Author Archives: Pam de Rocquiny

How to Assess Corn After a Hail Event

Damage to a corn crop by hail can differ in severity, ranging from mild to total crop loss.  Yield loss will be dependent on the stage of crop at the time of the hail event and the level of crop damage.  In corn, most yield reduction due to hail damage is a result of leaf loss but can also be from reduced stands.

To determine yield loss due to defoliation, both the growth stage and the percent leaf area removed from the plant must be determined (Table 1). Significant yield damage due to defoliation occurs immediately after silking and decreases as the plant matures.  When making this estimate of defoliation, consider both leaf area removed and leaf area still attached to the plant but no longer green.  Live green tissue, although damaged, should not be considered as leaf area destroyed.  It can also help delaying your assessment seven to 10 days to provide a more accurate picture as it can be difficult to distinguish living from dead tissue immediately after a storm.

Table 1. Estimated Percentage Corn Grain Yield Loss
Due to Defoliation at Various Growth Stages
1
Growth
Stage
2
% Leaf Defoliation /% Yield Loss
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
7 leaf 0 0 0 0 0 0 1 1 2 3 4 4 5 5 6 7 8 9 9
9 leaf 0 0 0 1 1 2 2 3 4 5 6 6 7 7 9 10 11 12 13
11 leaf 0 0 1 1 2 3 5 6 7 8 9 10 11 12 14 16 18 20 22
13 leaf 0 1 1 2 3 4 6 8 10 11 13 15 17 19 22 25 28 31 34
Tassel 3 5 7 9 13 17 21 26 31 36 42 48 55 62 68 75 83 91 100
Silked 3 5 7 9 12 16 20 24 29 34 39 45 51 58 65 72 80 88 97
Silks brown 2 4 6 8 11 15 18 22 27 31 36 41 47 54 60 66 74 81 90
Pre-blister 2 3 5 7 10 13 16 20 24 28 32 37 43 49 54 60 66 73 81
Blister 2 3 5 7 10 13 16 19 22 26 30 34 39 45 50 55 60 66 73
Early milk 2 3 4 6 8 11 14 17 20 24 28 32 36 41 45 50 55 60 66
Milk 1 2 3 5 7 9 12 15 18 21 24 28 32 37 41 45 49 54 59
Late milk 1 2 3 4 6 8 10 12 15 18 21 24 28 32 35 38 2 46 50
Soft dough 1 1 2 2 4 6 8 10 12 14 17 20 23 26 29 32 35 38 41
Early dent 0 0 1 1 2 3 5 7 9 11 13 15 18 21 23 25 27 29 32
Dent 0 0 0 1 2 3 4 6 7 8 10 12 14 15 17 19 20 21 23
Late dent 0 0 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Nearly mature 0 0 0 0 0 0 0 0 1 2 3 4 5 5 6 6 7 7 8
Mature 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1Adapted from the National Crop Insurance Services Corn Loss Instruction (Rev. 1984). 
2As determined by counting leaves using the leaf over method (i.e., those with 40% – 50% of leaf exposed from whorl and whose tip points below the horizontal).

After silking, and if the hail event hasn’t caused total crop loss, additional assessments are made including determining:

  1. yield loss due to stand reduction,
  2. yield loss due to defoliation,
  3. direct ear damage, and
  4. impact of bruising and stalk damage.

Remember that estimating yield loss due to hail is only an estimate, particularly if the damage is not severe and depending upon growth stage of the plant when the hail event occurred.  The remainder of the growing season will help determine final yields.  Please contact your hail insurance provider for their procedures in assessing hail damage as they may be different that when has been provided here.

Originally Posted on Crop Chatter on September 3, 2013; Updated June 15, 2018

Did Hail Result in Bruising and Stalk Damage?

Hail was reported in many areas of Manitoba as severe weather systems moved through Manitoba the evening of June 14, 2018. More information on impact of hail to grain corn is available at How to Assess Corn after a Hail Events and Hail Damage in Young Corn.

However, there can be an impact if hail injured the stalk (see Figure 1).

Figure 1: Bruising of Corn Stalks from Hail (Photo by P. de Rocquigny, June 2016)

The following information is adapted from articles “Recovery From Hail Damage to Young Corn” by R.L. Nielson of Purdue University and “Differentiating Superficial and Deeper Hail Damage” by C. Shapiro of Haskell Ag Lab.

