GAINESVILLE, Fla. — Recent news accounts of horses falling ill or dying after consuming the weed creeping indigo have raised concerns among horse owners. So, University of Florida experts have released a new publication to educate the public and help prevent future incidents.
It’s the latest in a series of educational efforts on creeping indigo led by faculty members with UF’s Institute of Food and Agricultural Sciences and UF’s College of Veterinary Medicine, said weed scientist Jason Ferrell, a UF/IFAS agronomy professor. For the past year, Ferrell and colleagues have been giving live presentations to horse owners and reaching out to veterinarians, Extension agents and fellow scientists with information.
“We want to heighten people’s sense of awareness, heighten their vigilance, teach them about good pasture management practices and improve their horses’ health,” Ferrell said.
The publication is available free at http://edis.ifas.ufl.edu/ag399. It provides color photos of creeping indigo, along with information on its toxic effects, preventive steps to discourage establishment of the plant, and herbicide recommendations for treating infested pastures. The publication is part of the UF/IFAS online Extension library known as the Electronic Data Information Source, or EDIS.
Known scientifically as Indigofera spicata, creeping indigo is native to East Africa, Madagascar, Indonesia and the Philippines. It’s a subtropical legume that grows close to the ground, sending multiple runners out from a central stem. The plant produces clusters of small pink flowers, probably its most identifiable feature.
Creeping indigo has reportedly grown wild in Florida for decades. It can sicken or kill horses that frequently consume the plant in moderate to large quantities, Ferrell said. Unlike many noxious weeds, creeping indigo apparently tastes good to horses, meaning that horse owners shouldn’t expect their animals to naturally shy away from it.
Creeping indigo’s toxic effects arise from two chemicals contained in the plant: one causes eye abnormalities and ulcers on mucous membranes, the other causes neurological damage. Symptoms of creeping indigo poisoning in horses include neurologic abnormalities, lethargy or poor coordination, ulcers on the gums and tongue, and watery discharge from the eyes.
There is no antidote for creeping indigo poisoning, although many horses recover partially or completely once they stop consuming the plant, said equine Extension specialist Dr. Amanda House, a clinical associate professor with UF veterinary college. Supportive care can enhance recovery, and is often recommended.
Horse owners who suspect an animal is suffering from creeping indigo poisoning should take two steps – stop grazing the horse in its usual pastures and have it evaluated by a veterinarian as soon as possible, she said.
“They should also consider contacting their local Extension office for information on creeping indigo,” House said. “There are quite a few look-alike plants and it’s important to identify the weed accurately.”
Creeping indigo has been officially reported in two-thirds of Florida’s counties, Ferrell said, and it’s most likely present in the remaining counties as well. Hawaii is the only other U.S. state reporting creeping indigo, but scientists believe it could become established in southern Georgia, Alabama and Mississippi.
Hard freezes can kill the plant, limiting its presence in North Florida, but for those in Central and South Florida, creeping indigo can appear at any time of year, he said. Heavy infestations have come and gone unpredictably in various counties.
Scientists believe creeping indigo is toxic to many mammals, but research on the plant is sparse, said Brent Sellers, an associate professor and associate center director at the UF/IFAS Range Cattle Research and Education Center in Ona. Among domestic animals, horses seem to be at greatest risk because the plant is palatable to them and their jaw structure enables horses to browse on plants growing close to the ground, something cattle can’t do.
“I think cattle ranchers have less reason to worry about creeping indigo than horse owners do,” Sellers said. “But if someone believes their cow or bull is sick from eating creeping indigo they should consult a veterinarian right away.”
Anecdotal evidence suggests that creeping indigo often becomes established in bare, trampled or overgrazed areas, he said.
“If a horse owner or cattle rancher is concerned about the possible presence of this weed, the biggest thing is to scout their pastures,” Sellers said. “I would say to look in high-traffic areas, anywhere the grass is usually short or grass doesn’t grow.”
The vast majority of Florida’s horse and range cattle pastures are planted in bahiagrass and the EDIS system offers numerous resources on bahiagrass that may be helpful in pasture-management efforts, including this overview, http://edis.ifas.ufl.edu/ag342.
Writer: Tom Nordlie, 352-273-3567, firstname.lastname@example.org
Sources: Jason Ferrell, 352-392-7512, ext. 209, email@example.com
Amanda House, 352-392-2229, firstname.lastname@example.org
Brent Sellers, 863-735-1314, ext. 207, email@example.com
Photo credit: Tyler L. Jones, UF/IFAS