Be sure you aren’t importing noxious or invasive weeds, or potentially injurious herbicide residues if hauling in hay from other areas this year, say Mike Moechnig and Roger Gates, South Dakota State University Extension weed and rangeland specialist, respectively.

“It is illegal to transport hay containing noxious weed seeds in South Dakota regardless if the hay is from this or another state,” Moechnig says. “In fact, this is a Class 2 misdemeanor that could be punishable by 30 days in prison and/or a $500 fine.”

The law applies to situations in which the violation constitutes a “substantial” risk of contaminating land, says Gates. “Avoiding known weed patches at harvest will reduce contamination. Hauling bales that are net-wrapped or tarping the load will minimize the risk of excessive weed-seed distribution.”

Avoiding weedy hay can also help producers prevent possible infestations on their property, the specialists say. “Fortunately, weed infestations generally do not explode in a single season, so watching for noxious or invasive species next year should enable effective control of new infestations before they become a costly problem,” Moechnig says.

“Leafy spurge, Canada thistle and yellow toadflax are likely some of the most difficult weeds to control that may be present in grass hay, so it is particularly important to be watching for these weed species next year.”

The need to hay areas normally not harvested could also increase the risk of having toxic weeds in the hay, he says. “Perhaps the most toxic weeds are poison hemlock and water hemlock. Lethal doses for some livestock species may be only 0.2-0.8% of their body weight.” Poison hemlock populations seem to have expanded the past couple years, particularly in northeastern South Dakota, which may partly be due to greater precipitation rates, he says. “Hemlock species are in the carrot plant family, so flower clusters resembling carrot flowers may be visible in hay. Whorled milkweed is another weed of concern, but populations are often not very dense, particularly in areas with taller grass that may be hayed. Common weed species, such as kochia, lambsquarters, pigweeds, thistles and others, can also increase hay nitrate concentrations if present in large quantities.”

Unknown herbicide residues could also cause problems, Gates says. “Grass treated with herbicides such as picloram (Tordon, Grazon), aminopyralid (Milestone and ForeFront) or clopyralid (Curtail, Stinger) could still contain residues of these herbicides that will quickly pass through livestock and can remain in their manure.

“Spreading this manure or feeding bales on fields that may be planted to broadleaf crops next year could result in severe crop injury. These residues could persist in the soil for two to three years. Therefore, it is important to keep manure in pastures if it is not known exactly what herbicides were applied to the hayfield.”

Careful management of hay-feeding areas can lessen infestation risks. Drought conditions reduce pasture vegetation vigor, increasing bare ground and enhancing weed germination and establishment. Feed imported hay in a restricted area or even in corrals to contain an area that can be carefully monitored the following spring.

For photos of noxious weeds and control recommendations,