The fungus lives in the stem of the grass, between cells, so it doesn't harm the plant. Equally important, the fungus and fescue interact to produce an array of alkaloids that help the plant persist. The alkaloids deter attacks from viruses and other diseases, as well as from insects and microscopic worms that eat plant roots. The alkaloids also affect livestock grazing behavior. Unfortunately, the result can be serious production losses, particularly when they cause cows to stop eating.
Tall fescue persists better with grazing than any other cool-season grass.
That's why it is grown throughout the world. It's an important cool-season perennial forage for many cattle producers in the southeastern United States, in addition to its importance as a lawn grass. Kentucky-31 tall fescue, an old standard, covers 35 million acres of pastures in the Southeast. Agricultural Research Service scientists and their university colleagues have found that the N. coenophialum fungus seems to perform an important ecological function, helping the plant store more organic carbon and nitrogen in the soil. They have also found that it helps fescue close its leaf stomates quicker to conserve moisture in a drought, as well as improve growth efficiency.