NEWS HIGHLIGHT
Downy mildew alert in Ontario
Downy mildew (Pseudoperonospora cubensis) has been found in some
greenhouse cucumber operations in Southwestern Ontario and will most likely
spread to field cucumbers.
June
10, 2010 – Downy mildew (Pseudoperonospora cubensis) has been found in some
greenhouse cucumber operations in Southwestern Ontario and will most likely
spread to field cucumbers.
To
date, there have been no reports of this disease in Ontario field cucurbit
crops but it is still very early. Downy mildew has been reported in a several
commercial cucurbit fields in Florida during April and the beginning of May
2010.
The
disease has been spreading around the southern US state and has recently been
found in commercial cucurbit fields in Georgia, Texas and North Carolina. The
pathogen does not over-winter outside in Ontario; however, it can over-winter
inside Ontario cucumber greenhouses. Historically the disease is carried by
weather fronts moving from the southern U.S. into Ontario. During warm wet
conditions, the disease can spread rapidly resulting in complete defoliation of
entire fields within one week.
In
recent years, the disease has arrived in Ontario in early June. In 2006, the
early arrival of this disease caused significant losses to the Ontario cucumber
industry. Subsequently, several fungicides have been registered through the
Minor Use Program for the control of downy mildew in cucumbers.
It
is imperative that growers keep up to date on the downy mildew situation in
Ontario and when the disease shows up in field cucumbers, growers act
accordingly by applying a recommended registered fungicide to protect their
crop from this disease. Since the disease has been found in a few greenhouse
cucumber crops in Essex County, it is recommended that field cucumber growers
apply a targeted fungicide to protect the young crop. By spraying early and
preventatively before the disease shows up in the field crop will significantly
reduce the impact of this disease on yield.
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