The Cropwalker - Volume 4 Issue 14

Always read and follow label directions.

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Crop Conditions

Weather – April showers bring May flowers and they have started now. As a result, very little field activity last week. A few acres of cereals and forages and early peas. Nothing major planted. Winter wheat is greening up nice. A few more acres being ripped up but nothing major. Still will be less than 1-2% lost. A significant amount of Manganese (Mn) deficiency showing up. (Read more below and there is a lot to read) Forages you can now see how winter survival is. One field of extensively managed alfalfa is looking very poor. But if you intensively manage alfalfa, it will kill out. Manure if it is too wet to plant you will compact the ground by spreading manure. If you don’t have to consider saving it for later applications even if it means applying before beans.

Articles

Patching up alfalfa fields. You can no till annual rye grass into existing this alfalfa stands. This will give very little growth by first cut but will give feed for second and third cut. You do not have to be very precise. If the alfalfa is growing the annual rye grass will not establish. If the alfalfa has died out the grass will grow. You cannot seed alfalfa, but could seed red clover.

New seeding reminders

1.     Most common reason for failure is seeding depth. Generally, too deep. You want seed ½” deep. I like to see some seed on the top.

2.    Phosphorous is the most critical nutrient for establishment. If you cannot apply P with the seed broadcast on at least 2 years’ worth and work it in.

3.    Early seeding does better with no nurse crop. Once you get to mid-May or later using a nurse crop of oats helps establishment. Oats help to suppress weeds so that you may not have to spray. Typically spraying later seeded forages occurs when weather is hot and you risk damaging new seeding.

4.    If using a nurse crop of oats and peas, harvest the nurse crop when oats are in the boot stage. Leaving it later risks hurting the new seeding.

5.    If using a brillion seeder and the weather turns dry there is a good chance the seed will be too shallow to give a good stand.

6.    You can broadcast a nurse crop and then seed your forage crop with a drill or air seeder attached to a tillage tool or even an air seeder.

Manganese Deficiency in Winter Wheat

Is showing up in some wheat fields. It looks a bit like N or S deficiency, but if you have those on already you can rule them out. Severe symptoms are light green to grey to necrotic flecks between the veins. In oats it was once called grey fleck. Manganese must be in the Mn ++ form to be taken up by the plant. If there is air in the soil it converts to Mn O2 (manganese oxide). This manganese oxide cannot be taken up by the plant. If the soil is wet, this soil holds less oxygen and the manganese coverts to the readily available Mn ++ form. You often see streaks through the field where compaction from a floater or tracker has forced air out of the soil. These strips appear green. Remedy you must foliar spray manganese to correct the deficiency. If you apply Mn to the soil, it will quickly become unavailable. Products the standard for years has been Manganese sulphate. There are now numerous foliar products. Research by University of Copenhagen tested numerous products and all except the most popular product were as effective in curing Mn deficiency as was manganese sulphate. These products need a surfactant to glue the Mn to the leaf. Mn only enters through the leaf stomates. Manganese does not translocate within the plant. That means you have to coat the leaves with Mn. I have seen research where they painted part of a leaf with Mn. Within a few days the “painted “portion turned green but not the unpainted portion. You will need at least 2 applications. In Denmark where Mn deficiency is common, they may make 4-5 applications.

Variety Differences to Mn Deficiency

There is a wide range in varietal susceptibility to Mn deficiency. Part is to do with the plants ability to forage for Mn. Part is to do with the root exudates that lower the soil pH around the roots making Mn more available.

Significance of Mn Deficiency

This is a nutrient that can seriously reduce yield without any visible symptoms. In Denmark they use a rating of 0-90 on their spectrometer to measure the severity of Mn deficiency. If the field is 60 or lower symptoms are visible. But in the range of 60-90 you can have yield loss without and visible symptoms.

Mn and Winter kill

If plants are low in Mn going into the winter, they can winter kill. It is quite possible that some of the winter kill we are seeing is due to low Mn levels. Generally last fall was dry. This meant Mn not as available as in wet fall year. It is quite possible that individual plants or small areas of plants died due to lack of Mn. In Denmark on their deficiency soils, they make a fall application of Mn.

Spectrometer to measure Mn Deficiency in the field

This instrument takes readings that are instantaneous. The hand-held instrument sends a flash of light and the amount of light refracted indicates the Mn level in the plant. They are also experimenting using it to measure P sufficiency in a plant. (Different light waves)

Other Mn facts

1.     Mn helps form lignin in leaves. Mn deficient plants have a sort of floppy leaf. There is research to show that plants low in Mn are more susceptible to some foliar diseases.

2.    Mn deficiency is most apt to appear on soils with high pH. In Denmark growers use an ammonium-based nitrogen fertilizer placed under the seed to lower the soil pH to make Mn more available.

