Agriculture: Walnut Pest Management Guidelines

Most Effective Treatment Timing for Key Diseases

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

Disease Catkin emergence Terminal bud break 7-10 day intervals April May June July August October November (1st week)
Anthracnose ---- ---- ---- ++4 +++ ++ ---- ---- ---- ----
Botryosphaeria blight ---- ---- ---- + ++ +++ +++ ++ + +
Walnut blight 1,2,3 ++ +++ +++ +++ ++1 + ---- ---- ---- ----
Rating: +++ = most effective, ++ = moderately effective, + = inconsistently effective, ---- = ineffective, and ND= no data.
1 A temperature-leaf wetness model (e.g., XanthoCast) is available for determining optimum timing of bactericide applications.
2 Late spring rains are less conducive to disease, provided bloom is not delayed by low chilling.
3 Male and female flowers are susceptible beginning with their emergence, depending on wetness and temperatures conducive to disease development.
4 Make the first application when the size of the expanding leaves is about half of its final size. This first application stage is critical.

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: 06/17