Lawn & Turf Tips:  Dollar Spot (Small Brown Patch)

Dollar Spot-(Small Brown Patch) 

Disease Description

Spots of straw color, roughly circular, recognizable when 1 to 2 cm in diameter with delicate mycelium stretching from leaf to leaf, apparent when dew is present. Individual leaf blades may show both damaged and uninfected sections. Spots may remain discrete to about 7 cm in diameter in fine turf and then coalesce. In longer tuff, individual spot margins are not so clearly defined. Disease occurs from late spring through fall and is most active during times of warm humid days (70° -85° F).   Water, mowers and other equipment, or shoes spread the fungus.  On fine textured and close-cut turf, round, bleached out or straw-colored patches occur which are sunken and approximately the size of a silver dollar.  In coarse textured or high-cut turf, the dead spots are larger and more diffuse.  Under these conditions, dollar spot is sometimes confused with brown patch.  Characteristic spots on leaf blades readily distinguish dollar spot from brown patch.  Light tan spots with reddish-brown borders radiate from the edge of the leaf blade.  These spots may cover the width of the leaf.  When the disease is active, cobweb-like mycelium of the fungus can be seen growing on affected areas early in the day before dew dries.

Predisposing Factors

Occurs from late spring through fall and is most active during times of warm humid days (70° -85° F).  Most grasses are susceptible, but  Agrostis sp. (Bentgrass) are usually infected.

• low soil fertility
• heavy, prolonged dews
• uncontrolled infection from previous year

Continual use of one fungicide will allow the fungus to develop resistance.

Cultural Control

Symptoms may be suppressed by application of nitrogenous fertilizer during summer. Attend to overall soil fertility. Remove clippings which carry infection. Remove excess thatch.  Maintain proper fertility and adequate soil moisture.  Aerate compacted soils.  Choose a less susceptible turf grass.

Chemical Control

Fungicide applications are most critical during moist weather in spring and fall when day temperatures are between 70° -80° F.  Where disease is prevalent fungicide applications will be needed from late June to autumn, at 7 to 28-day intervals. Alternate systemic materials with protectants to reduce tolerance developing in fungus. Systemics give longer residual protection than do protectants.