MORDEN, Man. – Crop producers in Manitoba are advised to be on the lookout next year for biennial wormwood, a native weed that appears to be making a comeback.
The weed was evident from Boissevain in southwestern Manitoba to Winnipeg this year, according to Brian Hunt, a weed control specialist with Manitoba Agriculture
He said biennial wormwood can produce as many as one million seeds per plant. Although referred to as a biennial, it can also act like an annual – growing, flowering and setting seed in the same year.
Read Also
Farming Smarter receives financial boost from Alberta government for potato research
Farming Smarter near Lethbridge got a boost to its research equipment, thanks to the Alberta government’s increase in funding for research associations.
It has a thick stem, grows vigorously and can be competitive against other plants.
Hunt said biennial wormwood prefers areas with wet, undisturbed soil, such as the edges of fields or a field that has not been tilled for a month or two.
“It’s very good at scavenging water to fulfill its life cycle.”
Some people mistake it for kochia because of its appearance. However, one of its distinctive features is that its seeds and flowers give off a strong sage smell when crushed by hand.
Biennial wormwood is relatively easy to control with herbicides.
On pasture and noncrop land, 2,4-D Ester is recommended at 1.78 litres per acre.
Hunt said when used in-crop, phenoxys at lower rates such as half a litre will work if the plant is at the two- to four-leaf stage, but become less effective as the plant gets older.
Higher doses of glyphosate also seem to be effective as a preseed burnoff, he said.
In bean crops, Basagram seems to work well when applied early. A split application can also be beneficial to catch the later flushes.
Hunt said some biennial wormwood plants proved true to their name this year, germinating in the fall in time to harden off for the winter, making it likely that they will re-emerge next spring.
“Just keep a lookout for it because it is out there.”
He said biennial wormwood ranges from Oklahoma to Alaska and is easily spread by wind, water and human activity.
