When clusters of small, round, sunken patches of straw-colored grass about the size of a silver dollar start showing up on your otherwise beautiful green lawn, there's a good chance the culprit is a fungus called dollar spot. Once primarily known for wreaking havoc on golf courses and recreational turf, dollar spot has become a common lawn problem for homeowners as well.

Dollar spot affects most types of warm- and cool-season grasses, but especially fescues, ryegrasses, bentgrasses, bluegrasses, bermudagrasses, and zoysiagrasses. It tends to occur from late spring to late fall, especially after a period of extremely moist weather. Dollar spot favors high humidity and temperatures ranging from 60 to 85 degrees F.

The bad news: How you care for your lawn can actually stimulate the spread of dollar spot. The good news? There's plenty you can do to help control it.

Here are 3 reasons your lawn may have dollar spot – and what to do about it.

The cause: Mowing too closely.

Because they hold moisture on grass leaves, short lawns (under 3 inches) are more susceptible to dollar spot infection.

The fix: Adjust your cutting height. Raise your mower blade to the recommended 3 to 4 inches. The exception is zoysiagrass, which can be cut a little shorter (but not less than 1 inch). Never cut more than one-third of your lawn's grass length at a time, no matter how tall it gets.

The cause: Not enough lawn food.

The average lawn cannot make enough of its own nutrients to thrive, so you have to supplement it with fertilizer. Undernourished grass is more likely to be susceptible to diseases like dollar spot.

The fix: Nourish and strengthen your lawn by feeding it 4 times a year starting in the spring. Every 6 to 8 weeks, fertilize it with Scotts® Turf Builder® Lawn Food (for Northern lawns) or Scotts® Turf Builder® Southern Lawn Food, following label directions.

The cause: Persistently wet leaves.

Dollar spot thrives in wet, humid conditions, so heavy dew, over-watering, late-day irrigation, and anything else that keeps grass leaves wet for long periods of time could lead to dollar spot.

The fix: Water deeply but infrequently, and water in the early morning hours so leaves won't stay too moist for too long. Prune overly shady trees and shrubs so sun and air can get through to help dry grass faster.

Another important step to take to prevent dollar spot—or to control it if your lawn has already been infected—is to apply a fungicide at the prescribed rate, especially when weather conditions for the disease are at their peak. (Be sure to follow the directions on the label.) Once dollar spot is under control, fix the bare patches left behind with Scotts® EZ Seed®, a combination of grass seed, fertilizer, and absorbent growing material.