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ISU Extension Logo

Northwest Iowa Crop Update Newsletter
by Todd Vagts
ISU Extension Crops Specialist
Counties Served:  Carroll, Calhoun, Crawford, Ida, Monona, Pocahontas and Sac.

   
[Home][Special Topics][Field Problems][Weather Data][Subsoil H20][PDF Info] [ISU Extension][IA State University]

 

ISU Extension
Hail Damage Assessment to Corn

By Todd Vagts, ISU Extension Crops Specialist

Many fields across the area experienced hail damage from this week’s storms that has led to concerns with corn and soybean stands, survival and their impact on final grain yield.

Questions arise as to:

  • What is and will be the final stand of the corn field?
  • How healthy is the corn plant?
  • Given the current stand and defoliation, how much yield impact will the reduced stand have?
  • Should the crop be replanted?
  • What are the replant options for corn or soybeans?

How old was the corn plant and where is the growing point?

The growing point on corn is below ground until V5 (5 leaf collars visible). Prior to this time corn will generally re-grow from hail damage. Data from the National Crop Insurance Service’s "Corn Loss Instructions" indicate that less than 11 percent yield loss will occur with 100 percent defoliation up through the eight leaf stage .

To evaluate the location and health of the growing point, make a horizontal cut through the corn plant and look for the "small triangle" near the base of the plant. The tissue should be white in the center. Sometimes even though the growing point was not cut off, diseases set in after the hail and causes rot to occur. Generally, some re-growth from the growing point can be seen 3-4 days after the hail.

Use the following table to determine the length of row to evaluate corn populations.

Row spacing

Distance for 1/1000 A.

Distance for 1/100 A.

30 inches

17 ft. 5 inches

174 ft.

36 inches

14 ft. 6 inches

145 ft.

38 inches

13 ft. 9 inches

138 ft.

Planting date and Plant population table

Determining Yield Loss Due to Stand Reduction

When a hailstorm occurs early in the growing season, an accurate stand reduction assessment is important if replanting is a management option. Because it is difficult to distinguish living from dead tissue immediately after a storm, the assessment should be delayed for a week to 10 days. By that time, re-growth of living plants will have begun and discolored dead tissue will be apparent. (Another reason for delaying assessment is that some plants initially surviving a storm may soon die because of disease infection entering at the sites of plant damage.) To get an accurate estimate of the extent of damage, observe and sample plants from at least three parts of affected fields, totaling about 1/100 acre

Table 2 is based on research on stands and planting dates by Dr. Dale Farnham (ISU Extension corn specialist). Although results will vary somewhat due to location, season, hybrid, and other factors, Table 2 serves as a good starting point in decision-making.

Once you have evaluated stand level and uniformity, compare that yield percentage with a full stand at the expected replant date. Convert the difference to bushels per acre. If the replant yield is lower, do not replant. If it is greater, consider the cost of replanting (tillage, planting, seed, and other factors) to see if the extra yield is enough to make replanting profitable.

Additional considerations:

  • If you tear up a marginal stand, what will be the affect on your rotation? By replanting to soybeans, you’ll have second year soybeans on some fields. Will soybean cyst nematode or soybean diseases become a serious problem? An estimate is that soybean yields are reduced by 10 percent when following a previous crop of soybeans.
  • What herbicide has been applied to the field already? Refer to the herbicide label to determine rotations period for soybeans. Or refer to the on-line document Replant options following herbicide applications by Brent Pringnitz, extension program specialist and Bob Hartzler, extension weed scientist, Department of Agronomy. The document can be accessed on-line at http://www.ipm.iastate.edu/ipm/icm/1998/6-8-1998/replant.html

 

Estimating Yield and Dollar Returns from Corn Replanting

Bob Nielsen, Extension Agronomist, Department of Agronomy, Purdue University

http://www.agcom.purdue.edu/AgCom/Pubs/AY/AY-264.html

Worksheet

Step 1. Original target plant population

  1. Original seeding rate (from your records):_____seeds/a.
  2. Seed germination percentage (from seed tag): _____%
  3. Expected plant survival rate (use 95% if you're not sure):_______%
  4. Original target population (#1a x #1b x #1c):plants/a.
 

Step 2. After-damage plant population (Repeat steps #2b thru #2d at each site inspected.)

