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The Cropwalker - Volume 3 Issue 19

Always read and follow label directions.

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Crop Conditions

Winter wheat earliest fields have flag leaf showing. Most fields have 1-2 nodes. (A rule of thumb is 10 days between 2nd node and flag leaf emerging with current weather) No serious diseases showing yet, but if you are spraying for weeds consider adding a fungicide. Corn Survey suggests 85-90% planted. Some areas such as Haldimand have not started. Earliest fields are emerging. Current weather suggests a lot of corn will come up in a hurry. Watch for crusting. Looks like we will get some days of sun later this week. If you can walk in the field and the soil moves, you do not have to worry about a crust. Soybeans Our survey suggests 40% of the crop is in and a lot will go in this week. If you are considering using dicamba on your beans now is a good time to use it so there is less chance of off target damage. Spring cereals are emerging well. Biggest mistake in growing cereals is delaying weed control. Once you can see the spring grain from the road get ready to spray. Critical weed free period in spring cereals is 3-5 leaf stage. New alfalfa is emerging well. You want to control weeds at 1-3rd trifoliate. If some plants are at unifoliate, they are safe to spray.

Figure 1 - Ontario Twitter Crop Progress for Corn
Figure 2 - Ontario Twitter Crop Progress for Soybeans


What does Frozen corn seed look like?

The picture below shows 1) frozen looking kernels that eventually emerge. The last picture shows one plant emerging normally while the one beside it has the tip frozen.

Layman’s Terms of Corn Emergence

The corn kernel germinates once it takes in water. This activates enzymes that start growth. The radicle (roots) start first. Then the part that will become the above ground portion starts to grow. The mesocotyl is protective tissue that guards the coleoptile as the seedling emerges. The mesocotyl pushes through the ground protecting the coleoptile. Once the mesocotyl detects light it stops growing. The coleoptile inside has been growing and continues to grow. The pictures below show corn (May 2) that has germinated. Then you see frozen tissue on the germinating kernel. This frozen tissue is part of the mesocotyl and some cells on the coleoptile. Fortunately, the first leaf inside was not frozen. That is because the cell sap is very concentrated, acting like anti-freeze. When the coleoptile emerges, the plant continues to grow. On May 19th you can row the corn. Thanks to Bob Thirlwall (Bayer) and one of his customers for sharing these pictures.

Figure 3 - Various Corn Pictures with Cold Weather Symptoms

Question Are you seeing any N / S deficiency in wheat in your area (even on fields that have had it applied?). I assume the cold weather is to blame.

Answer Yes. You could add more or just wait for the plant to take it up. S deficiency looks somewhat like N deficiency. BUT N deficiency appears on older leaves since the plant will take N from the lower leaves and move it to the new leaves. S is not mobile in the plant so the older leaves will show the light green colour attributed to N or S deficiency. And S will be more pronounced in areas that shed water and/or have low organic matter content.

Figure 4 - Sulphur Deficient Wheat

Sulphur Deficiency in Wheat (Source: IPNI)

Fungicides Increase Straw Yield

Data forwarded by BASF shows that spraying spring wheat with Caramba increased the straw yield by 303 lbs/ac and the grain yield by 7.8 bu/ac. But, if you also sprayed Headline AMP at growth stage 32 (2nd node), the straw yield was 644 lbs/ac vs. check. This also increased grain yield by 10 bu/ac vs check. This data was from spring wheat. BASF suggests that you should expect equal or higher yield response from winter wheat.

Cobutox/Embutox on Seedling Alfalfa

Cobutox or Embutox tends to be applied on the late side, time gets the best of us. Label states 1 to 4 trifoliates for crop safety purposes. Can go earlier, better to base on weed stage than alfalfa stage, but if possible, would not recommend going later than 3 trifoliate. Controls Lamb’s Quarters, Pigweed, and Ragweed. Add 28 mL/ac of MCPA Amine to improve control of Wild Mustard/Vol. Canola.

Weed Control in Spring Cereals – What’s registered, what’s crops safe and what to control?

If you can spray it on winter wheat, it is crop safe on spring wheat and Barley. Oats are the most sensitive. Here is a list a list of the most common cereal herbicides.

Figure 5 - Spring Cereal Herbicide Crop Safety

Weed Control in Winter Wheat Flag Leaf Emerged

Once the flag leaf emerges you must be careful spraying. Typically, by this stage weeds like chickweed, dandelion and field violet have done their damage as far as yield reduction. Generally, once weeds flower, they have done maximum damage. If you have small ragweed and lamb’s quarters, you can control them. Certain herbicides can be harder on wheat than others. Once flag is visible the number of products that can be applied really is a handful, the chart below from North Dakota State provides a good visual. Please note that not all trade names/actives have the same registration in Ontario. And as the graphic says, the label is the law.

