Every lawn eventually becomes a victim of lawn grass diseases, from the well-manicured expanse of the golf course to the sometimes neglected yard. This problem is devastating to the landowner following a large investment in creating and maintaining his turf. However, the destruction of lawn grass infection is not irreparable. General Cause and Prevention Lawn diseases, like human diseases, infect susceptible hosts. Likewise, the identification of lawn diseases is sometimes difficult, because they do not always have distinct characteristics and tend to manifest themselves with the same symptoms. Herbs vary in their disease resistance; however, when environmental conditions are favorable for specific pathogens, infection occurs. Proper watering, mowing, aeration, sunlight and fertilization help prevent or control problems by providing a disease-resistant environment. High Moisture Grass Diseases Brown Spots: This lawn grass disease commonly infects most grasses initially manifesting as a small patch of wet, dark grass before progressing to circular or horseshoe-shaped patches of brown grass surrounded by a yellowish ring. The patches expand rapidly, progressing in size to several feet wide. According to American-Lawns.com, this disease thrives in daytime temperatures between 75 and 85 degrees and evening temperatures above 65 degrees. Brown Patch disease responds well to consistent fertilization, morning watering, keeping the grass a little tall, and bagging grass clippings to prevent contamination of previously infected areas. Healthy grass later returns after the infection is cleared. Using fungicides before infection occurs serves as a preventative measure. Dollar Spot: Dollar Spot thrives in... middle of paper... its disease. American-Lawns.com suggests controlling this disease by applying fungicide in October or early March, after which thorough watering is necessary. The arrival of warm weather kills infected grass. Striped Smut: This cold-weather lawn grass disease is generally not serious and thrives in temperatures between 50 and 60 degrees. It may not appear in prolonged hot temperatures of around 90 degrees. Stripe Smut affects grass growth, making lawns appear patchy and uneven. Infected blades show yellowish-green streaks that over time turn gray and black. The black streaks break, splitting the leaves and scattering black, powdery spores. John Swenson suggests preventing the progression of Stripe Smut by applying nitrogen and watering deeply, preferably in the morning. Severe cases, although rare, require the use of fungicides in late fall or early spring.