Q: What will be the impact to yield? The eventual yield effects of severe bruising or damage of the stalk tissue itself can be quite difficult to predict. Consequently, it can be difficult to determine whether to count severely bruised plants in assessing plant stands. Observations reported from an Ohio on-farm study suggest that bruising from hail early in the season does NOT typically result in increased stalk lodging or stalk rot development later in the season.

Early season bruising of stem tissue may, however, have other consequences on subsequent plant development; the occurrences of which are hard to predict. If the plant tissue bruising extends as deep as the plant’s growing point, that important meristematic area may die; thus killing the main stalk and encouraging the development of tillers. If the plant tissue bruising extends into the area near, but not into, the growing point; subsequent plant development may be deformed in a fashion similar to any physical damage near the hormonally active growing point.

Q: How can I tell how badly damaged corn may be from bruising?  Bruising is difficult to determine. You can make an initial assessment about a week to 10 days after the storm. Peel the sheaths away from the stalk and determine if the damage has actually penetrated the stalk. The outer stalk (rind) is strong and can resist some damage. However, if the stalk has brown areas, that may indicate stand problems later in the season.

Cutting the stalk vertically from node to node will help determine the extent of damage (Figure 2). Brown areas in the pith where the hail hit indicate the potential for problems later in the season. The stalk in Figure 2 does not show any bruising from the pith. These areas will disrupt the movement of fluids in the plant and reduce growth. Bruised plants that show stalk damage in the pith should probably be considered as missing plants in yield calculations.

Figure 2. Cut the corn stalk vertically from node to node to help determine the extent of damage. Source: Differentiating Superficial and Deeper Hail Damage

Remember that estimating yield loss due to hail is only an estimate, particularly if the damage is not severe and depending upon growth stage of the plant when the hail event occurred.  The remainder of the growing season will help determine final yields.  Please contact your hail insurance provider for their procedures in assessing hail damage as they may be different that what has been provided here.

Originally Published on CropChatter on June 30, 2016; Updated June 15, 2018

Hail Damage in Young Corn

Severe weather went through many areas of Manitoba the evening of June 14th. Hail was reported in several areas, impacting corn acres.

Generally, young corn has the ability to recover from early season hail damage.  In corn, the growing point remains below the soil surface until the V5 to V6 stage. Therefore, the growing point should be protected and the young corn plants can recover even with significant damage to leaves.  However, it is still important to examine the growing point to see if hail has by chance damage the growing point or the stalk below the soil surface.  To examine the growing point, cut the stalk vertically. A healthy growing point is creamy white in color. If the growing point is watery with a brownish color, the plant is likely dying.  Remember that producers and agronomists are encouraged to wait a few days to allow the crop to improve before doing any decision-making assessments.

Another consideration in corn is plants that are damaged by hail are susceptible to Goss’s Wilt infection as the bacteria can enter through the wounds caused by hail. As you are scouting for Goss’s Wilt throughout the season, focus your attention on fields that are:

  • planted to a Goss’s susceptible hybrid,
  • have a history of Goss’s Wilt,
  • have surface corn residue, and
  • may have been injured by severe weather.

Initial symptoms of Goss’s Wilt include water-soaked lesions on the leaves later accompanied by “freckling”. Bacterial ooze may also occur on the lesion, giving it a wet or greasy appearance. When the ooze dries, it leaves a shiny residue on the surface of the lesion.  More information and photos can be found at https://www.gov.mb.ca/agriculture/crops/plant-diseases/goss-wilt.html.

Originally Published June 23, 2014 on CropChatter; Updated June 15, 2018

MCGA & NSAC share field and research agronomy positions

 

 

 

The Manitoba Corn Growers Association (MCGA) and National Sunflower Association of Canada (NSAC) are happy to announce the organizations will be sharing field and research agronomy staff, providing value to Manitoba’s corn and sunflower growers.

Morgan Cott is returning after a one year leave to her position as Field Agronomist. Morgan has been with the MCGA since 2012. She will be responsible for communicating corn and sunflower agronomic information to MCGA and NSAC membership, as well as industry. She will also be responsible for planning and developing outreach activities and extension material with the goal to improve corn and sunflower grower’s profitability.

Daryl Rex is NSAC’s Research Agronomist, hired in March 2017. In addition to his sunflower research program, Daryl provided support to the MCGA coordinating the Manitoba Corn Committee during Morgan’s leave. Under this new structure, Daryl will be responsible for the various adaptation and performance trials for both corn and sunflower, the confection sunflower variety development program and MCGA’s on-farm trial programming.

