C.O.R.N. Newsletter 2013-21

Dates Covered: 
July 9, 2013 - July 16, 2013
Editor: 
Rob Leeds

Late-season Rainfall, Late Harvest and Wheat Grain Quality

The month of June was fairly cool which resulted in an extended grain fill period. Combined with low disease levels and low grain contamination with vomitoxin, wheat quality is expected to be good this season. However, growers are now finding it hard to get their crop harvested. It has rained consistently across most of the state over the last two weeks and growers are understandably concerned about grain quality. Indeed, rain and late harvest can certainly reduce test weights, increase fungal colonization of the heads, and cause pre-harvest sprouting.       

What is test weight? Test weight is used to take into account varying densities (weight per given volume) of grain. It is an indicator of grain quality. Generally the higher the test weight the higher yields will be for flour and starch. The standard commodity weight for soft red winter wheat is 60 pounds per bushel at 13.5% moisture. If test weight is below the acceptable range (low test weight), the wheat sale could be “docked.” Depending upon the elevator, dockage for test weight generally does not occur unless the value is below 58 lb/bu. Some elevators will give a premium for test weights 60 and above. 

What causes low test weight? Grain density can vary based on weather, production practices, variety, and pests. Low test weights occur if grain is prevented from filling completely and/or maturing and drying naturally in the field. Rewetting of grain in the field prior to harvest can also reduce test weight.  When grain is rewetted, the germination process may initiate causing photosynthates (i.e., starch) to be digested. This leaves small voids inside the grain which decreases test weight. Additionally, grain will swell each time it is rewetted and may not return to its original size as it dries which will reduce test weight. Thus the enlarged kernels will take more space but weigh the same allowing fewer kernels to pack in the measuring container, lowering the test weight. If possible, for maximum test weight, it is best to harvest wheat on the first dry-down.    

Should I be concerned about sprouting? Rain and harvest delay may lead to pre-harvest sprouting in some varieties in some areas. Sprouting is characterized by the swelling of kernels, splitting of seed coats, and germination of seeds (emergence of roots and shoots) within the wheat heads. Some varieties are more tolerant to sprouting than other, and for a given variety, sprouting may vary from one field to another depending on the duration of warm, wet conditions. Sprouting affects grain quality (test weight). Once moisture is taken up by mature grain, stored reserves (sugars especially) are converted and used up for germination, which leads to reduced test weights. Even before visual signs of sprouting are evident, sugars are converted and grain quality is reduced. Since varieties differ in their ability to take up water, their drying rate, the rate at which sugars are used up, and embryo dormancy (resistance to germination), grain quality reduction will vary from one variety to another.

Why are heads turning black? In addition to sprouting, the growth of mold is another problem that may result from rain-related harvest delay. To fungi, mature wheat heads are nothing more than dead plant tissue ready to be colonized. Under warm, wet conditions, saprophytic fungi (and even fungi known to cause diseases such as wheat scab) readily colonize wheat heads, resulting in a dark moldy cast being formed over the heads and straw. This problem is particularly severe on lodged wheat. In general, the growth of blackish saprophytic molds on the surface of the grain usually does not affect the grain. However, the growth of pathogens, usually whitish or pinkish mold, could result in low test weights and poor grain quality. In particular, on scab-affected heads, molds may produce toxins such as deoxynivalenol (DON), leading to further grain quality reduction and dockage. While DON contamination is generally higher in fields with high levels of wheat scab, it is not uncommon to find DON (above 2 ppm) in late-harvested fields that have been exposed to excessive moisture. Even in the absence of visual scab symptoms, the fungi that produce DON may still colonize grain and produce toxin. 

 

What can we expect after a week of rain?  Is it Phytophthora, flooding or both?

What can we expect after a week of rain? Is it Phytophthora, flooding or both?

Rainfall this past week around the Midwest was extensive.  We know that a week after a rain, we will start to see the above ground symptoms of Phytophthora root rot on susceptible varieties.  So, this week will be a good time to scout to see if the Rps genes in your varieties are still effective and if the field resistance/partial resistance levels are high enough.  From tours around the state last week, there was also ponding & flooding.  When soil is saturated for more than 3 days and anoxia – low oxygen, high carbon dioxide sets up, flooding injury occurs.  Some plants will die and others will be set back until new roots form.

