Spinach peptide discovery leads to citrus greening treatment

Scientists from Texas A&M AgriLife Research have discovered a novel treatment for citrus greening disease by harnessing naturally occurring antimicrobial peptides found in spinach. The therapy, developed over more than a decade of research, has now received unconditional approval from the U.S. Environmental Protection Agency (EPA) for commercial use.

The product, manufactured by Maryland-based Silvec Biologics Inc., relies on spinach defensins, which can protect citrus trees from Huanglongbing (HLB), the primary cause of citrus greening. The EPA registration, issued under the Federal Insecticide, Fungicide and Rodenticide Act, enables the spinach defensin-based therapy to be sold without a tolerance limit, reflecting the extensive safety data amassed through the research effort.

Following years of collaborative research involving the citrus industry and private sector entities, the spinach defensin therapy represents a significant milestone for the U.S. citrus industry, which has long struggled to prevent the devastating impacts of citrus greening. The treatment involves grafting a specially developed citrus tree with a benign strain of citrus tristeza virus (CTV), which is engineered to produce the spinach-derived defensin peptide, effectively immunizing the tree against HLB.

The research, which began at the Texas A&M AgriLife Research and Extension Center at Weslaco and expanded to include the University of Florida, has resulted in multiple patents for both the defensin technology and the CTV delivery system. While the spinach defensin therapy is still in the process of being made available to Florida growers in late 2026, the research partnership continues to explore additional applications of spinach defensins, including potential treatments for zebra chip disease in potatoes and other crop biothreats.