Anthony Keinath, Extension Pathologist
In June 2026, Interns Will Dalton and Adam Padgett conducted two bioassay experiments to test several fungicides recommended against powdery mildew. In the first test, Early Prolific summer squash was treated with Torino, Gatten, Vivando, Quintec, and Procure at the low-label rate on the top of leaves. Possible fungicide resistance prompted a second test with Gatten and Procure applied at a range of concentrations to both the top and bottom of the leaves.
Results:
- All fungicides reduced powdery mildew compared with untreated plants.
- Torino, Vivando, and Quintec provided the best control at the low rates.
- Procure and Gatten showed higher levels of powdery mildew, suggesting fungicide resistance.
- When Procure and Gatten treatments were retested, Procure was effective against powdery mildew only at the 8 oz rate, with lower concentrations performing similarly to the water control.
- In contrast, Gatten performed well across all concentrations when both the top and bottom of the leaf surfaces were sprayed.
Take-home Messages:
- When treating cucurbits for powdery mildew, Torino, Vivando, and Quintec provide effective control when applied at their lowest labeled rates. These fungicides are recommended for Fall 2026 in South Carolina.
- If Procure is used, apply it at a high-label rate.
- For the best control of powdery mildew, make sure fungicide applications reach both sides of the leaf.
The South Carolina Grower 