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The Cropwalker - Volume 3 Issue 26

Always read and follow label directions.

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Crop Conditions

Weather - drought continued until July 10th or so in some areas. Some areas received a nice rain. Others nothing. There were strong winds that put some corn down. It will come back up. Probably areas with hail as well. Winter wheat harvest started on July 2nd in Essex. First acres were early September planted. Yield was around 90 which was better than expected. They are 20-25% done. Later harvested fields have small shrunken kernels and lower yield. Grade is number 2. Earliest planted and earliest harvested had benefit of rains that later planted fields did not get. Harvest is continuing through Kent and Lambton with yields variable. Lots of straw. Soybeans are flowering, so at R 1.5-2.5. This will likely be past the ideal time for spraying for white mould, check your field to confirm. Spraying now will be to help against other diseases. Some spraying for spider mites (see below) Soybean aphids have not taken off. First generation bean leaf beetle was noticeable. First generation generally does not cause a problem. Second generation can be a concern especially in IP beans, as they will feed on the pods. Corn continues on. Lots of fields showing moisture stress during the drought. Leaves roll because the stomates in the leaf cells close to reduce water loss. In fields that received rain, the drought did not have a permanent affect. Will start to see tassels this week so spraying to reduce mycotoxins is the next concern. Forages second cut is finished on many farms. Yields were average or less. Make sure you have enough fertilizer for the next cut.


Send us your cover crop questions

We will be doing a few articles on cover crops, have a particular topic you would like for us to cover? Please send it in.

Thoughts on Spraying a Fungicide on Corn

Research shows you have an increase in yield by increasing populations, N rates and using a fungicide. The biggest yield increase comes when you do all 3. The yield of each practice added together is less than the yield you get when you do all three (synergy effect). That suggests that you consider applying a fungicide to your best fields that have a good population and you applied adequate nitrogen. Drought stressed fields, fields where population is low due to cold at emergence have less probability of yield increase. If spraying for mycotoxin reduction the products of choice are Caramba (or Caramba plus Headline AMP), Miravis Neo or Proline. Corn silage fields should be sprayed. The high levels of mycotoxins in corn silage has been well documented the last 3 years. One of our reader’s uses a fungicide on corn silage, to reduce the rapid drop in plant moisture at harvest. He feels that fields sprayed with a fungicide have healthy leaves that stay green longer, and, you do not experience that sudden drop in silage moisture content.

What are the Main Corn Leaf Diseases that Might Develop This Year?

No one knows for sure. I will depend on what happens south of us and of course the weather. Main diseases that could be a problem in Ontario are Northern Corn Leaf Blight, Rust (never really bad) Gray Leaf Spot, Tar Spot (which was in some of the Northern US States last year). Chart in last issue on what the most common yield robbing diseases are year in year out (CPN Survey).

Figure 1 - Corn Yield Losses by Disease for NE US and Ontario

Spider mites are bad this year in Ontario and across parts of the US (from Tracy Baute)

Some fields have been sprayed

Hot, dry weather at the start of wheat harvest signals spider mite infestations to move into soybeans, dry beans and possibly even the corn crop. Spider mites are currently on grass plants including wheat and ditch bank grasses. As these plants dry down for harvest or get cut, mites move to other hosts. Infestations tend to start on the field edge’s but with enough windy days, they can get carried deeper into fields.

Scout field edges first. Look for plants that are yellow or bronze in colour, look drought stressed or sand blasted. Signs of stippling (white or yellow dots) on the upper surface of the leaf are caused by mites feeding and collapsing individual plant cells in the leaf. Turn the leaf over and look for webbing or what appears to be dust on the leaf. Watch for tiny moving dots. A hand lens is best to see the actual mites and also to look for their eggs which are tiny, clear spheres stuck to the leaf. Check random areas within the field and look again for signs of bronzing plants that look off from the rest of the field.

Picture 1 - Stippling symptoms on upper surface of leaf. T. Baute, OMAFRA

Action Threshold for beans and soybeans: 4 mites per leaflet or 1 severely infested plant. Rain can help knock populations down, If the infestation is limited to the field’s edge and at threshold, a perimeter spray might be all that is needed.

Dimethoate (Cygon/Lagon) is the only product registered for spider mites on soybeans and edible beans. DO NOT use Matador, it does not control spider mite and will kill beneficial insects which include ladybird beetle, thrips, and predaceous mites. To protect pollinators, spray at night when bees are less likely to be foraging. With temperatures remaining warm in the evenings, bees could still be actively foraging until dark. Contact local beekeepers within 5 km of the field so they can take precautions to protect their hives.

