over 15 years and was supported by multi-state, coordinated agricultural projects from the U.S. Department of Agriculture National Institute of Food and Agriculture Emergency Citrus Disease Research and Extension Program, AgriLife Research Insect Vectored Diseases program and Texas A&M University Division of Research Advancing Discovery to Market funding program.

According to Silvec, citrus growers, starting in Florida, are expected to gain access to the product beginning in late 2026.

“We are excited to build on 15 years of pioneering work by Southern Gardens Citrus, the University of Florida, and Texas A&M, and we look forward to beginning to partner with growers in late 2026 through the Florida CRAFT (Citrus Research and Field Trial) program,” said Rafael Simon, Ph.D., co-founder and CEO of Silvec. Silvec and Mandadi’s team continue to investigate additional applications of spinach defensins, including in potatoes affected by zebra chip disease and other crop biothreats. They are also pursuing new peptide combinations and delivery systems aimed at broader crop protection.