Cucurbit downy mildew has been reported on pickling cucumbers and cantaloupe in Essex County. This is the first field report for this disease in 2017.
All Ontario cucumber growers should now switch from a broadspectrum program to a 3-product rotation using targeted downy mildew fungicides.
The following products have shown the most consistent results in fungicides trials at the University of Guelph, Ridgetown and Simcoe campuses. Under high downy mildew pressure, follow a spray interval that is no longer than 7-days.
- Orondis Ultra A (mandipropamid) + Orondis Ultra B (oxathiapiprolin) + Bravo (chlorothalonil)
- Torrent (cyazofamid)
- Zampro (ametoctradin/dimethomorph)
For more information about the most effective spray rotations, see: 2016 University of Guelph Cucumber Downy Mildew Results.
July 5th, 2016: cucurbit downy mildew was identified today in a processing cucumber field in Kent County, Ontario. Now that the disease is present in the great lakes region, growers should immediately move to a targeted downy mildew spray program.
See the 2016 Downy Mildew Control Strategy for Cucumber Crops for an up-to-date list of registered control products.
Use only the downy mildew targeted products listed in the strategy. Research trials in Ridgetown, Simcoe and in the neighbouring states have shown these products to be the most consistent from year-to-year.
Rotate between all three of the targeted downy mildew products, starting with the most effective product, Orondis Ultra, and then rotate to either Zampro or Torrent within 7-days.
If you have any questions about the cucumber downy mildew control strategy, please call 519 674 1616 or email email@example.com
By Cheryl Trueman, College Professor, University of Guelph – Ridgetown Campus and
Elaine Roddy, Vegetable Specialist, OMAFRA
We are getting many questions from growers with regards to the “best” fungicide program for managing cucurbit downy mildew. The early detection and subsequent wet weather conditions have resulted in higher-than-usual amounts of downy mildew in cucumbers and cantaloupe.
The Ridgetown fungicide efficacy trial was seeded June 24. Treatments applied July 7, 14, and 21. The first fungicide application was made prior to the first observation of symptoms. The following results are from the initial disease assessment, completed July 21 (Table 1). These results are preliminary. The completed trial will include at least three visual assessments and yield data.
These results indicate that among registered products, Torrent 400SC and Zampro are providing the highest level of control.
Table 1. Efficacy of fungicides for management of downy mildew in pickling cucumbers ‘Vlasstar’ at Ridgetown Campus, University of Guelph, July 21 2015.
|Treatment (per Ha)
||% Infected Leaves a, c, d
|Leaf area affected (%) b, c. d
|Bravo ZN (4.8 L)
|Manzate Pro-Stick (3.25 kg)
|Torrent 400SC (200 mL) + Sylgard (150 mL)
|Tattoo C (2.7 L)
|Presidio 4 SC (256 mL)
|Zampro (1 L) +
Sylgard (150 mL)
|A20942 (6 L)
|Phostrol (5.8 L)
a Leaves in the whole plot were evaluated. The percentage of leaves infected was calculated based on the number of leaves in a representative 1 m section of the trial.
b Leaves in the whole plot were evaluated. The leaf area affected by downy mildew was estimated on symptomatic leaves only.
c Data was transformed for analysis using a log transformation; the original means are shown here.
d Numbers in a column followed by the same letter are not significantly different at P ≤ 0.05, Tukey’s HSD. Numbers highlighted in BOLD are significantly different than the nontreated control.
Over the past few years there have been a number of new fungicide registrations for cucurbit crops in Canada. Each one has its own particular strengths; however it is important to find the right fit within the fungicide program.
Depending on the disease, the actual infection rates greatly between the different cucurbit crops. For example, cucumbers are highly susceptible to downy mildew while pumpkins typically have a much greater level of tolerance to this disease. The more significant diseases for each cucurbit type are listed below (Table 1. Significant Cucurbit Diseases by Crop). When planning a preventative fungicide program, it is useful to keep these diseases in mind. Continue reading New Cucurbit Fungicides for 2014