Homes throughout North America grow grass as an attractive groundcover. Most turfgrass species are hardy and will thrive with standard lawn practices like regular mowing and fertilization, but even the most well-maintained lawn can sometimes have problems. Whether it's a disease or an insect pest, treat the problem immediately to defend your yard's health and beauty. An untreated problem will typically grow worse and can end up killing your entire lawn.
Lawns that don't receive adequate irrigation will become drought stressed. The point at which a grass becomes stressed due to dehydration varies widely according to the grass species. For example, bermudagrass is much more drought-tolerant than annual ryegrass. Apply water as soon as you notice symptoms of drought stress. Symptoms include the grass turning a blueish-gray in color; widespread wilting of the grass leaves; and the grass not springing back into shape after being walked on or driven over with a lawn mower (i.e., footprints or track marks persist).
Various beetle species, including the notorious Japanese beetle, lay their eggs in the ground. These eggs hatch in the spring and summer, and the larvae can wreack havoc on the lawn as they eat away at the roots of the turfgrass. Surface signs include irregularly shaped yellow or brown spots in the grass. Use a spade to peel back a portion of the sod. If you count more than 10 grubs in a square foot of grass, the lawn needs to be treated. Standard acephate- or permethrin-based lawn insecticides effectively kill grubs.
Necrotic Ring Spot
The necrotic ring spot disease is caused by the Leptosphaeria korrae fungus. It's common in high-maintenance lawns like Kentucky bluegrass and is most prevalent during the moister fall and spring seasons. Symptoms include large ring-shaped spots in the grass made up of red- or yellow-hued grass. Reduce the chances of contracting this lawn disease by regularly reducing thatch to less than 1/2 inch every fall or spring, and regularly aerate to keep soil from compacting and to improve water and air movement. Overuse of nitrogen-rich fertilizers is also a common factor. If the fungus doesn't recede after changing these management practices, apply standard lawn fungicide to kill it.
Powdery mildew (Erysiphe graminis) leaves grass covered in a white powder and, if left untreated, can kill the grass. Because the mildew requires moisture, you can kill it by reducing the amount of water applied to the lawn. Trimming overhead trees and surrounding shrubs can also help dry out the fungus by increasing sunlight on the lawn and opening up the area for increased airflow.