C.O.R.N. Newsletter 2011-18

Dates Covered: 
June 14, 2011 - June 20, 2011
Editor: 
Jon Rausch
Head Scab is Not the Only Cause of Bleached Wheat Heads

Head Scab is Not the Only Cause of Bleached Wheat Heads

We have received several reports of bleached wheat heads in fields across the state. The distribution of symptoms in the affected fields ranges from individual bleached heads scattered throughout the field to huge sections of fields or entire fields with bleached heads. Timing of symptom development ranges from one to three weeks after flowering. In some instances, bleached heads are empty (blank). Such a wide variety of patterns and symptom characteristics is causing considerable confusion among producers as to whether they are dealing with head scab or some other problem. Scab does indeed cause bleached heads, but it is not the only cause of this type of head disorder. Along with head scab, take-all, hail, frost, flooding, and injuries caused by insects (wheat stem maggot) may all lead to bleached or white discoloration of wheat heads.

Useful information to help you determine whether you are dealing with scab include 1) the weather condition shortly before and during flowering, 2) the timing of symptom development after flowering, 3) the bleaching pattern on the head and the plant, and 4) the distribution of affected heads in the field. First of all, we have had head scab favorable weather in several parts of the state this season. It has been wet and humid during flowering in some areas, and these conditions are highly favorable for head scab. Infection by the scab fungus occurs at flowering and early grain fill, resulting in symptom development between 18 and 21 days after flowering. However, under wet, humid conditions, symptoms may develop earlier. Scab symptoms appear as partially (one or a few spikelets) or completely bleached heads, usually borne on green, healthy stems. With flood damage, wheat stem maggot injury, or take-all disease, completely bleached heads are usually borne on bleached stems, as a result of premature death of the entire plant, not just the head. With scab, symptoms are usually seen scattered throughout the fields, with partially or completely bleached heads intermingled with healthy-looking heads. This is contrary to what is usually seen with damage caused by flooding or take-all, where all heads in certain sections of the field or even entire the field may be affected. Although scab may cause heads to be partially or completely blank, scab infected heads normally produce grain, however, these are usually small and lightweight, with a pinkish-white discoloration. Completely blank heads are very common with frost and flooding injuries.

Adding to the confusion is the fact that some of the bleached heads are showing up in fields that were treated with a fungicide for head scab control, leading some producers to believe that they should not be seeing scab after having their fields treated. Remember, even the best fungicides (Prosaro and Caramba), applied at the right time (at flowering) will not provide 100% scab control. Fungicides are about 50% effective against scab. Think about this in a very simple way; a field that would have had 50% of the spikes infected without a fungicide treatment, will end up having about 25% of the spike infected after fungicide application, not 0%.    

It is important to be able to tell scab apart from other problems, since scab infection is usually associated with vomitoxin contamination of grain, which does not occur with damage caused by take-all, hail, frost, flooding, or insects. Separate grain handling, processing, storage, and feeding guidelines need to be followed when dealing with vomitoxin contaminated grain. These will be addressed in next week’s issue of the C.O.R.N newsletter.

Flooding and ponding effects on corn and soybean

Flooding and ponding effects on corn and soybean

“Pop up” thunderstorms during the past week resulted in localized ponding and flooding of corn and soybean fields (most of these recently planted). If the ponding and flooding was of a limited duration, i.e. the water drained off quickly within a few hours, the injury resulting from the saturated soil conditions should be minimal. 

CORN
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. Prior to the 6-leaf collar stage (as measured by visible leaf collars) or when the growing point is at or below the soil surface, corn can usually survive only 2 to 4 days of flooded conditions. Since much of the corn that’s been planted so far is not beyond the V3 to V4 stage, it’s especially vulnerable to damage from ponding and saturated soil conditions. The oxygen supply in the soil is depleted after about 48 hours in a flooded soil. Without oxygen, the plant cannot perform critical life sustaining functions; e.g. nutrient and water uptake is impaired, root growth is inhibited, etc. If temperatures are warm during ponding (greater than 77 degrees F) plants may not survive 24-hours. Cooler temperatures prolong survival so the relatively cool temperature forecast for the next couple of days should be beneficial. Once the growing point is above the water level the likelihood for survival improves greatly.

