Dollar Spot Information
Causal Agent(s)
- Clarireedia jacksonii
- Clarireedia bennettii
- Clarireedia monteithiana
- Clarireedia homeocarpa
Hosts
All turfgrass species
Symptoms & Signs
Stand symptoms of dollar spot on closely mown turfgrasses (i.e., golf course putting greens, tees, and fairways) appear as 1-2” diameter, roughly circular spots that are straw colored. Spots may coalesce into patches that can exceed 5” in diameter. On individual leaf blades straw-colored lesions can be visible. On coarser textured grass these lesions can girdle leaf blades and take on an hourglass shape. However, on closely mown turfgrasses leaves will typically die back from the tip instead of having distinct lesions appear. Under periods of favorable environmental conditions and high early morning humidity, white cottony mycelia may emerge from infected turfgrass.
Images of dollar spot symptoms:
When Does it Occur?
Dollar spot develops in the spring and fall when air temperatures are between 60° and 80° F. Extended periods of leaf wetness, from heavy dew, fog, or irrigation, are needed for the pathogen to infect the turfgrass. Pathogen activity can be slowed down when daily high temperatures exceed 90° F. Under-fertilized turfgrasses are highly susceptible to dollar spot development. Excessive thatch accumulation and low soil moisture also favor disease development.
Cultural Management
Improved cultivars have some tolerance to dollar spot, though no complete resistance exists. Maintain adequate N fertility during periods of favorable dollar spot conditions. Reduce leaf wetness periods through irrigation timing and dew removal. Improve air circulation to reduce humidity where possible. Perform regular vertical mowing, aerification, and topdressing to reduce thatch accumulation.
Chemical Management
Preventative programs provide the best results in managing dollar spot, and should begin when nightly lows are consistently above 50° F. The Smith-Kerns Dollar Spot Forecasting model has been reliable for predicting outbreaks of dollar spot on putting greens. Using this model can help inform product selection and application timing. Uniform spray coverage is critical to reliable performance from preventative fungicide applications. Apply fungicides in 2 gal carrier per 1000 ft2.
The dollar spot pathogen is highly prone to developing fungicide resistance. Use best management practice to reduce fungicide utilization. Rotate chemistries between each fungicide application, and tank-mix multiple modes of action under periods of high disease pressure.
Selected fungicides for dollar spot management
1 Trade products containing the same active ingredient(s) labelled for use on turfgrasses may be used according to label directions. Mention of specific products does not constitute endorsement.
2 Always check product label for current use rates, application directions, and rate restrictions.
3 Relative efficacy. + = Marginally effective; ++ = Moderately effective; +++ = Effective; ++++ = Very Effective; ? = Limited information at this time.
4 Fungicide Resistance Action Committee code(s). Products sharing a code contain active ingredients with the same mode of action. Always use resistance management practices.
