April 4, 2013

Aster leafhoppers arrive later in 2013

Aster leafhopper adult. The white bar indicates 1 mm. Adults are about 3 mm long, which is quite small. Photo credit: Tyler Wist

It will come as no surprise, but winds from the deep south have not arrived on the Canadian Prairies yet this year. This is quite different from 2012, when a mild winter and early spring helped make it a bad year for aster yellows in canola in Western Canada. The first south winds in 2012 arrived on April 1, which provided a very early opportunity for aster leafhoppers to migrate up from Texas and surrounding states. This event prompted Canola Watch to offer spring wind trajectory maps for 2013.

The following maps present two different wind trajectory approaches that AAFC and Environment Canada use. A “back trajectory” shows where winds converging on Saskatoon had traveled to get there. We choose Saskatoon for its central Prairie location. Wind patterns will not be identical for the Prairies.

That is why we’ve also included the second type of wind map — a “forward trajectory” — showing where winds from Brownsville, Texas are predicted to go over the next 5 days. Central Texas is a common area where aster leafhoppers (and diamondback moth) winter in large numbers. These insects eventually blow into Western Canada in spring and summer when the south winds arrive. Forward trajectory maps from AAFC and Environment Canada show that winds from Central Texas have been blowing eastward to the U.S. East Coast and have not yet blown north toward the Canadian Prairies.

Delayed arrival of southerly winds in 2013, together with the colder start to the growing season, may lessen the risks associated with these migratory insect pests.

Thanks to Owen Olfert, entomologist with AAFC in Saskatoon, for providing these maps. He will provide Canola Watch with weekly updates over the coming weeks.

20130513_r_saskatoon_sk copy
As of May 13, winds into Saskatoon are still coming from the west, although from farther south than last week. Scroll down to see last week’s map and older maps.
As of May 13, winds out of Brownsville, Texas are forecast to move north and then east, except for one track that heads south. Nothing is headed to Western Canada yet.
As of May 13, winds out of Brownsville, Texas continue to move north and then east, except for one track that went south.
As of May 6, south winds still have not arrived in Saskatoon, so leafhoppers should not have blown into that region yet.
As of May 6, south winds still have not arrived in Saskatoon, so leafhoppers should not have blown into that region yet.
Winds from south Texas are arcing more northward but still have not reached Western Canada as of May 6.
Winds from south Texas are arcing more northward but still have not reached Western Canada as of May 6.

 

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Back trajectory wind map for Saskatoon, April 29. Owen Olfert from AAFC says, “We’ve still had no back trajectories from the Prairies that have were predicted to have originated in the southwest USA or Mexico,” which is where leafhoppers winter in large numbers.
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Forward trajectory wind map for Brownsville, Texas, April 29. The wind paths have shifted northward in the past week, but the south winds are still not reaching Western Canada.

 

The April 22 forward trajectories out of Brownsville, Texas, for example, are predicted to head east over to the Atlantic.
The April 22 forward trajectories out of Brownsville, Texas, for example, are predicted to head east over to the Atlantic.
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Back trajectory wind map showing where winds arriving April 22, 2013 in Saskatoon had come from. As Owen Olfert from AAFC says, “The back trajectory maps for the most of the prairies suggest that our winds have come primarily from the northwest.” They won’t be bringing leafhoppers.
The April 22 forward trajectories out of Brownsville, Texas, for example, are predicted to head east over to the Atlantic.
The April 22 forward trajectories out of Brownsville, Texas, for example, are predicted to head east over to the Atlantic.
Back trajectory wind map showing where winds arriving April 1, 2013 in Saskatoon had come from. These Northwest winds won't be bringing any aster leafhoppers.
Back trajectory wind map showing where winds arriving April 1, 2013 in Saskatoon had come from. These Northwest winds won’t be bringing any aster leafhoppers.
Winds from Brownsville, Texas on April 1, 2013 are heading east toward the Atlantic Ocean and Gulf of Mexico.
Winds from Brownsville, Texas on April 1, 2013 are heading east toward the Atlantic Ocean and Gulf of Mexico.
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