Should I apply fungicide after a hail event?

Originally Published August 19, 2014

A fungicide application cannot recover yield potential lost due to hail damage. Fungicides protect yield potential by reducing disease.  Many studies have been conducted in the United States looking at fungicide application to hail damaged corn crops.  Most results show no yield response when a fungicide has been applied to hail damaged corn.  If after the hail event, conditions are conducive for fungal disease development, an application of fungicide may provide yield protection.  But again it won’t recover the yield lost due to the hail event.

Also keep in mind that bacterial diseases, such as Goss’s Wilt that infect plants through wounds, are not controlled by fungicide application.  And many diseases do not require a wound to infect the plant, including common smut and stalk rots.  Furthermore, foliar diseases that can be managed with foliar fungicides, such as gray leaf spot, do not need wounds for infection.

Bottom line is disease pressure plays a critical role in the magnitude and consistency of a yield response to a foliar fungicide application in corn.  So instead of basing a fungicide application on the fact that it hailed, it should instead take into account disease risk factors such as:

  • Susceptibility of the corn hybrid to various diseases that would be controlled by a fungicide application.
  • Previous crop as many foliar pathogens can survive on corn residue.
  • Weather since the risk for disease development will increase in rainy and/or humid weather.

If you do choose to apply a fungicide to hail damaged crops this year, it would be a good idea to conduct a replicated on-farm trial in the field to allow for a comparison of treatment effectiveness at the end of the growing season.

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture


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My corn is quickly approaching knee-high in height and with the wet conditions it’s been a struggle to get on the field. What are some N application options?

Nitrogen application is critical to corn as it nears the knee high stage.  Up to this point, the plant has consumed  little N but will be taking up 2.5 lb/ac/day as it approaches tasselling.

Broadcasting granular fertilizer such as urea can cause leaf scorching from those granules that end up in the whorl.  Likewise, dribble UAN application can cause substantial leaf burn since droplets either run either off the leaf or into the whorl. And corn may be too large or soil too wet to allow side-dress injection of  ammonia or UAN into the ground.

A safe option is to dribble UAN (28-0-0) using drop pipes so it contacts the ground and avoids the leaves.  This simply means plumbing the high clearance sprayer with nozzles every 30” (rather than the current 20” for pesticides) and attaching flexible hoses to direct liquid to the soil.  In the USA, one brand of  the off-the-shelf units called Y-Drop Applicators have been so popular they are sold out.  If soils are moist and temperatures hot, you should consider adding Agrotain to minimize volatilization loss from the applied fertilizer.

Submitted by:  John Heard, Crop Nutrition Specialist, MAFRD

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Strong Winds & Impact to Corn

Strong winds over the past several days have impacted corn fields across Southern Manitoba.  I have attached a link to an article “Damage to Corn Plants by Strong Winds” written by Bob Nielsen of Purdue University.  The article was written in 2013 but still provides extremely relevant information.

Submitted by:  Pam de Rocquigny, Cereal Crops Specialist, MAFRD

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GOT YELLOW CORN? Using Tissue & Soil Analysis to Confirm Nutrient Deficiency

Not only are soybeans turning yellow in Manitoba, but corn is as well.   So how do you confirm a nutrient deficiency is causing the yellowing?

John Lee of AGVISE Laboratories provided MAFRD staff last year (2013) with the below information on how to properly determine if nutrient deficiencies are playing a role in the ‘yellowing’ corn seen across Manitoba.   It is a great article so thank you to John Lee!

Using Tissue and Soil Analysis to Confirm Nutrient Deficiency in Corn

A cool, cloudy spring with excessive moisture has affected many areas.  One effect of these conditions has been yellow corn from Manitoba to South Dakota.  Using plant tissue analysis along with soil analysis can help determine if the yellow corn is a result of sulfur or nitrogen deficiency.