Morgan and Daryl will assist each other due to many of the natural synergies that exists between the positions. In addition to working with each other, they will also be working closely with Lori-Ann Kaminski who is MCGA’s Research Manager. Operating as a team, MCGA and NSAC will realize efficiencies that will better serve both corn and sunflowers growers.

Morgan Cott can be reached at 204.750.2489 or by email at morgan@manitobacorn.ca.

Daryl Rex can be reached at 204.750.2561 or email daryl.rex@canadasunflower.com.

Frost Prior to Physiological Maturity in Corn

When frost occurs in the early fall before corn has reached physiological maturity (black layer), there is always concern about impact to yields and quality. The stage of crop, minimum temperature reached, relative humidity and duration of cool temperatures all contribute to the impact frost will have on the crop. Generally speaking, a light frost is considered below 0 but above -2°C, where a heavy frost is -2°C and greater.

In corn, grain yield and quality losses become less of a concern the closer the corn is to physiological maturity.

At R5, or the dent stage, crop impacted by either a light or heavy frost will be harvestable but there will be an impact to yield and quality (see Table 1). Within R5, kernels are often staged according to the progression of the milk line, i.e. ¼, ½, ¾. At ½ milk line (R5.5), moisture content of kernels is 35-40% and days to maturity is approximately 13-18 days away.

The stage R6, or physiological maturity, is reached when the milk line disappears and the starch line has reached the base of the kernel. Kernels have reached maximum dry matter accumulation and kernel moisture can range between 30 to 35% (but does vary by hybrid and environment). The formation of the black layer serves as a visual cue that the plant is mature.  At this stage, frost will have minimal impact to yield or quality.

Table 1: Relationship between corn growth stages and calendar days to maturity, yield loss, and other kernel characteristics

A killing frost (-2°C) any time prior to physiological maturity (R6) will kill the entire plant which will stop kernel development. However, if the frost is not a killing frost and the leaves/stalks and husks are still green afterwards, grain filling will continue until maturity.  Frost symptoms are water soaked leaves that eventually turn brown. Because it is difficult to distinguish living from dead tissue immediately after a frost event, the assessment should be delayed for a few days after a frost.

Even though the leaves may be impacted, the plants will continue to scavenge nutrients from the remaining plant material to help complete growth and maturity.  However, the crop will still need the necessary heat units to aid in maturity.  If the necessary heat units aren’t received, a premature black layer may form, ending further grain fill, potentially impacting yield but more likely quality.

Originally Posted on Crop Chatter in September 2016
Last Revised October 2017

The Slow Dry Down of the 2017 Grain Corn Crop

October has arrived and Manitoba grain corn farmers are anxious to start harvesting their 2017 crop. Minimal acres have been harvested (as of October 5, 2017), and fields that have reached maturity are slow in drying down due to cool and rain weather over the past few weeks.

What are normal dry down rates in corn? The best dry down rates are in September. Under good weather conditions from the mid to end of September, dry down rates can vary from 0.75 to 1.0% per day (can be greater in some cases when conditions are warm, sunny and dry, or zero on cool, rainy days!). Into early October, dry down ranges from 0.5% to 0.75% per day. In late October, dry down rate will decrease to less than 0.33% per day. And into November, dry down rate will further decrease to 0.15% per day to negligible amounts.

It is important to keep in mind that moisture loss for any particular day may be higher or lower depending on the temperature, relative humidity, sunshine, wind or rain conditions that day.

Potential Yield Loss. If the crop remains standing in the field, there is the potential for yield loss. The extent of loss will depend on many factors, including stalk strength, ear drop or wildlife damage. Ear drop will vary by hybrid and environmental conditions as well as the amount of grain on the ear (smaller ears should stay attached better than larger ears).  Stalk strength should also be considered when evaluating harvest timing (and this includes assessments of stalk rots). Compromised stalk strength could lead to increased stalk breakage, resulting in lost yield.

As corn matures and dries down, it will be a more common sight across Manitoba in the coming weeks to see farmers harvesting their grain corn.

Originally Posted on Crop Chatter in November 2016
Last Revised October 2017

Weather & Hybrid Characteristics – Their Roles in Grain Corn Dry Down

Grain corn in Manitoba is maturing quickly, and as seen on Twitter, some of the earliest planted fields have reached physiological maturity. Normal plant processes and weather conditions are the major influences on grain dry down, although hybrid characteristics can also play a role. As corn harvest approaches, a quick review of the facts concerning grain drydown might be helpful.

