ndsucpr_L_sm_PS.jpg (12513 bytes)

pscience_Logo_Lg.jpg (12372 bytes)


ISSUE 13  July 26, 2001

 

GUIDELINES FOR HARVEST LOSSES

What’s a good guide to determine the amount of any given crop loss in a field prior to or following harvest? There can be pre-harvest losses due to shattering, gathering losses at the combine header and also separation losses due to the threshing operation itself. In the chart below is an approximate loss guide to determine how much if any is being left in any given field. Usually crop harvest losses in the 2 to 3 percent loss range are tolerated.

Kernels or seeds per pound and number per square foot to equal one unit loss per acre at harvest.

Species

Seeds/pound*

Seeds/ft. To
equal 1 bu/Acre

Spring Wheat

14,300

20

Durum Wheat

11,500

16

Barley

13,500

15

Oats

15,500

11

Flax

88,000

113

Rye

18,000

42

Soybeans (small)

3,300

4.5

Soybeans (large)

2,400

3.5

Corn (Med. grade)

1,500

2

Sunflower (oil)

9,000

5

Sunflower (Conf.)

5,000

2.5

Navy beans

3,000

4

Pinto beans

1,400

2

Sorghum

15,000

18

Sundangrass

44,000

40

Proso millet

80,000

84

Foxtail millet

220,000

242

Buckwheat

15,000

16

Canola

150,000

172

*These are average numbers from past seasons, and individual varieties or hybrids will vary among themselves as well as be influenced by environmental factors.

Duane R. Berglund
Extension Agronomist
dberglun@ndsuext.nodak.edu

 

SCOUTING CORN FROM TASSELING TO MATURITY

A. Plant leaves show damage or affects from a detrimental cause:

1. leaves are eaten

* look for tracks of livestock or wild animals
* insect damage (consider armyworms, grasshoppers, corn borers, Japanese beetles or even katydids)

2. leaves are shredded

* hail damage
* wind damage
* disease (sorghum downy mildew)

3. leaves have a dead "frosted" appearance

* frost or freeze
* drought
* disease (stalk and root rots, leaf blights or anthracnose)
* insects (corn leaf aphid, spider mites or corn borers)

4. leaves are spotted or dead

* disease (leaf blights, rust, Physoderma brown spot, eyespot, Goss's wilt, gray leaf spot, Helminthosporium leaf spot or anthracnose)
* chemical damage (check for possible spray drift)

5. leaves show a discolored sheath

* insects (corn leaf aphid)
* disease (purpling at these later stages can be caused by saprophytic organisms)
* leaf injury

6. leaves are red or purple

* mechanical injury
* barren plant (sugars which cannot be translocated to an ear will accumulate in the leaves with the anthocyanins expressing color)
* disease (maize chlorotic dwarf virus, corn stunt or rust)
* genetics of the hybrid

7. leaves show white striping with white, downy growth on the upper and lower leaf surfaces

* soghum downy mildew

B. Plant silks are affected

1. silks are eaten off

* insects (corn rootworm beetles, corn earworm, caterpillars, katydid, western bean cutworm, Japanese beetle, grasshoppers or armyworms)

2. no silks or they are delayed many days after tasseling

* heat
* drought
* nutrient deficiency or imbalance (usually nitrogen or phosphorus)
* temperature variation (usually cold followed by warm)
* insects (corn leaf aphid or spider mites)
* excess stand population for conditions

3. silks are trapped or balled within the husk

* drought
* nutrient deficiency
* insects
* temperature variation (usually cold followed by warm)
* genetics of the hybrid

4. silks are red or green in color

* fresh silk color is genetically controlled

C. Plant tassel is affected

1. tassel failed to emerge

* drought or heat stress
* nutrient deficiency (usually boron)
* insects (corn leaf aphid pressure has stressed the plant)

2. tassel is replaced by a mass of leaves

* disease (crazy top, sorghum downy mildew or head smut)

3. tassel is replaced by one or more small ears

* genetic and environmental interaction (will be more common on tillers)

4. the tassel is broken off and the corn stalk is tunneled

* insects (European corn borer)

D. Corn stalk shows symptoms

1. stalk is red or purple

* mechanical injury
* barren stalk (anthocyanins are expressing color due to sugar accumulation)
* genetics of the hybrid

2. barren plant or no ear enlargement

* drought
* heat
* nutrient deficiency or imbalance
* insects (corn leaf aphid or spider mites)
* silks were eaten off prior to pollination
* disease (head smut, viruses or mildews)
* excess plant population for the conditions
* tillers (seldom carry a full ear as long as the main plant has dominance)
* silking or pollen shed disrupted (environmental stress)
* mechanical damage

3. stalk is broken below the ear

* wind (green snap)
* disease (stalk and root rots)
* nutrient imbalance (usually excess nitrogen, insufficient potassium)
* insects (corn borer)
* weather stress (drought, heat or other conditions limiting photosynthesis)
* mechanical damage (machinery, livestock, other animals)
* excessive plant populations for the conditions
* delayed harvest

4. stalk is broken above the ear

* wind
* insects (European corn borer or fall armyworm)
* mechanical damage
* delayed harvest

5. plant has multiple ears at one node

* genetics of the hybrid
* mechanical plant injury
* cold temperatures when the ears formed
* disease (viruses or mildews)
* insects (any that cause silk feeding may actually result in multiple, small ears)

6. plant is leaning (lodged) but not broken

*wind and wet soil
* poor root development (drought, fertilizer placement, soil compaction, low soil pH or poorly drained soil)
* insects (corn rootworms or other root feeders)
* nematode activity (usually not in the Valley)
* disease (stalk and/or root rots)
* nutrient deficiency (usually potassium)
* herbicide damage (usually a growth regulator)
* mechanical damage
* delayed harvest

