Fruit & Vegetable Magazine

Features Fruit Production
Downy mildew confirmed in Ont. cucumber field


June 21, 2010
By OMAFRA

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June
18, 2010, Guelph, Ont – Downy mildew was confirmed in a field of fresh market
cucumbers near Milton, Ont. on June 17, 2010.



June
18, 2010, Guelph, Ont – Downy mildew was confirmed in a field of fresh market
cucumbers near Milton, Ont. on June 17, 2010.

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The
arrival of this disease is very early and the first confirmed report of this
disease in field cucumbers in Ontario this season. It is very possible that
other fields may have the disease or will soon. The infected cucumbers plants
were at about the four to five leaf stage and growing on black plastic mulch.
Approximately 10 per cent of the field was infected with 10 per cent of the
leaf area affected. No sporulation was found in the field at the time; however,
lesions on leaves brought back to a lab at the University of Guelph began to
sporulate within 12 hours.

Cucurbit
growers should have their fields scouted regularly for this disease. Successful
management of this disease is accomplished when fungicides are applied prior to
the disease infecting the crop so it is imperative that growers apply a
fungicide to prevent the establishment of downy mildew in their crops on five
to seven day schedule. If possible, apply a fungicide before a rainfall event,
dew or prior to overhead irrigation.

When
implementing a fungicide program it is important to avoid the potential of resistance
developing to fungicides by rotating between fungicides from different chemical
families.

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