Tall fescue is a cold-season turfgrass used to brighten areas during the winter. It is a hardy turfgrass, able to survive most of the year. Tall fescue seed is often used to overseed lawns during the fall. Although it's weather-hardy, several diseases that affect the growth and development of tall fescue.
Brown patch is a disease caused by the fungus Rhizoctonia solani, and is the most common diseases of fescue grass. According to North Carolina State University's website, brown patch begins when night temperatures reach 60 degrees Fahrenheit, but is more prevalent when high and low temperatures are between 70 and 90 degrees. Brown patch creates off-color brown patches in the lawn in large, circular patches that grow together over time.
Helminthosporium Net Blotch
Helminthosporium net blotch, says the University of Delaware website, occurs mainly during cool, moist periods in the spring and fall. Brown or purple specks appear on the fescue leaf blade, which develop further into a series of net-like brown spots and necrotic lesions along the blades.
Gray Leaf Spot
Gray leaf spot creates small, grayish brown spots along the leaves of fescue grass along the sheaths, says the Alabama Cooperative Extension. The spots increase in size, and the spot turns from brown to completely gray. Spots are usually found along the leaf vein. Irregular patches of discolored turf may appear when severely infected.
White patch creates circular patches of white grass. Because of its circular pattern, it is often mistaken with brown patch. Patches are 3 to 6 inches in diameter before they sink and grow to 8 to 12 inches. Tiny gilled mushrooms, white to tan, appear along the length of blighted fescue grass leaves.
Pythium blight, known also as cottony blight or grease spot, creates water-soaked areas in the lawn that are several inches in diameter. The spots look greasy and slimy, before the spots dry and turn brown. Pythium blight in fescue lawns may reach a diameter of 1 foot.