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Futures

Bluegrass is becoming a problem in Ontario

03/12/2021
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By Mark McKerrall, 
Crop Sale Specialist, CCA-ON, 4R NMS
AGRIS and Wanstead Farmers Co-operatives

Cash crops

There are two types of bluegrasses that are showing up in our field crops in southern Ontario. One of the reasons for this proliferation and spread of these 2 types of grass is the inconsistent control achieved from glyphosate use in herbicide-tolerant corn and soybean crops. The other reason is the lack of a residual herbicide in your spray programs.

Annual bluegrass and roughstalk bluegrass are the most common bluegrass species that are showing up across the local landscape. It is important to be able to distinguish between the two as they are not controlled by the same herbicides.

Annual bluegrass

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Figure 1. Source: Mizzou Weed ID website.


Annual bluegrass (figure 1) grows in clumps; the leaf blades are smooth and light green. Annual bluegrass can act as both an annual and perennial life cycle. In southern climates, a winter annual life cycle is most common. In northern climates, perennial biotypes exist which creep along the ground by way of stolons that root into the ground at each node. Both biotypes likely exist in Ontario and reproduce mainly from seed. Winter annual seed germinations tend to occur between September and October (60-80%) while the rest germinate in April through June. The seed of perennial biotypes can germinate throughout the season.

Roughstalk bluegrass

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Figure 2. Source: Country Guide article by Mike Cowbrough, OMAFRA

Roughstalk bluegrass, as can be seen in (Figure 2) is a perennial the spreads along the ground by stolons that root at each node. As the name implies the leaf blades are rough in texture. It reproduces by roots and seeds.

Control in cereals

If you have roughstalk bluegrass in a cereal crop your option for control is Axial herbicide. If you have annual bluegrass, Focus herbicide prior to planting winter wheat provides good control. If annual bluegrass appears in established winter wheat then control can be obtained by using Simplicity GoDRI. Emerged bluegrass species are more easily controlled when small, 2-4 inches tall, control can be reduced by up to 25% when spraying 10-inch-tall bluegrass.

Control in soybeans

Annual bluegrass

Glyphosate will control emerged annual bluegrass but does nothing for late-emerging new seedlings. Ontario research has shown that by including soil-applied herbicides in your spray program you can reduce late-emerging seedlings and seed dispersal. Pyroxasulfone, the active ingredient found in Fierce EZ, Zidua SC, and Focus, works well on controlling new seedlings. These products in Ontario trials showed 80% control; when tank-mixed with Sencor, control was raised to 90% effective.

Zidua SC by BASF has recently added a post-harvest application for annual bluegrass which coincides with the germination of winter annual biotypes. Trifluralin (eg. Treflan, Rival, Bonanza) is the only other herbicide with annual bluegrass on its label. It can be used in soybeans, dry beans and canola.

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Annual bluegrass control 8 weeks after application of Engenia + Zidua SC + glyphosate (left) compared to Engenia + glyphosate (right).

Roughstalk bluegrass

There is little to no research done in Ontario using Pyroxasulfone for control of seedling roughstalk bluegrass. Glyphosate, if sprayed early spring, is effective at controlling roughstalk bluegrass, but the later you delay application the control diminishes accordingly. In corn, nicosulfuron (eg. Accent) showed effective control. In soybeans, high rates of quizalofop (eg. Contender, Assure II, Yuma) also showed good control.

Scout your fields this spring and if you see anything unusual or new weeds popping up on the horizon be sure to contact your AGRIS or Wanstead Farmers Co-op crop sales specialist and we will be glad to assist you.

Have a safe and prosperous #plant21.

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