Potatoes in Canada

Features Agronomy Diseases
Late blight found in Ontario

July 9, 2015 - Late blight was found today in a potato field near Orangeville.

Eugenia Banks, potato specialist with OMAFRA, says it was not easy to determine the source of infection, but there are several home gardens close to the field.

A small section of the field was disked to avoid a source of spores all season long. Banks says the grower is following an aggressive fungicide program: Curzate tank mixed with Bravo plus Kocide applied back-to-back at a four-day interval.

She adds that after this aggressive treatment, Revus is a good choice tank mixed with a broad spectrum product.

"I collected samples of leaves and stems to send to Dr. Larry Kawchuck in Lethbridge, Alta.," Banks says. "He will identify the strain and its susceptibility to Ridomil. I expect to have the results by the end of next week."

Dr. Gary Secor spoke at this year's 2015 Potato Conference. These are his recommendations:

  • Specialty fungicides are necessary if late blight is present. Many of them are translaminar.
  • Curzate: has kickback - two days back, three days forward. Use after a storm if late blight is in the area to stop new infections that might have occurred when fields were too wet to spray.
  • Revus Top: rainfast, translaminar, apply anytime.
  • Gavel: especially good at the end of season; it reduces tuber Infection.
  • Allegro, Ranman: best for late-season use.
  • Acrobat: an antisporulant; helps to slow spread of epidemic.
  • Late blight-specific fungicides should always be tank mixed with Bravo or an EBDC.
  • Also, Copper hydroxide (Parasol, Kocide) provides tuber protection.
  • Always after spraying an infected field, clean up your sprayer.