A weed once studied for its potential as a livestock feed is sickening Florida horses and threatening to invade pastures along that state’s border with Georgia.

In the 1930s University of Florida scientists began studying trailing indigo, also known as creeping indigo, for its potential as a nutrient-rich, easy-to-cultivate plant that had potential as forage for livestock, said Rob MacKay, BVSc, PhD, Dipl. ACVIM, a professor of large animal medicine at the University of Florida, in Gainesville. The researchers’ investigation ultimately revealed that creeping indigo was toxic to horses and other livestock, so they abandoned their studies into the plant.

“It became a problem when, somehow, the plant was introduced into the wild,” MacKay said.

Over the past 10 years, creeping indigo began to show up in southern Florida pastures. Since then, the plant has traveled northward to invade pastures in central parts of the state including Ocala, where some horses have become sick after eating the toxic vegetation