To separate flooding injury from Phytophthora, dig up symptomatic plants.  Pull on the outer epidermis of the roots.  If it collapses between your fingers, it is Phytophthora or root rot caused by another watermold, Pythium.  If you can pull off the epidermis and the nodules on the root and find the white root stele, it is flooding injury.  

If it is Phytophthora, the final check to see if this is a highly susceptible variety is to look for the chocolate brown canker on the main stem.  Leaves will be yellow and wilted.  Go back to your seed catalogue and see what the field resistance levels were listed for that variety.  Make a note, because you will want a better score for the next time you plant soybeans in that field.  Read the fine print, every company has bit different scoring system.  Ohio State uses the score from 1 to 9 – 1 is for no root rot and 9 is dead.  Other companies use the reverse, in reality they are all close.  For scoring systems of 1 to 9 where 9 is dead, you want a score of 3 to 5; for scoring systems where 9 is best – you want 5 to 7.  The reason why I am not recommending scores of 1 to 2 or 8 to 9, is that this means the R-genes was expressed.  An effective R-gene will mask the presence of partial resistance.

Lots of flooding and ponding on our clay soils also indicate that it is time to have the field checked for drainage.  The longer the field is saturated that is also the amount of time available for the watermolds to infect plants.  The drier the field, the less time for infections to occur.     

For flooding injury, there will be yield loss, the plants will re-root and new nodules will have to form.  So the plants will look at bit yellow for a while.  But the plants will recover.  Phytophthora, those plants are gone.  If you decide to replant, take the time to pick a variety with better levels of partial resistance and use a seed treatment.

 

Impact Of Ponding and Saturated Soils On Corn

Impact Of Ponding and Saturated Soils On Corn

Persistent rains during the past two weeks have resulted in ponding and saturated soils in many Ohio corn fields and led to questions concerning what impact these conditions will have on corn performance.  

The extent to which ponding injures corn is determined by several factors including: (1) plant stage of development when ponding occurs, (2) duration of ponding and (3) air/soil temperatures. Corn is affected most by flooding at the early stages of growth. Once corn has reached the late vegetative stages, saturated soil conditions will usually not cause significant damage. Since most corn in Ohio is approaching the silking stage, this bodes well. Although standing water is evident in fields with compacted areas, ponding has usually been of limited duration, i.e. the water has drained off quickly within a few hours, so the injury resulting from the saturated soil conditions should be minimal. Moreover temperatures have been moderate.

However, under certain conditions saturated soils can result in yield losses. Although plants may not be killed outright by the oxygen deficiency and the carbon dioxide toxicity that result from saturated soils, root uptake of nutrients may be seriously reduced. Root growth and plant respiration slow down while root permeability to water and nutrient uptake decreases. Impaired nutrient uptake may result in deficiencies of nitrogen and other nutrients during the grain filling stage. Moreover, saturated soil conditions can also result in losses of nitrogen through denitrification and leaching.

Past research at Iowa State University evaluated flood damage to corn that was inundated for variable periods of time at different stages of growth (including silking). Two different N levels ("high" N ‑ 350 lb N/ac vs. "low" N‑50 lb N/ac) were also considered to determine how N affected corn response to flood injury. Low N plots yields were reduced by 16% at silking when plots were flooded for 96 and 72 hours. In the high N plots, flooding at silking had little or no effect on yields.

According to Dr. Emerson Nafziger at the University of Illinois  (http://bulletin.ipm.illinois.edu/?p=1240) “…At the time the crop reaches stage V13 (about head-high), it still has to take up 110 to 120 lb of N, and in years when June is wet, a common question is whether or not the crop might run out of nitrogen, leaving the crop short. While the need for 20 or more lb of N per week would seem to raise the possibility of a shortage, the production of plant-available N from soil organic matter through the process of mineralization is also at its maximum rate in mid-season. For a crop with a good root system growing in a soil with 3 percent organic matter, mineralization at mid-season likely provides at least half the N needed by the crop on a daily basis. This means that normal amounts of fertilizer N, even if there has been some loss, should be adequate to supply the crop.”

