Category Archives: Cucumber

Cucurbit Downy Mildew Report for the Week of June 19th, 2017

Cheryl Trueman, University of Guelph – Ridgetown Campus

Scouting for downy mildew in pickling cucumber fields in Norfolk County began on June 13 and in Kent County on June 19.

You can track sightings of downy mildew in North America on the IPMpipe Cucurbit Downy Mildew website.

More information:
2017 Downy Mildew Control Strategy for Cucumber Crops

2016 Fungicide efficacy and fungicide program results

The downy mildew scouting program is sponsored by the Ontario Cucumber Research Committee. Field scouting in Norfolk County is managed by Tania Keirsebilck-Martin at the Norfolk Fruit Growers’
Association. Field scouting in Kent County is managed by Cheryl  Trueman at the Ridgetown Campus, University of Guelph. We thank Elaine Roddy, OMAFRA vegetable specialist, for her guidance with
implementing this program.

Downy Mildew Report for the week of June 12, 2017

By Cheryl Trueman, University of Guelph – Ridgetown Campus

Scouting for downy mildew in pickling cucumber fields in Norfolk County began on June 13 (3 of 5 sites) and will begin in Kent County on June 19.You can track sightings of downy mildew in North America on the IPMpipe Cucurbit Downy Mildew website.
More information:
2017 Downy Mildew Control Strategy for Cucumber Crops
2016 Fungicide efficacy and fungicide program results.

 

2017 Downy Mildew Control Strategy for Cucumber Crops

In 2016, Cheryl Trueman compared several different cucumber downy mildew control programs in plots at the University of Guelph Ridgetown Campus. These studies indicated that the highest level of control was achieved using a three product rotation of Orondis Ultra A+B, Torrent and Zampro.

Several different product rotations were compared including:

  • Bravo-only applied 6 times.
  • a high input strategy that focused on optimal control and resistance management: Orondis Ultra A+B; Torrent; Zampro; Orondis Ultra A+B; Torrent; Zampro.
  • a low-input strategy that focused on early control and resistance management, switching to lower-cost fungicides in the final weeks of harvest: Orondis Ultra A + B (plus Bravo); Torrent; Zampro; Bravo; Bravo; Bravo.
  • a single application of Orondis Ultra, applied early followed by the other targeted downy mildew  fungicides (Orondis Ultra A + B; Torrent ; Zampro; Torrent; Zampro; Torrent).
  • Control – no fungicides applied
Product Rotation Leaf Area Infected Defoliation
Bravo Only
(6 applications)
45% 23%
High Input 3% 0%
Low Input 40% 20%
Single Orondis Ultra in rotation 28% 8%
Control 80% 80%

Final yields for both the high input and single Orondis Ultra (in rotation) were both significantly higher than the Bravo only programs. The yields for the high input program, were significantly higher than all other treatments.

See the 2017 Downy Mildew Control Strategy for Cucumber Crops for more information.

Cucumber Downy Mildew Confirmed in Kent County, Ontario

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 elaine.roddy@ontario.ca

Research Update – Fungicide Efficacy on Downy Mildew in Cucumbers

Cheryl Trueman, College Professor, University of Guelph – Ridgetown Campus
Rachel Riddle, Research Technician, University of Guelph – Simcoe
Elaine Roddy, Vegetable Crops Specialist, OMAFRA

Over the past two years, there have been several changes in the efficacy of fungicides commonly used to control downy mildew in cucumbers. The results from field trials conducted by the University of Guelph reflect trends also observed in Michigan and North Carolina.

Figure 1 and Figure 2 show the results of the Ontario 2015 downy mildew fungicide trials conducted at Ridgetown and Simcoe. Note that in both trials, a significant decline was observed in the efficacy of both Presido 4SC and Tattoo C. Presidio preformed no better than the untreated control, while the results from Tattoo C were no different than chlorothalonil (Bravo Zn).

The Canadian Pest Management Regulatory Agency (PMRA) is currently evaluating a new active ingredient called oxathiapiprolin (Orondis Ultra). In both of the University of Guelph studies, oxathiapiprolin demonstrated good control against cucumber downy mildew. If approved, this product will provide a good option for rotation with currently registered downy mildew fungicides.

Figure 1. AUDPC (area under the disease progress curve) for leaf area affected by cucurbit downy mildew in cucumber cv. Vlasstar, Ridgetown, ON, 2015. Fungicides were applied on a 7-day interval July 7-Aug 4. Columns with the same letter are not significantly different from each other.
Figure 1. AUDPC (area under the disease progress curve) for leaf area affected by cucurbit downy mildew in cucumber cv. Vlasstar, Ridgetown, ON, 2015. Fungicides were applied on a 7-day interval July 7-Aug 4. Columns with the same letter are not significantly different from each other.

 

Figure 2. AUDPC (area under the disease progress curve) for leaf area affected by cucurbit downy mildew in cucumber cv. Vlaspik, Simcoe, ON, 2015. Fungicides were applied on a 7-day interval July 16-Aug 6. Columns with the same letter are not significantly different from each other.
Figure 2. AUDPC (area under the disease progress curve) for leaf area affected by cucurbit downy mildew in cucumber cv. Vlaspik, Simcoe, ON, 2015. Fungicides were applied on a 7-day interval July 16-Aug 6. Columns with the same letter are not significantly different from each other.

Preliminary Results from the 2015 Ridgetown Campus Downy Mildew Efficacy Trails

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
Nontreated control 10.2 a 21 a
Bravo ZN (4.8 L) 8.2 ab 14 ab
Manzate Pro-Stick (3.25 kg) 5.8 ab 10 ab
Torrent 400SC (200 mL) + Sylgard (150 mL) 0.4 c 2 cd
Tattoo C (2.7 L) 9.5 ab 13 ab
Presidio 4 SC (256 mL) 10.4 a 19 a
Zampro (1 L) +
Sylgard (150 mL)
1.9 bc 6 bc
A20942 (6 L) 0.0 c 0 d
Phostrol (5.8 L) 5.6 a 11 ab

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.