Grain drydown can be separated into two stages: the grain fill period and after physiological maturity.

Drydown During Grain Fill. The grain fill stages (R1 to R5) begins at flowering and is completed at physiological maturity. Grain filling is characterized by the rapid accumulation of dry matter in the kernel and the rapid movement of water out of the kernel.  Decreases in kernel moisture occur from a combination of actual water loss (evaporation) from the kernel surface and the accumulation of dry matter.  The corn plant uses “internal plumbing” to move water out of the kernel since water movement out of the kernel is regulated by how much dry matter is being forced into the kernel.  The corn plant is much more efficient in removing water from the kernel using its “internal plumbing” instead of physical evaporation through the kernel surface.

Drydown After Physiological Maturity. Physiological maturity (R6) occurs when kernel moisture is at approximately 30 to 32% (but can vary).  At this stage of growth, a layer of cells at the base of the kernel dies and turns black (hence black layer), the “internal plumbing” is therefore disconnected, and a barrier is formed between the kernel and the corn plant.  For this reason, post-maturity grain moisture loss occurs primarily by evaporative loss from the kernel itself. Research many years ago established that post-maturity moisture loss through the kernel connective tissues (placental tissues) back to the cob is essentially non-existent.

Role of Weather. As moisture loss after maturity is due to physical evaporation, field drying of mature corn grain is influenced primarily by weather factors, especially temperature and humidity.  In simple terms, warmer temperatures and lower humidity encourage rapid field drying of corn grain.

Because moisture loss is greatest just after physiological maturity, both because the weather is usually warmer and because wet kernels lose water more easily, it stands to reason that a corn crop that matures earlier in the season will dry down faster than a crop that matures later in the season.  However, it is important to keep in mind that grain moisture loss for any particular day may be quite high or low depending on the exact temperature, humidity, sunshine, or rain conditions that day. It is not unheard of for grain moisture to decline more than one percentage point per day for a period of days when conditions are warm, sunny and dry. By the same token, there may be zero dry down on cool, rainy days.

Role of Hybrid Characteristics.  A number of hybrid characteristics can influence the rate of dry down, but to a lesser degree than weather. However, when weather conditions are not favorable for rapid grain dry down, hybrid characteristics that influence the rate of grain drying become more important.  The relative importance of each trait varies throughout the duration of the field dry down process and, as mentioned earlier, is most influential when weather conditions are not conducive for rapid grain drying.

  • Husk Leaf Number. The fewer the number of husk leaves, the more rapid the grain moisture loss.
  • Husk Leaf Thickness. The thinner the husk leaves, the more rapid the grain moisture loss.
  • Husk Leaf Senescence. The sooner the husk leaves senesce (die), the more rapid the grain moisture loss.
  • Husk Coverage of the Ear. The less the husk covers the tip of the ear, the more rapid the grain moisture loss.
  • Husk Tightness. The looser the husk covers the ear, the more rapid the grain moisture loss.
  • Ear Declination. The sooner the ears drop from an upright position to a downward position, the more rapid the grain moisture loss.
  • Cob Diameter. The narrower the cob diameter, the more rapid the grain moisture loss.
  • Kernel Type.  Flint-dent kernel types tend to dry down slower in comparison to dent kernel types due to the harder nature of the kernel.

Originally Posted on Crop Chatter in September 2016
Last Revised September 2017

Did You Plant Non-BT Corn & Not Spray for ECB? Researchers Need Your Fields!

European Corn Borer Larvae – Photo Credit: Manitoba Agriculture

Dr. John Gavloski with Manitoba Agriculture is collecting European Corn Borer (ECB) larvae to have populations tested for potential resistance to Bt toxins. John will send the larvae to Ontario for this resistance monitoring study.

John Gavloski is looking for fields that were planted to a non-Bt corn hybrid and preferably not sprayed for ECB. If you have a field that meets those requirements, please email John at john.gavloski@gov.mb.ca or call 204.745.5668.  You can also call the MCGA office at 204.745.6661 and we will forward the information to John.

 

Estimating Grain Corn Yields

 

The time of year is approaching where yield estimates can be done on grain corn.  Remember that grain corn yield is a function of the number of ears per acre, number of kernels per ear, and the weight per kernel.   Using the yield component method that was developed at the University of Illinois, yields can be estimated as early as the milk stage of development.

