'It's an aggressive competitor': Manitoba farmers warned about noxious weed

The province is warning farmers about an aggressive, invasive weed that's spreading in Manitoba.

Manitoba Agriculture weed specialist optimistic invasive tall waterhemp can be eradicated

Tall waterhemp can grow as much as three centimetres a day, with multiple growth cycles per season, and is likely resistant to some herbicides, said Tammy Jones, a weed specialist with Manitoba Agriculture. (Submitted by Tammy Jones)

The province is warning farmers about an aggressive, invasive weed that's spreading in Manitoba.

Tall waterhemp was reported in four spots this summer, including sightings in three southeastern rural municipalities — the RMs of Reynolds, Whitemouth and Ste. Anne — where the noxious weed hadn't previously been seen, as well as the RM of Rhineland.

The plant can produce between 250,000 and one million seeds per season, and can grow up to three centimetres per day, said Tammy Jones, a weed specialist for Manitoba Agriculture. The plant can germinate from May through to August, and populations in the U.S. are resistant to as many as seven types of herbicides.

"Imagine you have two or three plants one year, you [could] have a million plants the next year," Jones said. "And it just keeps going from there."

In the sunny spaces between row crops like soybeans or corn, tall waterhemp can rapidly out-compete crop plants, Jones said.

"For a landowner that is trying to control and destroy this weed, it's an aggressive competitor, so it reduces the output. It contaminates seed. And because it is a 'tier one' weed for Manitoba, we prohibit it being transported in any way, whether that's in hay or whether that's in a grain crop" she said.

"It could be something that impacts on the value of that land, also the value of the crop that's on that land."

Plants can be designated as "tier one" noxious weeds if they pose a "significant threat" to agricultural operations, or are likely to do so if they become established.

'Disappointing, to say the least'

Jones said the province is working with farmers and municipalities to spread awareness about the plant and how to destroy it. Manitoba Agriculture has held meetings with communities and is working with farmers to make sure producers know the risks of the plant and what to do about it.

When Jones started in her position in early 2017, the weed had been spotted a handful of times in the province. Experts weren't expecting the number of reports this year, or the size of some patches of the weed, she said. 

Tall waterhemp plants crowd rows of corn in a farmers' field. (Submitted by Tammy JOnes)

A release from Manitoba Agriculture earlier this month said some of the patches spotted this year involved "a substantial number of acres [and] significant hours of roguing, mowing and spraying to destroy plant material."

The plant has caused headaches for jurisdictions in Ontario and the midwestern U.S., Jones said.

"We knew there was the chance that it would be here at some point in time. Because it is a heat-loving plant, the hope was that it wouldn't establish well, and that it wouldn't like our conditions," Jones said. "Unfortunately … it has managed to do quite well in Manitoba, which is disappointing, to say the least."

Jones said she's optimistic it's still possible to eradicate the weed in the province.

Experts have yet to confirm whether the Manitoba waterhemp population is resistant to herbicides like U.S. populations. Jones said she suspects the plants in Manitoba will be resistant to some types of herbicide, which could make tackling it trickier. Strategies like changing the timing of planting, or choosing more competitive crops could be used in the fight, she said.

If farmers think they might have the plant on their property, they're encouraged to contact the province to confirm, she added.

"It is not widespread at this point in time, and we have lots of great farmers that are really looking to make sure that this weed is kept in small areas and destroyed as effectively as possible," she said.

"So I think we're all pulling in the right direction. There is a huge opportunity to keep this under control."