Knowing a bit about barley anatomy will help you get the best results from your fungicide applications and seed treatments.
Although the flag leaf is a big contributor to wheat yields, it’s quite small in many barley varieties. The biggest yield contributors for barley are the penultimate leaf, the leaf before it, the head and the flag-leaf sheath, Kelly Turkington, a plant pathologist with Agriculture Agri-Food Canada, told attendees at the recent Lacombe Field Day.
He’s looked at what happens when herbicide was applied at the flag-leaf stage, and found it didn’t result in any advantages in disease management, crop productivity or yield increases. Dual and split applications didn’t give any benefits either. The only benefits occur from a single application of fungicide at the flag-leaf emergence stage.
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“Why that difference?” asked Turkington. “If you look at the physiology of the barley plant, it’s the top leaves in that canopy that are key for grain filling and yield. The lower leaves contribute relatively minor amounts to the yield. By this time, a lot of the lower leaves present in the two- to three-leaf stage would actually be senesced (fully mature) and would be lower down in the canopy and quite heavily shaded.”
Fungicides have limited ability to eliminate pathogens from well-established lesions, he said.
“If you have a lot of net blotch or scald lesions or septoria on those lower canopy leaves at that seedling stage, spraying a fungicide does not eradicate the pathogen from those leaves,” Turkington said. “At best, you might see some suppression.”
To get the best results, producers need to target upper canopy leaves. To attack disease at the bottom of the plant, you need a good seed treatment to manage seed-borne diseases such as smuts and fusarium head blight. However, seed treatments for root rots have a minimal impact because fungicides move with the water transpiration stream and don’t penetrate the root tissue. Seed treatments can help early-leaf disease suppression development, because they could move into the first, second and third true leaves, providing protection as soon as the leaves develop and start photosynthesis
To test this hypothesis, researchers are investigating the interactions between seed treatments to control early-leaf disease, fungicide application at flag leaf, and plant growth regulators. Turkington said he observed better canopy lower-leaf health in plots and better senescence in crops given two doses of Ensure, a BASF seed treatment, compared to those that received no seed treatment at trial plots in Indian Head, Sask.
“There was something there. There appeared to be less net blotch,” said Turkington.
Trials are in their first year and are running at research stations across Canada.
