Fungicide resistance is becoming an increasingly important concern for California almond growers as key diseases show reduced sensitivity to commonly used chemistries. In a recent interview, Kendall Johnson, Technical Services Manager for the Pacific Northwest with UPL, explained why resistance management needs to be a top priority in almond disease control programs.
Johnson noted that several major almond diseases, including scab, brown rot blossom blight, anthracnose, and Alternaria, have documented cases of resistance development. Many of these issues are tied to repeated use of highly effective, single-site fungicides that are categorized under FRAC (Fungicide Resistance Action Committee) groups 3, 7, 9, and 11. “They’re under a lot of heavy pressure use because they work well,” Johnson said, which increases selection pressure on pathogens over time.
One of the most concerning pathogens is Monilinia, the causal agent of brown rot blossom blight, which has shown resistance to Group 3 fungicides. Alternaria, scab, and anthracnose have also developed resistance to Group 11 products in some orchards.
Early warning signs of resistance include reduced disease control despite proper applications, rapid disease development, and early defoliation. Johnson emphasized the importance of monitoring orchards closely and recognizing when products are no longer performing as expected.
To help growers strengthen resistance management, Johnson highlighted Axios® 20SC, a new fungicide from UPL powered by KINOPROL® active. Axios 20SC is classified as FRAC Group 52, a novel mode of action not previously used in almonds and the only active ingredient in its group, eliminating concerns for cross-resistance. Incorporating this new FRAC group into spray rotations can help reduce pressure on existing chemistries while maintaining disease control.
Axios 20SC features a low use rate of four to five fluid ounces per acre and a 14-day pre-harvest interval, making it a flexible option during busy spray periods. By rotating fungicides with different modes of action, growers can better protect their orchards and extend the life of existing disease control tools.
For more information on fungicide resistance management or details about Axios 20SC, growers can contact their local pest control advisors (PCAs) and UPL representative or visit UPLCorp.com/US.