Almond Growers Advised to Stay Vigilant Against Alternaria This Summer

As California’s almond orchards transition from bloom to petal fall, growers are being advised to shift their focus to managing leaf diseases, particularly Alternaria. According to Katie Driver, UPL Technical Services Manager, Alternaria is one of the most consistent and damaging diseases affecting almond trees, especially in areas with high humidity and stagnant airflow.

Alternaria primarily affects the leaves of almond trees, appearing as large brown or black spots. These spots, sometimes referred to as leaf spots, can reach up to three-quarters of an inch in diameter. As the disease progresses, the fungus produces spores that turn the spots black. If left unchecked, Alternaria can cause significant defoliation by early summer, impacting future yields and even leading to limb death.

“Monitoring for signs of the disease should begin in early April and continue through June,” Driver advised. “However, if growers have a history of Alternaria in their orchards, they should take preventive measures even before symptoms appear.”

Fungicides have traditionally been a key tool in combating Alternaria, but resistance to some chemical groups is becoming a concern. To address this, UPL has introduced a new fungicide, Axios, powered by KINOPROL®. Axios is a preventative treatment that offers systemic activity, protecting new growth for up to 25 days. While growers are allowed up to three applications per season, they are encouraged to rotate different modes of action to prevent resistance buildup.

Beyond fungicides, Driver recommended cultural practices such as pruning to improve airflow and reducing orchard humidity during peak disease periods. Additionally, researchers have developed forecasting models based on temperature and leaf wetness levels to help growers determine optimal timing for disease management actions.

For more information on disease management and the new Axios fungicide, growers can visit UPL’s website at uplcorp.com/us.

By staying proactive, almond growers can protect both their current crop and the long-term health of their orchards.