12 min read

The Cropwalker - Volume 4 Issue 22

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Crop Conditions

Weather – we continue to be ahead of average for CHUs. Soil moisture across the province is generally pretty good. Some farms got a good 2” rain and many farms received at least ½”.  Winter wheat is progressing quickly and could see some wheat harvest in last days of June. Lots of fields sprayed for Fusarium last week. Corn is 5-8 leaf stage so many fields are at or past the stage for many herbicides. When counting corn leaves, do not forget to count the ones that were frosted off. Soybeans emerging to second trifoliate. We will see first flowers probably by June 25th. Many post herbicides should be sprayed before soybeans flower. First flower will probably be a week earlier than normal. Forages new seedings are 3rd -4th trifoliate. Be careful about spraying for weeds now. First cut is continuing with most fields having better than average yields. Second cut in earliest fields is about 12-14 days away.

1.     Spraying Be sure and double check all of your mixes. Have had a few noticeable errors this year. Someone spraying a wheat herbicide/fungicide mix soybean ground. Thought Infinity and Stratego Pro were soybean herbicides. Another spraying 2,4DB on established alfalfa. And a few others.

2.    Spraying IP soybeans for broad leaf weeds or forages be sure to use 20 gallons of water. If you are a custom sprayer insist. If you are getting a custom sprayer, tell them you want 20 gallons.

3.    Watch for conditions that can cause off target movement of dicamba. Here is BASF website again https://www.engeniaspraytool.ca/

4.    If you just have to spray, crops will break down herbicides in the first 8-12 hours. Much better to spray in the evening than in the morning. Night spraying of some products might be an option. Currently day time winds are preventing a lot of spraying

5.    There are a lot of products sold out. You will need to go back to Publication 75A to check for your replacement product will do.


Do not pass go, do not collect $200, go directly to controlling your weeds.

Alfalfa weevil This insect obviously can’t read. The book says that if you cut alfalfa that will be good enough control. Ryan Benjamins CCA in Sarnia area has fields that were cut and 2 weeks later weevil have eaten pretty much everything. It appears that the cutting occurred before all the weevils had hatched. I wonder also that since we are cutting at 2 ½” – 3” whether that is making a difference. When original research was done on alfalfa weevil, we were cutting shorter. The higher cutting height is leaving more uncut stems that include weevil eggs.

Book your soil testing for post wheat harvest now.

If you have not already lined it up, now is the time to book any soil testing/field mapping to be done post-wheat harvest. Especially those critical acres getting a manure application or fall fertilizer.

What soil sample package should you be requesting for fall soil testing?

It depends on a few factors, known fertility issues, soil type, crops in the rotation. Typically, at a minimum I would do Package III if ordering from SGS, or S1B from A&L. Then add micronutrients as required.

Perennial Sow thistle

How much can Perennial Sow-Thistle reduce yields? In corn, 4% at 1 plant per meter squared, 15% at 5 plants per meter squared. Soybeans 5% at 1 plant per meter squared, 20% at 5 plants per meter squared. This is under the assumption plants are not controlled in season. This weed is easy to suppress. It is a perennial, so you need to control it at least 3 times. Most growers spray it two times and figure it is gone. But it is not. You have to be serious about controlling it. In Roundup Ready soybeans use 2x rate of glyphosate.

Best Herbicides for Perennial Sow-Thistle in Conventional Corn following are the top-rated options.

Marksman – 90% @ 1.5 L/ac, Distinct – 80 % @ 115 gr/ac; low rate dicamba – 80%; Peak 80%. Round-up – Ready corn -> Lontrel + glyphosate – 90% (watch rates for recropping).

For conventional soybeans, the top-rated options are.

Clean Sweep, Basagran Forte, Blazer or Classic all provide similar level of top growth control at 70%. My pick is usually Classic. Best option is glyphosate pre-harvest, to reduce populations long-term.

