Fruit & Vegetable Magazine

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Downy mildew confirmed in Norfolk County


July 5, 2010
By Michael Celetti OMAFRA

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downymildewJuly 2, 2010, Guelph, Ont – Downy mildew was confirmed
in two fields of cucumbers in Norfolk County over the past week, however downy
mildew has not been found in any of the scouted fields in Chatham-Kent or Elgin
Counties yet.



July 2, 2010, Guelph, Ont – Downy mildew was confirmed
in two fields of cucumbers in Norfolk County over the past week, however downy
mildew has not been found in any of the scouted fields in Chatham-Kent or Elgin
Counties yet.

The disease has also been
found in Ohio and has been spreading throughout the southern United States.
With the unsettled weather conditions in Ontario over the last week, which was
favourable for infection and disease development, more cases of downy mildew
will most likely be reported in Ontario over the next week. However, with the
return to warmer dryer conditions forecasted for many parts of Ontario over the
next few days, disease spread and infections should slow down a bit.

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Since downy mildew is
spreading around the province, growers should keep up to date on the progress
of 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 a five to seven day schedule. If possible, apply a
fungicide before a rainfall event, dew or prior to overhead irrigation.

There have been several
reports that Bravo tank mixed with mancozeb has done a very good job of keeping
downy mildew at bay this year. In my experience, Bravo tank mixed with mancozeb
for many diseases in other crops works very well when applied early and on
continual program. Although there is a low risk of resistance developing to
Bravo or mancozeb, it is important to avoid the potential of resistance
developing to any fungicides by rotating between fungicides from different
chemical families. Never apply the same fungicide from the same family back to back
in the field.

There have been a few
fields with some plants showing symptoms of angular leaf spot, gummy stem
blight and Fusarium wilt. There have also been a few fields with cucumber
beetle damage. Cucumber beetles can transmit the bacteria pathogen that causes
bacterial wilt, so growers should keep an eye out for symptoms of this disease
over the next couple of week particularly in fields that have cucumber beetle
damage.


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