Canada fleabane (Conyza canadensis)

Canada fleabane description

Canada fleabane is typically found in no-till production. It thrives under cool, damp conditions and little soil disturbance. The annual weed has become a serious management issue for Ontario farmers since 2010 when the first herbicide-resistant Canada fleabane was reported in Essex County.

Propagation

Canada fleabane reproduces by seed, which are spread through the air. Canada fleabane, growing in an uncompetitive environment, can produce more than 200,000 seeds per plant.

Similar species

Fleabane is also known as horseweed and mare's-tail.

Management

An integrated weed management approach will help to reduce herbicide-resistant fleabane:

Practice diversified crop rotation
Reduce reliance on glyphosate and use multiple modes of action on every acre
Incorporate tillage strategically
Plant cover crops to prevent weeds from becoming established
Strive for near-perfect weed control to reduce weed additions to the seedbank

According to OMAFRA Publication 75, good control of glyphosate-resistant Canada fleabane in corn can be achieved with pre-emergence herbicides such as CALLISTO + AATREX 480.

Sources
http://www.omafra.gov.on.ca/english/crops/field/weeds/canada_fleabane.htm#history
https://ontariograinfarmer.ca/2016/04/01/a-plan-for-resistant-fleabane/

Distribution

As of 2016, glyphosate-resistant populations of fleabane have been confirmed in 28 Ontario counties – from Essex County in the southwest, all the way to Glengarry County on the Quebec border.

Identifying Canada fleabane

Seedling

Canada fleabane germinates mostly in the fall while a small portion of seeds will germinate in the spring. Emergence has sometimes been observed during the winter months during warm spells, which shows this plant’s adaptability.

Fall-emerging Canada fleabane grows to a rosette stage before overwintering, then resumes its growth in the spring when it bolts and flowers. Spring-emerged weeds go straight to the flowering stage. Canada fleabane will germinate throughout the year if not shaded by a crop canopy.

Mature plant

Canada fleabane is a very hairy weed species that can reach heights of up to 1.5 metres. Its leaves are dark green, linear and lanceolate with small hairs. Lower leaves have toothed margins, while upper leaves have smooth ones. The weed has small white flowerheads that appear ‘fluffy’ at maturity. Peak flowering occurs between early summer and late autumn.