Agriculture: Almond Pest Management Guidelines

Treatment Timings for Key Disease

Note: Not all indicated timings may be necessary for disease control.

Disease Dormant Bloom Spring1 Summer
Pink bud Full bloom Petal fall 2 weeks 5 weeks May June
Alternaria leaf spot ++ +++ +++
Anthracnose2 ++ +++ +++ +++ +++ +++ ++
Bacterial spot + ++ +++ +++ ++ +
Brown rot blossom blight ++ +++ +
Green fruit rot +++ ++
Hull rot7 +++
Leaf blight +++ ++ +
Rust +++ +++ +6
Scab3 ++ ++ +++ +++ +
Shot hole4 +5 + ++ +++ +++ ++

Rating: +++ = most effective, ++ = moderately effective, + = least effective, and — = ineffective
1 Two and five weeks after petal fall are general timings to represent early postbloom and the latest time that most fungicides can be applied. The exact timing is not critical but depends on the occurrence of rainfall.
2 If anthracnose was damaging in previous years and temperatures are moderate (63°F or higher) during bloom, make the first application at pink bud. Otherwise treatment can begin at or shortly after petal fall. In all cases, application should be repeated at 7- to 10-day intervals when rains occur during periods of moderate temperatures. Treatment should, if possible, precede any late spring and early summer rains. Rotate fungicides, using different fungicide classes, as a resistance management strategy.
3 Early treatments (during bloom) have minimal effect on scab; the 5-week treatment usually is most effective. Treatments after 5 weeks are useful in northern areas where late spring and early summer rains occur. Dormant treatment with liquid lime sulfur improves efficacy of spring control programs.
4 If pathogen spores were found during fall leaf monitoring, apply a shot hole fungicide during bloom, preferably at petal fall or when young leaves first appear. Reapply when spores are found on new leaves, or if heavy, persistent spring rains occur. If pathogen spores were not present the previous fall, shot hole control may be delayed until spores are seen on new leaves in spring.
5 Dormant copper treatment seldom reduces shot hole infection but may be useful in severely affected orchards and must be followed by a good spring program.
6 Treatment in June is important only if late spring and early summer rains occur.
7 Make application at 1-5% hull split to manage hull rot caused by Rhizopus stolonifer.

Acknowledgment: Adaskaveg et al., 2017. Efficacy and Timing of Fungicides, Bactericides, and Biologicals for Deciduous Tree Fruit, Nut, Strawberry, and Vine Crops (PDF).

Text Updated: 08/17