  1. Length of row equal to 1/1000th acre (from Table 1, based on a row width
    of _____in.): ________ ft.-in.
  2. Number of live plants in three 1/1000th-acre lengths Site 1 Site 2 Site 3 Site 4 of
    row: (1st)____ +(2nd) _____ +(3rd)_______ = ______ ______ ______ ______
  3. Average plants per 1/1000th acre (#2b / 3 rows): ______ ______ ______ ______
  4. Average live plants per acre for site (#2c x 1000): ______ ______ ______ ______
  5. After-damage plant population for all sites inspected (sum of #2d at each site / number of sites):
    _______plants/a.

Step 3. After-damage stand uniformity

  1. Average length of evident gaps within rows (more)(less) than 3 feet?: _________

Step 4. After-damage plant defoliation

  1. Average plant leaf area lost or destroyed:______%
  2. Growth stage of corn:_____ exposed leaves

Step 5. Original planting date

  1. Month and day that planting began (from your records):______

Step 6. Likely replanting date, if justified

  1. Month and day that replanting could begin: _______

Step 7. Likely replanting costs

  1. Seed cost: $ ______/a.
  2. Fuel cost: $ ______/a.
  3. Herbicide cost: $ _____/a.
  4. Insecticide cost: $ ______/a.
  5. Other replant costs (e.g., dryer fuel, interest): $______ /a.
  6. Total replant costs (sum of #7a through #7e): $ ________/a.

Step 8. Expected "normal" yield

  1. What the field would likely have yielded under normal conditions: _________ bu/a.
  2. Step 9. Expected market price for corn

  3. Price expected when the grain from this field is marketed: $______ /bu.

Yield Potential If Damaged Field is Not Replanted

Step 10. Estimated yield of the after-damage plant population

  1. From Table 2, based on the field's after-damage plant population (#2e) and the original
    planting date (#5): _________% of optimum yield
 

Step 11. Additional yield loss due to uneven plant stands

  1. If common gap size (#3) is more than 3 feet, enter 5%; if it is less than 3 feet,
    enter 2%: ________% yield loss

Step 12. Additional yield loss due to defoliation

  1. Based on percent of leaf area lost or destroyed (#4a) and the corn's growth
    stage when damaged (#4b): _________% yield loss

Step 13. Yield potential of the damaged field

  1. (#10)_____% - (#11)______% - (#12)_______% = ______% of optimum yield

Yield Potential if Damaged Field is Replanted

 

Step 14. Replant target population

  1. Planned seeding rate: _____________ seeds/a.
  2. Seed germination percentage (from seed tag):________%
  3. Expected plant survival rate (use 95% if you're not sure): ________%
  4. Replant target population (#14a x #14b x #14c):___________plants/a.

Step 15. Expected yield from replanting

  1. From Table 2, based on the likely replanting date (#6) and the replant target
    population (#14d): _________% of optimum yield

Feasibility of Replanting

Step 16. Yield gain or loss from replanting 
  1. (#15)______% - (#13)________% = ______% of optimum yield
  2. If there is a yield loss, replanting is not warranted and should not be done. If there is a
    yield gain, go on to Steps #17 and #18.

Step 17. Gross income from a replant yield gain

  1. (#16)_______% x (#8)_______ bu./a.= ________ bu./a.
  2. (#17a) _______ bu./a. x (#9)$_________ /bu. = $ _______/a.

Step 18. Dollar gain or loss from replanting

  1. (#17b)$______ /a. - (#7f) $_______ /a. = $ _______/a.

 

Replant options following herbicide applications

by Brent Pringnitz, extension program specialist and Bob Hartzler, extension weed scientist, Department of Agronomy. http://www.ipm.iastate.edu/ipm/icm/1998/6-8-1998/replant.html

Due to the recent severe weather and hail occurring throughout Iowa, there are many situations where replanting the crop may be necessary. However, it is important to remember that some herbicides limit replant options. For example, if a cornfield treated with atrazine was destroyed by hail in early June, the only crop options are corn and sorghum, regardless of the atrazine application rate. If a herbicide tank mixture was applied, the most restrictive replant label must be observed. This table lists replant options, time delays for replanting, and approximate herbicide persistence. Always refer to the herbicide label for specific information.

