Labour Day: A Signal to Control Problem Weeds

Labour Day is a reminder that weed challenges are moving into many fields. These weeds will be difficult to control next spring, especially once they start to flower.

What weeds?

• Winter annuals germinate now into a low-growing rosette to overwinter. Eg. Common chickweed, thyme-leaved sandwort, night-flowering catchfly, corn gromwell, mustards (garlic mustard, wormseed mustard, common peppergrass, shepherd's purse), Canada fleabane
  
• Biennial weeds may also establish in the fall as rosettes. Eg. Celery-leaved buttercup, yellow rocket, some fleabanes
  
• Perennial weeds Eg. Dandelions, yellow wood sorrel (oxalis), common mallow, common mullein, toadflax, ox-eye daisy, milkweed, goldenrod.
  
• Annual weed problems may also increase in the fall. Eg. Dwarf snapdragon and groundsel are shedding seeds extensively through the fall. Field violet may survive the winter to flower and seed again the next year, especially under mulch.

Milkweed

Quack grass

Toadflax

Wood sorrel

What to do at Labour Day (or shortly afterwards)?

• Strawberries: Apply Sinbar @ 0.18 to 0.28 kg/ha (even sensitive cultivars may be tolerant to this low rate). Where groundsel or grasses are a problem, apply Devrinol as well (Note:
  Devrinol may only be applied once per season, and moisture is required for incorporation)
  
• Harvested fields: Work fields down soon after harvest to
  prevent seed shed. Plant cover crops to smother weeds, and scout for rosettes and other germinating weeds - treat with
  hormone herbicides like 2,4-D if needed.
  
• Field edges: Mow weeds to prevent seed shed. Weeds on the edge produce more seeds.
  
• Perennial weeds: Apply systemic herbicides like glyphosate to weeds to regrow after mowing. Fall is an excellent time to treat quackgrass.

Remember Labour Day as a window for weed control. Herbicide applications or preventative cultural practices at this time can reduce problem weeds next year.

| Top of Page |