![]() ![]() A preventive fungicide program may be needed to stop the development of Pythium during extended periods of warm, humid weather. Increasing the mowing height and following other practices that promote good root growth will lessen damage from Pythium root rot.Ħ. Selectively prune trees and shrubs growing near the area to improve air circulation.ĥ. Remove thatch when greater than 1/2 inch.Ĥ. ![]() Generally speaking, water in the early morning.ģ. If your lawn has the disease, do not water in the late afternoon or early evening. Test the soil every 3–5 years to understand and correct nutrient deficiencies.Ģ. Maintain soil pH in the neutral to slightly acid range. Maintain grass growth by low to moderate rates of balanced fertilizers. Alkaline- or calcium-deficient soils also tend to favor the disease.ġ. High nitrogen fertility favors the disease on many grass varieties. Movement from these areas can be rapid in wet or humid, hot weather. These fungi may also attack the plant roots and crowns, causing reduced growth, off-color, and thinning (Pythium root and crown rot).ĭiseased plants serve as infection centers from which the pathogen spreads. It can be moved from one area to another by soil movement, by transporting diseased plants or plant parts, and by equipment, shoes, or surface water.ĭamping-off, seed decay, or a seedling blight of turf grasses can also be caused by Pythium fungi. The pathogen survives over winter and periods adverse to disease development as spores associated with debris in the soil. Grass blades may twist and collapse at the lesion. If a sudden drop in temperature or humidity or the application of a fungicide halts the development of Pythium blight, distinct strawcolored spots develop. Under favorable conditions for the disease development, these streaks may coalesce to form large areas of dead grass. These streaks are caused by the water or equipment picking up the fungus and spreading it along its path. In many cases, these patches develop into diffused streaks that follow water drainage patterns or mowing patterns. When observing these patches in early morning, cottony fungal growth can usually be seen on the foliage, although not always. As the disease progresses, the leaves shrivel and the patches fade from green to light brown. In the early stages, the grass leaves may appear water-soaked, slimy (greasy), and dark. Pythium blight is most readily recognized as small spots or patches of blighted grass that suddenly appear during warm, wet periods. This disease occurs mostly during warm to hot weather. When root and crown tissue is attacked, Pythium root and crown rot results. The disease can also occur at lower temperatures during cool (55 degrees to 65 degrees F) wet weather. The disease can spread rapidly, killing large areas of seedling or established turf in as little as a day during conditions of high temperature (80 degrees to 90 degrees F), high soil moisture, and little air movement. This disease is most common during hot, very humid weather especially in golf courses, less so in home lawns. All turfgrasses, warm and cool season, are susceptible to attack. Pythium blight, also called cottony blight or grease spot, is a fungal disease of turfgrasses. Dead spots in lawn caused by pythium blight using a pen for scale ![]()
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