Category Archives: Soybean

Soybean Sprouting in the Pods/Pod Splitting

We are seeing immature soybean once again sprouting in the pods in Suffolk and Gloucester County, and I heard of this happening in other states.  This seems to occur every 3-6 years somewhere.  Although I don’t have a great explanation for why this occurs, it usually happens when there are good growing conditions early followed by 2-4 weeks of drought stress during pod formation, and then excellent conditions return for seed fill.  Typically, it happens in big-canopied soybean (lots of leaf area) with lots of yield potential, but not enough pods (or big enough pods) to fulfill that potential.  I think that the seeds enlarge so much that the pod splits.

Keep in mind that I’m talking about immature seeds and pods.  This can also occur after the crop matures (R7 to R8) when we get excessive rainfall after the seed in question has dried down.  But, I have not seen that yet this year.

There is little that you can do about it.  Those sprouted seed will usually dry up on the plant and be blown out the back of the combine.

Although there has to be some yield loss, I’ve not seen it to be very great.  And, I suspect that if you did not notice the sprouted seed, you probably would not know that you had a loss.

For more information, see previous blogs on this subject.

Wet Conditions May Lead to Soybean Seed Sprouting

The Good and Bad of a Wet September

Calibrate your yield monitor – a checklist

While this post is likely too late for corn, it does apply to other crops.  If you have yet harvested all of your corn, it’s never too late to calibrate your yield monitor.

First, I am no expert in calibrating yield monitors.  My experience with the process only involves showing up to the farm with an accurate weigh wagon (or we use their grain cart), riding with the combine operator as he harvests a known area of the field, weighing the load and obtaining a moisture from the load (with a calibrated moisture tester), then watch him do the calibration.

Still, I understand the need for calibration although it takes time and may mean looking in the manual to learn or refresh one’s memory on the process.

John Barker, Knox County Extension Educator (Ohio State Extension) wrote an excellent article, “It’s almost that time of year … Don’t forget to calibrate your yield monitor!”, which is a step-by-step checklist of how to do this.  I highly encourage all to read it.

We do have several weigh wagons located around the state that Virginia Cooperative Extension uses for our on-farm research.  If you want me or one of your County Agents to help with this process, let us know.

Finishing Out the Soybean Crop – What do we need for Good Yields?

In general, we’ve had a good, but not great year for soybean in Virginia.  Although many areas were hit with a 3 to 4 week dry spell during July, August rains kept us in the game.  However, we did not see the ample  rains or cool temperatures that we experienced in August of 2017, which resulting in record yields.  Below is a summary of August rainfall and temperature anomalies for the U.S.

 

 

 

 

 

 

 

 

As you’ll notice,  we had about average or slightly below average precipitation and average to slightly above average temperatures for most of Virginia’s soybean growing areas.

So, I do not suspect that our yields will be as good as last year.  Still, our earlier-maturing varieties planted in April or May should yield quite respectably considering that most have made over 50% of their yield – they have reached the R6 stage (see photo below).  Yield of our later-maturing varieties, planted in May and early June, and our double-crop plantings are not quite there yet – much of our yield is yet to be determined – R5 soybean have only made roughly 25% of their yield at that time.

So, what do we need for good yields?  Rain is obvious.  Full-canopied plants with adequate soil moisture will draw about 0.25 inches of water/day from the soil.  But, we also need cool temperatures – soybean do not generally like 90+ degree days, especially when forming seed.

Below is the 10 day rainfall and temperature forecast for the U.S., and it does not necessarily look good for us.  Note that the rainfall is predicted accumulation and the temperature map shows anomaly.  Although we should get some rain this weekend only (more in northern parts), temperatures are supposed to be above average.  But, forecasts are only forecasts.  The weather does change.  I hope we will get the needed rainfall that they are predicting this weekend.  But a big ridge appears to be setting up over the Mid-Atlantic states for next week.  This usually means warm weather and only at the edges of ridges do we normally see rainfall – note the heavy rainfall predicted from Nebraska through Michigan.

 

 

 

 

 

 

I don’t mean to discourage, just to inform.  We still have decent soil moisture, at least in the subsoil.  With rain this weekend, we should get through next week without too much harm to the crop.

