Soybean Midge Tillage Considerations  11/27/18 9:58:23 AM

INITIAL 2018 Asgrow and DeKalb Yield Review
We would like to thank all our customers and plot cooperators, for without all of you this information would not be possible.  It is our hope that this yield information will provide you with the product knowledge and facts that you need to make profitable decisions for the 2019 growing season.  We look forward to meeting with you this fall and winter to discuss results and challenges we faced this past season.  What can you change?  Should you change?  We are in constant pursuit of answers to these questions.   We are committed to a sustainable, profitable future and working together with you puts us in the best position to find new and better ways to help you, the growers be more successful.
We can get a good “true” handle on the genetics we plant in the spring if they are able to perform agronomically in all environments—THIS IS THE REASON—for the annual yield grid.   We typically talk about the tough environments being the testing grounds for most genetics to perform.  All genetics should perform well when conditions are ideal.    How do they do when conditions are not the greatest.  Granted we have been on a bit of a production roll lately.  Much of SE Nebraska has experienced decent growing conditions over the past few years….I said most of SE Nebraska—not all.  Some areas have been dry the past couple of years as well.  SO, we try to look at all perspectives and environments when it comes to genetic performance—not only this year but the previous years as well when determining what genetics consistently works in all environments in which it was exposed too. 
The grid is not complete yet as we are still gathering the last of the data-- Here is an initial take on what we’re seeing this year
DKC70-27 – plot average yield of 243 bu./A in common plots – DKC70-27 is again showing its high yield ability by being in the top 3 of the plots 65% of the time and in the top half 85% of the time.  Very similar track record to the last 2 years’ percentages. 
DKC65-95 – plot average yield of 240 bu./A in common plots – Just as we predicted, this was the sleeper product from last year.  This product went from 5% in the top 3 in ’17 to being in the top 3 of the plots 53% of the time in ’18 and went from 54% in the top half in ’17 to being in the top half 77% of the time in ‘18.   
DKC66-75 – plot average yield of 240 bu./A in common plots – Speaking of the previous year’s “sleeper”, it’s showing great strength in performance and plant health again.  It’s in the top 3 of the plots 42% of the time and in the top half 77% of the time. 
DKC60-88 – plot average yield of 238 bu./A in common plots – This early RM is quite consistent with a 32% top 3 rating and a 68% top half rating.  This is a hybrid that we should again be on everyone’s order.  It’s a hybrid that can be planted early so it can be harvested early.
DKC64-35 – plot average yield of 233 bu./A in common plots – For some folks, this hybrid was in the wrong growth stage at the wrong time for the June/July windstorms and yet it’s still only 4% off of the average yield of DKC70-27.  It’s in the top 3 of the plots 29% of the time and in the top half 45% of the time which is off from where it was the last 2 years.  Some of that can be attributed to spots of greensnap, some to it being a year where the fuller and shorter season corns just hit the niche better. Even DKC70-27 and DKC66-75 aren’t as strong on percentage wins this year simply due to the fact that it’s tougher to have just a few clear cut winners in a DeKalb portfolio that is performing maturity wide. 
DKC63-57 – plot average yield of 235 bu./A in limited plots – This NEW hybrid is running with top performers very well in common plots and is probably one of our “sleepers” of 2018.  It’s in the top 3 of the plots 27% of the time and in the top half 40% of the time, (which is far better than DKC65-95 and DKC66-75 in their first years). 
DKC61-98 – plot average yield of 228 bu./A in limited plots – This NEW hybrid is running within 4% of the yield of DKC60-88 in common plots and is definitely feels like another “sleeper” of 2018.  It’s harvest appearance has been great, (it’s a Disease Shield product)
AG36X6 – plot average yield of 69 bu./A in common plots – In the top 3 of the plots 75% of the time and in the top half 88% of the time.  This should go on everyone’s order, HOWEVER, keep in mind that we have other great products in the portfolio and I will always encourage you to think about genetic balances, averages, etc. when reaching for the low hanging fruit.   You always want genetic diversity out there! 
AG37X8 – plot average yield of 66 bu./A in common plots – In the top 3 of the plots 42% of the time and in the top half 83% of the time.  This versatile dryland bean is a solid companion to AG36X6 and performing even better than it did last year.
AG33X8 – plot average yield of 65 bu./A in common plots – In the top 3 of the plots 29% of the time and in the top half 63% of the time.  This is another bean that will compliment AG36X6 very well, performing just as well as it did last year,
AG39X7 – plot average yield of 64 bu./A in common plots – In the top 3 of the plots 18% of the time and in the top half 50% of the time.  This is the bean that probably got the nod over AG37X8’s simply due to its later maturity and strong performance on the tougher dryland acre.  It’s probably our closest “look alike” to AG4034’s.
