Most lawn disease starts with a fungus. Fungi are an oddity because they don’t set seeds; instead, they propagate by distributing spores in their surrounding area. Some of the spores are picked up by wind or animals and distributed in new locations.
One of the biggest problems in controlling lawn diseases is diagnosis. By the time signs of infection are evident, the fungus that causes it is often difficult to control. Although there are dozens of types of lawn disease, most can be prevented through regular lawn care. Most fungus spores lie dormant until conditions are right for them to grow and infect your lawn. Generally, fungus spores need warm temperatures, a moist environment, a source of nutrition and a susceptible host. Although you can’t control the weather, you can deprive them of the nutrients they need as well as a susceptible host.
Water your lawn deeply and infrequently to deprive fungus of the damp environment it needs. In addition to helping the prevention of lawn disease, deep and infrequent watering encourages your turf to sink deeper roots. Water only when the surface soil is dry to your touch and then water to a depth of two to three inches. You can gauge how much water your lawn is getting by “planting” a small container (such as a rain gauge or tuna can) in a corner of your yard. In addition, schedule irrigation in the morning to give excess water a chance to evaporate. Never water at night.
Heavy thatch layers (over ½ inch) hold both heat and moisture and provide fungus with a ready supply of nutrients. Thatch also impedes drainage and blocks the airflow your lawn needs to thrive. Annual core aeration in the spring is the best way to control thatch buildup. You can also control thatch during the growing season by maintaining your lawn at a 2 ½ to 3 inch height and cutting no more than ⅓ of the height when you mow.