Our double-crop soybean (assuming late maturity group 4’s and group 5’s planted in late June to July) are just now in the R5 stage – it usually takes 80 to 100 days from planting to reach R6, depending on maturity and planting date.  So some timely September rains will usually result in good double-crop soybean.

When will our yield be “made”?  Below is table showing the number of days to soybean physiological maturity (R7; 95% of yield has made).  When can we expect to be harvesting our soybean?  Full maturity is reached about 2 weeks after R7 and harvest can proceed after the soybean have dried down to a harvestable moisture, usually within a week after R8.

Is it too late to apply foliar fungicides in soybean?

Hillary L. Mehl, Extension Plant Pathologist & David Holshouser, Extension Agronomist

The wet weather conditions, along with relatively cool temperatures over the last few weeks have been nearly perfect for disease development in soybean.  As always, keep in mind the disease triangle – all 3 conditions must be met before a disease can form.

In most cases, one or more soybean pathogens are out there.  Refer to previous blogs for more information on common soybean diseases: Now is a Good Time to Evaluate Your Varieties for Foliar Diseases and Foliar Fungicides for Soybeans.  You can also access the Mid-Atlantic Soybean Disease Scouting Guide here. For a positive identification of the disease, send leaf samples to our diagnostic lab.

We also need a susceptible soybean variety (host).  Some varieties are resistant to specific pathogens; others have some tolerance; many have neither.

Of the 3 conditions, the environment is the most difficult to assess.  In general, we need high relative humidity (RH) for an extended period of time, usually over several days, and cool to moderate (e.g. not hot) temperatures.

Our research indicates that about 1/3 of the time, a foliar fungicide will result in yield increase.  The probability and amount of response will of course depend on the disease.  Frogeye leaf spot can be a quite devastating disease in susceptible soybean that have not been rotated.  Cercospora leaf blight (sometimes called late blight) is less devastating, but is common in almost all of our soybean when conditions are right.

We have attempted to create a foliar fungicide decision aid that would help decide on whether or not to spray.  The decision aid is based on the total number of favorable days for disease development, based on the data shown below.

We think that during the period of 1 week before and 1 week after mid-R3, yield-robbing disease levels may develop if we have 3 favorable days with 10 or more hours of relative humidity at or above 95%  and temperatures in the optimum range (77 to 86 F).  When these conditions are met, we would suggest a fungicide application.

However, after 3 years of on-farm testing we only improved the predictability of a yield increase slightly (approximately 50% versus the 33% we see on average).  Why?  We have not been able to predict the weather after the fungicide application.  If things turn dry, the disease will decline and a yield response is not likely.  If conditions remain favorable for disease, then a yield response to a fungicide application is more likely.

So, back to our original question, is it too late to apply a fungicide?

Most of our full-season soybean are past the R3 stage (though many acres were planted in June due to wet weather); so a yield response is not likely if fungicides are applied now.  Generally, it takes about 65 to 80 days after planting to reach the R3 stage, depending on planting date and relative maturity.

Double-crop soybean will usually take 40 (MG 4 planted in July) to 60 days (mid- to late-5 planted in June) to reach R3.  Since most double-crop soybeans recently entered or will enter the R3 stage, a yield response to a fungicide application is more likely.

What about seed quality?  We’ve seen little relationship between an R3 fungicide application and improved seed quality.  To insure good seed quality, we would suggest 2 applications (R3 and R5).  The R5 application might help with our biggest seed quality issue, Phomopsis seed decay, which tends to develop later in the season.  For seed growers, a late application is a good insurance treatment, but keep in mind that if long periods of wet weather delay harvest, seed quality will deteriorate even if a late fungicide was applied.  Be aware that most fungicide labels restrict applications once soybean enter the R6 stage.  Always follow label instructions.