Re-scout the field after an application has been made. If there were a lot of eggs on the plants, there could be a new generation start up, since dimethoate only controls adults and nymphs. Dimethoate will have rapid break down in areas with high pH water. Use LI700 as acidifying agent to prolong the insecticide activity in areas with high pH water.

Bean Leaf Beetle. The adult is typically dark yellow; however, it ranges between yellow, orange and red with black markings Adults are about 5 mm (1/5 inch) in length and have four, large, quadrangular, black markings on the elytra (forewings). Occasionally, these four rectangular marks are reduced to two, or they may be completely absent. The most constant identifying character for this beetle is the presence of a black triangle at the “neck" region. The first generation is complete. The adult’s laid eggs and the larva are now feeding on soybean roots. The real damage is when the adults emerge later this summer and feed on pods damaging the beans inside. Check label requirements if you had used a neonic seed treatment up front.

Leaf Hoppers in Alfalfa

By now you have either sprayed new seedings or have decided it is not worth the bother. If your new seeding has been cut in the last 7-10 days strongly consider spraying for leaf hoppers. If your new seeding is short and stunted it will not grow back until it is cut. Consider cutting it, wait for new growth, then check to spray for leaf hoppers.

Thoughts on Spraying Fungicides on Soybeans

Summary of research trials show an average increase of 2-3 bushels per acre on good yielding fields. That do not have white mould. If you are in a drought area probably insect control is a higher priority than disease control. White mould control is paramount for areas that get it. Can be a 20-30 bu/ac yield loss.

White Mould Alert

In the area I live, there has been fog the last day or so when getting up in the morning. This means we are at risk of white mould in flowering oilseed and pulse crops. The UKKO Agro weather station in my neighbourhood has also indicated we are at risk. If your soybean crop is still flowering, consider making an application to prevent white mould. More or less looking at three products if white mould is your concern. BASF's Cotegra, Bayer's StrategoPro, and Corteva's Acapela. Syngenta's Allegro is a fit as well, however, it is only registered for white mould, vs the other products treating other leaf diseases as well. See this and this past issues on proper products and rates.

Picture 2 - Ukko Agro White Mould Alert and Crop Stage
Picture 3 - Ukko Agro White Mould Disease Favourability Graph

How to Sweep Net A Field and What the # Means by Crop Stage

You have purchased a sweep net and want to know how to properly sweep net a field. From the OMAFRA Publication 811 - Agronomy Guide for Field Crops

“While walking through the canopy, swing the net from side to side in a pendulum-like motion, across the top of the canopy so the top of the net is sweeping the top 37 cm (15 in.) of the canopy. Avoid collecting soil in the net during the sweeping procedure.

Pest management thresholds are established using one of two methods:

1. Single sweep — two 180° arcs: Some researchers set thresholds based on the definition that one sweep consists of two 180° arcs, bringing the net across from one side of the body to the other, and back to home, while walking slowly forward

2. Single sweep — one 180° arc: Other researchers set thresholds based on the definition that one sweep consists of only one 180° arc bringing the sweep net from one side of the body to the other only once

In order to avoid over- or underestimating the average number of insects per sweep, first determine which definition of a sweep was used to establish the specific threshold. In this publication, the definition of a sweep (i.e., either one 180° arc or two 180° arcs) is listed for each insect pest threshold, if it is known.

After completing the indicated number of sweeps, quickly close the top of the net by grasping it just below the ring. Slowly open the net, remove any plant debris collected, identify, and count the insects captured. Though sweep nets will not give an absolute number, they will provide a relative estimate of insect pressures, allowing for a quick assessment of the presence of a particular insect.”

Soybean Flowers

Soybeans have an almost unlimited potential to produce flowers, however a lot of these flowers abort and never produce pods. Eliminating or mitigating stress ensures a great number of flowers will survive to produce pods. I was taught that for pods to survive and become seed-bearing, they need to reach a length of at least a quarter of an inch. (Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics.).

Research by Dr Dave Hume when he was at the University of Guelph showed that about 64% of soybean flowers abort. So, don’t fret when you see small soybean pods on the ground.

Soybean Aphids (notes from July 24 2001)- the dry weather has continued to allow this pest to multiply. In many fields there are plants with thousands of aphids. If you have a field with extremely high numbers and you feel that you are in a Crop Insurance claim position, there is probably little value in spraying. Most fields are not in a Crop Insurance claim position. Spraying -If spraying be sure to leave a check strip to allow the natural predators a chance to rebuild. We sprayed a field near Lake St Clair. The aphid numbers were kept low for 14-15 days. If your field is taking on a shiny appearance this is the “honeydew” that is being excreted by the aphids. Lots of honeydew is an indication of high aphid numbers. In edible beans - this aphid becomes a problem once it “colonizes” (starts to build rapidly, because the winged adults are giving birth) a plant. To date we have seen many edible bean fields where the soybean aphid is present. However, we still have not seen them colonize in an edible bean field.

