By now everyone is familiar with the yellow peril, leafy spurge.
Now, the Manitoba Weed Supervisors Association is asking ranchers and forage growers to also be on the lookout for the “red menace.”
“Usually, by the time you notice it, it’s already a big issue,” said Fred Paulson, weed supervisor for the Interlake Weed District, in a presentation at the MWSA’s annual general meeting.
“If you can detect this weed early and deal with it when it’s still a small patch, you’ll be way ahead of the game.”
Red bartsia, an alien, invasive, noxious weed species, is believed to have first come over in the 1950s from then-West Germany in hay stuffed in glider crates at Gimli airforce base.
It was first noticed alongside the runway, and then spread to other parts of the Interlake after farmers hayed the area and transported the forage back to their farms.
By the 1960s, it had spread from Gimli to the Rural Municipality of Armstrong. In 1980, it could be found near Riverton, Arborg, Teulon and Netley Creek.
From there, it has appeared in small pockets as far away as Falcon Lake, Gypsumville, Souris, Portage and Beausejour.
It is now found in almost all Canadian provinces, as well as the northeastern United States, although the origins of those infestations is unknown.
An annual, woody-stemmed species that spreads by seed, red bartsia is very competitive on overgrazed pastures, and marginal, low-fertility soils. It is hemiparasitic, which means it can steal nutrients and moisture from the roots of neighbouring plants and quickly choke them out.
The seed germinates in late April or early May, but development can be delayed by a cold, late spring. In a typical year, seedlings are apparent by May 15 to mid-June, and in some cases, as late as July, but successive flushes may occur throughout the growing season.
Growth is slow at first, and the tiny seedlings are easy to overlook. Once the plant breaks through the canopy, such as after the first cut of hay, the extra sunlight triggers swift growth to a height of anywhere from six to 12 inches, or as tall as two feet.
The flowers, which are reddish-pink and resemble tiny snapdragons, first appear in the last two weeks of July, and continue until the first hard frost.
Soon after flowering, the plant takes on a reddish-purple tinge, making heavy infestations in fields clearly visible.
Once it reaches that stage, it is very difficult to control with herbicides, said Paulson. Cultivation keeps it at bay, but mowing only slows it down, he added.
The tiny seeds shell out in late September. Each plant produces 400 to 1,400 seeds, which float easily on water and stick to animal fur, equipment and clothing, and remain viable in the soil for up to nine years.
“Once you’ve got a patch developed, you’ve got a long-term problem,” he said.
“Once in a pasture, it quickly takes over. Livestock won’t graze it. On roadsides, it is quickly spread by mowers and graders.”
The main vector of spread appears to be in shipments of contaminated hay, however. Even early, first-cut hay isn’t safe because seeds from the previous fall or past years may still be picked up along with the hay.
As with all noxious weeds, an ounce of prevention is worth a pound of cure, he said.
Hay or seed buyers should know where their hay is coming from, clean their equipment, and even check the headlamps of their vehicles regularly in summer to ensure that seed isn’t brought in from roadsides to their farms.
If the land is suitable, ripping up an infested pasture and sowing annual crops works if continued for at least nine years. However, if the land is left in alfalfa for a number of years, the red bartsia will come back, he said.
Red bartsia infestations cost a lot of money to control. In the year 2000, his district spent $52,500 spraying 600 roadside miles of known infestations. Five years later, the weed had spread to 1,000 miles, and the cost of spraying rose to $67,000. By 2008, that figure had grown to 1,350 miles, and fighting the weed cost of $97,000.
In the seedling stage when the plant is still green, red bartsia can be killed with 2,4-D at a rate of one litre per acre. But once the plants turn red, 2,4-D is not effective at that rate.
Simazine 480, a liquid formulation which is registered for roadsides, at one litre per acre provides “excellent” control, he added.
On town boulevards, public areas and subdivisions where drift and odour is a concern, 2,4-D Amine 600 is used. For spot control in August and September, two litres per acre of 2,4-D Ester 700 seems to be the “magic” formulation.
Unlike leafy spurge, no livestock species readily eat red bartsia. Burning ditches has been tried in some areas, but with little success, Paulson added. [email protected]