Hay Herbicides Not a Risk to Horses, Despite Manure-Fertilized Crop Loss

Recent reported crop losses in North Carolina and several other states are linked to certain broad leaf herbicides containing aminopyralid, clopyralid, and picloram, according to researchers. In North Carolina, people with gardens and organic farms who rely on horse manure or compost for fertilizer are noticing that some of their plants are dying.

The herbicides, used by hay producers to produce weed-free hay, are applied to hay grown in every state and ingested by horses and other species.

"Based on the published reports it appears these herbicides pass through the animal basically intact," said Jeanine Davis, PhD, associate professor and extension specialist in horticultural science at North Carolina State University. "After being excreted in the urine and manure they still act like herbicides."

"There is no adverse health impact or risk to humans, horses, livestock, or any animals from this," said Bob Bruss, PhD, risk assessment manager, pesticide division of the North Carolina Department of Agriculture and Consumer Services. "It's more injury to broadleaf plants if they get treated with the manure."

Generally the herbicides are used on hard-to-control weeds. "They may carryover and be able to kill weeds for more than one season," said Bill Yarborough, regional agronomist at the NCDA&CS. He said the problem is more prevalent in home gardens. "People will see it in fruits and vegetables where people are using manure."

According to Sue Ellen Johnson, PhD, assistant professor-Forage Specialist at NCSU, "Not all hay has these herbicides applied; a good indicator that these particular products were not applied is if the hay includes a legume.

"As a member of the greater agricultural community it's important for horse owners to be informed and ask how our hay was grown and with what materials and then make sure we make the right decisions on how we dispose of our horses' manure," Johnson said.

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Rhona Melsky

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