Fungicide Resistance Management

Note: Not all indicated timings may be necessary for disease control (see TREATMENT TIMING FOR KEY DISEASES). If treatments are needed based on weather monitoring or environmental monitoring models, suggested fungicide groups are listed for each timing.

How to use this table:

1. Identify the disease(s) that need(s) to be managed. Know the disease history of the orchard, especially from the previous season.
2. Select one of the suggested mode-of-action group numbers¹. Numbers separated by slashes are pre-mixtures, whereas numbers grouped by pluses are tank mixtures. If several diseases need to be managed, select a group that is effective against all diseases. Refer to FUNGICIDE EFFICACY FOR NECTARINE DISEASES—CONVENTIONAL PRODUCTS table for fungicides belonging to each FRAC mode-of-action group. Group numbers are listed in numerical order within the suggested disease management program.
3. Rotate groups for each application within a season and, if possible, use each group only once per season, except for multi-site mode-of-action fungicides or natural products/biological controls (e.g., M2, BM 01, BM 02, NC, P).

		Bloom		3 to 6 weeks	Preharvest
Disease	Dormant	20 to 40%	80 to 100%	Postbloom	3 weeks	1 week
Brown rot	—	13, 2+oil, 3, 3/7, 3/9, 3/11, 7, 9, 19	13, 2+oil, 34, 3/7, 3/9, 3/11, 7/11, 9, 17, 19	3, 3/7, 3/11, 7/11, 17	3, 3/7, 3/11, 7/11, 17, 19	34, 3/7, 3/11, 7/11, 17, 19
Leaf curl	M1, M3, M5, U12	M3, M5, U12	—	—	—	—
Powdery mildew	M22	13, 2+oil 3, 3/7, 3/11	13, 3, 3/7, 3/11, 7/11, 13, U8	3, 7, 3/7, 7/11, 11, 13, 19, M1, M22, U12, BM 01, BM 02, NC5	—	—
Rust	M22	—	—	13, 3, 7/11, 11, M22	3, 7/11, 11, M22	—
Scab	—	13, 3, 3/11, 7/11, 9/11, M3, M4, M5, U12	13, 3, 3/9, 3/11, 7/11, M3, M4, M5, U12	13, 3, 3/9, 3/11, 7/11, 11, M22, M4, M5, U12	—	—
Shot hole	M1, M3, M4, M5	2, some 3s, M3, M4, M5, U12	2, some 3s, 7/11, M3, M4, M5, U12	7/11, 11, M4, U12	—	—

1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Group numbers are listed in numerical order within the suggested disease management program. Fungicides with a different mode-of-action group number are suitable to alternate in a resistance management program. Refer to the Fungicide Efficacy table for fungicides belonging to each FRAC group.

2 Efficacy of liquid lime sulfur in dormant applications has not been determined for powdery mildew. Use liquid lime sulfur in dormant applications and wettable sulfur at and after pre-bloom.

3 Strains of Monilinia fructicola resistant to Benlate (label withdrawn), Topsin-M, and T-Methyl are present in some California peach orchards. Resistant strains of the jacket rot fungus, Botrytis cinerea, and powdery mildew fungi have been reported in California on crops other than almond and stone fruits and may have the potential to develop in peach with overuse of fungicides with similar chemistry. Subpopulations of both Monilinia spp. have been shown to be resistant to AP (FRAC 9) fungicides on prune in CA.

4 Among the Group 3 fungicides, only Teb/Orius and Quash have some activity against Botrytis cinerea.

5 FRAC M1 - copper, M2 - sulfur, BM 01 - Natural products, BM 02 - Biological controls (Streptomyces lydicus - Actinovate AG, Bacillus pumilus - Sonata, Bacillus subtilis - Serenade, Aviv), or NC (potassium bicarbonate - Kaligreen).

Acknowledgment: Adaskaveg et al., 2022. Fungicides, Bactericides, Biocontrols, and Natural Products for Deciduous Tree Fruit and Nut, Citrus, Strawberry, and Vine Crops in California. (PDF)