Dollar spot

What is dollar spot?

Dollar spot is one of the most common turf diseases in the country. Penn State and UMass now name the fungus Clarireedia jacksonii, formerly Sclerotinia homoeocarpa. Older guides from Purdue, Missouri and UC IPM still use the old name. It attacks bentgrass, Kentucky bluegrass, perennial ryegrass and annual bluegrass most. Missouri Extension also finds it on zoysia, bermuda and buffalograss, but rarely on tall fescue.

The fungus makes no spores. It survives the winter as crusts of tough fungal threads in dead grass and thatch. In spring and summer, it spreads on bits of infected clippings carried by mowers, shoes, aerators and running water. Purdue calls it a natural part of the turf's microbe community, so it is almost always present.

Dollar spot is a warning sign of hungry grass. Purdue says outbreaks on home lawns often follow the normal run-down of nitrogen in late spring or summer, and Missouri Extension says damage is worst on nitrogen-starved turf. A light feeding and good watering habits usually bring a lawn back without any fungicide.

Symptoms and signs

• Many small, round, bleached tan spots scattered across the lawn
• On home lawns the spots are usually 2 to 5 inches across
• Spots can run together into large, uneven dead areas
• Leaf spots shaped like an hourglass, tan in the middle with reddish-brown edges
• Fine white cobweb-like fungus on dewy grass early in the morning

Dollar spot identification: what to look for

• Symptoms: Round, bleached spots. Penn State gives sizes by mowing height: silver-dollar size on golf greens, 1 to 3 inches on fairways, and 2 to 5 inches on lawns mown at 2 to 3 inches.
• Symptoms: Leaf spots start as yellow-green blotches and turn tan with reddish-brown borders. On Kentucky bluegrass, Missouri Extension says they are often hourglass shaped, near the middle of the leaf and stretching across it.
• Signs: Small white cotton-like webs on wet leaves early in the morning. Missouri Extension warns this is not reliable alone because spider webs and other fungi look alike.
• Timing: Late spring, summer and early fall. Penn State says peak activity in Pennsylvania is late summer. Purdue links infection to dew periods longer than 8 hours.

Disease cycle

The fungus rests over winter as crusty clumps of fungal threads inside dormant, infected grass. When spring temperatures rise, it starts growing again. It infects leaves when there is a thin film of water on them and temperatures sit around 60 to 85°F. Each spot grows outward from where it started. New spots begin when mowers, aerators, shoes or water carry infected clippings to clean grass. It makes no spores, and Purdue says long-distance spread is not a serious concern.

When to look: Late spring through early fall. In Pennsylvania it can show any time in summer, peaks in late summer, and can flare again in early to mid fall when nights are cool and days warm.

Dollar spot look-alikes

A few things get mixed up with it:

• Brown patch (Rhizoctonia solani): Brown patch patches are usually larger, from several inches to several feet, mostly in hot midsummer. Its leaf spots are tan with dark brown borders, not hourglass shaped.
• Red thread (Laetisaria fuciformis): Red thread patches look tan or pink from a distance. Up close you will see red or pink thread-like strands on the leaf tips, which dollar spot does not make.
• Cutworm damage: Missouri Extension lists cutworm feeding as a look-alike. Check for chewed blades and small caterpillars instead of leaf spots.

How to manage dollar spot

Cultural control

• Keep nitrogen adequate. A light feeding in late spring or midsummer helps lawns that get dollar spot each year.
• Water deeply and less often, so the whole root zone gets wet and the grass is not drought-stressed.
• Water between midnight and early morning, not in the evening, to keep dew periods short.
• Knock dew off the grass early in the morning by mowing, dragging a hose or poling.
• Raise mowing height. Purdue suggests 2 to 3 inches on home lawns to speed recovery.
• Keep thatch thin and improve air flow and drainage where spots cluster.

Biological control

• UC IPM says composted topdressings reduce how often and how badly dollar spot shows up.
• Purdue and Missouri Extension say biological products and compost amendments gave mixed or inconsistent results. They are not stand-alone fixes.

Chemical control

Purdue says fungicides are rarely needed on home lawns, and Missouri Extension says lawns generally do not need preventive sprays. Golf greens are different and often need repeated protection. Extension guides list contact fungicides and several penetrant groups for dollar spot. Penn State warns this fungus has developed resistance to penetrant fungicides, and UC IPM and UMass name benzimidazole and DMI types among them, so rotate groups and lean on good culture first. Use only products labeled for this use; the label is the law.

Use only products labeled for this disease and this site; the label is the law. For trees, work with an ISA Certified Arborist. If you hire someone to apply pesticides, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Prevention

• Follow a steady fertilizer program so the grass never runs hungry in late spring or summer.
• Choose bentgrass or other cultivars rated for dollar spot resistance in NTEP trials.
• Water early in the morning, deeply and infrequently.
• Prune trees and shrubs so air moves and the grass dries faster, as UMass advises.

When to call a pro

For a home lawn, try fertilizer and watering changes first. If spots keep coming back on a high-value lawn or sports field, talk to a licensed pesticide applicator. See our pesticide applicator license guide.

Related guides: Weed identification guide · All pests and diseases

Questions about dollar spot

Similar pests and diseases