Tank mixing herbicides and fungicides may be convenient for farmers, but it doesn’t provide effective results, researchers say.
Fungicides for cereal leaf diseases are most effectively applied on the top two leaves in wheat and the top three leaves in barley, said Agriculture Canada research scientist Kelly Turkington.
Spraying fungicide earlier, when timing is more optimal for herbicide weed control, could be a waste of time and money.
The upper canopy leaves are crucial for grain filling and yield, Turkington told the July 11 Farming Smarter field school in Lethbridge.
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If producers delay their herbicide-fungicide combination until the five or six leaf stage, their weed management is compromised.
He advised careful scouting for tan spot and septoria in wheat, and net blotch and scald in barley.
“If you’re seeing general development of those diseases in the field, to me that serves as an indication that you’ve got a risk developing and you’d better monitor that crop very closely as it’s approaching that flag leaf emergent stage, the key time to put a fungicide on as far as protecting the upper canopy leaves in those cereal crops.”
Brian Beres, also of Agriculture Canada, said there was confusion this year about the best time to spray fungicide for stripe rust, which reduced yields significantly in southern Alberta last year.
“I don’t see how you can have an effective timing of weed removal coincide nicely with when you want to apply that fungicide,” said Beres.
“By applying a fungicide prophylactically, or perhaps creating additional agitation by combining it with the herbicide, some unexpected results can happen in the field, in spring or winter wheat.”
The need for cereal leaf disease fungicide is new territory in typically dry southern Alberta, but Beres said two fairly wet springs have created the need.
Many fungicides used for cereal leaf disease are systemic, but they tend to move within the leaf rather than between leaves. Turkington said that’s why fungicide must be directly applied to the leaves most important for grain filling.
Fungicides work best before the disease is extensive because it is not effective against well advanced fungus.
