So Where Are We At for Heat Units?

If there is one question that makes me smile, it has to be this one.  I think it is asked with the expectation of an intelligent answer that will make perfect sense and provide some insight into whether the corn crop will make maturity. Unfortunately, I have to admit I don't pay much attention to heat unit reports in August and September.  The answer to this question that immediately pops into my head  is "who really cares"?  It doesn't matter right now whether we are on average pace or 100, 200 or 300 heat units behind normal. What matters is the stage of the crop in our field.
Thanks to the wonders of digital photography date stamps I stumbled on some pictures I took last year on August 28 from a plot that was planted on May 3, 2013.  In 2013 most of the corn crop was planted before the middle of May.
As a comparison, I thought it would be interesting to take some pictures of the same hybrids this year on the same date, August 28.  I chose a plot that was planted on May 25 which coincides closely to the date when the majority of acres were planted in 2014.  We must remember this is not meant to be a 100% valid comparison because we are talking about different fields and rotations, but I still find it educational.

This picture above is P0216AM planted on May 3 2013.  The picture below is P0216AM planted on May 25, 2014.  Both pictures taken on August 28 of the respective year.

No big surprise that this full season hybrid is now not as developed as it was last year.  It was planted almost one month later.  But what does this difference mean?  There are two ways to look at it.
If we take the heat unit approach we see that by August 28, 2013 there were approximately 2500 heat units accumulated. This year adjusting for the later planting date we have accumulated approximately 2200 heat units by August 28. Does this tell us anything useful?  No.
Let's consider the stage of the crop.  The 2013 crop was in the dough stage while the 2014 crop is in the milk stage of development.  How do we know?  It is not that hard.  The fact that kernels are just starting to yellow in the 2014 picture indicates the beginnings of rapid sugar accumulation in the kernel.  This is the classic "sweet corn" stage.  All sugars are very liquid and very tasty.  There is no sign of an embryo.
In the late dough stage is the kernel is still very soft and mushy, but the embryo can be found.

The embryo is in the tip of the kernel.  If you take the tip off and squeeze the kernel, the embryo will slide right out.  This is shown below.  The embryo is a hard, oval shaped structure.

The difference between the milk stage and the dough stage is about 12-14 days of development time.  

The standard average time from silking to black layer formation is about 60 days.   

Corn in early milk stage corn is about 45-48 days away from black layer,   Dough stage corn is about 34-36 days away from black layer.  This gives a more accurate answer to the question of where we are at.

My experience has taught me that September is an important month 9 years out of 10.  We needed a good September last year and we got it.  This year P0216AM will  need a good September and some of October.  This is not that unusual.  It is very worth remembering that the average killing frost date for this area is October 7. One quick witted customer observed all that means is frost can happen any where from September 7 to November 7.  He is 100% correct with that conclusion.

Earlier hybrids like P9807AM are more advanced than P0216AM.  Very normal and what we expect to see.  Does it mean much?  If a killing frost happens before the end of September, yes it will mean that the earlier hybrid likely will have the advantage. 

Seed companies are already starting to jockey and talk about how one hybrid is more advanced than another.  "Our hybrid is denting and this competitor hybrid is not", which shows how smart we are, is the standard approach used.  When I sold my corn last year I was paid for dry bushels delivered and I know that fact has not changed.  We expect corn moisture to be high this fall and earlier hybrids will be drier, as they are almost every year.  However, it is way too early to make too many predictions on hybrid performance.

The Bermuda Triangle

This simple diagram is a depiction of why diseases occur, why they are sometimes severe and why they sometimes are not.  Let me explain.
White mold in soybeans is a good example.  It can devastate a soybean crop with yield losses as high as 50%.

