Time to Test for Endophyte in Pastures

Published: April 4, 2011

If you have a tall fescue pasture, chances are it is common Kentucky 31. Nearly all of Kentucky 31 tall fescue is infected with a microscopic fungus known as the tall fescue endophyte. The tall fescue endophyte gets its name from growing inside (endo) the plant (phyte).

The endophyte is seen here, appearing as strands of yarn growing between cells in the seed of tall fescue.

The common endophyte produces toxins that cause fescue toxicosis, the most serious forage-livestock disorder in Missouri. Symptoms of fescue toxicosis are not always noticeable. For example, it is hard to tell when steers are gaining 1.3 lb/day rather than 1.8 lb/day. But when steers go to the sale barn, the cost is very real. According to research in Georgia and Oklahoma, a steer on highly infected Kentucky 31 will go to the feedlot 100 lbs lighter than a steer on non-toxic tall fescue.

Some producers are electing to replace their old tall fescue with new cultivars. Others are learning how to manage the Kentucky 31. In either case, producers must first test for endophyte level. If the endophyte level is 20 percent or less, producers should manage what they have. If endophyte level is 55 percent or higher, they should consider replanting or seriously improving the management. It is critical to know the level of endophyte.

How do we test for the endophyte? This time of year, it is best to test the growing tillers. The testing process involves clipping each tiller at the soil surface, where it meets the root, then sending it to a good lab. Details about sampling, shipping and costs willbe provided by a lab you choose. A good lab is NOT a lab that is certified; this is because certification is based on fiber and protein, not the endophyte. In fact, there is no certification for endophyte testing. Therefore, a good lab is one with a good record of analysis.

Some test with the microscope. As your samples arrive, these labs unpack your sample, stain it, and look for the endphyte growing between the cell walls. These labs are accurate only if the technician is well-trained. If not, the lab will still give you a value. And you cannot be sure it is correct.

Other labs use a chemical procedure. The chemical labs treat your sample with reagents that eventually give off a color; this color indicates the presence or absence of endophyte. The chemical lab most often used by MU researchers and extension specialists is Agrinostics, a private lab located in Georgia. The Agrinostics lab has never given an inaccurate reading to our researchers or extension specialists and is therefore considered reliable. They also offer a quick turnaround time. For more information about testing, check out the Agrinostics website at www.agrinostics.com.