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The Cropwalker - Volume 3 Issue 21

Always read and follow label directions.

June 2020 Complimentary Issue; Next complimentary issue will be September 8,  2020.

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Crop Conditions

Winter wheat is heading in earliest fields. Lots of fields with heads half emerged in Lambton. Flowering normally starts 3-5 days after head fully emerged. Crop is on normal development schedule. Stripe rust is showing up in Michigan but still no reports in Ontario. Now is time for T2 fungicide application if not already done. Several acres were sprayed at T1.5 as conditions were not right at T1 time and growers did not want to wait for a full T2. We have fields with sulfur deficiency showing. Consider applying 5 gallons ammonium sulphate to these areas. Starting to see Cereal Leaf Beetle adults in cereal fields, keep an eye out for CLB when scouting for flowers. Spring cereals should have weed control applied. Spraying 28% on cereals Field experience indicates that if you apply liquid nitrogen when the leaves are dry there is less leaf burn. Spraying just before a rain is good if you can do it. Also diluting liquid N with water helps. Those that use Chafer bars, instead of streamer nozzles, also have less burn. Corn Earlier concern about cold imbibing and frozen soils seems to have been unwarranted as most fields are emerging pretty good. Some areas of poor stands. At this point keep stands with 20,000 good plants. If you are considering replanting, best way is to kill stand with Assure II (if not Enlist corn) and replant. Earliest is 3-4 leaf stage and growing fast. There are numerous plants that are not emerging properly. This happens every year. Canada #1 seed must have 90% germination. So, if you have corn that is say 95% germ then 5 out of every 100 plants will not germinate. Or 1.3 plants in 1/1000 of an acre. When germination tests are done, if the seed produces a root (radicle) but not mesocotyl (top part) that counts as non-germinated. If you are checking a field and one is missing your eye is naturally attracted to the missing plant. On digging it up it may only have a root. That is normal. When you do your stand count If you dropped 34,000 seeds you should expect to have 32,000 plants. Dropping 32,000 seeds should get 29-30,000 plants. This year one CCA commented he is finding 2-5,000 fewer plants than seed dropped. Soybeans Some acres are being “touched up”. Tend to be heavier soils that crusted. Consider dropping 120,000 seeds/ac. Check out https://www.engeniaspraytool.ca/ for help with spraying dicamba. You can allow it to use your location to give probability of an inversion event. BASF have a great web site.  Forages first cut is started. Yields are average. One reader commented that by increasing the % grass in the mix and applying manure the grass is killing out alfalfa. If applying manure after first cut do it before there is much new growth. Typically, this is about 48 hours after cutting. New seedings are generally ready for weed control. Embutox has less injury if applied prior to the 4th trifoliate. Following the 4th trifoliate, the alfalfa plant metabolizes the Embutox, and leads to injury.


Question: I sprayed Glyphosate and the Plants Still Look to be Alive

Answer They may look alive, but they are dead. There will be an unsprayed area somewhere in the field that is the check. If you cut flowers and put them in the water in the fridge, they will look alive for at least a week. But they are dead. The same goes with the plants you sprayed with glyphosate. The cool weather and lots of moisture in the soil makes them appear to be alive but they are dead. Respraying will not make them die faster.

Embutox RatesThe high rate of Embutox was registered when most fields had a nurse crop to protect the alfalfa. Once growers went to direct seeding, they found some damage with the high rate especially if sprayed when hot. An accepted rate for Embutox is 0.5 L/ac. This rate does not give as much weed control as the 0.7-0.9L/ac but seems to hold the weeds back.

Powdery Mildew in Wheat – With warmer temperatures, we are seeing increasing levels of powdery mildew in wheat. The fungus overwinters in crop residue. Spores are dispersed in early spring by wind and infect susceptible plants. The disease favours warm humid weather. It does not need wet conditions, unlike many other fungi. Dense canopies are ideal for powdery mildew growth. Small whitish-grey fluffy/powdery spots grow on the upper leaf surface while the underside of the leaf will turn pale green to yellow. Powdery mildew seriously reduces yields if the flag leaf and second leaf become infected and reduces straw quality. Early-season control is recommended when 5-10% of the lower leaves are infected (this will also help to limit later infection). Symptoms on the flag leaf (1% of leaf) and the second leaf (3-5% of the leaf) call for immediate action, especially if the weather forecast calls for warm, humid conditions

Aphids in wheat We can probably find some aphids in every wheat field every year. This year a little bit more looking going on. There are numerous beneficial insects that control aphids. You need 15/stem before heading and 50 per head after head emergence to warrant control. They tend to build faster when it is hot and dry. I believe some rains will wash some of them from the plants. What about spraying for them when applying a fungicide? Naa Not a good idea. Adds to cost and reduces the number of beneficial insects.