Alternatively, if you have a roundup-ready crop planted; glyphosate @ 1 REL/acre is the best value for the control – 75%. The 2x rate provides 85% control.

Lontrel EC (clopyralid) is an old herbicide. It is a group 4, which is the same group as dicamba, 2,4-D, MCPA. It does not have the volatility of some of the other actives in this group. It does not have as severe temperature restrictions as some other Group 4 actives. Last year it was introduced in a significant way. It was very successful. As a result, there is a bigger demand for it this year, resulting in it being in short supply. Growers that have used products such as dicamba or Peak in-crop on corn are giving this herbicide a shot to control perennial weeds. Many reports positive results from the experience. But watch recropping. Current registration allows you to plant soybeans 10 months after 101 ml rate. Still 22 months for alfalfa. This year they are researching the replant time for alfalfa.

Problem weeds

Glyphosate Resistant Fleabane in corn.

Acuron up to 6 leaf, Marksman up to 5 leaf, Distinct up to 6 leaf, (do not mix with glyphosate), Engenia/Xtendimax up to 5 leaf, Pardner + Atrazine 4-8 leaf. Lontrel up to 8 leaf.

Tufted Vetch – Distinct or Callisto in conventional corn has been proven to be the most effective. Callisto, or Dicamba can be tank-mixed with glyphosate in Roundup Ready. Late post is ideal for maximum kill, will require a two-pass approach to avoid significant yield loss. I have also been using Lontrel with very good success as well.

Controlling Volunteer Corn in glyphosate tolerant Soybeans

It is much cheaper than in the past to control volunteer corn. If you must spray for weeds, and already have volunteer corn up, add the graminicide to your glyphosate on the first pass. If you have to come back a second time, so be it. Only time I would wait, is if volunteer corn was the only weed in the field. This is the opposite of what we use to recommend in the past, which was wait for everything to be up, and then spray, just prior to canopy closure.

Ragweed Control in IP Soybeans

If ragweed got by your pre emerge product there are some choices. Basagran, Reflex, Classic (if not 2 group resistant, almost all areas growing soybeans are likely to have group 2 resistance), will control smaller ragweed (2-6lf) Blazer will control ragweed up to 8 leaf. I have found the lower rate of Blazer with surfactant can be more effective than the full rate. You will have more burn with surfactant. High water volumes are a must regardless of product.

Spraying Reflex, Pinnacle and Classic on Hot Days

Reflex is safer on white and black beans than on soybeans. If spraying soybeans, you cannot reduce the surfactant rate and maintain weed control. On hot days with bright sunlight (27-28 C and up), it is best to wait until 5:00 p.m. before spraying. If you can wait until later in the evening, even better (weed control may suffer with group 14 herbicides, like Blazer and Reflex). You want the plant to be able to break down the herbicide in the first few hours after application. The same is true with Classic and Pinnacle. Do not apply full rate Classic and Pinnacle in a tank-mix. These three products can all damage beans. You have to decide if the weeds will hurt yield more than the damage the herbicide will cause. There are a lot of other tank mix dos and don’ts. Check with your dealer. The hottest tank mixes are combinations of Reflex and Classic +/- grass herbicide or Reflex and Pinnacle +/- grass herbicide. I would rather injury the beans and control the weeds than see weed escapes.

Getting the Most from Reflex

Notes from Brian Woolley with Syngenta. Count on spraying Reflex for ragweed 20-21 days after planting. To get the most from Reflex on hot days when the weeds have “hardened off” you must do certain things. 1) Use flat fan nozzles not AIs. 2) Use 20-25 gallons of water. 3) Use the high rate of Turbo Charge (or similar surfactant) at 5L/1000 L water. 4) Add 1.0 L/ac 28%. 5) Spray before 9 P.M.

The common factor of Blazer, Liberty and Reflex

All three require sunlight to kill the weed. Think about Eragon. You get the best burndown or pre-harvest control when you spray it during the middle of the day. Eragon is in the same herbicide group as Reflex and Blazer. We typically don’t recommend that these be applied in the middle of the day due to crop injury, but it would provide the best weed control.