7. plant has a premature death

* disease (stalk/root rots or leaf blights)
* insects (corn borers)
* frost or freeze
* severe drought
* lightning (plants will be killed in a circular pattern)

8. stalk appear black and moldy

* saprophytic organisms have built-up under warm, humid weather conditions, harvest early

E. Corn ears show symptoms

1. numerous ear shoots that are only leafy (barren)

* disease (crazy top, sorghum downy mildew or a virus)

2. smut galls appear

* disease (common corn smut)

3. ear tips are poorly filled

* nutrient deficiency (usually potassium or nitrogen)
* excess stand population for conditions
* insects (clipped silks before pollination)
* disease (foliar diseases reduced photosynthesis of the plant)
* drought
* favorable growing conditions after pollination (rarely occurs, but allows cob to elongate without setting kernels)
* low light, carbon dioxide or temperature conditions (reduces photosynthesis, tip kernels abort)

4. ears are small, malformed or even light weight

* nutrient deficiency (usually phosphorus)
* drought or heat stress
* plant damage (mechanical or disease)
* excessive plant populations for conditions
* it is a second or third ear on the stalk or a tiller
* insect-caused plant stress (corn leaf aphid and others)
* disease (virus, leaf blight or stalk and ear rots)
* soil compaction

5. ear has short husk with tip exposed

* weather (usually drought or heat that stopped husk development)

6. barren ear

* disease (head smut or virus)
* pollination failure (drought, heat or other stress, insects, chemical damage)

7. dropped ears

* drought (shank was weakened)
* nutrient deficiency (shank was weakened)
* genetics of the hybrid (ears may drop free of the husk)
* insect damage of shank (European corn borer)

8. ear shows a scattered kernel set

* lack of viable pollen
* silks eaten
* heat or drought at pollination
* nutrient deficiency
* chemical damage (growth regulators or thiocarbamates)

9. ears have kernel feeding

* insects (corn earworm, bean cutworm, corn borer or fall armyworm)
* birds or animals

10. ear has rotten spots on parts or all of the ear

* disease (ear/kernel rots or Helminthosporium leaf spot)
* insects (often followed by weathering and disease)
* bird feeding
* hail or other mechanical injury

11. kernels have been eaten from the ear tips

* birds
* wild animals or rodents
* insects (corn earworm, fall armyworm or bean cutworm)

12. insect has tunneled into the ear, cob, shank or stalk

* European corn borer

F. Kernels on the ear show symptoms

1. broken seed coats give the kernels a "popped" appearance

* popped kernels (a genetic by environment interaction which usually occurs under high temperatures)

2. seedcoat is split

* silk cut (a genetic by environmental interaction which is usually not visible until the kernels are shelled)

3. kernels have pink or red streaking, especially over the crown area

* kernel red streak (caused by wheat curl mite feeding and the toxin secreted, usually more pronounced toward the ear tip, not detrimental)

4. sprouted kernels

* high rainfall and warm temperatures while the ear remained on the stalk (usually is accompanied by ear mold)

 

HAIL ON CORN EFFECTS ESTIMATED BY LEAVES

Estimated corn grain yield loss due to defoliation in corn can give you an idea of where your corn crop is in areas where hail recently hit. Total corn loss from hail damage is estimated by adding the expected yield loss caused by stand reduction, the expected loss caused by defoliation and the expected loss caused by direct ear damage. This, however, is only an estimate of the percent yield loss. Complete green snap of plants below the ear will result in loss of the plant. Unfavorable weather later in the season can cause yields to be lower than expected or favorable weather can cause yield increases.

 

Growth Stage

% Leaf Defoliation

 

10

40

60

80

100

 

% Yield Loss

Later leaf stages prior to tasseling

3

18

38

64

96

At tasseling

3

21

42

68

100

Silking

3

20

39

65

97

Silks brown

2

18

36

60

90

Pre-Blister

2

16

32

54

81

Blister

2

16

30

50

73

 

HAILED SOYBEANS MAY COMPENSATE BUT WATCH FOR DISEASE

Yield loss in soybeans is determined on the stage of growth of the soybeans at the time of damage and the degree of plant damage. Damage can be due to leaf defoliation, stand reduction, stem damage and pod damage. The calendar date and pest control later also affect ultimate yield.

Check stands 7-10 days after a storm to determine the stand reduction. Determine the current stand versus the original stand. Count these losses as total losses if the plants are totally damaged below the cotyledons. Shredded or cut stems may lead to bruised plant stems. Mild bruising may only break in the outer stem tissue but severe bruising may expose the central stem tissue and lead to more loses. Unfortunately, bruised stems that recover may break any time before harvest as they are weakened. They may lodge and make harvest very difficult. It is very difficult to determine yield loss from bruised plants until harvest.

Defoliation is a measure of the leaf area destroyed by the storm. Leaf loss on soybeans during vegetative stages has little effect on yield (if only the leaves are shredded); however, defoliation during reproductive stages does affect yield. Added damage to stems and branches may also decrease yields more, depending on how the weather progresses during the remainder of the season and if additional disease or insect damage results on damaged soybeans. The further along in maturity a soybean plant is, the more effect on yield.

 

Growth Stage

% Defoliation

 

10

40

60

80

100

% Yield Loss (estimated–with no flower/pod loss)

R1-R2

0

5

7

12

23

R3

2

6

11

18

33

Loss of excess flowers beyond the normal losses on soybeans or losses of pods may increase yield losses.

Denise McWilliams
Crop Production Specialist
dmcwilli@ndsuext.nodak.edu


cprhome.jpg (3929 bytes)topofpage.jpg (3455 bytes)tableofcontents.jpg (4563 bytes)previous.jpg (2814 bytes)next.jpg (1962 bytes)