| Bactericide | Resistance risk
(FRAC group number)1 |
Fire blight4 | Phytotoxicity6 | Plant growth regulator/SAR |
|
|---|---|---|---|---|---|
| contact | systemic | ||||
| Actigard5 | low (P 01) | 0 | 2 | 0 | 2 |
| Ag Streptomycin**, Agri-Mycin, Firewall | very high (25) | 5 | 4 | 1 | 0 |
| Apogee4 | low (PGR) | 0 | 2/3 | 0 | 3 |
| Captan2 | low (M 04) | 3 | 0 | 0 | 0 |
| Copper3 | low (M 01) | 3 | 0 | 2 | 0 |
| Dithane, Manzate, Penncozeb2 |
low (M 03) | 3 | 0 | 0 | 0 |
| Kasumin | high (24) | 5 | 5 | 1 | 0 |
| Mycoshield, FireLine | high (41) | 4 | 4 | 1 | 0 |
Rating: 5 = excellent and consistent, 4 = good and reliable, 3 = moderate and variable,
2 = limited and/or erratic,
1 = minimal and often ineffective, 0 = ineffective.
| 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 | These fungicides show some efficacy and should be used in mixtures with antibiotics as a component of resistance management programs. |
| 3 | Though copper may be effective for scab and blight control under low disease pressure, copper products may cause fruit scarring or russeting. |
| 4 | Plant growth regulators (PGR) such as prohexadione calcium (Apogee) can be used in an integrated approach to reduce host susceptibility but do not have direct activity against fire blight. |
| 5 | Acibenzolar-S-methyl (FRAC P 01) is a host plant defense or systemic acquired resistance (SAR) inducer known to stimulate the salicylic acid pathway. |
| 6 | Higher numbers indicate higher phytotoxicity. |
Acknowledgment: Adaskaveg et al., 2025. Fungicides, Bactericides, Biocontrols, and Natural Products for Deciduous Tree Fruit and Nut, Citrus, Strawberry, and Vine Crops in California.