Dollar spot is one of the most prevalent diseases affecting turfgrasses in our region. And it’s a costly blight as well. Landscapers, golf course superintendents and other turfgrass professionals spend more money on chemicals to control dollar spot than any other disease.
The fungus is a common problem in any setting, whether residential or commercial landscapes, golf courses or athletic fields. Dollar spot affects all varieties of both warm and cool season turfgrasses, but tends to be most severe in Bermuda grasses.
Dollar Spot Identification
This white, web-like fungus branches out from one blade to the next, infecting the grass in small round spots. The fungus secretes toxins that cause white lesions on the grass blades, multiplying and expanding until the green color disappears from the blade completely.
Most noticeable will be the telltale round and sunken spots, usually straw-colored or white and ranging from half an inch to four inches in diameter. In severe cases, the round spots may converge to create large irregular patches.
Unfortunately, dollar spot does not die during winter, but persists season to season. It spreads most readily when temperatures fall between 60 and 85 degrees.
The disease may spread inadvertently when people, animals, equipment, water or wind move infected leaf debris from one area to another. Not only unsightly, the damaged turf often becomes thin and susceptible to weed invasions.
Preventing Dollar Spot
Since stressed grass is more susceptible to disease, prevention starts with choosing the variety of turfgrass best suited to the area’s conditions. Dry soil, compacted soil, excessive moisture and other stresses encourage dollar spot, so strong cultural practices, like proper mowing and watering, are important as well.
Dollar spot thrives in excess moisture left sitting on the grass blades for extended periods. Mow regularly to improve air circulation, and irrigate in the morning before the dew dries to help discourage fungal growth.
Removing thatch deeper than one inch also helps eliminate excess moisture and reduce turfgrass stress, while removing sources of bacteria that may lead to dollar spot.
Paradoxically, dry or drought conditions also encourage dollar spot. Protect turfgrass from stress by watering deeper and less often. Most turfgrasses need at least one inch of water twice per week and more during extremely hot or dry spells.
Mowing below recommended heights can dry and scorch grass and soil. Grass blades shield the soil from wind and sun, helping regulate temperature and moisture levels. Scalping disrupts this balance, placing undue stress on turfgrass roots and encouraging dollar spot.
Maintaining optimum fertility helps defend against the fungus while keeping grass strong. Dollar spot spreads more readily in grasses with poor fertility, especially low nitrogen. However, over-fertilizing with nitrogen can invite other diseases, like brown patch or Pythium blight. Be sure to follow recommended fertility guidelines for the specific turfgrass variety.
Few fungicide options available to homeowners effectively control dollar spot, so professional treatment is always recommended.
Several effective fungicides and biological fungicides are available to turfgrass professionals. Apply when conditions are most conducive to dollar spot development for best results. Alternating classes of fungicides helps prevent fungicide resistance.