LETHBRIDGE, Alta. – Dandelions and foxtail barley can be the bane of a no-till farmer’s life.
“Within two to three years of a direct seeding system is when people encounter a wreck with dandelions,” said crop specialist Rob Dunn of Alberta Agriculture.
Only diligence can evict dandelions from a field, Dunn told a conservation tillage conference.
A dandelion scourge may be caused by the farmer’s own management decisions.
The farmer may have decided to skip a glyphosate burnoff in the fall. By waiting for the first flush of weeds in spring, the dandelions may be two years old and harder to kill by the time spraying starts for broadleaf weeds.
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Another difficulty can be when the first application of spring herbicide has been delayed. Dandelions that emerged the year before begin growing in mid-April and by the time the spray hits, the plants are robust enough to withstand lower rates of glyphosate or Rustler.
To get an effective kill, farmers need to know the plant’s growth stages.
Dandelion seeds must be on the soil surface to germinate. Plants emerge when the soil temperature is over 10 C. New plants can appear anytime from May to early July.
If they survive for two years or more, they develop a hardy taproot and become prolific seed producers.
Roots take hold
Sometimes, farmers are surprised by a dandelion’s tenacity. This happens when they mistake an older plant for a seedling. What likely happened is a farm implement clipped off the top of the plant. The root formed a callus and grew a new plant with a powerful root system.
“They usually emerge four or five days after you have done your in-crop spray,” Dunn said.
Post-emergent broadleaf herbicides can prevent establishment of seedlings. Older plants are tougher and can bounce back.
Most dandelions succumb to applications of a litre per acre of glyphosate in the fall when there is some new growth in the centre of the plant.
Fall applications of products containing glyphosate, dicamba, 2,4-D or MCPA along with Amitrol-T can zap seedlings.
In one field study, 95 percent of the dandelions were killed with a mid-October spray, said Dunn.
A spring application of glyphosate at half a litre per acre will control young, actively growing plants.
Older perennial dandelions develop a tolerance toward herbicides. Long-term control with fall, spring and post-emergent herbicide may be required.
Controlling foxtail barley also takes persistence.
Foxtail is tolerant to salinity and is common in salt affected areas across the Prairies. It can disperse seeds in the wind and germinate during cool, moist conditions.
Seedlings are susceptible to RoundUp, Poast and Assure. The plants are more herbicide tolerant after heading and as they develop a stronger root system.
Research at Lethbridge showed Assure controlled foxtail in broadleaf crops. Anthem and Sundance worked well in wheat fields.