 

Calculating Estimated Grain Corn Yield:

Step 1.  Ear Number  – Using a row length equal to 1/1000th acre (row width 30 ” = 17′ 4″; row width 36 ” = 14′ 6”), count and record the number of ears in the length of row that are harvestable.

Step 2. Average Number of Kernels per Ear – Pick 3 representative ears and record the number of complete kernel rows per ear and average number of kernels per row.  Multiply each ear’s row number by its number of kernels per row to determine total number of kernels for each ear.  Calculate the average number of kernels per ear by summing the values for all the sampled ears and dividing by the number of ears.

Note – Don’t count the extreme butt or tip kernels, but rather begin and end where you perceive there are complete “rings” of kernels around the cob.  Do not count aborted kernels.

Step 3. Estimate yield by multiplying the ear number by the average number of kernels per ear, then dividing the result by 90:  Yield (bu/ac) = (ear number) x (average # of kernels per ear) / 90.

Note:  The value of 90  is a “fudge factor” for kernel weight and it represents the average number of kernels (90,000) in a bushel of corn at 15.5% grain moisture.  If grain fill conditions have been excellent (larger kernels, fewer per bushel), use a lower value (80).  If grain fill conditions have been stressful (smaller kernels, more per bushel), use a larger value (100).

Here’s an example:  Field has 30” rows.  You counted 24 ears (per 17’ 5” length of row).  Sampling three ears resulted in 480, 500 and 450 kernels per each ear, where the average number of kernels per ear would be (480 + 500 + 450) divided by 3 = 477.  The estimated yield for that location in the field would be (24 x 477) / 90, which equals 127 bu/ac.

Remember that yield estimates are only as accurate as the number of samples taken so repeating this exercise in several areas of a field will improve accuracy.  Since corn is in the early grain filling stages, water availability, insects, weeds, diseases, and other factors can still affect seed fill and therefore final yields.  However, as the plant approaches maturity, environmental stresses have less impact on final yield so yield estimates made that are closer to maturity should be more accurate.

Originally Posted on Crop Chatter in August 2012
Last Revised August 2017

 

Bird Damage in Corn

It is not uncommon at this time of year to hear of blackbird damage. Birds will often feed on developing ears in corn fields following pollination and early in the grain filling period.

What Does Bird Damage Look Like? Typical symptoms include missing or damaged kernels on the cobs.  In the first photo, shredded husks is the key symptom in identifying birds as the culprit.  Secondary damage can result from ear rots as kernels eaten by the birds will often turn brown or black once the ear rots begin infecting the damaged tissue.

DSCN1711

Corn Ear Damage Caused by Birds. 2014. Photo Courtesy of Earl Bargen, Manitoba Agriculture 

FullSizeRender

Corn Ear Damage Caused by Birds. 2014. Photo Courtesy of Lionel Kaskiw, Manitoba Agriculture

R.L. Nielsen in his article ‘Corn Ear Damage Caused by Bird Feeding‘, indicates birds, especially large flocks, can cause quite a bit of damage. The most damage occurs along field edges or by wooded areas such as bush, but damage can extend throughout an entire field.

Preference for one hybrid over another? It is not unusual for birds to prefer one hybrid over another, although the reasons are unclear.  Perhaps it can be attributed to birds being able to detect slight differences in kernel maturity or other kernel characteristics between hybrids. Bollinger and Caslick (1985) indicated that kernel maturity (as measured by date of silking) was the most important factor in determining the level of blackbird damage to corn.  Within a field, the degree to which the husk leaves extended beyond the tip of the ears (husk coverage) was also strongly correlated with the severity of damage.

Hybrid specific feeding has been observed in past corn committee trials, and not only with birds but with other animals such as raccoons.  Amazingly, the animal can pick out a hybrid within each replicate of the trial without damaging other hybrids.

Control? As seen in other crops such as sunflowers, damage from blackbirds can be an on-going, variable, and uncontrollable natural phenomena with no practical means of management or mitigation. Current scare techniques such as cannons offer little relief as the birds quickly become accustomed to the sounds.

References:

Nielsen, R.L. (Bob). 2008. Corn Ear Damage Caused by Bird Feeding. https://www.agry.purdue.edu/ext/corn/news/timeless/birddamagedears.html

Bollinger, Eric and James Caslick. 1985. Factors Influencing Blackbird Damage to Field Corn. J. Wildlife Mgmt 49(4):1109-1115.

Originally Posted on Crop Chatter in October 2014
Last Revised August 2017