AGVISE staff recently worked with a local grower to help him determine why one of his corn fields was yellow while the adjacent neighbor’s field was dark green.  Tissue and soil samples were collected from the yellow corn field and also from the adjacent corn field planted the same day.  The concentration of sulfur in the plant tissue from the yellow corn field was well below the sufficiency range established for sulfur at this stage of growth.  The nitrogen concentration in the yellow corn was good and in the middle of the sufficiency range for this stage of growth.  A tissue sample from the adjacent corn field with dark green color was also tested and found to have sulfur and nitrogen levels well within the sufficiency ranges (see tissue and soil test results and pictures of corn at  There were also a large difference in the soil nitrate and sulfate sulfur levels in the soil samples from the yellow field and the adjacent green field.

The soil type in these fields is a sandy loam which is subject to leaching of sulfur and nitrogen with excessive rainfall like this spring.  The yellow field did not have sulfur fertilizer applied this spring while the adjacent dark green corn did have sulfur fertilizer broadcast and tilled in before planting.  The grower was planning on sidedressing the yellow corn with nitrogen fertilizer, but but now with the additional information from the tissue and soil tests, he is going to include some sulfur fertilizer in the sidedress application as well on this sandy loam soil.

This is just one example of how using tissue analysis along with soil analysis in season can help figure out if symptoms are being caused by a nutrient deficiency and which nutrient is the main cause of the symptoms.

Note:  If agronomists/producers send suspected nutrient deficiencies to MAFRD’s Crop Diagnostic Lab, please send samples for tissue and soil analysis simultaneously to an appropriate laboratory.  Then follow up with Crop Diagnostic Lab on the results from the tissue and soil analysis.

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Hail Damage in Young Corn

Originally Published June 23, 2014

Over the last few days, hail has been reported in several areas of Manitoba.  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:

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD





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Why is My Corn Purple?

Several farmers will be noticing the incidence of purple corn in their fields.

Phosphorous Deficient Corn

P-deficient Corn. Note the purpling of the leaves.

Purple corn syndrome results from a number of stress factors.  The purple colour results from anthocyanin production in the leaves due to the accumulation of simple sugars.  The simple sugars build up in the plant because some other factor is limiting their further transformation or translocation in the plant.  Sometimes you will see the purpling at leaf tips of corn that are kinked by damage and the leaf can no longer transport or process the accumulating sugars resulting from the photosynthesis that is still occurring there. Many associate the purpling to reduced phosphorus nutrition of the plant.

Factors that can lead to reduced uptake of phosphorus – either due to lack of phosphorus (low testing soils, inadequate sidebanded application) or reduced rooting efficiency in taking up soil P (lack of mycorrhizae following canola,  root injury by toxic fertilizer bands, cold soils temperatures, dry soils, saturated soil, compaction, herbicide injury, insect feeding, etc).  And usually this is associated with adverse growing conditions – usually cold or saturated soils.

The crop usually “grows out” of this funk once weather and soils warm up and it is rarely seen beyond the V6 stage.  Some hybrids exhibit the purpling more than others.  This does not mean the other hybrids are any better at tolerating low P or cold conditions- they just hide their hurt better.  It would be negligent to shrug and chock it up to cold stress alone – consider whether you P fertilization practices, crop rotation or soil management are contributing to the syndrome,  then plan changes for 2015.

Submitted by: John Heard, MAFRD Crop Nutrition Specialist

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Uniform Plant Spacing in Corn = Greater Yield Potential!

Corn producers should evaluate their uniformity of plant spacing.  A well-tuned planter operating at a reasonable speed should optimize uniform plant spacing within a row. Planting at high speeds with a poorly maintained planter can result in a large number of doubles (two-plant hills) and skips (missing plants), both resulting in lost yield potential for the field.

There is a quick and easy way to determine yield potential  yield loss from non-uniform plant spacing.

#1. Take a 20-ft tape measure and lay next to the row of plants to be evaluated for uniformity of spacing (see figure below).


#2. Record the location within each row in inches of each corn plant (up to 20 ft).

#3. Enter the data into a spreadsheet where average plant spacing and standard deviation (SD) can be calculated.  See below for an example.  Yield loss due to non-uniform plant spacing is estimated using the following equation:

yield loss = (present plant spacing SD – 2.0) x (4 bushel per acre per inch of SD improvement)

Figure 2:  Example spreadsheet, including equations used, for calculating plant spacing uniformity.

