Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu
There are many new fungicide products for management of powdery mildew on cucurbits such as pumpkin, squash, cucumber and melon. Last year we conducted a trial at the University of Maryland’s research farm in Salisbury that included some of these new fungicides (and a few “old” fungicides). The fungicides tested in this trial are in Table 1. Note that some of these fungicides, such as Quintec, are not labelled on all cucurbits, so check the labels carefully.
Table 1. List of fungicides and Fungicide Resistance Action Committee (FRAC) Code tested in 2015.
| FRAC Code M5 (Contact fungicide) | Bravo Weatherstik |
| FRAC Code 3 | Proline |
| FRAC Code 3 | Procure |
| FRAC Code 7 | Fontelis |
| FRAC Code 3 + 7 | Aprovia Top |
| FRAC Code 3 + 7 | Luna Experience |
| FRAC Code 13 | Quintec |
| FRAC Code U6 | Torino |
Several lessons could be gleaned from this trial that confirm results from other trials.
1) Always rotate fungicides with products in different FRAC Code groups. When rotated with Procure, Luna experience performed significantly better than when used without a rotation partner.
2) Products that have some systemic activity perform better than products with only contact activity. In our trial, when Aprovia Top was alternated with Bravo Weatherstik, it was only moderately effective in reduction powdery mildew. However in alternation with Procure, Aprovia Top was much better at reducing powdery mildew.
3) Using the best fungicides earlier in the season will improve control. We designed some treatments to see if applying the most effective rotation partner early or late was better for control. The differences were small, but when the better product was applied early, the control was marginally better.
The two best treatments in this trial were Luna Experience alternated with Procure, and Quintec alternated with Procure. Aprovia Top alternated with Procure, and Torino alternated with Procure significantly reduced powdery mildew, but were not quite as effective. Better than the control, but even less effective was Fontelis alternated with Torino.