Pre-Harvest Glyphosate in Winter Wheat

If I had to pick one application timing out of the entire crop rotation to control perennial weeds such as Canada Thistle, Perennial Sowthistle and Quack grass, it would be pre-harvest in winter wheat. You can apply glyphosate at the lowest registered rate (i.e. 0.67 L/ac of Roundup Transorb HC). It is safe to apply once the peduncle (stem below the head), has turned yellow. The other way to check is to ensure you can no longer leave a thumbnail in the kernel. You can apply up to 7 days prior to harvest. If harvest is delayed, there are no issues if it ends up being longer due to rain delays. One grower I have worked with that does this application on an as needed basis, does not battle either of these thistles, or quack grass in any of their fields.

Question - Can I use a Tissue Sample to Make Nitrogen Recommendations for Corn?

Answer - Short answer, No. Tissue samples provide a snapshot in time of what is available in the plant at that growth stage. You are applying nitrogen for the entire growth season, not just at that time, so unless you plan on doing tissue sampling every week and at peak growth, you will not be able to make a nitrogen recommendation off of a tissue sample. Tissue samples measure the total concentration of nutrients as a percentage of dry weight. It is a great diagnostic tool and can help pinpoint nutrient availability issues or to confirm nutrient deficiencies, but it should not be used to determine nutrient application rates during vegetative growth stages. That is what soil samples are for. Tissue samples determine if the plant has been able to pick it up.

Question - I’ve used nitrate samples in the past, but haven’t found it effective in making my nitrogen recommendations for my corn crop, why is this?

Answer – There could be a few reasons. One reason is that yield (sink size) is still a moving target when doing the sampling (see chart below for example on the different rates by yield potential). Another is the mixing of soil for different fertility response and yield zones (i.e. differences in nitrogen supply and/or water availability, see an example field from this spring, in another article below). A third is the samples were not properly handled during sampling and shipping to the lab (sampling in the row vs out of the row, proper depth, proper storage during transport). A fourth is you had significant nitrogen loss post sampling (usually due to leaching or denitrification).

Figure 2 - Corn Sidedress Nitrogen Recommendation by Nitrate PPM

What happens when I mix different response zones when nitrate sampling?

The first step is ensuring you are pulling a representative sample in the field. Why? See below. This 45ish acre field had 5 nitrate samples pulled. They were pulled in very particular positions given how those areas of the field respond and perform to applied inputs. If you had taken the sample by accident in the depressions, you would have put no nitrogen on the field. If you have taken the sample on the upper slopes, you would have significantly over applied for a large portion of the field. Getting the right rate on the field is site specific when it comes to nitrogen (both for the supply and sink side, especially with variable rate (VR). Add a soil moisture probe or historical yield data to the map below, and you have a fairly accurate way of fine-tuning your N-recommendations (see the over/under difference comparing flat rate vs VR nitrogen).

Figure 3 - Nitrate Recommendation by VR vs. Flat Rate
Picture 4 - Example SWAT Map Field with Definitions

The map below is what actual got sent to the rate controller for this field, as the sprayer was unable to do an extremely wide rate range. In the future using a dry spreader to top-dress might be more appropriate for wide rate ranges. The client was not comfortable putting a zero rate on in the depressions, so we put the lowest possible rate the equipment was capable of.

Picture 5 - Example Field VRN Script

Glyphosate May Increase Dicamba Moving Off Target

There are several factors that affect the amount of dicamba that moves off target. These factors include warm, humid weather, temperature inversions, dicamba rate, rainfall after application, (even 1/10” of rain after application reduces amount of volatilization.) presence of leaves at spray time (keeping dicamba off soil) and low pH of a dicamba tank mix, and often the result of adding glyphosate. Adding glyphosate to a mix with dicamba lowers the pH of the spray solution and increases the probability of volatilization.

Hand Spraying

If you are using a 2 gallons hand sprayer to do some spot spraying what rate are you spraying? I have done a lot of hand spraying and when I walk quickly, without a sideways spray motion, I am applying about 20 gallons per acre. So, if you want to know how much herbicide to add to a 2-gallon sprayer. Say you want to spray 1.0 L per acre of glyphosate You want 1000 ml/ac in 20 gallons of water or 100 ml in 2 gallons.

Register for Free for Ag In Motion Virtual Farm Show and Equipment Demonstrations

This is a great opportunity to see what is going on in Western Canadian Agriculture. It is a virtual show. Click on the URL to register Dates are July 25-27th. Registration is free


"The biggest generator of long term results is learning to do things when you don't feel like doing them."

-Shane Parrish