Wheat School: Getting the better of bluegrass


Grain growers are reporting that bluegrass is becoming a growing weedy issue in many Ontario field crops. There are three types of weedy bluegrass species that are being found: annual bluegrass, rough-stalk bluegrass, and Canada bluegrass.

As Mike Cowbrough, Ontario Ministry of Agriculture, Food and Rural Affairs weed specialist explains in this Wheat School episode, the reason bluegrass is such a problem is because all three species are prolific seed producers and spreaders. The latter two species, rough-stalk and Canada bluegrass, also spread by stolons — root stems that travel along the surface of the soil, send out nodes, and root themselves in.

“Populations can build up in a hurry, and in a winter wheat crop like this, Michigan State University has seen as much as 50 per cent yield loss from this species being in the field,” says Cowbrough.

Bluegrass also heads out at the same time that wheat does, so when applying a fusarium fungicide, the bluegrass head can obstruct the spray application.

To quickly identify bluegrass, Cowbrough says to pull back the leaf blade and look at the spot where the leaf blade attaches to the main stem, where there’s a membraneous ligule. The seed head is an open panicle, and the leaf blades are folded and there’s a unique bend to the top of the leaf. (See video for even more detail, story continues below)

Cowbrough also says that a sample can be sent to a diagnostic lab, where DNA testing can confirm exactly which species of bluegrass is present.

A field trial that Cowbrough has been keeping an eye on this season, has taught him two things: applying herbicide when bluegrass is less than 10 cm tall is key to getting good control; and timing of that herbicide application can affect bluegrass’ reproduction chances.

“You always have to be a little bit careful about environmental conditions at the time of application,” warns Cowbrough, but adds to focus on staging of bluegrass — smaller is better.

Bottom line, Cowbrough says is to scout fields in the fall and early spring to be on the lookout for bluegrass in between the rows of winter or spring wheat. If there’s significant pressure, it needs to be dealt with when plants are small to have the best chance at control.

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Wheat School (view all)Season 12 (2021) Episode 11

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