Herbicide

Replant options

Delay before replanting

Approximate herbicide persistence (in months)

Accent

Corn, soybeans

c-None, s-15 days

1

Accent Gold

Corn

None

2-8

Atrazine

Corn, sorghum

None

2 -8

Authority Broadleaf

Soybeans

None

4-10

Axiom

Corn, soybeans

None

1-4

Banvel/Clarity

Corn

None

1-1.5

Basis

Corn, soybeans

c-None, s-15 days

0.5-1

Basis Gold

Corn

None

10

Beacon

Corn

14 days

1-2

Bicep II, Bicep II Magnum

Corn, sorghum1

None

2-8

Bladex

Corn, sorghum

c-None, s-30 days

2-3

Broadstrike + Dual

Corn, soybeans

None

2-4

Broadstrike + Treflan

Soybeans

None

2-6

Bronco

Corn, soybeans, sorghum1

None

1-2

Bullet

Corn

None

2-8

Celebrity

Corn

None

1-1.5

Command

Soybeans

None

3-9

Commence

Soybeans

None

3-9

Contour

IMI-corn

None

3-11

CropStar

Corn, soybeans

None

1-2

Dual II, Dual II Magnum

Corn, soybeans, sorghum1

None

1.5-2.5

DoublePlay

Corn

None

2-3

Eradicane

Corn, sorghum

c-None, s-30 days

1-1.5

Exceed

Corn

4 weeks

4-12

Extrazine

Corn, sorghum

None

2-3

FirstRate

Soybeans

None

9

Frontier

Corn, soybeans, sorghum

None

1-2

FulTime

Corn

None

2-8

Gramoxone Extra

Corn, soybeans, sorghum

None

not applicable

Guardsman

Corn

None

2-8

Harness

Corn

None

1-2

 

Herbicide

Replant options

Delay before replanting

Approximate herbicide persistence (in months)

Harness Xtra

Corn

None

2-8

Hornet

Corn

None

2-4

Laddok

Corn, sorghum

None

2-8

Lariat

Corn, sorghum1

None

2-8

Lasso

Corn, soybeans, sunflowers, sorghum1

None

1-2.5

Lexone/Sencor

Soybeans, corn2

None

1-2

Liberty

Corn, soybean, sorghum3

None

1

Lightning

IMI-corn

None

3-11

Lorox

Corn, soybeans

None

2-4

Marksman

Corn

None

1-4

OpTill

Corn, sorghum

None

1-2

Partner

Corn, soybeans, sunflowers

None

1-2

Permit

IR/IMR corn, IT/regular corn, sorghum

IR/IMR-None, IT/Reg-1 month, sorg-2 months

2-4

Pinnacle

any crop

45 days

1-2

Princep

Corn

None

2-8

Prowl /Pentagon PPI

Soybeans, sunflowers

None

3-6

Prowl/Pentagon PE

Soybeans, corn4, sunflowers

None

3-6

Pursuit/Pursuit DG

IMI-corn, soybeans

None

3-11

Pursuit Plus

Soybeans

None

3-11

Python

Corn, soybeans

None

2-4

Raptor

Soybeans

None

3-9

Ramrod

Corn, soybeans for seed, sorghum

None

1-1.5

Reliance STS

Soybeans

None

3-9

Resolve

IMI-corn

None

3-11

Roundup Ultra

Any crop

None

0-1

Salute

Soybeans

None

3-6

Scepter

Soybeans

None

3-18

Scorpion III

Corn

None

4-10

Shotgun

Corn, sorghum

None

2-8

Skirmish

Soybeans

None

3-9

Sonalan

Soybeans

None

3-6

Spirit

IMI-corn, corn

IMI-None, Corn-4 weeks

4-12

Squadron

Soybeans

None

3-18

Steel

Soybeans

None

3-18

Stinger

Corn

None

10

Surpass

Corn

None

1-2

Surpass 100

Corn

None

2-8

Synchrony STS

Soybeans

None

3-9

 

Herbicide

Replant options

Delay before replanting

Approximate herbicide persistence (in months)

TopNotch

Corn

None

1-2

Touchdown

any crop

35 days

0-1

Tough

Corn, soybeans

c-None, s-30 days

0-1

Treflan

Soybeans, sunflowers

None

3-6

Tri-Scept

Soybeans

None

3-18

Turbo

Soybeans

None

1-2.5

2,4 -D

Corn, soybeans

1 week

0.5-1


1 Only if safener-treated seed is used.
2 Do not rework soil.
3 Liberty-Link only.
4 Rework soil, if necessary. Plant below depth of tillage.

 


Todd Vagts
Iowa State University Extension
Field Crops Specialist
1240 D. Heires Avenue 
Carroll, IA 51401 
Office: 712-792-2364; Cell: 712-249-6025;  Fax: 712-792-2366
Email: vagts@iastate.edu  

 

 


 


For questions or comments please respond to vagts@iastate.edu

This page last updated on 05/24/04

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