Those grassy weeds popping out of the ground might be hiding a noxious surprise.
Tammy Jones, Manitoba Agriculture’s weed specialist, says she is concerned about both downy and Japanese brome, both Tier 2 noxious weeds that have been digging roots in parts of Manitoba.
Both species have been present in Manitoba for years, although Jones says it is difficult to say how large the range is since a noxious weed database is still under construction.
“Weed supervisors do keep a collection of weed control records for their area,” she said. “What we’re working on now is amalgamating some of that so that we can start to generate some distribution maps so that we can give people a better idea of where some of those (weeds) are.”
Why it matters: Manitoba’s weed experts are still on the watch for two brome grass invasive species.
The province has reviewed data from the last major survey in 2016, she said, but noted that wet conditions that year might mean that current distribution is vastly different, given several years of dry conditions since.
In 2011, the Invasive Species Council of Manitoba released a distribution map with downy and Japanese brome spotted sporadically across southern Manitoba. The council marked two municipalities along the Saskatchewan border and one directly south of Lake Winnipeg with anywhere from five to 50 per cent of sections infested. No higher levels were reported.
Both winter annuals were heading out as of the last week of May, Jones said, something that may be useful for identification, although the foxtail barley shares a similar early start.
Foxtail barley, however, is more of a blue-green plant, compared to the purple or tan stems and brighter-green leaves in the brome species, she said.
The grasses’ lack of auricles do little to set them apart from wild oats or Manitoba’s various flavours of foxtail, which also lack the ear-like structures at the base of the leaf. Likewise, both brome grasses share their membrane-like ligule found in the same area with foxtail barley and wild oats.
Instead, Manitoba Agriculture has pointed to the “V-neck” sheath in both species, compared to foxtail barley’s overlapping sheath and the split sheath in both green and yellow foxtail barley and wild oats.
Colour and panicle (the multi-branched seed structures) will also differentiate between the two brome species. The Invasive Species Council of Manitoba says downy brome panicles will droop more, while Saskatchewan’s Ministry of Agriculture points out that downy brome is more purple in colour.
“Often (Japanese brome is) kind of missed when it’s moving into a field,” Assiniboine Community College agriculture instructor Danielle Tichit said.
The college included Japanese brome into its weed identification training garden this year.
Both brome grasses have fewer herbicide options and less management knowledge than foxtail barley, according to Jones.
“We’ve done more research on foxtail barley and we have more labels that have an indication of where the herbicides work really well, and Japanese brome and downy brome aren’t as frequently researched,” she said.
The two weeds have only been on her priority list in the last year, following changes to the Noxious Weeds Act that came into force in 2017, she said.
Tillage is a viable strategy for both brome grasses, Jones said, pointing out that both are bunch grasses like foxtail barley, compared to the rhizome-based quackgrass that only spreads when disturbed.
“Bunch grasses tend to be a little bit more difficult to control, just because of how their growing points are all located in a very dense sort of clump at the base of the plant,” Tichit said. “The other thing with something like Japanese brome is that it is very hairy, so if you have a very fine leaf covered in hairs, that can make it difficult if you were trying to use a herbicide option… it could be difficult to get it to stick and actually get it to absorb into the plant.”
Saskatchewan’s Ministry of Agriculture notes there are no herbicides registered to control those species in perennial forage, although farmers looking for control in broadleaf crops can still expect good control of Japanese brome and suppression of downy brome if they turn to Group 1 herbicides while the plants are still seedlings. The ministry suggested hand roguing for small infestations before seedset.