Symptoms and Signs
Russet scab, also known as lacey scab, is a physiological disorder that causes a superficial russeting of fruit; most prevalent on stylar end.
Comments on the Disease
Russet scab develops in years of excessive rain during and soon after bloom. Research has shown that prunes with 75% scab are not contributing to off grade.
Management
Treat just before or at full bloom in fresh market prunes.
| Common name | Amount to use | 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. | ||||
| A. | CAPTAN 50WP | 6 lb | 4 days | 0 |
| (various products) | ||||
| MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M4) | ||||
| COMMENTS: Do not apply in combination with, immediately before, or closely following oil sprays. | ||||
| B. | CHLOROTHALONIL | |||
| (Bravo Weather Stik) | 3.125–5.5 pt | 12 | 0 | |
| (Echo 720) | 3.125–4.125 pt | 12 | 0 | |
| MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M5) | ||||
| COMMENTS: Use higher rate on trees taller than 20 ft and lower rate on smaller trees. Do not use with or closely following oil sprays. | ||||
| 1 | Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. 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. |
| ‡ | 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. |