Figure 6 - Spring Cereal Herbicide Application Timing Safety

Question. I seeded alfalfa on September 9th last year. It looked great last fall and now most of it is dead. What happened?

Answer Alfalfa needs to have a significant root mass to get through the winter. In Ontario, I like to have alfalfa summer seeded by August 10th or earlier. This allows the plant enough time to build root reserves to get through the winter.

Question I used 220 gm active metribuzin (Sencor) to control fleabane. I decided to plant shallow when the soil was cold. Is there a risk of injury since the label suggest I plant closer to 2” when using metribuzin?

Answer The label is old and has not been updated regarding planting depth. When the label was written there were a significant number of soybean varieties that were sensitive to metribuzin. The newer varieties appear to be more tolerant to metribuzin. When you plant with a drill there are often soybean seeds anywhere from 2” deep to lying on the ground. I do not ever remember seeing any of these shallow planted soybeans showing metribuzin damage symptoms.

Soil Crusting – Rain, especially heavy pounding rain, followed by bright sunny days. leads to crusting. If you leave a footprint when you walk across the field, you do not have a crust to worry about. Once you see a crust developing in the heaviest part of the field, know it will develop in the rest of the field. If you have a corn field that normally crusts, consider rotary hoeing before the crust develops. A rotary hoe will work if you get to it soon enough. The best rotary hoeing will occur when the ground is still wet in places. If the crust has already developed growers have successfully used corn planters, Aerway, RTS, and even cultivators to remove a crust. The process is not rocket science. Do two passes and if you like what you see, keep going. If you do not, try something different. If you have a crust in a soybean field the rules are different. Soybeans do not recover from crusted soils as well as corn does. Generally, your best bet on soybean fields that have crusted, and the beans have not emerged is to replant. The replant policy from seed companies and crop insurance does not discourage replanting.

Pre-Emerge Corn Herbicides

A brief opinion on which pre-emerge corn herbicide should be used where (based upon opinion and grower experience). Mileage may vary on your weed spectrum and management practices.

Acuron – best fit has been growers looking for full-season annual grass and broadleaf control. Must be applied pre-plant to 6-leaf. Good PRE option for conventional corn, provided you have a plan to control perennials in-crop.

Converge XT – Found best success at the 20-ac. rate when targeting warm-season broadleaves (Lamb’s Quarters, Pigweed, Ragweed). Use the 15-ac. rate if targeting Proso Millet. Weakness can be grasses and perennial weeds, if high or severe infestation. Narrow window for application at PRE to 2-3 leaf. Need to reduce the rate to 30 ac/unit when tank mixing with glyphosate on emerged corn.

Engarde – pre-mix of Elim and Callisto. Add Aatrex for more consistent broadleaf control. Crop safe from PRE to 2 leaf.

Focus/Zidua – Group 15 like Dual or Frontier. Adds residual bluegrass control. Do not apply Focus in-crop. A tank mix partner is suggested (Aatrex or Marksman).

Dicamba/Marksman – Corn must be planted prior to application. Less risk of crop injury if corn has emerged. Provides both knockdown and residual. Higher rate gives longer residual

Halex GT – Is a one-pass program for the one to three leaf in-crop on RR corn. It could be used PRE, prior to crop emergence, however, you have any some late season perennial weed escapes. Do not apply in-crop on conventional corn or with 28% UAN.

Integrity – best for growers on worked ground and wanting to apply 28% UAN. Can work on no-till or strip-till corn provided perennials are not too big, otherwise, regrowth can occur if the glyphosate does not translocate. Even at the high rate (0.45 L/ac), you may have to come back into cleanup with glyphosate, because of this, not targeted for conventional corn.

Lumax – is being phased out, it is a pre-mix of Callisto + Primextra. Performs best in the PRE to 3 leaf market on unmerged annual grasses and broadleaves. If emerged, add a tank-mix partner such as glyphosate.

Primextra II Magnum –Can be strip-tilled, worked in, left on-top or used in-crop. While the 1 L/ac rate has been promoted extensively, best performance has been at the 1.2-1.6 L/ac rate, especially when any incorporation occurs. Growers that use this product on its own pre-emerge will need to plan on a clean-up spray in-crop. Performs best when combined with a group 27, like Callisto, or a group 4, such as dicamba, in-crop.

2nd Pass of Wheat Timing – Do it!

