The Prairie Giants Crop Report

Field observations at your fingertips

September 16, 2021

Taylor Kurtenbach

Welcome to the Prairie Giants Crop Report! We’ll be breaking down our observations from the field into a concise, semi-regular report.

Wild oats

Managing Resistant Wild Oats
Combines are rolling, with majority of the wheat off and many working on canola! Yields are better than expected considering the moisture constraints growers faced this year. Inglis area has received approximately 5” of rain this fall, which should help replenish the soil reserves for next year! Over the past few years, we have been noticing more wild oat escapes. These escapes are especially evident at harvest. We have done a fair bit of testing and have found lots of group 1 and 2 resistance.

Wild oats are one of the top herbicide resistant weeds in the Prairies, with known resistance to herbicide groups 1, 2 and 8[1]. It is also likely that wild oats will develop glyphosate resistance in the future[[2],[3]]. In 2016, Hugh Beckie conducted a weed survey in Manitoba. Of the

fields surveyed that had wild oats present, 79% of them had herbicide resistance of some kind; 78% of the fields had group 1 resistance, 43% had group 2 resistance, and 42% had group 1 and 2 resistance[4]. The following table from Saskatchewan’s 2021 Crop Diagnostic School[5] (Herbicide Resistant Weeds and Herbicide Resistance session) shows how quickly the population of herbicide resistant weeds can increase. If there is one plant in a million that is naturally resistant to the applied herbicide, by the 5th application of the same herbicide up to 60.5% of the population may be herbicide resistant.
Treatment Year% of Population Herbicide Resistant
Base population0.0001% (one plant in a million)
1st application0.01%
2nd application0.02%
3rd application0.3%
4th application4.2%
5th application60.5%

Did you know, one plant per square foot can reduce yields of wheat, barley and canola by 10%[6]? This is significantly less when wild oats are less advanced than the crop. For instance, in wheat when there are 10 wild oats per square metre the yield loss is:

10% when the wild oats are 1-leaf stage ahead of the crop

%

6% when the wild oats are the same stage of the crop and

%

3% when the wild oats are 1-leaf stage behind the crop[1].

%

Therefore, anything you can do to get the crop ahead of the wild oats will make a big difference. Management strategies include:

1. Ensure good crop establishment – use certified seed, be mindful with fertilizer placement, and increase your seeding rate.

2. Grow a diverse crop rotation – include crops with different life cycles (winter annual, perennial), different crop types (winter vs. spring, grass vs. broadleaf, perennial vs. annual), and at least 3 different crops in rotation. By varying the crops you grow, you are also switching up the herbicide groups you use. Crops like barley, canola and wheat are stronger competitors than flax and oat[7].

3. Apply a pre-seed burndown prior to crop emergence. By using multiple modes of action (glyphosate + tank mix partner) that are both effective against the target weed, it decreases the odds of the weed developing resistance as it is unlikely that it would be resistant to both MOAs. Products Focus and Olympus are both registered for suppression of wild oats. 

4. Practice herbicide rotation – rotate between in-crop applications of groups 1 and 2 in your wheat.

5. Scout – checking for herbicide efficacy after application can help to identify resistance early.

6. Sample suspected plants for herbicide rotation.

7. Use soil applied herbicides like Avadex, Edge and Fortress in your rotation for wild oat resistance management. 

Fall is a perfect time to apply these products! By applying in fall there is no delay in seeding, like with a spring application, and it is one less thing to worry about during the busy spring season. The product you use depends on your main weed concerns.

Avadex

Control of wild oats only.

Fortress

Control of wild oats and suppression of select broadleaves.

Edge

Control of select broadleaves and suppression of wild oats.

Avadex and Fortress are registered in a variety of crops including wheat, barley and canola while Edge is registered in broadleaf crops only.

For a full list of weeds controlled and registered crops, check out the product labels here.

Rates vary depending on time of year, crop and organic matter levels. Products can be applied anytime after October 1st and should be the last pass of the field. After application, products need to be incorporated with heavy harrows to reduce volatilization losses. Interested, but need help deciding on the best product and rate for your farm? The crew at Prairie Giants is here to help!

Wishing everyone a safe and successful rest of your harvest!!

Sources
[1] Government of Manitoba. 2021. Guide to Field Crop Protection 2021.
[2] Jones, T. Herbicide Resistance in Manitoba. Manitoba Pulse and Soybean Growers. [Online] Available: https://www.manitobapulse.ca/2019/06/herbicide-resistance-in-manitoba/
[3] Hilderman, Andrea. 2014. Manage Wild Oats with These Five Tools. Grainews. [Online] Available: https://www.agcanada.com/wp-content/uploads/2014/04/GNN140408.pdf
[4] Beckie, Hugh J., Shirriff, Scott W. and Leeson, Julia Y. 2016. Manitoba Weed Survey Herbicide-Resistant Weeds. Agriculture and Agri-Food Canada. [Online] Available: https://www.gov.mb.ca/agriculture/crops/weeds/pubs/hr-weed-survey-aafc-report.pdf
[5] Government of Saskatchewan. 2021. Crop Diagnostic School (Herbicide Resistant Weeds and Herbicide Resistance session)
[6] Barker, Bruce. 2020. Weeds to watch for in Manitoba. Top Crop Manager. [Online] Available: https://www.topcropmanager.com/weeds-to-watch-for-in-manitoba/
[7] Government of Manitoba. Wild Oats. [Online] Available: https://www.gov.mb.ca/agriculture/crops/weeds/wild-oats.html

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