In summary, there are several things that you need to keep in mind that will affect whether or not you will see a yield response to fungicides:

  • Non-rotated soybean will generally have more disease.
  • Variety Resistance. Many varieties have very good FLS resistance; some have only moderate resistance – this may work pretty well if soybean are rotated, but don’t depend on it if soybean were grown last year (or many of the previous years).  Generally, soybean are not resistant to Cercospora blight, but we have seen differences in varieties.  We measure % purple seed stain in our variety tests; however, this is not always a good indicator for resistance to the leaf spot and blight.
  • Timing & Soybean Stage. R3 applications are usually best; not always, but most of the time.  Still, we occasionally see a response with R5 applications.  I (David) have only seen a yield benefit from 2 applications (R3 and R5) once – this was in 80-bushel double-crop soybean in a very wet and cool year.
  • Historically, strobilurin fungicides were our most effective on most soybean disease.  However, FLS is now largely resistant to that class of fungicides, and control of our other diseases have declined.  However, the strobilurins still have utility.  We suggest a fungicide containing a strobilurin along with a good triazole. The 2018 soybean fungicide efficacy table can be downloaded here.
  • Spray Volume & Droplet Size. Good coverage of fungicide throughout the canopy is necessary.  Use at least 15 gallons per acre spray volume and make sure that your nozzles will deliver medium-sized droplets.  Small droplets will not penetrate the canopy to the lower leaves, where the fungicide is most needed.  Large droplets will not provide uniform coverage.  For more detail on this, see Application Equipment for Effective Insect Pests and Foliar Disease Control.
  • Seed Quality. Although, we don’t always see a seed quality benefit from an R3 application, two applications should improve seed quality.  Furthermore, a late-season (R5) application should help with certain seed diseases such as Phomopsis seed decay. However, keep in mind that if cool, wet conditions delay harvest seed quality will deteriorate even with a late fungicide application. Controlling late season insects such as stink bugs is also critical for preventing fungal infection and maintaining seed quality.

 

 

 

2018 survey of field corn for corn earworm larvae

Statewide, approximately 18% of ears were infested with corn earworm larvae. Corn is considered a nursery crop for corn earworm, allowing the pest to complete a lifecycle and then move on to other crops such as soybean, cotton, and peanut in August. There is a linear correlation between the infestation level in corn and the amount of soybean acreage that gets treated with insecticide for this pest. Please see the attached pdf for more details: CEW_survey_results_2018

Walk Your Fields

For greater soybean yields, one of the best things that you can do is walk your fields.  Many problems reveal themselves during the summer.  Actions taken or not taken can be very noticeable.  By walking fields, we can see what’s working and what’s not working.  Certain problems can be solved, some cannot.  For those that cannot be solved this year, we can do better next season by understanding why we have the problem.  Therefore, a review of how to diagnose your crop will likely beneficial.

A few years ago, I published “Troubleshooting The Soybean Crop“.  Although a little dated, most of the information is still good.  This publication will guide you through how to go about diagnosing problems, includes a vegetative- and reproductive-stage outline with lots of photos, and also includes a sample crop scouting and diagnostic form.  You can download a view a PDF copy, or contact me – I still have a few hard copies left.  By following some general guidelines, one can become quite good at diagnosing problems.  Below is a summary.

First, document everything!  Memories tend to fade.  We often forget or overlook details. You can document by taken notes (many phone apps or iPad/tablets work well for this).  Make a recording.  Take pictures – this is especially useful when you need help – and send those photos to others.

PRELIMINARY FACT FINDING.  You can obtain plenty of information before you even get to the field.  Although I call this preliminary (as if you’ve not seen the problem), you may need to go back to the office to refresh your memory of what you did.  Information that can be acquired beforehand or back in the office includes:     

  • Cropping History
  • Equipment
  • Soil Information
  • Weather
  • Pest Management Information
  • Tillage and Other Cultural Practices

THE FIELD VISIT

  • Take all materials and equipment needed (e.g., phones, paper, shovel, plastic bags, soil probes, etc.)
  • Windshield/Whole Field Investigation
  • Above-Ground Inspection
  • Take Appropriate Plant or Soil Samples
  • Equipment Check
  • Interaction with Others
  • Document Everything!

ANALYSIS OF DATA AND FINDINGS

  • Patterns
  • Look-Alike Symptoms
  • Interacting Factors/More Than One Problem

DRAWING A CONCLUSION. Review the facts and data.  Eliminate unlikely causes.  Validate likely causes.  You may be able to drawn a conclusion in the field, but lab analysis may be needed.