Much has been said, in somewhat speculation, regarding what caused all of the ill-fated edges of many soybean fields this year.  Among the topics of discussion to the cause of this is a relatively “new” insect—The Soybean Gall Midge.  Soybean Gall Midge is not necessarily new to this area.  It is however, the first time that at least I can remember, that it has been accused of causing economic damage to row-crop soybeans.  So, the following is a general discussion from UNL entomologists discussing this pest and this year’s developments.
Soybean Gall Midge: Adult Stage Identified—from UNL CropWatch
NOVEMBER 7, 2018
Justin McMechan - Crop Protection and Cropping Systems Specialist
Thomas Hunt - Extension Entomologist
Robert Wright - Extension Entomologist
In late June of 2018, entomologists in Iowa, Nebraska, and South Dakota began receiving reports of soybean fields with visible signs of dead or dying plants that were found to be associated with soybean gall midge infestations. Field surveys were initiated in these states and in neighboring Minnesota to determine the distribution and the extent of the damage.
Results found that soybean gall midge was present in 66 counties across the four states. This multistate map was the result of a collaboration with Erin Hodgson, Iowa State University Extension entomologist; Adam Varenhorst, South Dakota State University Extension field crops entomologist; Bruce Potter, University of Minnesota integrated pest management specialist; and UNL entomologists.
 A portion of the fields surveyed had significant levels of damage with a high frequency of dead plants at the field edge with decreasing damage from the edge into the center of the field. Live soybean plants in damaged areas of the field had dark discolorations at the soil surface that extended up to the unifoliate node. These plants easily snapped off at the soil surface revealing white to orange larvae that appeared to be feeding on the darkened areas of the plant. Additionally, infested plants were observed to have swollen stems near the soil surface or in close proximity to the feeding larvae. 
Soybean Gall Midge Adults Identified
Adults of soybean gall midge had not been observed. In Nebraska, emergence cages were placed over midge-infested soybean plants on August 1 and adults later identified to the genus Resseliella were collected within 24 hours from these cages. Emergence of these adults continued for the next 18 days with the last observation on August 19. These specimens were sent to Raymond Gagne, collaborator in the USDA ARS Systematic Entomology Laboratory, and Junichi Yukawa, emeritus professor of Kyushu University, Japan, leading authorities in midge identification.
Raymond and Junichi were able to connect these adults to the maggots that we had been observing in soybean fields. The identification of the adults will be critical for monitoring their emergence next spring in fields where there was a problem the previous year. Producers, consultants, and other ag professional are encouraged to follow UNL CropWatch or the authors on Twitter (@justinmcmechan@BobWrightUNL) for updates on soybean gall midge emergence this spring.
Little to no information is available on soybean gall midge. As of now, soybean gall midge has only been identified to the genus Resseliella which encompasses 55 species worldwide, 15 of which have been identified in the United States. None of these species are known to occur on soybeans. DNA and morphological comparisons conducted by Junichi and Raymond indicate that it is likely a new species.
Management Practices
Studies with management practices such as planting date and soybean maturity group were evaluated for soybean gall midge damage at the Crop Management Diagnostic Clinic plots at the Eastern Nebraska Research and Extension Center near Mead. These plots are used for demonstration purposes and are not replicated. Soybeans were planted every three weeks beginning in late April through the end of June. Each planting date consisted of four maturity groups (1, 2, 3 and 4).
Dissections of random plants from each plot showed that all maturity groups within each planting date were infested with the exception of a late June planting date. This matches observations of later planted soybean fields in Iowa and South Dakota having reduced visual symptoms and lower infestation rates. Maturity groups 1 and 2 showed visible signs of damage at or near the soil surface whereas groups 3 and 4 showed signs of plant damage in the axils of the trifoliate approximately 6-8 inches from the soil surface.
Yield Losses
In heavily damaged fields, losses associated with soybean gall midge are inevitable due to the number of dead or dying soybean plants. Damage to the phloem and xylem of the plant is likely to result in yield reductions for surviving soybean gall midge infested plants. Additional losses are also anticipated due to the lack of stem strength, predisposing plants to increased risk of lodging if harvest is delayed. Yield loss estimates on a small sample of plants from a heavily damaged field indicate nearly complete yield loss from the field edge up to 100 ft., with about a 20% yield loss 200 and 400 ft. from the field edge.
