Symptoms and Signs
The pathogen that causes shot hole disease may kill buds during winter and cause spots on fruit and leaves in spring. If severe infestation occurs, leaf drop may occur in spring. Fruit lesions are light brown with dark purple margins and usually are clustered on the upper sides of fruit. Fruit spotting can be severe, and as fruits mature, spots become scablike and may flake off, leaving roughened areas beneath. Leaf spots fall out (shot hole).
Comments on the Disease
The fungus survives within infected buds and on twigs. Spores are rain splashed, and disease increases during the rainy season. Fruit infection is favored by wet spring weather.
Shot hole is often confused in coastal orchards with fog spot, which is believed to be an environmentally-induced condition, although Alternaria spp. have been implicated to play a part in the disease. Fog spot, however, does not cause leaf lesions, and the lesions it causes on fruit have a red margin. There is no control for fog spot.
Management
Buds can be protected from shot hole during the dormant season (mid-November to mid-December) by a fungicide application before the long winter rains begin. One application should be sufficient. The number of bloom applications needed depends upon the amount of rain.
Take a fruit damage sample at harvest to assess the effectiveness of the current year's IPM program and to determine the needs of next year's program (see FRUIT SAMPLING AT HARVEST). Record results (sample form—).
| Common name | Amount per acre | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used. | ||||
| Caution: Never apply sulfur to apricot trees or captan to apricot fruit. | ||||
| DORMANT | ||||
| A. | BORDEAUX MIXTURE# | |||
| 10:10:100 | Label rates | See label | See label | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M1) | ||||
| COMMENTS: For information on creating a Bordeaux mixture, see UC IPM Pest Note: Bordeaux Mixture. Check copper label to determine if product is organically acceptable. | ||||
| B. | FIXED COPPER# | Label rates | See label | See label |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M1) | ||||
| COMMENTS: Not all copper compounds are approved for use in organic production; be sure to check individual products. | ||||
| RED BUD, FULL BLOOM, AND PETAL FALL | ||||
| A. | PYRACLOSTROBIN / FLUXAPYRAXAD | |||
| (Merivon) | 4–6.7 fl oz | 12 | 0 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Succinate dehydrogenase inhibitors (7) | ||||
| COMMENTS: To reduce the potential for the development of resistance, do not make more than two consecutive applications or more than four applications or 20.1 fl oz per season of Merivon or other quinone outside inhibitor (11) or succinate dehydrogenase inhibitor (7) fungicides. | ||||
| B. | PYRACLOSTROBIN / BOSCALID | |||
| (Pristine) | 10.5–14.5 oz | 12 | 0 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Succinate dehydrogenase inhibitors (7) | ||||
| COMMENTS: To reduce the potential for the development of resistance, do not make more than five applications per season of Pristine or other quinone outside inhibitor (11) or succinate dehydrogenase inhibitor (7) fungicides. | ||||
| C. | PENTHIOPYRAD | |||
| (Fontelis) | 14–20 fl oz | 12 | 0 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Succinate dehydrogenase inhibitors (SDHI) (7) | ||||
| COMMENTS: Resistance warning: do not make more than two consecutive applications and no more than 61 fl oz/acre per year of Fontelis or other SDHI fungicide. | ||||
| D. | TEBUCONAZOLE / TRIFLOXYSTROBIN | |||
| (Adament 50WG) | 4–8 oz | 120 (5 days) | 1 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3), Quinone outside inhibitor (11) | ||||
| COMMENTS: Use allowed under a Supplemental Label. | ||||
| E. | DIFENOCONAZOLE / CYPRODINIL | |||
| (Inspire Super) | 16–20 fl oz | 12 | 2 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3), Anilinopyrimidine (9) | ||||
| COMMENTS: Begin applications at full bloom. Do not apply more than two consecutive applications and no more than four applications per season. | ||||
| F. | DIFENOCONAZOLE / AZOXYSTROBIN | |||
| (Quadris Top) | 12–14 fl oz | 12 | 0 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3), Quinone outside inhibitor (11) | ||||
| COMMENTS: Begin applications at full bloom. Do not apply more than two consecutive applications and no more than four applications per season. | ||||
| G. | AZOXYSTROBIN / PROPICONAZOLE | |||
| (Quilt Xcel) | Label rates | 12 | 0 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11), Demethylation inhibitor (3) | ||||
| COMMENTS: Begin applications at full bloom. Do not apply more than two consecutive applications and no more than four applications per season. | ||||
| H. | IPRODIONE | |||
| (Rovral 4) | 1–2 pt | 24 | NA | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Dicarboximide (2) | ||||
| COMMENTS: Addition of a narrow range oil (Superior, Supreme) at 1 to 2% increases the effectiveness of this material. Do not apply after petal fall. | ||||
| I. | AZOXYSTROBIN | |||
| (Abound) | 12–15.5 fl oz | 4 | 0 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) | ||||
| COMMENTS: Do not apply more than two sequential sprays before alternating with a fungicide that has a different mode of action and no more than four applications per season. | ||||
| J. | CHLOROTHALONIL | |||
| (Echo 720) | 3.125–4.125 pt | 12 | NA | |
| (Bravo Ultrex) | 2.8–3.8 lb | 12 | NA | |
| (Bravo Weather Stik) | 3.125–4.125 pt | 12 | NA | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M5) | ||||
| COMMENTS: Do not use with or closely following oil sprays. Do not apply more than 20.5 pint Bravo Weather Stik/acre per season. Do not apply more than 18.8 lb Bravo Ultrex/acre per season. | ||||
| K. | CAPTAN 50WP | |||
| (Various) | 3–5 lb | 24 | 0 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M4) | ||||
| COMMENTS: Check with your processor before using this material. Do not apply in combination with, immediately before, or closely following oil sprays. Do not apply after 75% petal fall. | ||||
| L. | TRIFLOXYSTROBIN | |||
| (Gem 500SC) | 2.9–3.8 fl oz | 12 | 1 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) | ||||
| M. | ZIRAM | |||
| (Ziram 76DF) | 6–8 lb | 48 | 30 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M3) | ||||
| COMMENTS: Do not apply more than 30 lb/acre per season. | ||||
| N. | PYRIMETHANIL | |||
| (Scala SC) | 18 fl oz | 12 | 2 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Anilinopyrimidine (9) | ||||
| COMMENTS: Resistant populations have been identified in Californian stone fruit orchards. Do not apply more than two consecutive applications or more than four applications per season of pyrimethanil or other anilinopyrimidine Group 9 fungicides. | ||||
| O. | CYPRODINIL | |||
| (Vangard WG) | 5 oz | 12 | 2 | |
| MODE-OF-ACTION GROUP NAME (NUMBER1): Anilinopyrimidine (9) | ||||
| COMMENTS: Resistance warning: do not apply more than two consecutive applications or more than four applications per season of cyprodonil or other anilinopyrimidine Group 9 fungicide. | ||||
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest. |
| NA | Not applicable. |
| # | Acceptable for use on organically grown produce. |
| 1 | Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Fungicides with a different group number are suitable to alternate in a resistance management program. For fungicides with mode-of-action group numbers 1, 4, 7, 9, 11, or 17, make no more than one application before rotating to a fungicide with a different mode-of-action group number; for fungicides with other group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode-of-action group number. |