EPA clears spinach-peptide graft therapy for citrus greening, with no tolerance limit

The Environmental Protection Agency has granted unconditional registration to a citrus greening therapy built on antimicrobial peptides from spinach, with Maryland-based Silvec Biologics Inc. as the registrant ^[1][2]. The registration is issued under the Federal Insecticide, Fungicide and Rodenticide Act and allows the product to be sold commercially without a tolerance limit, a designation that Texas A&M AgriLife Research attributes to years of safety data gathered through the research partnership ^[3].

The underlying finding is that naturally occurring spinach defensins can protect citrus trees from Huanglongbing, which the announcement calls one of the most destructive diseases in modern agriculture ^[4][5]. The work was led by Kranthi Mandadi at the Texas A&M AgriLife Research and Extension Center at Weslaco, with Bill Dawson, emeritus professor at the University of Florida, and Choaa El-Mohtar, a research scientist at the Citrus Research and Education Center ^[6][7]. Mandadi's line of work started with Erik Mirkov, an AgriLife Research plant pathologist at Weslaco, and the pair identified the defensin peptides as a possible treatment ^[8]. The full effort ran about 15 years across multiple public and private institutions ^[9].

The delivery method is the part growers will have to plan around. According to Mike Irey, director of research at Southern Gardens Citrus in Clewiston, Florida, the product uses a naturally non-transmissible strain of citrus tristeza virus already common in Florida citrus, reprogrammed to prompt the tree to produce the spinach defensin ^[10]. The approach, developed by Dawson's team, does not alter the tree's genome and works by grafting a small piece of plant material from a specially developed source tree onto an existing tree ^[11][12]. Once the benign CTV is established, it continues producing the defensin, which the announcement says helps fight the bacteria associated with citrus greening ^[13]. That is a per-tree operation, not a tank mix, so the constraint on deployment is grafting labor and source-tree supply rather than sprayer passes.

The intellectual property is split and stacked. The defensin is patented by The Texas A&M University System and the CTV delivery technology by the University of Florida; both are licensed to Southern Gardens Citrus, which funded the sponsored research leading to registration, and both were sublicensed to Silvec to obtain the registration and commercialize the treatment ^[14][15].

What the announcement does not contain is the operator's decision data: no efficacy figures, no price, no application-rate or grafting-throughput numbers, and no statement of how long expression persists in the field. Mandadi's own framing of the no-tolerance-limit designation is that it is a testament to safety, not to performance ^[16]. Dale Murden, president of Texas Citrus Mutual, likewise stayed conditional, saying growers "will have new, sustainable treatments that could keep citrus trees productive under disease pressure" ^[17]. Cliff Lamb, director of AgriLife Research, cast the milestone as a return on long-term public investment in commercialization ^[18].

Watch for the first commercial availability, which Silvec expects to begin with Florida growers ^[19], and for the specifics that follow a registration into the market: labeled use directions, per-tree cost, and independent field data on how much yield or tree life a graft actually buys.