The name is pretty, but the impact of the disease Aster
Yellows on Western Canadian crops this year could be ugly, says one plant
pathologist estimating crop yield losses will run into the billions of dollars.
The disease, which usually appears as a yellow discoloring
of leaves, is often around in lose doses, but Ieuan
Evans, a senior coach with
Agri-Trend Agrology, says the pest that carries the disease from the southern
U.S. into Canada, arrived in such vast numbers across Western Canada that it
has spread the disease across the Prairies and it is affecting nearly ever
in Canada’, Canadian Phytopathological Society)
“I believe on average we will see a 10 to 15 per cent yield
loss in canola across Western Canada,” says Evans. “It is a disaster. Some
fields in Manitoba and Saskatchewan have up to 40 per cent yield loss, while in
Alberta it is more in the 15 to 20 per cent range, although I have seen it at
40 per cent losses in some areas.”
ACROSS THE BOARD
And it is not just canola, says Evans. Wheat, barley and
flax are also being infected by the disease. “I have seen 40 per cent yield
losses in wheat in Manitoba,” he says. “Crops are showing signs of yellow
leaves, and some people are blaming it on root rot. It is not root rot, it is
aster yellows. This disease has a wide host range.”
Along with cereals and oilseeds, Evans says aster yellows
affect the germination quality of all seed as well.
The aster yellows phytoplasma, or micro-organism, is carried
by the aster leafhopper, also known as the six-spotted leafhopper. The pest is
common in the southern U.S. and is carried into Canada on prevailing winds.
“Other years there have been sporadic cases of it appearing,
but this year the conditions apparently were ideal – perhaps due to the dry
conditions in the United States — and the pest arrived in Canada by the
trillions,” says Evans.
The pest is carried on wind currents perhaps 3000 to 4000
feet up and as temperatures cool the leafhoppers will just drop. It is not necessarily an even
distribution either. One area could be heavily infected and other nearby areas
hardly have any.
In some fields near Swan Lake, Manitoba for example, he
describes “the ground was moving” with the pest during an inspection of field
crops. The pest, which is a small whitish fly — 3.5 to 4 mm in
length— behaves similar to flea beetles as it hops and scurries around plants.
GAME PLAN NEEDED
There is no known treatment for the pest or the disease, but neither normally over winters in this part of the country. However, with severe
losses expected this year, Evans says farmers need to be aware of pest and the
problem, and perhaps should develop a “fire escape plan” if the disease comes
back with this pressure again. “People develop a fire escape plan at home, in
case there is a fire, and we have to be thinking along these lines in case we
have another outbreak of the disease,” says Evans. “We need to be looking at control options to at least minimize the impact of the
He says applying an insecticide when the pest
first appears, might help minimize disease spread.
“Our team at Agri-Trend is looking at options in hopes of developing a plan,” says Evans. “”We don’t know what will work, but a treatment with products such as Decis or Matador might control
the pest to the extent to hold yield losses to 10 per
cent instead of 40 per cent. It is important that we look at our options.”
Lee Hart is a field editor
for Grainews in Calgary, Contact him at 403-592-1964 or by email at [email protected]