It has been what one plant pathologist for the province called a “banner year” for stripe rust but that is not the only cereal leaf disease farmers need to watch for.
“There are a number of fungi out there that will colonize and cause these leaf spots on cereal crops like barley and wheat,” said Mike Harding, plant pathologist for Alberta Agriculture and Rural Development.
On July 14, Alberta Agriculture and Rural Development released a crop disease update, alerting farmers of diseases to keep an eye on. Some diseases listed – root rot, clubroot, sclerotinia and blackleg – do not affect cereal crops, Harding said.
Others, such as tan spots, septoria and stagonospora do, he continued.
Harding said the various diseases are an annual occurrence and their severity depends on a number of factors.
“These are organisms that survive in our agricultural production regions from year to year and show up regularly,” he said. “In some years, they become much more severe than others and that would depend on things like crop rotation, weather, what kinds of chemical treatments, either seed treatments or fungicides applied.”
Dark spots and yellow halos on leaves serve as visual clues for farmers to check if their crops have been infected, Harding said.
He added that if unsure, people should consult a local agronomist.
Just like in the case of stripe rust, the advice to survey fields also applies, first checking the lower canopy and working up, he said.
“So scouting regularly for these diseases lets you know, is the disease present in the lower canopy, is it building, is it getting worse, is it moving up on to the upper canopy and if it is, then I'm going to consider applying a fungicide to protect those upper canopy leaves and head,” he said.
However, Harding said a fungicide application is only worthwhile under certain conditions: high potential for yield, disease and good timing.
That timing depends on the crop stage and the pre-harvest interval listed on a fungicide, he said.
Safety regulations only allow a certain amount of residue on food products and the pre-harvest interval is the time that must be given between fungicide application and harvest.
“If you don't have those three things: yield potential, disease potential and a well-timed fungicide, then your fungicide might not provide any economic return,” he said.
