Note: Timings listed are effective, but not all may be required for disease control. Timings used will depend upon orchard history of disease and weather conditions each year.
| Disease | Catkin emergence | Terminal bud break | 7–10 day intervals | Apr. | May | June | July | Aug. (3-wk before hull split) |
Sept. (20–30% hull split) |
Oct. | Nov. (1st wk) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Anthracnose1 | 0 | 0 | 0 | 24 | 3 | 2 | 0 | 0 | 0 | 0 | 0 |
| Botryosphaeria blight | 0 | 0 | 0 | 1 | 2 | 3 | 3 | 2 | 0 | 1 | 1 |
| Kernel mold2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 2 | 0 | 0 |
| Walnut blight3, 4, 5 | 25 | 3 | 3 | 3 | 2 | 1 | 0 | 0 | 0 | 0 | 0 |
| Rating: 3 = most effective, 2 = moderately effective, 1 = least effective, and 0 = ineffective |
| 1 Make the first application when the size of the expanding leaves is about half of its final size. This first application stage is critical. |
| 2 Timing for kernel mold is based on a mixture rotation of Merivon (FRAC group 7/11) and Teb (FRAC group 3) followed by Rhyme (FRAC group 3) at the timings indicated. This mixture rotation is ‘3' based on the ratings in the efficacy table above. |
| 3 A temperature-leaf wetness model (e.g., Xanthocast) is available for determining optimum timing of bactericide applications. |
| 4 Late spring rains are less conducive to disease, provided bloom is not delayed by low chilling. |
| 5 Male and female flowers are susceptible beginning with their emergence, depending on wetness and temperatures conducive to disease development. |
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)