Corn Emergence ProblemsCorkscrew mesocotyl The mesocotyl is that part of the corn seedling below the spike. If conditions are unfavourable, it takes a corkscrew appearance. The mesocotyl emerges from the corn seed and grows to the dent end of the seed. If the corn seed is lying so that the mesocotyl is below the seed, it can develop the corkscrew appearance. If corn seed is laying the other way, the mesocotyl grows straight up. The fluctuating soil temperatures are the main reason for the cork screwing this year. It can be caused by sidewall compaction, lumpy soils, or herbicide uptake. This year the dry soils, sunny days, and cold nights lead to wide soil temperature fluctuations. Yellow corn is caused by delay in emergence. Some corn that was planted deep, or just took a long time to emerge is yellow. It will turn green once the sun hits. Purple corn should become more prevalent this week. It is caused by hot sunny days and cool nights. During hot sunny days, the plant produces sugars. It generally translocates these to parts of the plant during the night. If nighttime temperatures are cool there is less translocation. These untranslocated sugars form anthocyanins that give corn its purple colour. There is a difference in hybrids for tendency to produce purple colours.

Picture 1 - Corkscrew Corn

Leaf over vs. Leaf tips vs. Leaf Collars

Occasionally I will hear various people in the industry talk about different corn staging methods when it comes to assessing growth stage. Now that we are well into corn herbicide timing, it is critical to ensure we are on the same page. Most herbicides labels in Canada use the leaf over method, in the United States, many labels will use either plant height, or the vegetative method. And yet others talk about leaf tips. Chart below from OMAFRA Publication 811 – Agronomy Guide to Field Crops. Most post-emerge corn herbicide labels in Ontario end at 8 leaf-over.

Figure 1 - Corn Vegetative Staging Methods (OMAFRA Pub 811)

Three Possible Types of Fleabane

When scouting fields, it is important to mark which ones have fleabane, as Canada Fleabane can become a significant problem in 3 years. However, there are two other biotypes that are common in Ontario that are not glyphosate resistant. These are Annual and Philadelphia fleabane. If you are still getting good control of fleabane with glyphosate, it could be one of these other biotypes. The Ontario Weed ID Guide for Field Crops provides a few clues on how to tell the differences. The guide is available at this link; https://fieldcropnews.com/2016/09/weed-id-guide-for-ontario-crops/

  1. Canada Fleabane - Canada fleabane has narrower and darker green leaves with margins that are generally less toothy. Annual fleabane has larger and broader leaves and showy “daisy-like” flowers.
  2. Annual/Rough Fleabane - The leaves of annual or rough fleabane are much broader, more coarsely toothed and are usually lighter green. The flowers of annual or rough fleabane are much different than Canada fleabane, resembling a daisy flower, although much smaller.
  3. Philadelphia Fleabane - The flower heads of Philadelphia fleabane are like annual fleabane in shape and size but are usually pink to purple in colour. Its upper leaves are broader and strongly clasp the stem.

Picture 2 - Canada Fleabane (Source: fieldcropnews.com)
Picture 3 - Annual Fleabane
Picture 4 - Philadelphia Fleabane (With some deer feeding)

Spraying new seedings This is the week to do it on most farms. Alfalfa should be at the 1-4 trifoliate to apply 2,4-DB (Caliber, Cobutox, Embutox) 2,4-DB is the butyric form of 2,4-D. Young alfalfa plants cannot change the butyric form to the amine form. Once they get to the 4th trifoliate, they can change the butyric form to the amine form. Weeds and older alfalfa plants are killed by the amine formulation. It was originally registered at 0.8 L/ac. It was weak on common mustard. I worked with the company that figured out that adding 28 ml of MCPA Amine 500 would control mustard. But this small amount of MCPA was hard on alfalfa so the rate was reduced to 0.5 L/ac 2,4-DB when MCPA was added and timing reduced to the 3rd trifoliate. Since then spraying 2,4-DB at 0.5 L/ac has become a common use. This rate is not as effective but slows weeds down to let the alfalfa get ahead. Adding CropBooster has become common.

Spraying Oats, Peas Underseeded to alfalfa. There is no product registered to spray this crop mix. Using 2,4-DB is hard on peas. If the weeds are bad better to sacrifice the peas rather than the new seeding.