White mold, caused by sclerotinia spp, is a garden variety common disease pest.  It affects many different plant species including crops such as white beans, peas, canola, sunflowers and many vegetables.  I have also seen it on weeds like pigweed and lambsquarters.  In other words the pathogen is always present in big numbers because of the diverse host species. Because of this fact we can safely predict the pathogen part of the triangle is a permanent fixture.
The two environmental factors that have the biggest influence on white mold are moisture and temperature. As white mold growth matures, the white cotton moldy growth bonds together and forms sclerotia.  Sclerotia are hard black bodies, commonly referred to as "rat turds".  The sclerotia overwinter in the soil and can survive for up to 5 years when they are buried by tillage.  High soil moisture levels encourage the sclerotia to "germinate" and produce fruiting bodies shaped like small mushrooms.  The mushrooms produce spores and the cycle continues.
The temperature that favours white mold growth is 10-20 degrees C.   If you think about the temperatures that occur under a dense canopy of soybean leaves combined with lots of soil moisture, you can begin to appreciate how the disease can flourish in this "environment".
Given the fact that the pathogen and environment part of the triangle are often present, why do we not see it expressed in every soybean field?   They are all lush with dense canopies this year.  The answer to this question is found in the host part of the triangle.  In our immediate area it had become uncommon to find white mold in soybeans. In fact several times this year some intelligent growers have asked what is causing the dead plants to show up in soybean fields.  They have not seen the disease for many years and have just forgot what it looks like.  Going back 30 years to when soybeans were first becoming popular it was very common to have white mold infection in the soybean crop.  That was due to the fact that a couple of the popular soybean lines were very susceptible to white mold.  Any one remember the variety Evans?  There were not many varieties to choose from so growers were forced to take chances with susceptible varieties.  It takes a lot of work, but smart soybean breeders have been able to screen for white mold susceptibility within the genetic lines they work with.  There are many soybean varieties that are just not very susceptible to the white mold infection. Growers are quick to toss out varieties that they discover to be white mold susceptible in their fields because there are other options.  Despite this, extremely high pressure of white mold can on occasion overwhelm genetic defenses.
So the disease is predictable to a point.  We understand the disease, the environment and we know a lot about the genetic component.  We can identify fields and soil types that are more prone to infection.  We have some fungicide tools that reduce the impact of white mold, but the fungicide has to be applied at high rates, which is expensive if there is no white mold present and need to be applied at first flower.  We should be able to scout a field and identify the potential risk.  Just look for the mushroom shaped structures on the soil surface that I referred to earlier and you would know where and when to spray, the same way we do with weeds.  Not so simple.  Many pathogens in nature most of them harmless to the crop, use similar looking mushroom bodies as part of their life cycle.  Deb Campbell, a sharp eyed agronomist, has spent years trying to identify the specific white mold "mushrooms" as a service to her clients.  She admits to still not being able to positively identify the pathogen at that stage.  If Deb can't find them the rest of us don't have a ghost of a chance.
Farm management has a significant impact on white mold.  If we go back 30 years, conventional tillage was the norm for every crop.  No-till was a "radical fringe" element.  In the last 20 years no-till has become a normal farm practice.  The adoption of no-till had an impact on white mold because the turds laying on the soil surface are subject to predation by insects and mice.  And they need to be buried to germinate well. In the last 5 years, tillage has become much more fashionable again.  I believe, at least in this immediate area that the return of tillage is having a positive influence on white mold infection.
Thanks to the skill and effort of soybean breeders the disease is not as devastating as it once was.

In the corn crop leaf diseases that enjoy cool weather are now easy to identify.
The one disease that is on everyone's radar after last year is northern leaf blight.

You can find it in many fields by the cigar shaped lesions, but at the moment it is at low levels.

Common eyespot is a also present.  It is easy to identify because it looks like an eye.

This picture is not great, but I believe it is the early stages of common rust.
How much of a problem the combined effect of these leaf diseases have on the corn crop will depend on the weather in September.  It is the goal of fungicides to reduce the effect of these diseases and they do a good job in that respect.  It is well known that fungicides keep the plant alive longer by reducing the level of infection.  It is also why some of you resist fungicides because the plant is slower to die and the resulting drying bill causes heart burn.  It is important to remember fungicides they are not 100 % lethal to every fungal disease and you may still find leaf disease in a treated field.

While you are out looking, please remember that not every symptom found is disease.

 

This ugly spot is not something you do anything about.  It is pollen that was caught in the leaf collar and is now rotting.  I guess you could say the pollen is composting inside the collar and consuming some green tissue in the process.

  

War & Peace

Last week nature unleashed a blitzkrieg of sorts in parts of southern Ontario.  Jeff Steiner, a Pioneer sales rep posted this shot of a soybean field near Oshawa.  Devastating to say the least.  I think hail has the greatest traumatic effect on growers of any weather event.

The yields losses due to hail damage are well documented.  Hail is among the most studied of weather events by crop physiologists because it is a very common event and easy to simulate.

This is an example of research conducted by Pioneer studying the effect of severe hail damage.  Hail during the pollination period of corn produces the highest yield losses.  If you strip the tassels and silks off a corn plant it stands to reason that yield will be low. Fortunately this amount of severe damage is a rare occurrence in Ontario.

On the north edge of St Marys last week a couple strips of hail also fell.  Thankfully, nothing like Jeff's field.

A few shredded leaves, but tassels and silks are still in one piece.  

In fact the tassels were starting to shed pollen while I took these pictures the morning after the storm.  

A check of the leaves near the ear shoot reveal that these leaves are more or less intact.  

The ear leaf is where a large portion of yield drive comes from.  If the ear leaf is intact yield losses are small.

An adjacent soybean field looked like this.

A few broken stems and partially shredded leaves.

The problem with assessing hail damage is the fact that farmers over estimate the effects of the damage. Understandably so because it is a traumatic effect.  However, in both these corn and soybean fields yield losses will be greater from waterlogged soils thanks to the rain that accompanied the hail.  The yield loss effect from this amount of hail is in the less than 5% category.  If it was your field would you agree?

The typical question following these events involves fungicide application.  There is a feeling that fungicides will help hail damaged crops.  The research on this topic does not agree.  The benefits of fungicides are no greater on hail damaged crops than non-damaged crops. 

Do you know what this weed is?

I know I am short, but the stature of this weed is still impressive.  It is giant ragweed.  Is proliferates along creek and stream banks throughout the area.  Why is this important? Giant ragweed is one species of weed that can exhibit glyphosate resistance.  Some strains of giant ragweed are not killed by glyphosate.  Multiple applications of glyphosate alone will select for these plants.  It can destroy a soybean field.

There are soybeans under the the umbrella of giant ragweed. In this case it is not glyphosate resistant ragweed because the field was not sprayed with glyphosate.  But you get the idea how this weed can take over. Please remain vigilant. 

Finally, a peaceful intruder was found in Cathy's garden.

Cathy planted a row of butterfly weed and sure enough the monarch butterflies located it. How they find one row among other flowers is amazing. A new generation of monarchs are on the way.