 Column A Column B
  Measured location of each corn plant Spacing between each pair of plants measured Equation Used
3 0
4 2 2 =A4-A3
5 17 15 =A5-A4
6 33 16 =A6-A5
7 38 5 =A7-A6
8 39 1 =A8-A7
9 44 5 =A9-A8
10 52 8 =A10-A9
11 55 3 =A11=A10
12 60 5 =A12-A11
13 68 8 =A13-A12
Average 6.8 =AVERAGE(B4:B13)
Standard Deviation (SD) 5.1 =STDEV(B4:B13)
Estimated Yield Loss (bu/ac) 12.5 =(B15-2)*4


So what should producers be aiming for?  Doerge and Hall (2000) previously found a standard deviation of 2 inches is the best spacing uniformity that a commercial producer can typically expect to obtain under normal production planting conditions. They found that if the SD is greater than 3, then the planter needs calibration. If the SD is less than 3, then calibration is not required.

The entire article titled “Estimating Corn Yield Losses from Unevenly Spaced Planting” by Carlson, Doerge and Clay can be found at:

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist

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Time to side dress corn is now

Many of the corn fields in Manitoba have emerged and for those fields that have not yet received their full complement of nitrogen fertilizer – now is a good time to make that application.  There is no need to wait until corn plants are large before side-dressing with anhydrous ammonia or UAN solution.  The time to apply is when the fields are suitable for traffic and injection.

One of our greater risks on non-tiled drained fields is that wet soil conditions in mid-June may hinder field applications of side dressed injected nitrogen.  Although alternatives are available, they come with some potential damage and reduction in nitrogen efficiency.  Broadcast urea to larger plants may leave some pellets in the whorl which cause  leaf burn.  Liquid 28-0-0 (UAN solution) may cause leaf burn when leaves are contacted.  Dribble banding reduces leaf area affected compared to broadcast application, although dribbles tend to run into the whorl of larger plants. Surface applications to moist soil is subject to volatilization loss so Agrotain treatment may be necessary.

Submitted by:  John Heard, Crop Nutrition Specialist, MAFRD

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Update to Historical Seeding Progress in Manitoba

Another week has passed and seeding progress was made in some areas of Manitoba, while some producers wait for warmer and drier conditions.  Hopefully many producers are able to make good seeding progress while the sun shines over the next few days.

Last week I provided an update “What is ‘normal’ seeding progress for this time of year?”  That information covered up to end of Week 1 in May.

In Table 2 below, cumulative seeding progress to the end of Week 2 in May for six crop types is provided.  The last five year (2008-2012) average cumulative seeding progress is noted, along with what was seeded in the same timeframe in 2013. (In 2013, Week 2 ended on May 18th).   Please note that data is for final insured crop in the ground.

Table 2:  Historical seeding progress in Manitoba by end of Week 2 in May (2:05).

Crop Cumulative 5 yr Cumulative 2013 (%)
(2008-2012) (%)
Red Spring Wheat 65 54
Barley 58 38
Oats 56 36
Argentine Canola 36 22
Grain Corn 62 79
Soybeans 22 28

Good luck to everyone with their seeding operations and keep safe!

Submitted by:  Pam de Rocquigny, MAFRD Provincial Cereal Crops Specialist

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How many acres of grain corn can Manitoba producers plant in a day?

Producers have the amazing ability to plant a significant number of acres in a short amount of time once weather and seedbed conditions allow it.  Producers report planting date information to MASC and using that database I can provide you an estimate of how many acres of grain corn Manitoba producers can plant in a day under good conditions.

In 2013, producers planted approximately 212,000 acres of grain corn in a 7 day period….that equates to just over 30,000 acres per day!  

Putting it another way, if Manitoba producers plant the intended Statistics Canada’s acreage of 300,000 acres of grain corn, producers can plant that amount in 10 days, if conditions are right!

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist

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