The persistent turfgrass disease, dollar spot, is making an early return in 2025. Recent periods of abundant moisture and optimum temperatures have created highly favorable conditions for outbreaks across many turfgrass species. To effectively manage dollar spot and reduce the risk of fungicide resistance, it is essential to implement a fungicide rotation and tank mixture strategy that utilizes products from different FRAC (Fungicide Resistance Action Committee) groups. Although multiple fungicide classes remain effective, cross- and multi-resistance has already been reported in several key groups, including the DMI, benzimidazole, SDHI, and dicarboximide groups.
Below is a summary of fungicide efficacy against dollar spot, based on recommendations from Clark et al. (2024). The information is organized by active ingredient (trade name), average efficacy rating (on a 1-4 scale, with 4 being most effective), and recommended application interval in days.
DMI fungicides (FRAC 3)
| AI (trade name) | Efficacy rating | Interval (days) |
| Flutriafol (Rayora) | 3 | 14-21 |
| Mefentrifluconazole (Maxtima) | 4 | 14-28 |
| Metconazole (Tourney) | 4 | 14-21 |
| Propiconazole (Banner Maxx, Spectator, Savvi) | 4 | 7-28 |
| Prothioconazole (Densicor, Prothioconazole Select) | 4 | 14-21 |
| Tebuconazole (Torque, Mirage Stressgard, Clearscape ETQ, Offset, TEB360) | 4 | 14-28 |
| Triticonazole (Tremis) | 3.5 | 14-28 |
SDHI fungicides (FRAC 7)
| AI (trade name) | Efficacy rating | Interval (days) |
| Boscalid (Emerald, Cadence, Ruby) | 1^ / 4 / 3.5# | 14-28 |
| Fluxapyroxad (Xzemplar) | 1^ / 4 | 14-28 |
| Isofetamid (Kabuto) | 1^/ 3.5 | 14 |
| Penthiopyrad (Velista) | 2^/ 3.5 | 14-21 |
| Pydiflumetofen (Posterity) | 2^/ 4 / 3.5# | 14-28 |
QoI fungicides (FRAC 11)
| AI (trade name) | Efficacy rating | Interval (days) |
| Fluoxastrobin (Fame, Floxcor) | 3 | 14-21 |
| Mandestrobin (Pinpoint) | 4 / 3.5# | 14-21 |
| Pyraclostrobin (Insignia Intrinsic) | 3.5 | 14 |
Benzonitrile (FRAC 29)
| AI (trade name) | Efficacy rating | Interval (days) |
| Fluazinam (Secure, Rotator, Soteria, Downforce ETQ, Flex-guard, Wingspan) | 4 | 14 |
Nitrile (FRAC M5)
| AI (trade name) | Efficacy rating | Interval (days) |
| Chlorothalonil - multi-site, good for resistance management - (Daconil Ultrex, Manicure, Concorde SST, Chlorostar, Echo, Pegasus L) | 3 | 7-14 |
Dicarboximide (FRAC 2)
| AI (trade name) | Efficacy rating | Interval (days) |
| Iprodione (Chipco 26GT, Raven, 18 Plus, Iprodione Pro) | 3.5 | 14-28 |
Benzimidazole (FRAC 1)
| AI (trade name) | Efficacy rating | Interval (days) |
| Thiophanate-methyl (Fungo, Systemic Fungicide, Systec 1998, Cavalier, T-Storm) | 1^/ 4 | 10-21 |
Table footnotes:
#A rating of 4 reflects efficacy at a 2-week spray interval, while 3.5 applies to 3- or 4-week intervals.
^Lower efficacy may occur when Clarireedia spp.isolates resistant to SDHIs and/or thiophanate-methyl are present. Resistance has been confirmed for several SDHI sub-groups. Although SDHI resistance is not yet widespread, thiophanate-methyl resistance is common in the U.S. Resistance to iprodione and reduced sensitivity to DMI fungicides have also been reported (Source: Clark et al., 2024).
Suggested Program Approach
- Preventative applications are more effective than curative treatments.
- Begin applications in spring, when daytime temps reach 60–80°F and high humidity or dew is persistent.
- Apply fungicides on a 14- to 21-day interval, adjusting based on product label and disease pressure.
- Always follow label rates and restrictions.
- Rotate or tank-mix fungicides based on FRAC codes to manage resistance effectively.
Tank-Mixing or Premixed Products
Fungicide tank mixes or premixes that combine multiple modes of action (e.g., a DMI + SDHI) can significantly improve efficacy, especially under high disease pressure or after an outbreak, while also enhancing resistance management.
Still experiencing control issues?
If dollar spot control remains unsatisfactory despite proper applications, consider submitting turf samples for in vitro fungicide sensitivity assays. Please contact Dr. Geunhwa Jung at: jung[at]umass[dot]edu (jung[at]umass[dot]edu)
Submitted by: Dr. Geunhwa Jung