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VOLUNTEER CANOLA IN WINTER WHEAT – A CAUSE FOR CONCERN?

With good soil moisture conditions, warm soil temperatures and generally favorable weather, winter wheat is emerging quickly across Manitoba. However, those same conditions are also allowing volunteer canola to grow very well.  And in some cases, volunteer canola will be present in establishing winter wheat fields in higher than wanted populations.

There are really two camps in regards to management of volunteer canola post-emergence in winter wheat in the fall. One is to wait for the first killing frost of the fall to control the volunteer canola, with the assumption the weed pressure is not sufficient to impact yield or crop establishment.

The other is to remove the early weed competition through herbicide application. There are a few products available for fall application after winter wheat emergence for control of volunteer canola. These include a bromoxynil/MCPA ester tank mix, Infinity (pyrosulfatole & bromoxynil) and Simplicity (pyroxsulam – does not control Clearfield volunteer canola). However, remember that a fall application of 2,4-D or dicamba products is not recommended (or registered) as it can cause crop injury only seen the following year at heading, as well impact yield potential (see photos below).

2,4-D injury in winter wheat

2,4-D Damage to Winter Wheat (Photos by Manitoba Agriculture)

For more information on registered products, application timing and rates, refer to the Guide to Crop Protection at http://www.gov.mb.ca/agriculture/crops/guides-and-publications/pubs/crop-protection-guide-herbicide.pdf

If herbicide application is considered, are there economic thresholds available, i.e. what density volunteer canola will cause yield losses that are economically greater than the cost of control?  Unfortunately, there is limited data available to assist producers and agronomists. In a 2-year study done in Ontario, yield response to increasing volunteer canola densities was variable in both years of the trial (Table 1). In 2004, the volunteer canola plant density of 760 plants/m2 was significantly lower than the other treatments.  However, there were no statistical differences in winter wheat yield at the various volunteer canola densities in 2005. Therefore, ‘it is inconclusive as to the density of volunteer canola that will significantly reduce winter wheat yields’.

Table 1. Winter wheat yield at various densities of volunteer canola in Ontario (2004 & 2005).

Winter Wheat Yield at various densities of volunteer canola 2004 and 2005

Source: Controlling Volunteer Canola in Winter Wheat
by F. Tardif, P. Smith (University of Guelph) and M. Cowbrough, OMAFRA

 

Fertility Considerations – N Uptake. Another factor to consider with a significant growth of volunteer canola is the amount of nitrogen the canola is utilizing prior to being killed by fall frost or herbicide application. A former Manitoba Agriculture staff person based out of Stonewall did some investigating in fall of 2008 into how much N uptake by volunteer canola was occurring in one of his producer’s fields.

Volunteer canola in winter wheat

Volunteer Canola in a Winter Wheat Field near Stonewall, MB. (Photo by Manitoba Agriculture)

He collected and weighed volunteer canola plants from two locations (2.79 square feet area) in one winter wheat field in early October. The dry matter weight of volunteer canola was calculated to be 791 lbs of dry matter per acre.  The samples were also submitted for tissue analysis and test results indicated the total nitrogen content at 5.02%.  Using 5% for the total nitrogen content results in 39.5 lbs of nitrogen taken up by the volunteer canola to that point. However, much of that nitrogen would be released for the crop next year.

Some other points to consider is some of that nitrogen might be lost overwinter in wet conditions – so the canola is functioning as a ‘catch crop’. However, the bad news is if producers have applied N during seeding or later in the fall, the canola is tapping into ‘applied N’ which is not desirable. And as always, banding is better than broadcast, especially to limit weed uptake of N.

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist; Jeanette Gaultier, Provincial Weed Specialist; and John Heard, Crop Nutrition Specialist; Manitoba Agriculture

Manitoba Agriculture on Twitter: @MBGovAg
Manitoba Agriculture on YouTube: www.youtube.com/ManitobaAgriculture
Manitoba Agriculture website: www.manitoba.ca/agriculture

 

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Warm Soil Means Fast Emergence….So Go Scout!

With most soil temperatures across Manitoba averaging over 10C, and the good soil moisture, crops planted are emerging quickly!

So, great news, but what this means is it is time to get out and start scouting!

Things to look for are:

  1. Emergence, plant stands, patterns in field – this can indicate if seeds planted evenly, but can also you could indicate early issues like cutworms, soil-borne disease and herbicide residue injury.
  2. Weeds species, numbers and size – if you crop is coming up this fast, so are the weeds!  Targetting the weeds when they are small and knowing the species so you can choose the right product and the right will really help with the control.  Make sure those little yield-robbbers don’t get to use the sun, moisture and fertilizer instead of your crop.
  3. Insects – cutworms were mentioned before, but more look more specifically for the damage on the plants if you can’t see the insect, as that can help with identification.  Are leaves clipped off leaves at or above the soil vs. chewed with ‘shot-gun’ hole marks in leaves.  Keep in mind the economic thresholds for control!
  4. Other funny stuff ?  Keep these in mind too when out scouting and mark down spots (or GPS tag) to monitor as the days go on to see how they progress, sometimes it takes a couple of days before things become obvious.  When in doubt give the Crops Knowledge Centre a call at 204-745-5663.

Submitted by: Anastasia Kubinec, Oilseed Crop Specialist, MAFRD Crops Knowledge Centre.

Resources:

MAFRD Guide to Crop Protection: http://www.gov.mb.ca/agriculture/crops/guides-and-publications/index.html#gfcp

Weed Identification: http://www.gov.mb.ca/agriculture/crops/weeds/

Insect Identification: http://www.gov.mb.ca/agriculture/crops/insects/index.html

 

 

 

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WHEN TO WORRY ABOUT HERBICIDE INJURY IN CROPS

Submitted by Jeanette Gaultier, MAFRI Pesticide Specialist

We cautioned last week about herbicide application in cool temperatures. Since the 2013 growing season has not been setting records for heat, you may be stuck trying to balance optimal temperatures with recommended herbicide application timings. 

Crop injury in some situations may be unavoidable since both temperature and incorrect crop staging affect crop tolerance to herbicides.  The good news is that you may not need to be concerned if you see symptoms in your crop post application since not all injury contributes to yield loss.  

  • Growth Setback – Stunting of cereal crops treated with certain group 2 herbicides (e.g. Everest, Simplicity) or with Avenge is possible but generally will not affect yield.  Improper timing or cool temperatures during group 1 herbicide application can also cause setback.  Do not worry about yield penalties though, unless stunting is severe or other growth setbacks, such as reduced tillering or stem/head kinking, are present.
  • Chlorosis –Pale plants and chlorosis are indicators of reduced photosynthesis, a process necessary for crop growth.  However, slight chlorosis of leaves and growing points will not lead to decreased yields if plants are able to ‘grow out’ of the stress early in the season.  For example, beans treated with Basagran + group 1 herbicide may have both green and yellow leaves on the same plant without affecting growth.  Cool temperature application of group 2 herbicides and/or glyphosate may also cause slight chlorosis, that crops can grow out, depending on the severity.  Do not worry unless symptoms are severe; plants are more chlorotic than not or deformed growth tips, necrosis are also present.

The above are generalizations and yield penalties from herbicide injury in specific crop situations can vary depending on the severity of injury symptoms, crop growth stage as well as other factors that may be contributing to crop stress.

If you are concerned about your crop or want a second opinion, crop samples can be submitted to your local GO office or the Crop Diagnostic Centre.  MAFRI staff are able to provide visual assessment of crop injury only; you may be referred to a private lab for herbicide residue or nutrient testing if assessment of the symptoms is inconclusive. 

 

 

 

 

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