FOLLOW UP. Revisit the field.  If you took corrective action, did it work?  Why or why not?

This is a very rough outline of the guide.  Again, if you want a hard copy of Troubleshooting The Soybean Crop, contact me.

Yellow soybean leaves may be due to manganese (Mn) deficiency

Manganese (Mn) deficiencies are common in Virginia soybean and are starting to appear in numerous fields.  These deficiencies are not necessarily due to low Mn levels in the soil, but are more likely related to high soil pH levels, as its availability decreases with increasing soil pH.

Although soils with a pH of 6.2 or lower can occasional show Mn deficiencies, it is most likely to appear when pH levels reach 6.5 or above.  Furthermore, Mn deficiencies are more common on our sandier soils because pH changes more rapidly and these soils typically have a lower concentration of the nutrient.

The deficiency will appear as interveinal chlorosis, usually on the younger leaves first since Mn is not a mobile nutrient.  MnDeficiency0721101059This may distinguish Mn deficiency from magnesium (Mg) deficiency.  Magnesium deficiency symptoms will usually appear on the lower leaves while the upper leaves remain green.  Still, I’ve seen Mn deficiency on the lower to middle leaves.  This usually happens when the field has not been checked in a while and the observer missed the symptoms when they were on the younger leaves.Cyst nematode on roots

Other problems can cause look-alike symptoms similar to Mn deficiencies.  In particular, interveinal yellowing is a common symptom of soybean cyst or other nematode damage.  Therefore, it may be prudent to further investigate the problem, especially the root system.

Use the following guidelines for Mn applications:

Scout your fields.  Mn deficiencies may or may not materialize.  The only sure way to determine a deficiency is to observe the deficiency symptoms through visual observation or tissue tests.  The characteristic visual symptom is yellowing between the veins on the new leaves.  Mn is an immobile nutrient.  Therefore, it will not move out of older leaves to the new leaves.  Symptoms will appear when the plant can no longer extract sufficient amounts of the nutrient from the soil.

Take a tissue sample.  If Mn deficiencies are suspected due to high pH and/or a field history of Mn deficiencies, but no symptoms have yet appeared, you should consider taking a tissue sample.  Tissue samples can reveal deficiencies before symptoms appear (hidden hunger).  We suggest a tissue test if lime, lime stabilized biosolids, or an ash product was recently applied.

Manganese application.  To overcome a deficiency, apply ¾ lb. chelated Mn (elemental basis) or 1 lb. inorganic Mn (elemental basis) per acre to foliage upon appearance of symptoms and prior to flowering.  More than one application may be required to correct a severe deficiency.

Don’t use low rates to correct a deficiency.  Note that many Mn products recommend applying lower rates of Mn.  However, the label usually states that these are maintenance rates.  Once a deficiency occurs, these lower rates will not correct the deficiency and the rates stated above will be needed.

Split Mn application on deficiency-prone soils.  An alternate method of application can be used before a deficiency is evident on soils that commonly show a deficiency, especially on soils that have a high pH (above 6.8 or so).  A lower rate (~ ½ of that listed above) can be combined with another scheduled application, such as a postemergence herbicide or insecticide.  This may be a sufficient rate to prevent a deficiency from occurring.  But, continue to scout the field and take future corrective measures if visual deficiencies appear.  If a visual symptom appears, you need to use the full rate.  I will remind you that this is a preventative treatment.  A deficiency may not occur.  Furthermore, these are only maintenance rates and another application will likely be needed if the field is truly deficient.

Use EDTA chelated Mn formulations when mixing with glyphosate.  Be reminded that some Mn formulations in combination with glyphosate herbicide (Roundup, Touchdown, many generics, etc.) will result in reduced weed control of certain weeds.  Other herbicides have not shown to interact.  If including Mn with glyphosate, use the EDTA chelated formulation as it has shown not to interact.

Don’t spray if you don’t need it.  In addition to the cost, Mn can be toxic to soybean.  Spraying greater than recommended rates or spraying as a preventative spray when soil pH is relatively low (5.7-5.9) could lead to toxicity problems