Recent cool, humid weather and extended leaf wetness periods have created highly favorable conditions for aggressive dollar spot outbreaks across New England golf courses. Preventive management remains the most effective strategy for achieving season-long control while minimizing fungicide resistance development.
Key Recommendations for Golf Course Managers
- Initiate preventive fungicide applications when daytime temperatures consistently range between 60–80°F, especially during periods of high humidity and prolonged leaf wetness.
- Maintain 14–21 day spray intervals based on product labels, environmental conditions, and disease pressure.
- Rotate fungicide FRAC groups throughout the season to reduce resistance risk.
- Utilize premix or tank-mix fungicides containing multiple modes of action to improve control efficacy and resistance management.
- Avoid reducing application rates in tank mixtures, as sub-lethal rates may accelerate fungicide resistance development.
Effective Fungicide Options
Fungicide groups that continue to provide strong dollar spot control include:
- DMIs (FRAC 3): resistance has been widely reported in dollar spot populations; rotation with other modes of action is essential.
- SDHIs (FRAC 7): resistance has been reported and should be carefully managed through rotation and tank-mixing strategies.
- Dicarboximides (FRAC 2): resistance has been documented in certain field populations.
- QoIs (FRAC 11): no confirmed resistance has been reported to date, but stewardship is still recommended.
- Fluazinam-based products (FRAC 29): no confirmed field resistance has been observed, although reduced in vitro sensitivity has been reported.
- Benzimidazoles (FRAC 1): resistance is widespread and limits their reliability as stand-alone applications.
- Chlorothalonil (FRAC M5): no reduced sensitivity or resistance has been reported and remains an important multi-site fungicide for resistance management.
Several premix products, including Encartis, Fame T, Honor, Kalida, Navicon, Posterity XT, and Traction, continue to perform well under high disease pressure.
If Control Failures Occur
Resistance to multiple fungicide classes is becoming increasingly common in dollar spot populations. If you observe reduced efficacy or the need for shortened spray intervals, consider submitting samples to the UMass Turf Pathology Laboratory for fungicide sensitivity testing.
For assistance, contact:
- GwangJae Lim: glim[at]umass[dot]edu (glim[at]umass[dot]edu)
- Dr. Geunhwa Jung: jung[at]umass[dot]edu (jung[at]umass[dot]edu)
Additional Cultural Practices
Enhance fungicide performance by:
- Removing early morning dew and leaf wetness
- Avoiding late afternoon or evening irrigation
- Managing excessive thatch accumulation
- Maintaining balanced nitrogen fertility
- Improving air circulation and utilizing lightweight rolling when appropriate
Early preventive action, proper fungicide rotation, and integrated cultural practices remain the best strategies for season-long dollar spot suppression.
Submitted by: graduate student GwangJae Lim & Dr. Geunhwa Jung