3.    High OM soils will have Mn deficiency

4.    If the wheat is green over the tile runs but light green between the tiles it is probably Mn deficiency.

Corn Burndown Products

Best option for crop safety is Eragon or Integrity. Can use the 30 mL rate of Eragon up to 120 mL/ac if you wanted, at more than 30 ml/ac of Eragon, I would switch to Integrity, as you gain residual grass, lamb’s quarters and pigweed control with the Frontier portion at a great price. Don’t forget the Merge and glyphosate!

Elevore is also registered. Apply Elevore 5 days prior to planting. This product would be preferred if the predominate weed in the field is dandelions, or you are trying to spray off in less than optimal weather conditions, saving the Eragon/Integrity for closer to planting if you have to respray.

Although the 2020 version of OMAFRA’s publication 75 Guide to Weed Control suggests you can apply dicamba prior to planting corn, I would not recommend this practice, and the Engenia label explicitly states do not incorporate dicamba prior to planting corn. All group 4s (2,4-D, Blackhawk, Dicamba, Elevore, Enlist Duo) should be used with caution prior to planting corn, especially if tillage is to be used.

Burndowns

I have never heard of a burndown being applied too early. Although lots of problems with burndowns being applied too late. Delaying burndown increases the probability of having big weeds to control and large root balls that will interfere with a good seed bed. If you have volunteer wheat plants, please do not try to “work them in”. Use a burndown to get rid of it. Tillage just moves the plants around. Extra tillage to break down roots destroys soil structure.

Winter wheat will be controlled with 0.5 REL/ac of glyphosate or 0.33 L/ac of what’s on the market today, (540 gm/L concentration) but since there are generally other weeds use a higher rate. Temperatures should be 7­C at time of spraying and overnight lows should be 5 C or higher for best control. The label says to wait 3-5 days between spraying glyphosate and working the ground. This is ideal and will depend on weed species, size and growing conditions. Bigger weeds and poorer growing conditions require a longer delay.

If you are spraying before Roundup Ready crop, time delay is not as critical as when crop is not Roundup Ready. If you are spraying 2,4-D to control Canada Fleabane a couple of things 1) The ester formulation is more active in cool weather and also breaks down faster than amine. Do not use the cheaper amine formulation, due to persistence of the residual.  2) You can spray 2,4-D ester one week before planting soybeans. But if you wait until one week before planting soybeans the weeds may be too big. Better to use a 2,4-D ester program now and if you have to come back to control more fleabane you can use a program with Eragon.

Reminder to use 2,4-D Ester for burndown, not Amine.

Have a few jugs of 2,4-D Amine left over and figure you will throw them in the tank to use them up when doing spring burndowns, think twice. You will run the risk of crop injury in beans due to the product being more persistent than 2,4-D Ester. How persistent? US data suggests waiting 30 days instead of 7 days if using the Amine formulation.

MCPA…

Hearing that anything co-packed with MCPA may or may not be in tight supply depending on how soon the supplier can have it here and what distributors/retailers have left over from last year. Products that have MCPA in it include Refine M/Barricade M, Pixxaro, Trophy, Buctril M, along with a few others.

Products that do not have MCPA in them include; Estaprop/Dicholoroprop, Infinity, Pardner, Refine SG, Enlist One, the 2,4-Ds, Simplicity, Lontrel, Peak.

Which wheat herbicide…?

At this point it might depend on what is available if you plan on going “early”. Buctril M or Badge for red clover if you can find it. Most of what is up right now is winter annuals/perennials, which should drive most of the recommendations. This means using something with more kick to it than Buctril M or MCPA. For fields with fleabane, top contenders are 2,4-D Ester, Estaprop, Infinity, Lontrel. Have mainly chickweed or speedwell? Maybe Refine SG + 2,4-D or Infinity is the right fit if Refine M isn’t available. Mainly dandelions/Sowthistle? Estaprop, Infinity + AMS, and Lontrel are all great options.

Wheat Spraying Weather Conditions

Just a reminder that as a rule of thumb, wheat herbicides should be applied 24 hours before or after a cold front (below 3C). If you have to, it is better to apply them coming out of cold front if you can’t observe the temperature restriction. This allows the plant to metabolize the herbicide. Some herbicides/fungicide combinations, such as Buctril M + Stratego Pro can cause more injury than others.

Growth Regulators

Keep an eye on wheat stage and weather conditions if you plan on using these products. For products that work on the lower part of the plant (Manipulator or Moddus), optimal timing is stem elongation to 2nd node (Z30 to 32). Ethrel works on the top part of the plant, and timing is at full flag leaf to swollen boot (Z37 to 45). Watch temperatures and tank mixing when applying these products. Observe similar restrictions to wheat herbicide/fungicide combinations. Belchim has indicated that Manipulator is still effective at cool temperatures due to its mode of action but should not be applied when there is a risk of frost.

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