Potatoes in Canada

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Two potato fungicides to keep in mind in 2017

Sept. 8, 2016 - Although harvest of the late maturing crop has not started yet, it is never too early to start thinking about disease management in 2017. Two fungicides to keep in mind in 2017 are QUASH for early blight and Revus as a seed treatment for late blight.

September 8, 2016
By Eugenia Banks Ontario Potato Specialist.



Early blight is a common fungal disease that develops each year regardless of the weather. Crop stress favours the development of early blight. There are a number of registered fungicides that provide good control of this disease, one of these is QUASH a Valent product with the active ingredient metconazole, a triazole or group three fungicide.

Jeff Miller, a well know researcher from Idaho, conducted a four-year trial evaluating QUASH as a foliar spray for early blight control. Quash was effective in controlling early blight and produced increases in total yield that could not be attributed to disease control. Jeff indicated that total yield increase was due to a physiological response to metconazole. This response occurred when metconazole was applied in the first or second spray of a four-application program. When metconazole was used one or two times in a ten-application program, the yield effect was not as pronounced.

According to Jeff Miller, metconazole is an effective fungicide for managing early blight and is a tool to manage fungicide resistance development in other fungicide classes.

Please see attached Jeff Miller’s research report.

Other noticeable effects of metconazole were:

  • Greener color of leaves
  • Shorter plants

If metconazole reduces the height of plants, is the energy saved by producing shorter stems redirected to the tubers resulting in higher yields?

QUASH is registered in Canada for controlling early blight and suppression of white mold.

Proposed Registration of REVUS as a seed treatment for late blight
Ontario potato growers are familiar with REVUS, a Syngenta late blight-specific fungicide that contains the active ingredient mandipropamid and provides very good control of late blight as a foliar spray.

The Pest Management Regulatory Agency (PMRA), has proposed expanding the registration to allow the use of Revus as a potato seed piece treatment to control seed- borne late blight. Revus is fully registered in Canada for foliar use on a variety of crops.

According to PMRA, an evaluation of available scientific information found that, under the approved conditions of use, the product has value and does not present an unacceptable risk to human health or the environment. The use of REVUS as a potato seed treatment is in the process of a consultation period. The deadline for the consultation period is Sept. 26, 2016.

REVUS as a seed treatment for late blight will be an effective tool to combat late blight as early as planting. This is extremely important for Ontario where the majority of the seed planted in the province comes from other jurisdictions.