Even if ponding doesn't kill plants outright, it may have a long term negative impact on crop performance. Excess moisture during the early vegetative stages retards corn root development. As a result, plants may be subject to greater injury during a dry summer because root systems are not sufficiently developed to access available subsoil water. Ponding can also result in losses of nitrogen through denitrification and leaching. Even if water drains quickly, there is the possibility of surface crusts forming as the soil dries that can impact the emergence of recently planted crops. Growers should be prepared to rotary hoe to break up the crust to promote emergence.

For corn that’s emerged, check the color of the growing point to assess plant survival after ponding. It should be white to cream colored, while a darkening and/or softening usually precedes plant death. For corn not yet emerged, evaluate the appearance and integrity of seeds or seedlings that have yet to emerge (likely rotting if discolored and softening). Look for new leaf growth 3 to 5 days after water drains from the field.

Disease problems that become greater risks due to ponding and cool temperatures include pythium, corn smut, and crazy top. Fungicide seed treatments will help reduce stand loss, but the duration of protection is limited to about 10-14 days. The fungus that causes crazy top depends on saturated soil conditions to infect corn seedlings. There is limited hybrid resistance to these diseases and predicting damage from corn smut and crazy top is difficult until later in the growing season.

SOYBEAN (the following is adapted from Palle Pedersen, former soybean extension specialist, Iowa State University) Water logging and poor aeration associated with localized floods and ponding can result in significant soybean yield reduction. The extent of ponding and flood damage to soybean is related to the temperature of the water, the amount of water motion and the duration of the flooding and ponding conditions.

Soybean prefers adequate soil oxygen for maximum productivity. Oxygen content of water is much lower than air therefore saturated soils and flooding reduces the amount of oxygen available to the plant. Research has shown that oxygen concentration can be close to zero after 24 hours in flooded soil, depending on water movement. Without oxygen, the plant cannot perform important functions like respiration, an important function of plant growth. Soybeans can generally survive for 48 to 96 hours when completely submersed. The actual time frame is dependent upon air temperature, cloud cover, soil moisture conditions prior to flooding, and rate of soil drainage.
 
Temperatures influence the speed of respiration so high temperatures will be more detrimental to soybean recovery since the faster the respiration is “running” the faster the oxygen is depleted and the plants then start rotting. Cool, cloudy days and cool, clear nights increase the survival of a flooded soybean crop.
 
Research from Minnesota shows that flooding for 6 days or more may result in a significant yield loss or loss of the entire crop. With temperatures in the 80s, soybean plants may only survive a few days. Ohio researchers found that plants in flooded fields are injured from a buildup of toxins and carbon dioxide, which is up to 50 times higher in flooded soils than in non-flooded soils. They concluded that plants are more injured from the buildup of carbon dioxide than from lack of oxygen. During emergence, soybean fields subjected to flooding and saturated soil conditions are at major risk from Phytophthora and Pythium damping-off.
 
Reference
Nielsen, R.L. 2011. Effects of Flooding or Ponding on Young Corn. Corny News Network, Purdue Univ. [On-Line]. Available at: URL: http://www.kingcorn.org/news/timeless/PondingYoungCorn.html
Pedersen, P. 2008. Effect of flooding on emerged soybeans, Department of Agronomy
http://www.extension.iastate.edu/CropNews/2008/0531PallePedersen2.htm

Potato Leafhopper Time!

With first-cut alfalfa finally being harvested in Ohio, we are entering that time of summer when potato leafhopper becomes a concern.  Growers should begin scouting for the leafhopper when alfalfa regrowth reaches sufficient height for sweep-net sampling.  A single sample is 10 sweeps of a sweep net.  When the average number of adults and nymphs in a sample is equal to or greater than the average height of the alfalfa stand, insecticide treatment is warranted.  For example, if the alfalfa is 6 inches tall and the average number of leafhoppers is 6 or higher, insecticide treatment is warranted.  If the average is lower, the grower should re-sample in a few days.   If the alfalfa is a glandular-haired, leafhopper-resistant variety, the economic threshold is 3X the normal threshold, or three leafhoppers per inch of growth (18 leafhoppers for 6 inch tall alfalfa, for example).  However, if the resistant alfalfa is a new planting this spring, growers might want to use thresholds meant for regular alfalfa during the very first growth from seeding.  After the first cutting, growers can then use 3X times the normal level threshold.   More information on potato leafhopper, including how alfalfa growing conditions might affect the threshold, is available at http://ohioline.osu.edu/ent-fact/pdf/0033.pdf .