So, soybean midge has been identified as to what it is and is in the infancy of establishing threshold and/or how to treat them……My current opinion is this—Remember this is not fact, just my opinion.  I was taught some time ago, and still believe the soybean midge is an opportunistic feeder, meaning that they feed prominently on dead or dying vegetative tissue.  The soybean in these cases this year, was likely already at some point within the death process before the midge presented themselves.  An on-going debate amongst the academic entomologist community is that they can also feed on viable healthy soybean tissue—I am not dis-agreeing, however, this has yet to be proven in a widespread fashion.  Midges are the last thing we see during crop scouting and automatically get blamed for why the soybeans died prematurely.  I am also of the opinion that there is likely some other factors involved here that is causing the beans, regardless of 1) general planting date, 2) Brand 3) Maturity 4) Crop Rotation, to die prematurely.  Soil compaction, additional insect feeding (Japanese Beetle?), Phytophora infection, grass waterways and ditches, SCN levels and or SDS infection all of which could have added to the ill-fate of the edges of so many soybean fields this year.    And why all of a sudden, this year???  We also forgot to mention the weather impact that many of these fields in question experienced that caused the perfect storm of influences to cause some pre-mature death to these plants. 
There are far too many questions than current answers.  For the near future, our suggestion is maintaining your current management strategies, but also evaluate your soil compaction status in high traffic areas,, and SCN levels where you had this problem in 2018 prior to these acres returning to soybean production.  On suspect acres, plant varieties with strong SCN and SDS tolerances.
Fall Tillage Considerations
No secret that the soil in much of our area is wet..  Some frost is already in the soil.  Why think of tillage now?  Maybe you are after incorporating the residue benefits from the fertility left in the stover.  Maybe you are after the winter annual weed control achieved with a tillage pass.  Maybe you are trying to pre-maturely “plant” volunteer corn in hopes of it dying off before planting next year’s crops, Maybe, and most likely, you are trying to “prep” for next year and knock out ruts in the soils created from harvest traffic and throw in gullies created via erosion. Maybe it is all of these things.
Soil compaction or “hard soil layers” are created when conditions such as wet/field capacity soils are tilled or (in this fall’s case)—wheel traffic/ruts Harvest activity under wet conditions with the “right” clay content and organic matter in the soil determine how hard a field or certain areas of a field can become.  Is tillage the answer?  I have to break up the hard pan—I had pancaked roots this year!  Sometime tillage and/or the type of tillage may actually make the compaction worse. The opinions are many as far as what is the right approach to deal with hard areas of fields.  Tillage can be an option as long as it is performed deeper than the compacted soil layer and when the soil at the tillage depth is also dry.  This fall, tillage may not even occur in widespread fashion due to weather, and that might be alright.  In many cases it might be better to conserve moisture, save surface residue, and let the freeze/thawing cycle of the winter run it’s course.  IF you have a know pre-existing issue such as ruts, pancaked roots, etc.—then tillage in some form is necessary to prep for next season as long as the soil conditions are right.     
Tillage dries the soil considerably and in that regard is generally best done in the fall—before it gets wetter in winter/spring.   Fall tillage also allows the freeze/thaw cycle of the winter to break down the lumps or clods that is an after affect of the tillage pass.  Certain forms of tillage (in-line ripping) provides a conduit for surface water and nutrient flow deeper into the soil profile for more efficient crop access
Certain tillage (disking specifically) destroys soil structure, thus decreasing it’s water holding capacities, increases the chances of surface erosion, and decreases soil porosity, among other things.  We already know this—Right??
I am a devote protector of soil water and really would rather avoid any form of tillage in an effort to preserve as much soil water, promote additional building of soil structure and tilth, and maintain as much surface residue as possible and reduce soil erosion.  We realize that there are soil types and situations (this fall more than normal) that will demand some form of tillage to prep for next season. 
How much impact does tillage have on your residue levels? 
Consider this: 
Influence of Field Operations on Surface Residue      
          Percent Residue Remaining
Tillage/Planting Implments     After each Operation
Chisel Plow            
  Straight shovel points     50-75  
  Twisted shovel Point     30-60  
Anhydrous Applicatior       50-80  
Disk (Tandem of Offset)          
  3" Deep         30-60  
  6" Deep         40-70  
Field Cultivator         50-80  
  No coulter or smooth coulter     90-95  
  Narrow ripple < 1.5" flutes     85-90  
  Wide fluted > 1.5" flutes     80-85  
  Disk Openers       90-95  
Winter Weathering         70-90  
Use the higher values for corn residue and lower values for soybean residue
Source: 1990 Univerisity of Nebraska Conservation Tillage Proceedings,  
 Dickey, E.C ; Jasa, P.J Conservation Tillage Myths pg 1-8    
The advantages soils with surface crop residue, i.e. increased infiltration, decreased runoff (Lal, 1976), and greater soil water availability. They both provide additional benefits, notably less soil water losses by evaporation, less weed incidence and water losses by transpiration, softer and more workable soils, increased earthworm activity (Lal et al., 1980), the incorporation of additional nutrients (FAO, 1999b) and frequently increased yields.
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