Top Crop Manager

Weather a factor in soybean rust progress

Storm systems have power, not certainty.

November 12, 2007  By Top Crop Manager

4aIf soybean rust is a factor in 2005, it will come on the winds of the same
weather patterns that routinely bring weather systems to the US midwest and
the Great Lakes Basin. The unknown qualification is at which point of the growing
season it might arrive.

According to climatologists and meteorologists, there is no question about
the origins of weather systems that enter into Ontario and western Quebec: they
come from the south central region of the US. And just as soybean rust entered
the US late in 2004 on the winds of successive hurricanes, naturally occurring
weather systems could deposit rust spores in Ontario in 2005.

David Phillips, senior climatologist with Environment Canada in Downsview,
Ontario, agrees the greatest unknown for soybean rust's entry into Canada will
be the physiology of the disease as winter turns to spring. But the origins
of Ontario's weather is all too certain. During most of the calendar year, weather
patterns that influence the Great Lakes Basin form in the southern Great Plains,
around Texas and Oklahoma. In spring and summer, the hot air that forms over
that region is carried by a general circulation pattern that is caused by a
series of high and low pressure systems.


As the circulation patterns move north, they draw moisture from the Gulf of
Mexico. "And as the seasons wear on, most of our flow, our circulation,
gets more prominent from the south and the west as we get into the warm season,"
says Phillips. As that air passes from the Gulf of Mexico and over the land,
it will draw spores with it, depositing them with the rains as they fall from
systems passing up the Mississippi River and into Ontario.

Potential for damage too much to ignore
Statements that soybean rust may not be a problem until 2006 or 2007 could be
viewed as overly optimistic to Tom Skilling, meteorologist for WGN-TV in Chicago.
Especially given the sometimes harsh realities of developing weather systems.
Even in winter, warm air masses can develop in the southern states, pick up
moisture from the Gulf of Mexico and influence a significant portion of the
middle of the continent, explains Skilling.

Like Phillips, he points to the potential for the relatively rapid transport
of a great deal of matter in a short period of time, and agrees that being prepared
is better than being optimistic. "There's no question about it: this moisture
and air can move great distances horizontally throughout the continent,"
says Skilling. At different times of the year, there can be a low-level wind
flow running from the mouth of the Mississippi River up into the upper Great
Lakes region. "At times, that flow can blow at 65 knots, that's over 75
miles an hour (120km/hr), so the rate of transport of air particles, moisture,
pollens and spores can be pretty substantial." 


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