Controlling Horsetail with Broadstrike Broadstrike can be applied in corn up to the 8-leaf stage. (Publication 75 says 2-leaf stage) but it is registered to the 8-leaf stage. It can be tank mixed with glyphosate. For soybeans, Broadstrike must be applied before the soybeans are up. Watch rates, as the registered rate in corn is lower than in soybeans.

2,4-D vs. MCPA and the Various Formulations

There are a few formulations of these phenoxy herbicides. Here is a quick rundown. Both 2,4-D and MCPA are group 4 – plant hormone type herbicides. 2,4-D’s formulation tend to be fast acting and have limited residual activity, relative to their MCPA counter parts. There is a difference among crops as to which is safest.

Esters vs Amines. Vs Sodium Salts. When 2,4-D or MCPA is produced, it is made as an acid, and then requires a salt formulation to stabilize it. The salt that is attached determines how persistence it is in the soil, how it enters the plant cuticle, and how volatile it is. It also determines mixability in tank mixes with other crop protection products or fertilizers. See chart below.

Figure 2 - Differences in between 2,4-D and MCPA and various formulations

Alfalfa Wheel Traffic Damage

Dr. Dan Undersander at the University of Wisconsin has researched the effects of wheel traffic following cutting. Bottom line, the yield for the following harvest was reduced by 6% for EACH day of delay in traffic after application. The yield loss was largely due to the stem breakage from tires. This means you should be applying manure immediately following harvest.

Figure 3 - Wheel Damage to Alfalfa Yields the Following Harvest

Tire Traffic Article on Alfalfa from UW

Looking Ahead for HarvXtra Alfalfa

As your harvesting your pure stands of HarvXtra or Roundup-Ready alfalfa make note of the weeds present. Of few of the stands I have been in, could warrant an application of glyphosate to clean up dandelions and common chickweed that has crept in. When making this application, consider adding Priaxor to control Common Leaf Spot. BASF has suggesting the timing for this tank mix is 10 days post cutting, with a pre-harvest interval of 14 days.

Roundup Transorb is registered up to 1.33 L/ac, so use the rate that will control the targeted species. Restrictions for the season are maximum of 3 applications of glyphosate, and a minimum of 5 days between application and cutting.

The tank mix for most fields would look like this; 20 US Gallons/ac water, 1.33 L/ac Roundup Transorb HC , 0.12 L/ac Priaxor.

Picture 5 - Common Leaf Spot on Alfalfa

Applying glyphosate to Direct Seeded HarvXtra Alfalfa (from the Roundup Transorb HC Label

New Stand Establishment (Seedling Year): Due to the biology and breeding constraints of alfalfa, up to 10 percent of the seedlings may not contain a Roundup Ready gene and will not survive or thrive after the first application of this product. To limit the undesirable effects of stand gaps created by the loss of alfalfa plants not containing a Roundup Ready gene, an application of this product should be applied at or before the 4 trifoliate leaf stage of alfalfa during the establishment (seedling) year.

Estimated Wheat Yields at Heading

This will be directionally correct. When timing for FHB application, to keep it interesting, I like to run a few scenarios on approximately what wheat yields will be for the year (using the previous year’s thousand kernel weight (TKW). Please note that grain fill can significantly impact the result (based upon my 2019 experience trying to estimate yields). Count the number of heads in a square meter or yard. Count the number of grains per head. Multiple by the historical thousand kernel weight. You could use the formula below to then get bushels per acre. This method will work with any cereal crop if you want to save it for future use. Example below.

Figure 4 - Estimating Cereal Yields

How temperature inversions form. During daytime hours, dry air naturally cools with higher altitude. Solar radiation warms the earth’s surface and, during days with little cloud cover, convection creates winds and gusts that transport air vertically. As sunset nears, the earth’s surface is no longer heated by the sun. As a result, the ground, and the air adjacent to the ground begins to cool more rapidly than parts of the overlying atmosphere. Heat from the warmer air is transferred back to the soil, creating a layer of cooler, denser air near the soil surface. This process creates a temperature inversion, where the cool air at ground level has warmer air above it through the very lowest levels of the atmosphere. (Notes from BASF)

Attitude gives you no advantage during good times because, during good times, everybody has a good attitude. When things are going my way, my attitude is fine. But it is when the adversity comes and the challenges come, that is when my attitude becomes what I call the difference-maker.

– John Maxwell