Two more cases of late blight have been confirmed in Manitoba, and the risk of the disease developing in other potato fields is high, says a potato specialist with the Manitoba government.
The province says two potato plant samples that were sent to Manitoba Agriculture’s crop diagnostic lab came back positive for late blight Aug. 17. One sample was from a potato field west of Carberry and the other was from near Winkler.
Three positive cases of late blight have now been found in the province this year, including a field near Holland earlier this month.
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“It (late blight) is present and it is definitely a risk …. The risk is high,” said Manitoba Agriculture potato specialist Brian Wilson.
Although 2011 has been a dry summer in most parts of Manitoba, irrigated potato fields have higher humidity within the plant canopy, which means there is a risk of late blight developing if innoculum is present.
“The conditions are not as severe, weatherwise, as they were last year, but it’s still very much a risk and farmers have to be diligent,” Wilson said.
“They (farmers) will be managing it right through until the crop is harvested.”
In areas where late blight has been found, Manitoba Agriculture usually recommends that potato growers closely monitor their crop and apply fungicides every five days to reduce the risk of a disease outbreak.
The two samples are now at the University of Manitoba, where plant pathologists are monitoring genetic changes in late blight.
Only one strain of late blight existed 30 years ago, but a U of M news release says new and aggressive versions of the disease, which are more resistant to fungicides, have since displaced the old genotype.
“In Canada, we started doing surveys in ‘94, and we noticed that every year the makeup of the (late blight) population landscape … has been changing,” said U of M plant pathologist Found Daayf.
A survey last year found another new genotype in Western Canada called US23.