If you have soft red or soft white wheat in the ground, you should have your 2nd pass of nitrogen on. If you are a hard-red wheat grower, and past 1st node (one bump on the stem), it is time to get your 2nd pass of N on. Hard Red Wheat research conducted by C&M Seeds and Yara suggests that waiting until the flag leaf has emerged will cause a yield reduction if using a product like 28% UAN streamed on over the top. Yield losses were minimized if a dry product like AmidaS (Urea/AMS compound prills) were used instead. Using AmidaS has provided as slight protein bump with minimal yield drag compared to using 28% UAN at growth stage 31/32. Food for thought. Data was replicated at Black Creek Research, sponsored by Yara Canada and C&M Seeds.

Figure 7 - C&M Seeds Fertilizer Timing x Product Type Trial HRW

Weed Density Ratings

Typically, a field requires “action” if you have a pressure rating of more than 5 light or 2 medium, or 1 high weed rating, depending on the weed species present.

Figure 8 - Herbicide Density and Action Threshold

Crop Yield Loss by Selected Weed Species by Weed Density

Figure 9 - Yield Losses in Corn and Soybeans by Selected Weed Species

Can I put too much fertilizer on?

I know more people that did not make it farming from not feeding the crop than people than did not make it farming from ensuring it had adequate crop nutrition. You cannot get blood from a stone. This does not mean you need to fertilizer the rented fields like your owned fields, but you should be feeding it something.

Weed Size Relative to Herbicide Label

The number one question I would ask when the inevitable phone call would come in around poor herbicide performance, was, what was the size of the weed at the time of application? After the grower assures that it was applied within the label, a quick trip to the field usually reveals that was not the case. For example, here is the registered weed stage for various products for a few different post-emerge products.

Figure 10 - Registered Herbicides and Weed Stage Example

Should I do a Burndown?

If the tillage pass is not going to take care of the weeds (dandelions, winter annuals, perennials, fleabane), you should do a burndown. Watch herbicide re-cropping or planting interval restrictions, if working the soil. Also, if you are no-tilling/strip tilling and going to a non-herbicide tolerant crop (conventional corn, edibles, non-gmo Soybeans) and have already sprayed a burndown, but did not apply a residual herbicide, you may need to add glyphosate when applying the residual herbicide. $5 worth of glyphosate goes a long way in ensuring you pre-emerge starts clean, and you are not relying on pull down.

What do Herbicide Weed Control Ratings Mean?

Figure 11 - PMRA Herbicide Label Effectiveness Rating Guidelines
Figure 12 - PMRA Herbicide Label Claim Guidelines

Source for charts: https://weedscience.ca/cwss-visual-ratings-scale/

Where do You Get the Response?

In discussion with another agronomist, some of the highest responding areas of the field to additional plant population, herbicides, or fertilizer amendments, are the lowest yield areas of the field. Consider the relative yield response in making agronomic decisions, not just the historical absolute yield in each field.

Last Week’s Mystery Weed – Another Winter Annual

Last week’s winter annual was common chickweed. It can also germinate in the spring, so calling it a winter annual is a bit of a misnomer. Main reason to control is that it can be a host for several non-beneficial insects such as wireworm, lygus bugs and thrips. In winter wheat the most effective herbicides are those that contain thifensulfuron-methyl/tribenuron-ethyl (Refine M/Barricade M), it is fairly easy to control in corn, as a number of actives are very effective, including glyphosate, Callisto, Atrazine and dicamba. Conquest can provide residual control in soybeans. For summer seeded crops, burning off Common Chickweed in the prior fall can ensure that it is not a hinderance or escapes spring tillage operations. Chickweed is very trouble some in some areas (Oxford county) in new seedings of alfalfa. I have seen numerous fields where chickweed prevented alfalfa from being established. Alternative is Harvxtra alfalfa. Control the chickweed with glyphosate and then seed a grass or grass mixture.

Picture 1 - Common Chickweed

Volunteer Soybeans Results in Corn Yield Loss?

Yield losses vary from 3.2 to 56% depending on plant density. Data suggest that low volunteer soybeans densities, yield losses are like velvetleaf or redroot pigweed, with 10% loss at 3 to 4 plants per square meter/yard. At the higher end of yield loss, I would expect that level to occur in fields with unharvested soybeans (which I have been getting a few calls on what to do). Best way to control volunteer soybeans, is to do a post emerge application at the V2 (2nd trifoliate) stage with a group 27 herbicide (Callisto, Impact/Armezon, ShieldEx) with atrazine or to use Lontrel. Dicamba is effective as well, however, it will not control Roundup Ready 2 Xtend Soybeans.

We hear a lot of people say that experience is the best teacher. Well, it’s a wonderful statement, it’s just not true. If experience were the best teacher, then everybody as they got older would be getting better. A lot of people go through experiences and they learn nothing. And they don’t improve themselves. I think evaluated experience is the best teacher. I think after the experience, we pull ourselves away and ask ourselves what did I learn from that?

- John Maxwell