References

Nafziger, E. 2013. Corn roots, wet soils, and nitrogen. The Bulletin. University of Illinois, Urbana-Champaign. http://bulletin.ipm.illinois.edu/?p=1240

Ritter, W.R. and Beer, C.E. 1969. Yield reduction by controlled flooding of corn. Trans. ASAE 12:46-47.

Weather Outlook:Wet weather will linger into the middle of this week followed by drier conditions through early next week

Wet weather will linger in Ohio into the middle of this week followed by drier conditions for the period of Thursday through early next week. Some scattered storms will likely return next week and humid and quite warm weather develops again.

Temperatures will remain above normal through July 21. Some cooler and less humid weather will return late this week into early next week before very warm and humid weather returns.

Rainfall is forecast to be normal to above normal through July 21 but much of that wetness is through the middle of this week.

Our latest 2 week rainfall forecast can be found at the following location, http://www.erh.noaa.gov/ohrfc/HAS/images/NAEFS16day.pdf

Summer so far is about normal to a half degree above normal temperatures across the state with rainfall averaging 0-2 inches above normal. However, the range in local conditions for rainfall is quite large.
 

Check Corn Roots for Presence of Bt resistance in Western Corn Rootworm

Last year, research led by Dr. Aaron Gassman at Iowa State University documented the presence of resistance to the protein Cry3Bb1 in western corn rootworm populations.  So far, resistance has only been documented in the western corn belt.  Most importantly, Dr. Gassman’s research shown a strong correlation between resistance and continuous corn fields that have used corn with Cry3Bb1 for at least 3 consecutive years.  In a previous CORN issue (2013-11), we mentioned the risk of resistance in Ohio, and the necessity of remaining vigilant in finding any suspected cases of resistance.  Over the next few weeks is the time that growers should dig corn roots and inspect them for rootworm feeding.  Dig at least 5 plants in 10 different locations in your field.  To determine the level of injury, use the Node Injury Scale—this scale ranges from 1 to 3, were 0.5 is half of a node of roots damaged, 1 is a full node of roots damaged, 2 is 2 full nodes damage, etc. Any rating more than 1.0 in corn fields containing Cry3b1, or any rootworm trait for that matter,  might suggest potential resistance (remember, if you are using a blended refuge and find a damage root, use Bt test strips to make sure you have inspected a Bt plant).  Based on the pattern in the western corn belt, continuous corn fields should be our first priority.  If you suspect any cases of resistance please contact state entomology specialists (michel.70@osu.edu, hammond.5@osu.edu) or your local extension educator.

Some Ohio Tobacco Patches Near a Total Loss

Heavy rainfall that has occurred in the Southern Ohio this past week has taken a toll on many things, but it appears the tobacco crop has been the hardest hit at this point, with more rain in the forecast.  Tobacco is a crop that grows better in well drained soils and can yield well with limited moisture.  The combination of heavy rains, that followed several days of off and on showers which saturated the soil, and a bright and warm sunny day has destroyed several acres of tobacco in Adams and Brown Counties.  Kentucky is reporting similar conditions with at least a 10% loss for most areas.

Basically the tobacco drowns.  The crop can survive the saturated soils, with some stunting and that normally will result in some yield loss.  The yield loss can go to 100% loss if shortly after the rain, and while the soil is still heavily saturated, the hot sun comes out. 

Most tobacco patches will be in fields that are rolling, and some areas will be more prone to standing water than others.  The low areas are where this most often occurs, but the recent rains have caused these areas to be a larger percentage of some fields.  Some farms have had more rain than others and the result has been that some farms have little to no loss, while others producers are reporting a large percentage their crop down. 

When the sun comes out hot following a heavy rain that saturates the soil, the leaves can’t transpire.  Transpiration is the evaporation of water from the leaf surface that cools the leaf, thereby preventing sunscald.  When this happens and leaves, or nearly the entire plant is wilted, the plant can’t recover.  The plant may recover somewhat overnight, once the sun goes down.  Depending on the amount of damage, few plants will recover.  Those that do recover will not likely completely recover, but simply survive.  The yield will be reduced.  In addition to yield loss, the quality will also suffer.  The curing of a crop damaged by scald like conditions will most likely cure with some degree of an undesirable green color that will result in a poor price in most years.  This year, the tobacco supply is low, and this issue of scalding has impacted a very large part of the burley belt, so the price may not be as affected as much as it may have been in former years.

