Tank-mixed fungicides are becoming more popular, but they’re not a cure-all.
“That’s a strategy that is attractive, because it represents a convenient, one-pass operation,” Kelly Turkington, an Agriculture Canada plant pathologist, told attendees at the recent FarmTech event.
But producers still need to carefully consider the goal of spraying, he said.
“What is the focus here?” asked Turkington. “Is it head blight? Is it leaf disease management or some combination of the two?”
Experiments conducted at Scott, Lacombe and Melfort during the past two years found the best control of scald is achieved when fungicide is applied at the flag-leaf stage. Split applications of fungicide applied at flag-leaf and heading stages also proved useful.
“Our best yields tended to be at half-rate or full rate of Tilt at flag-leaf emergence, or when we used the split application,” Turkington said.
The best way to select a fungicide, which generally only protects existing green-leaf tissue, is to learn what it does, and how it moves within the plant, the diseases that affect the crop, disease levels and weather conditions, he said.
“Any well-established infections, whether it is scald or net blotch in barley or septoria in wheat, will not be eradicated by fungicide,” said Turkington. “It has a very difficult time eradicating well-established infections.”
Diseases can then continue to cycle, because they haven’t been completely wiped out.
Applying fungicides at flag-leaf emergence will help protect upper canopy leaves.
“If you delay your application until the head-emergence stage, the risk here is that the disease will develop and start to affect the flag leaf, other leaves and the third leaf down from the head,” said Turkington. “By the time you get that fungicide on and heading, it may be a bit on the late side.”
When there is a dry May, the fungus may start to develop as the crop is coming into the flag-leaf stage, and a head-emergence application may actually provide better control than a flag-leaf application.
“You need to look at the nature of these fungicides, when the disease is coming into that crop to determine the fungicide timing that you use,” he said.
Fungicides do not move down the leaf or back into the base of the leaf, said Turkington. Most of the movement of the fungicide will be to the tip of the leaf.
“All of the cereal leaf fungicides that we have move with water transpiration,” he said.