| Common name (Example trade name) |
Chemical class | Activity | Mode of action (group number)1 |
Resistance potential | Comments |
|---|---|---|---|---|---|
| PREHARVEST | |||||
| azoxystrobin (Quadris, Abound discontinued)) | Qol2 (strobilurin) | contact and systemic7 | single-site (11) | high6 | |
| azoxystrobin/difenoconazole (Quadris Top) | Qol2/DMI3 | contact and systemic (local) 7 | single-site/ single-site (3/11) |
medium | premixture |
| Bordeaux | inorganic | contact | multi-site (M 01) | low | copper and lime based mixture that often includes a zinc adjuvant. |
| copper | inorganic | contact | multi-site (M 01) | low | fixed coppers (non-copper sulfate materials such as copper hydroxide and copper oxide) |
| fluopyram/trifloxystrobin (Luna Sensation) | SDHI4/Qol2 | contact and systemic7 | single-site/ single-site (7/11) |
medium | premixture |
| fluxapyroxad/pyraclostrobin (Priaxor) | SDHI4/Qol2 | contact and systemic7 | single-site/ single-site (7/11) |
medium | premixture |
| fosetyl-al (Aliette) | ethyl phosphonates | systemic | unknown (P07, 33) | low | resistant pathogen populations reported |
| hydrated lime | inorganic | contact | multi-site (M 01) | low | |
| mefenoxam (Ridomil Gold) | phenylamide | contact and systemic | single-site (4) | high6 | |
| oxathiapiprolin (Orondis) | oxysterol binding proteins | contact—fruit/ systemic (local)—roots |
single-site (49) | high | |
| oxytetracycline (Fireline) | antibiotic | contact | protein synthesis (41) | high | |
| polyoxin-D (Oso) | polyoxin | contact | single-site (19) | medium | biopesticide |
| potassium phosphite (Fungi-Phite, Prophyt) | Phosphorous acid or Mono- and dipotassium salts of phosphorous acid | systemic | unknown (multi-site?) (P07, 33) | low to medium | biopesticide, resistant pathogen populations reported |
| streptomycin (Firewall) | antibiotic | systemic | protein synthesis (25) | high | |
| POSTHARVEST | |||||
| fludioxonil (Graduate) | phenylpyrrole | contact | single-site (12) | medium | |
| fludioxonil/azoxystrobin (Graduate A+) | phenylpyrrole/Qol2 (strobilurin) | contact and systemic (local) | single-site (12/11) | medium | premixture |
| imazalil (FungaFlor 500EC) | DMI3 | systemic (local) | single-site (3) | high | resistant pathogen populations reported |
| pyrimethanil (Penbotec) | AP5 | contact and systemic (on some crops) | single-site (9) | high6 | resistant pathogen populations reported |
| 1 | Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action (for more information, see www.frac.info). Fungicides with different group numbers are suitable to alternate in a resistance management program. In California, make no more than one application of a fungicide with a mode-of-action group number associated with high resistance risk before rotating to a fungicide with a different mode-of-action group number; for other fungicides, make no more than two consecutive applications before rotating to fungicide with a different mode-of-action group number. |
| 2 | QoI = Quinone outside inhibitor (strobilurin) |
| 3 | DMI = Demethylation inhibitors |
| 4 | SDHI = Succinate dehydrogenase inhibitors |
| 5 | AP = Anilinopyrimidine |
| 6 | Resistance has been found in California for certain fungicides with a single-site mode of action. To reduce the risk of resistance development, take the mode of action into account when choosing a fungicide. At the beginning of a treatment program, use a fungicide with a multi-site mode of action; for subsequent applications rotate or mix fungicides with different mode of action FRAC numbers. Use labeled rates (preferably the upper range) of the single-site fungicides, and limit the total number of applications per season. |
| 7 | Unsure or lacking scientific evidence. For fungicides, this indicates general acceptance of systemic action based on performance data, but may not have been proven experimentally using lab assays (e.g., radioactively labeled compounds). |
Acknowledgment: Adaskaveg et al., 2025. Fungicides, Bactericides, Biocontrols, and Natural Products for Deciduous Tree Fruit and Nut, Citrus, Strawberry, and Vine Crops in California.
Text Updated: 07/24