Almond Diseases Rob Yields
and Tree Health
While there are numerous effective materials for controlling diseases in your almond orchard, disease resistance is a continuing threat to their efficacy. Resistance management is now a necessary component of all IPM programs in almonds.
The potential for resistance development is high with some of the newer classes of fungicides. For example, the pathogen that causes scab is becoming resistant to the strobilurin and benzimidazole fungicide classes, and pathogens that cause Alternaria leaf spot are losing their susceptibility to strobilurin fungicides. As a result, UC plant pathologists recommend making no more than four applications per season of strobilurins or carboxanilides to reduce the potential for increased resistance.
UC plant pathologists currently advise the following steps to maintain effective use of fungicides under high disease pressure that requires multiple fungicide applications:
- Use fungicides effective for the target disease(s).
- Time treatments for greatest efficacy at the appropriate stage of almond tree development.
- Use full labeled rates.
- Start with a fungicide that has a multiple site mode of action.
- Rotate from one chemical class to another within the same season.
- Use fungicides in combinations that provide multiple modes of action.
- Do not apply fungicides within any given high-resistance potential class more than twice per season.
- Discontinue use of alternate-row applications once flowers and leaves emerge.
- Do not apply fungicides by air at full canopy.
External Links:
Guidelines for Almond Scab Management
In collaboration with Western Farm Press magazine, The Almond Board of California created an e-learning course on disease management in almonds
UC IPM Almond Fungicide Resistance Management
UC IPM Pest Management Guidelines
Seasonal Guide to Environmentally Responsible Pest Management Practices in Almonds