Adding Non-Ionic Surfactant (NIS) to Soybean Herbicides

The amount of surfactant you add is an art. The surfactant helps to cut through the cuticle of broadleaf weeds. Weeds like ragweed and velvetleaf form a thick cuticle under hot, dry conditions. The hotter and drier the conditions are, the thicker the cuticle. Some products need a 0.2% NIS v/v. As weeds get bigger and tougher it is common to increase the rate up to 0.3% and even 0.5% v/v. The addition of 28% can make these products even hotter. For instance, adding 28% often helps to control velvetleaf and lamb’s-quarters. With many of the broadleaf products, spraying in the heat of the day gives the best kill but also burns soybean leaves more. A compromise is to spray mid- to late afternoon and evening. This gives the benefit of burning the cuticle of the weeds but allows the soybean plant to break down the herbicide in the cooler part of the day. Generally, broadleaf products are harder on soybeans than grass products. The table below converts rates of NIS to L/100 US gals.

Adjuvant Volume/Volume Chart

Whenever I don’t have this chart at my side during post-emerge spray season, I’m not long looking for it. Here’s a copy for you as well.

Figure 1 - Surfactant Rate Chart

Q I need more SureMix. What can I substitute?

Ans While not completely identical it is common practice to interchange SureMix and Turbocharge. For a complete list of adjuvants, additives, compatibility, and adjuvants, go to page 81 OMAFRA Publication 75 A Guide to Weed Control Field Crops

Publication 75 A

Guide to Weed Control - Field Crops

Spraying glyphosate on corn. Label states you can spray up to the 8-leaf stage. After that stage it is hard to get good coverage. You can spray glyphosate under hotter conditions without affecting corn than most other products. You have to be concerned about off target movement with glyphosate the same as with other products. Part of the issue with spraying glyphosate past the labeled stage is if one of the corn hybrids parents did not have the Roundup ready gene (usually the male), there is a portion of the kernels that will abort once the cob starts to form. Leading to a jumbled appearance at harvest.

Fertilizing pastures Most important nutrient is nitrogen. It is nice to have at least 50 lbs of N 20 of P and 50 of K. If half of the N comes from ammonium sulphate, you have enough S.

Spraying fungicides on spring cereals.

If you want oats and barley to yield, and to pay you must spray for at flag leaf or heading for leaf diseases. Fusarium is usually not an issue with barley, and oats as current varieties are not susceptible (flower in the boot) but leaf diseases are yield robbers. Spray a fungicide once the flag leaf emerges, which is now or soon in many fields. This has a fairly wide window, (emergence to heading). This will increase grain and straw yield. The straw should also be better quality, having considerably less dust.

More on frosted corn (notes from a long-time corn seed sales person)

During my wide and varied career in the seed business I noticed

there were hybrids that responded differently to a slight freeze when they were in the one to three leaf stage. This response occurred even though very few visible signs of damage could be seen. In order to correlate the yield loss with the weather at this early stage I was fortunate enough to have access to a weigh wagon and was (is) a keen observer and recorder of the weather. I observed that some of the variation in year over yield could be explained by the slight freeze/frost occurrence.

I mentioned this observation to our breeder and he dismissed it as B.S. However, some years later and a few more frost/freeze episodes his assistant said that they had noticed the same phenomenon.

So just because a hybrid appears to fully recover does not mean that hybrids of this genetic profile are not adversely affected.

Guide to Pigweed, Palmer Amaranth and Waterhemp identification

This guide is the simplest one I have found for the identification of these weed species. You can find it below.

Pigweed Identification Guide | Ohioline

A number of pigweed species are found in Ohio. These species can become very problematic and reduce crop yields. Pigweed identification can be difficult, especially at the seedling stage of growth. This guide will help in making a correct identification based on typical pigweed characteristics.

