Spore traps still positive for late blight in Alliston, Ont.

Potatoes in Canada
August 30, 2018 | Alliston, Ont.
By Potatoes in Canada
Photo of a US 23 strain of late blight lesion on a leaf.
Photo of a US 23 strain of late blight lesion on a leaf. Photo courtesy of Eugenia Banks.
As of August 28, 2018, the spore traps in Alliston, Ont. are still testing positive for spores of late blight. The positive results follow a discovery of late blight in a field near Alliston on August 14.

Last week, the spore traps also tested positive for late blight in the Shelburne-Melancthon area, but current results are negative for late blight in the Shelburne-Melancthon area.

Eugenia Banks, potato specialist, speculates that the spores detected came from a home garden. Banks says tomatoes in home gardens usually produce fewer spores compared to an infected commercial field. This explains why the spore traps in the Shelburne-Melancthon tested positive one week, and negative the week after.

Jeff Miller, researcher at Miller Research in Idaho, presented a list of late blight specific fungicides at the 2018 Potato Conference. Miller says all of the fungicides listed are effective on late blight and to use the rate labelled specifically for late blight.

List of late blight fungicides:
  • Orondis
  • Revus Top (Revus)
  • Ranman
  • Curzate
  • Zampro
  • Forum
  • Gavel/Zing!
  • Omega
  • Tanos (contains Curzate plus an early blight fungicide)

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