Thick grass is often a hallmark of a healthy lawn. If grass begins to thin, homeowners may feel as though all the time and effort they spent tending to their lawns was for naught.
Thinning grass can be caused by any number of things. And while it might take a little effort to address, thinning grass can be treated if homeowners correctly identify that cause of the problem.
The Center for Agriculture, Food and the Environment at the University of Massachusetts Amherst notes that leaf spot diseases affect both cool- and warm-season turfgrasses. Various fungi can cause leaf spot. Symptoms and the timing of the appearance of leaf spot will vary depending on which fungi is causing the problem. For example, bipolaris sorokiniana, which affects grasses in warm, wet summer months, produces small spots that are dark purple to black. Dreschslera poae is another fungi that causes leaf spot, and it also produces dark purple to black spots. However, it tends to appear in the spring when the weather is cool and moist. Understanding the different fungi and when they typically strike can help homeowners identify what is causing their grass to thin. In such situations, professional landscapers can be invaluable resources as well.
The University of Maryland Extension notes that stripe smut primarily poses a threat to Kentucky bluegrass that is older than three years. Pale green streaks that run parallel to the veins in the leaves and leaf sheaths are symptomatic of stripe smut, which tends to be noticed in spring and fall, when weather is cool. As the disease progresses, stripes turn black or a silvery gray, causing the leaf blade to shred and curl. After the blades have shred, they turn brown and die. The grass thins because stripe smut makes it vulnerable to problems like drought.
Ascochyta leaf blight
Lawns suffering from ascochyta leaf blight will become straw-colored. According to the lawn care and pesticide experts at Ortho, when a lawn is affected by ascochyta leaf blight, its healthy grass blades will be mixed in with diseased grass blades. Most prevalent in the spring, this disease can affect grass at any time during the growing season. That's because the ascochyta fungi invade leaf blades through wounds, such as those that can result from mowing. Ortho notes that dull lawn mowers can contribute to the disease, which might disappear on its own and can even return after it's seemingly been cured.
Various issues can cause grass blades to thin. Working with a landscape professional is a great way to combat such issues before they compromise the look of a lawn.