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)](https://extension.entm.purdue.edu/newsletters/pestandcrop/wp-content/uploads/sites/2/2023/08/johnsongrass.jpg)
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>