Dollar Spot Disease name comes from the silver-dollar sized straw-colored spots this disease causes on putting greens. On longer grass, the shapes are more irregular. When dew is on the grass, look for white cob-webby fungus. Blades of grass show straw-colored lesions with reddish-brown borders. Of the common lawn grass, bluegrasses and fescues are most affected. Improper mowing, watering and excessive thatch buildup are all contributing factors.
Fairy Ring—is caused by a number of species of mushroom-forming fungi. Visible signs of fairy ring disease are circular or semi-circular rings, usually darker in color than that of the surrounding turfgrass, which form in the turf and may or may not produce mushrooms within those rings. These rings can range in size from a few inches up to many feet in diameter. Excessive thatch and turfgrass growing in low fertility soils with insufficient irrigation appears to suffer more damage from fairy rings than turfgrass with adequate fertility and irrigation. Weeds will commonly invade infested areas. A turfgrass management program that provides proper fertilization and irrigation along with regular dethatching of the turfgrass will help prevent the development of this disease. Fungicide treatment or soil removal may be necessary if fairy ring becomes a problem. NOTE: The presence of mushrooms alone does not mean that your lawn has fairy ring disease (please see Mushroom photo below)
Leaf spots are most destructive during cold, wet, overcast weather in spring and fall. Look for gradual browning and thinning of grass. Small, dark-brown, purplish, or purplish-red colored spots appear on the leaves from the early spring to late fall. As these lesions increase in size their centers may fade to a straw or light-brown color. The spots are usually surrounded by narrow dark reddish-brown to purplish-black borders. Improper mowing, watering and excessive thatch buildup are all contributing factors.
Necrotic ring spot frequently occurs on two to five-year-old sodded lawns and is especially prevalent in vigorously growing lawns. These lawns often develop a thick thatch layer, which stimulates fungal growth. Necrotic ring spot is also common in lawns that have layered soil; one to two inches of topsoil laid down over hard compacted native soil, but not mixed together. This effect produces a lawn with shallow roots and poor drainage. The development of the “frog’s eye” lesions are tell-tale signs of the disease’s presence. Necrotic ring spot can be problematic, but implementation of proper cultural practices can manage this disease. Lawns that are compacted or have thick thatch layers promote the development of necrotic ring spot. Fungicides are available that manage the disease preventative, but are of limited use once disease symptoms are visible. However, if cultural deficiencies are not corrected, necrotic ring spot may persist in a lawn for many years. Kentucky bluegrass and fescue are the most common species of grass infected. Proper mowing, watering, soil aerification and keeping thatch buildup to a minimum are all important keys
Pythium Blight appears as small, usually irregularly-shaped spots 2 to 10 inches in diameter. The grass blades have a water-soaked appearance, and the diseased areas feel and look greasy or slimy. Upon drying, these killed areas of turf turn light brown or a straw-colored hue and may have a slight reddish tinge. Groups of affected patches may coalesce into larger, irregularly-shaped areas or into elongate streaks, which often extend in the direction of drainage flow or of mowing. Dead and dying grass blades may become matted together if conditions remain moist, especially in areas that are subjected to traffic. Diseased plants serve as infection centers from which the fungus spreads. Spread from these areas can be rapid in wet or humid, hot weather. High nitrogen fertility favors the disease on many grass varieties. Maintain grass growth with low to moderate rates of balanced fertilizers, and maintain soil pH in the neutral to slightly acid range. Avoid mowing when the grass is wet. Do not water in the late afternoon or early evening. If the disease occurs, fungicide use will probably be necessary to prevent spread under favorable conditions.
Rust Disease favors warm and humid conditions and develop most frequently on grasses subject to drought-stress conditions, low nitrogen fertility and shade. Low mowing heights, particularly on Kentucky bluegrass, also increase the susceptibility of grasses to rust.The disease first appears on grass leaves as small orange to reddish-brown flecks that enlarge to form raised pustules on leaves and stems (these are what turns shoes and socks orange). Individual pustules are usually oval or elongated and contain a powdery mass of orange to reddish-brown spores. As the pustules mature they turn brown to black. Heavily infested turf becomes thin with an overall yellow-orange to reddish-brown color. Infected leaves turn yellow, wither and die. Cultural practices which improve the vigor of the turf help prevent rust. To reduce the incidence of rust, keep nitrogen levels adequate for turf growth, avoid moisture stress or over watering and adjust mowing heights according to the grass needs.