Hard to believe, especially after this week, but fall and cooler temperatures will be here in less than a month. Soon after that, a frost will occur. Members of the sorghum family have a compound called dhurrin that will release hydrogen cyanide, commonly known as prussic acid, when plants are stressed by drought or frost. Johnsongrass, a perennial sorghum, is commonly found in southern Indiana pastures. Historically, Johnsongrass was planted for forage purposes, but soon received the label of a prohibited noxious plant because of its ability to be where it wasn’t desired because of seed shatter and rhizomes. Being a sorghum, Johnsongrass has the potential to produce hydrogen cyanide and cause livestock death when plants are stressed. Other desirable sorghums when stressed will produce hydrogen cyanide, too.
Johnsongrass, when damaged by severe drought or frost, has the potential to produce prussic acid (hydrogen cyanide). On the left is ungrazed forage in a paddock and on the right is a paddock that has been recently grazed. The tall plant on the left paddock is Johnsongrass. (Photo Credit: Keith Johnson)
Producers are encouraged to utilize sorghums before a frost occurs to reduce the possibility of prussic acid poisoning. Links below to a publication and video will discuss ways to reduce the fear of prussic acid poisoning.
In the near future, dhurrin-free sorghums will be available for seeding as a result of Purdue University work conducted by Dr. Mitch Tuinstra’s research group, most notably Dr. Shelby Gruss. Unfortunately, Johnsongrass will remain to be concern even when dhurrin-free sorghums are available.
Read our publication AY-378-W Managing the Prussic Acid Hazard in Sorghum <https://www.extension.purdue.edu/extmedia/AY/AY-378-W.pdf>
