Top Crop Manager

Features Agronomy Other Crops
There’s a new weed in town

Border patrol misses Japanese brome.


November 15, 2007
By Top Crop Manager

Topics

Creeping its way into Saskatchewan from the US, and causing management problems
for farmers is Bromus joponicus – a highly invasive noxious weed.
Commonly known as Japanese brome or Japanese chess, this 'new weed' is an annual
brome grass or cheatgrass, which exhibits habits similar to downy brome.

"Currently it is present in Saskatchewan in isolated areas or in mixed
populations with downy brome, but it is an aggressive enough weed to cause concern,"
comments Clark Brenzil, weed control specialist, Saskatchewan Agriculture, Food
and Rural Revitalization (SAFRR). "It is important to keep farmers aware
of new weeds that are being introduced. A new weed entering an area can add
another layer of complexity and cost to the existing weed management practices
on the farm."

Significant populations of Japanese brome have been found in southern Saskatchewan
across the Maple Creek, Rockglen, Frontier, Mankota, Gravelbourg and Mossbank
areas. Unlike downy brome, an arid region plant which prefers a drier habitat,
Japanese brome has a preference for somewhat moister habitats. Because of this,
it has also been found outside the Palliser Triangle in the Dark Brown soil
zones and on the edge of the Black soil zone.

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Japanese brome has been identified as far north as Nipawin, Saskatchewan, but
to-date the most significant populations have been recorded in the southern
part of the province and in the Biggar, Liberty, Craik and Imperial regions.

Japanese brome is not unique to Saskatchewan, either, as a single population
has been discovered in southern Manitoba. And, although it is not listed as
a noxious weed in Alberta, small populations have been discovered there as well.

With the ability to act as either an annual or winter annual, Japanese brome
can germinate in the fall in response to rain. However, when fall moisture is
lacking, it adapts and grows as a spring annual. Preferring zero-till environments
and using trash cover as a bed for germination, Japanese brome is typically
found in winter wheat crops, pastures and railroad rights-of-way. Brenzil also
notes frequent reports in spring crops, which suggests a growth habit similar
to other annual grasses such as wild oats or green foxtail.

Japanese brome reproduces only by seed, often in thick patches that out-compete
crops and permanent cover. It matures early in the season and acts as a source
of fuel for fires on native prairie.

On the radar for a relatively short time, Japanese brome population estimates
and invasive rates are hard to establish. And because it is often misidentified
as either downy brome or Persian darnel, Japanese brome may be a bigger problem
than anticipated. When misidentified, it can quickly become a problem.

Know your enemy
The easiest way to differentiate Japanese brome from downy brome is to look
at the awns at maturity. All bromes produce seed on a panicle with small spikelets
at the ends of the branches and the panicle appears to droop toward the ground
in several ways.

The awn on the seed of Japanese brome is equal or shorter than its seed and
curls up when mature. As a result, the awn points outward, perpendicular to
the seed head. The spikelet has an appearance similar to a miniature wheat head.

Conversely, the awn on a downy brome seed is straight, longer than the seed
and grows parallel to the long axis of the seed. This gives the spikelet an
overall 'V' shaped appearance.

At the mature stage, the seeds of Japanese brome are tan in colour, whereas
the seeds of downy brome are a reddish-purple colour. Downy brome is also a
more robust plant than the finely structured Japanese brome.

Japanese brome and Persian darnel are also often confused. The most significant
difference is that Japanese brome has hairy leaves, whereas Persian darnel has
no hair and is very waxy on the underside of its leaves, giving it a glossy
appearance.

What are the control options?
Brenzil notes that although Japanese brome is listed as a noxious weed under
Saskatchewan's Noxious Weeds Act, it is not listed as a noxious weed in the
Weed Seeds Order of the Federal Seeds Act. This means that there is a higher
tolerance for seeds of Japanese brome in certified seed, and that pedigree seed
growers are not required to list it on their seed tags, which are for recording
noxious weeds.

When purchasing seed, growers should ask for a complete list of weed seeds
to ensure their seed is free of Japanese brome. Ensuring that equipment is thoroughly
cleaned when moving from field to field also helps prevent the spread of unwanted
weeds.

Currently in Canada, in-crop herbicides are not registered for annual bromes
in cereals. In broadleaf crops, triflurilan and Edge are registered to control
Japanese brome and other cheatgrasses.

Brenzil says that research out of the US indicates the quackgrass rates of
Group 1 herbicides such as Select, Venture, Poast and Assure have reasonable
activity at the early seedling stage but are ineffective after the six leaf
stage, or once the plant begins to tiller. Research out of the US also suggests
that the 'fops', or Venture and Assure, may reduce seed production even if applied
later than the six leaf stage of Japanese brome. Because annual brome seed does
not last for long periods of time in the soil, this suppression of seed production
can have a big impact on future populations.

Jamie Salisbury, senior agronomist at Rack Petroleum in Biggar, Saskatchewan,
has seen good control with Assure in lentil fields and has also seen some success
with Everest in wheat. "One farmer that I recently talked to was very pleased
with the control that he obtained with Everest. He estimated his control of
Japanese brome to be about 80 percent and that the residual did a good job catching
his second flush," says Salisbury.

Everest is not registered for control of Japanese brome in Canada, but is registered
in the US for control of Japanese brome in fall applications and suppression
in spring applications. "Japanese Brome is becoming a more common weed
concern here in North Dakota and growers are finding it hard to ignore,"
comments Monte Kubas, Arvesta territory representative for North Dakota.

Dealing with another weed is hardly good news for wheat growers, but with early
identification it may be easier to combat and keep under control. -30-