What can I spray post-emerge in glyphosate tolerant (RR) soybeans?

If you do not have volunteer corn, there is essentially 4 products. Glyphosate, glyphosate plus Classic, glyphosate plus Pursuit, and Flexstar GT. Flexstar GT is a pre-mix of Reflex and glyphosate (please don’t make your own).

Why add something other than glyphosate (again if no volunteer corn)?

1.     Classic has activity on volunteer canola, Sowthistle, milkweed, yellow nutsedge, amongst others. Plus provides residual activity on weeds such as volunteer canola, and the polygonum family, and a few other annual broadleaf weeds if they are not group 2 resistant.

2.    Pursuit does not add much for post-emerge outside of residual activity on weeds such as fall panicum, proso millet, lamb’s quarters, pigweed, ragweed, nightshade and velvetleaf. Again, provided weeds are not group 2 resistant.

3.    Flexstar GT is great on glyphosate resistant volunteer canola and waterhemp, while also providing residual activity for weeds such as pigweed and common ragweed.

What can I spray post-emerge in E3 (Enlist) soybeans?

There are a few options.

1)    Glyphosate

2)    Liberty

3)    Enlist Duo (glyphosate plus 2,4-D Choline pre-mix) or Glyphosate plus Enlist 1 (2,4-D Choline)

4)    Liberty plus Enlist 1 (2,4-D Choline)

5)    Plus the mixes listed above under glyphosate tolerant soybeans

Please note that Liberty DOES require the addition of liquid AMS to improve efficacy, and fine water drops during the middle of the day (full sun) with high water volumes for maximum effectiveness. Glyphosate does not require high water volumes or application with fine water droplets for maximum effectiveness.

What can I spray post-emerge in dicamba tolerant soybeans?

1.)   Glyphosate

2.)  Glyphosate plus dicamba (low rate if high rate has already been applied)

3.)  Glyphosate plus dicamba (high rate if no previous dicamba applications)

4.)  Glyphosate plus Tavium (dual plus dicamba)

5.)  Plus, the mixes listed above under glyphosate tolerant soybeans

Do not add Ammonium Sulphate to any tank mixes with dicamba.

Consult the Engenia application tool listed at the top of the newsletter prior to making any application.

Should I add spray grade Ammonium Sulphate to improve my glyphosate performance?

In most situations, increasing the rate of glyphosate is more effective, both from a cost and weed efficacy standpoint.

See Lauren Benoit’s Twitter comments below based on Dr. Sikkema’s research.

Question – Jonathan, my digital weather service is reporting the same rainfall for all my fields, what is happening?

Answer – These types of services will take in weather information from various on-the ground weather providers, which then sell them as a digital feed. The difference between the systems is how they use the data. Almost all of them use a grid method within a given area to determine how much rainfall you received. The better services also incorporate radar along with the grid data to forecast what the expected rainfall was. I would also expect that there are differences in the resolution the various services are paying for. For instance, grids of 10 by 10 kilometers vs. those running for a given area.

One of the best pictures I have found to describe how these systems work is below, from weather station provider Arable. It provides a good view into why even with a good resolution (which maybe free), you will want local weather stations to assist with forecasting for disease or crop modelling. This helps to account for local topography (think frost events this spring), and variability in rainfall.

Figure 2 - Grid vs Real World Rainfall (Arable)

Source: https://arable.com/blog/new-partnership-aims-to-keep-2.4-billion-gallons-of-water-out-of-the-beef-supply-chain

Question - Jonathan, what do you mean by the various plant parts? Give me a picture.


Figure 3 - Corn Seedling

Source: Diagram of maize seedling parts. | Download Scientific Diagram (researchgate.net)


Figure 4 - Soybean Seedling

Source: Soybean Yield Barriers - International Ag Labs

"When everything seems to be going against you, remember that the airplane takes off against the wind, not with it."

— Henry Ford