For these reasons, the reduced yield and reduced quality, there is little hope of trying to harvest this crop for a financial gain.  The cost of harvesting will most likely outweigh the price at market, especially at the stage of growth most of this crop is currently in.  If tobacco was topped and only a couple of weeks from a normal harvest, you may be able to salvage enough of the crop by harvesting, but not for tobacco that is not even in bloom yet.

2013 Western ARS Agronomy Field Day - July 17

The Agronomy Field Day will be held 9AM to 3:15PM on July 17th. Pre-registration required by July 15th. Lunch included, cost is $20 per person payable at the door by cash or check made payable to Ohio State University.

Located at the OSU/OARDC Western Agricultural Research Station, 7721 South Charleston Pike, South Charleston, Ohio 45368. This is 3.5 miles northwest of South Charleston. Just south of I-70 on State Route 41 between Springfield and South Charleston in Clark County.

To register contact Harold Watters, OSU Extension, watters.35@osu.edu  or 937 599-4227 or Joe Davlin, Western ARS Manager, davlin.1@osu.edu or 937 462-8016

Tentative agenda below – we will modify to cover current topics of concern as necessary.

8:30 to 9AM check in

9 AM to noon wagon tour of the Agronomic Crops Trials at Western

  • Peter Thomison & Alex Lindsey – Drought Tolerance, Planting Date and Planting Depth Issues.
  • Pierce Paul & Anne Dorrance – scouting for that “Disease of the Year”.
  • Laura Lindsey – Soybean canopy development across planting dates.
  • Mark Loux – Weed Management Issues for 2013.
  • Andy Michel – There are more bugs this year, or are they insects?

Noon lunch – Rudy’s BBQ

12:45 Announcements and Updates

  • Harold Watters  – Phosphorus Management Strategies in a New Era 

1:15 - 3:13 PM in-depth discussion with the specialist of your choice, many of these stops will be back in the field with the state specialist’s plots. You will be able to attend two, at 50 minutes each.

  • Pierce Paul & Anne Dorrance – Scouting foliar diseases – it’s a wet year, right?
  • Andy Michel & Ron Hammond – Seed corn maggot management.
  • Peter Thomison & Alex Lindsey – Water Exclusion Experiment with Field Corn.
  • Laura Lindsey – Light Bar Demo in a Soybean Canopy, state-wide Soybean Omission trial site exploration.

We have 5.5 hours of approved CCA CEUs (NM 0.5, PM 1.0, CM 4.0); Pesticide Applicator recertification credits have been applied for, for both Commercial and Private applicators – those wishing PestEd recertification credits will pay an additional $20 for those credits above the $20 field day fee.

Impact and Management of Phosphorus across Various Tillage SystemsImpact and Management of Phosphorus across Various Tillage Systems

Impact and Management of Phosphorus across Various Tillage Systems

A field day focusing on the relationship of phosphorus (commercial fertilizer sources utilized) to various tillage systems will be held July 18, 2013.  The agenda for the field day follows: 

8:30       Registration

9:00       Welcome

9:30       Phosphorus (P) Basics

10:10     Cropping System Rotation #1

11:10     Cropping System Rotation #2

Noon     Lunch – Compliments of Northern Ohio John Deere Dealers:  Findlay Implement, Shearer Equipment, and Kenn- Feld Group

12:45     Cropping System Rotation #3

1:45       Phosphorus State of the Union

2:30       Adjourn

The field day will be held in Wood County, Ohio – a quarter mile west of the intersection of I-75 and Hwy 582 which is about 6 miles north of Bowling Green.  The program is free but an email RSVP is required to: nopat@live.com .    Four and a half hours of CCA credits have been applied for including 1 hour of soil and water and 3.5 hours in nutrient management.   Contact Steve Prochaska at 740-223-4041 or prochaska.1@osu.edu with any questions.

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About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.