Tag Archives: Fungicides

Making Lemonade Out of Lemons – A Tomato Fungicide Stewardship Tip Amidst Changing Regulations

Cheryl Trueman (Ridgetown Campus, University of Guelph) & Janice LeBoeuf (OMAFRA)

It seems like recently there have been a rash of proposed or pending pesticide regulation changes that affect field growers, and tomato growers are no exception. There are re-evaluations ongoing for a number of products used in tomatoes, including mancozeb, neonicotinoids, and Lannate, as well as Ethrel, but the big one that comes to mind for field tomato growers is the proposed changes to the use of chlorothalonil (Bravo, Echo). The final outcome of this review is not yet known, but it’s likely that significant changes to the chlorothalonil labels are coming.

Chlorothalonil is a go-to fungicide for tomato growers. Data from trials at Ridgetown Campus demonstrate its value. Chlorothalonil is often just as good at controlling early blight, Septoria leaf spot, and anthracnose fruit rot as alternative fungicides, and it also provides protection from late blight, which many targeted fungicides do not. It’s a good value active ingredient for tomato disease management and has a low risk of resistance development. But, if proposed changes go through, the number of chlorothalonil applications you can use will be drastically cut.

So, have you thought about how you are going to adapt? Continue reading Making Lemonade Out of Lemons – A Tomato Fungicide Stewardship Tip Amidst Changing Regulations

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.

66th Annual Muck Vegetable Growers Conference

The 66th Annual Muck Vegetable Growers Conference will be held April 12-13 at the Bradford and District Memorial Community located at 125 Simcoe St., Bradford, ON. The conference is free and registration starts at 8:30. For more details please see:  http://www.uoguelph.ca/muckcrop/muckconference.html

Continue reading 66th Annual Muck Vegetable Growers Conference

How to assess spray coverage in vegetable crops

From sprayers101.com. By Jason Deveau, OMAFRA.

Water sensitive paperSprayer operators recognize the importance of matching their sprayer settings to the crop to optimize efficacy. For example, spraying a protective fungicide in field tomato should require a different approach from spraying a locally systemic insecticide in staked peppers. Knowing this, many operators make ad hoc changes and then wait to “see if it worked”. A process is required that empowers the operator to make systematic changes to their program and assess coverage immediately. Continue reading How to assess spray coverage in vegetable crops

Tomato fruit rots

There are many potential causes of fruit rot in tomato. In processing crops, we often see them when crop maturity is getting ahead of harvest.

Anthracnose

Anthracnose on tomatoThe most important fact to know about anthracnose fruit rot of tomato is that while symptoms appear only on ripe fruit, infections can be initiated on green fruit (you can’t see those infections). Fungicide programs must begin early enough to prevent the initial infection of green fruit. You can’t spray away an infection that’s already happened.

Black mold (alternaria)

Black mold (alternaria) on tomato fruitOverripe tomato fruit may develop black mold caused by Alternaria alternata. Symptoms can range from small, dark blotches to large sunken areas Lesions may develop soft, black fungal growth in warm, humid weather. Black fungal growth may also develop on existing wounds or lesions. Continue reading Tomato fruit rots

Time to Start Scouting for Powdery Mildew

Powdery mildew typically arrives in Southern Ontario in mid-to-late July. Plants are most susceptible to infection during the fruit sizing and development. Poor control results in decreased yield and poor fruit quality at harvest. The threshold for treatment is 1 lesions/50 plants. Optimum powdery mildew control is a combination of variety selection, fungicide timing and fungicide selection.

Powdery Mildew Lesion on the Lower Leaf Surface
Powdery Mildew Lesion on the Lower Leaf Surface

Cheryl Trueman, a vegetable pest management researcher at the University of Guelph’s Ridgetown Campus, has been conducting powdery mildew efficacy trials since 2009. In these trials, several products consistently provided good control of powdery mildew. These products are powdery mildew targeted, and have a single site mode of action. To prevent the development of resistance, it is essential to always rotate between different fungicide groups and/or tank mix with a broad spectrum fungicide.

Powdery Mildew Targeted Fungicides Showing Consistent Control in the Ridgetown Field Trials:

Group 13: Quintec (quinoxyfen)
Quintec was the most consistent powdery mildew product tested in Ridgetown. It provided excellent control in 4/5 years and good control in 1/5 years tested.

Group U8: Vivando (metrafenone)
Vivando provided excellent control in 1/3 years and good control in 2/3 years and tested.

Group 7: Fontelis (penthiopyrad), Aprovia (benzovindiflupyr), Sercadis (fluapyroxad) and Pristine (boscalid/pyraclostrobin).
Fontellis was somewhat less consistent. Control with this produce ranged from excellent to poor, depending on the year. It provided excellent control in 1/5 years, good control in 2/5 years and poor control in 2/5 years. Note: Aprovia, Sercadis and Pristine were not tested in the Ridgetown Campus trials.

Group 3: Inspire (difenoconazole), Proline (prothioconazole) and Quadris Top (azoxystrobin/difenoconazole)
Inspire provided a level of control similar to Fontelis; good control in 3/5 years, and poor control in 2/5 years. Proline and Quadris Top were only tested for one year in the Ridgetown trials, in which they both provided good control.

Fungicides containing chlorothalonil (Bravo ZN and Echo) provided a lower level of powdery mildew control, but are still better than the untreated checks. They also control a broad range of other foliar diseases including scab and alternaria.

Research in Ontario and other jurisdictions indicates that the group 11 (QoI) fungicides, Cabrio (pyraclostrobin) and azoxystrobin (a component of Quadris Top) no longer control powdery mildew. However, they may provide control of other cucurbit diseases such as anthracnose and alternaria.

Additional reading: http://www.omafra.gov.on.ca/IPM/english/cucurbits/diseases-and-disorders/powdery-mildew.html#advanced

2016 Downy Mildew Control Strategy for Cucumber Crops

The 2016 Downy Mildew Control Strategy for Cucumber Crops contains an updated list of fungicides, including the newly registered Orondis Ultra. The restricted entry interval for Bravo has also been updated to reflect the new Bravo ZN label.

Due to the development of resistance and concerns about efficacy, Tattoo C and Presidio have been removed from the 2016 strategy. These products may provide  suppression under low risk conditions, however research results indicate that they are not sufficient controls under higher disease pressure.

For more reading:

Research Update – Fungicide Efficacy on Downy Mildew in Cucumbers

Ontario CropIPM – Downy Mildew

Angular, tan-to-brown lesions caused by cucurbit downy mildew
Cucurbit Downy Mildew