Early Season Hail Injury To Corn Usually Limited

Some of the thunderstorms that rolled through Ohio recently were accompanied by hail that may have caused damage to corn.  The impact of hail damage is largely dependent on the corn plant’s stage of development.  Presently there is not much corn in Ohio that’s beyond the six leaf collar stage (V6). Hail affects yield primarily by reducing stands and defoliating plants. Most of the hail damage results from defoliation. Generally, the corn plant is little affected by hail prior to the V6 leaf stage because the growing point is at or below the soil surface and in the leaf whorl. However, once the growing point is elevated above the soil surface due to internode elongation, the plant grows rapidly and becomes increasingly vulnerable to hail damage with the tassel stage/pollen shedding stage (VT) being the most critical period.

 Leaf damage by hail usually looks much worse than it really is, especially during the early stages of vegetative growth. Shredded leaves have some capacity to contribute to plant growth. Plants not killed outright by hail usually show new growth within 3 to 5 days after injury occurs (i.e. if damage occurs prior to tasseling). For this reason, estimates of hail damage should be delayed several days to allow for this period of re-growth. If rains associated with hail damage splash bacteria into hail damaged leaf whorls, bacterial soft rots may develop and destroy the corn growing point; this problem is more likely when ponding or standing water occurs after the storm.

 Severe hail damage prior to 6 to 7 leaf collar stage can also result in “twisted” or “tied” leaf whorls as injured plants recover and new leaves try to unroll. The twisted and tied leaf whorl occurs because damaged whorl leaf tissue dies and restricts expansion of unaffected whorl leaves.  However, most plants will grow out of this problem and tied whorls seldom cause major yield loss. Moreover, bruising from hail early in the season usually does not result in increased stalk lodging or stalk rot later in the season.  Results of an Ohio study that evaluated recovery of hail damaged corn in fields exhibiting severe twisted and tied leaf whorls are available online at http://ohioline.osu.edu/sc179/sc179_16.html

 The hail insurance adjustor's growth staging system counts leaves beyond the last visible collar to the uppermost leaf that is 40-50% exposed whose tip points downward - usually this results in a leaf stage that is numerically 2 leaves greater than the "leaf collar method" (e.g. a V6 plant according to the leaf collar method would probably correspond to a 8-leaf plant according to the hail adjustor's method).

Percent yield loss in corn based on growth stage & defoliation

(adapted from NCIA Corn Loss Instructions, rev. 1984)

 

 

Percent Leaf Defoliation

Growth Stage*

25%

50%

75%

100%

7-leaf (~V5)

0

2

5

9

8-leaf  (~V6)

0

3

6

11

9-leaf (~V7)

1

4

7

13

10-leaf  (~V8)

1

6

9

16

*as determined using the hail adjustor’s leaf staging method (approximate leaf collar stage indicated within parentheses)

For more on hail injury to corn, check out the following articles. The one written by Dr. Bob Nielsen at Purdue University, includes excellent pictures documenting corn recovery from hail damage -

Nielsen, R.L. 2011. Recovery From Hail Damage. Corny News Network, Purdue Univ. [On-Line]. Available at: http://www.kingcorn.org/news/timeless/HailDamageYoungCornGallery.html

Vorst, J.J. 1993. Assessing Hail Damage to Corn. Purdue Univ. Cooperative Ext. Service Publication NCH-1. [On-Line]. Available at http://www.ces.purdue.edu/extmedia/NCH/NCH-1.html

Other Insect Concerns on Field Crops

Other Insect Concerns on Field Crops

Last week we received a number of reports of three insects in sufficient populations to cause grower concern.   These insects are black cutworm on corn, armyworm on wheat (which perhaps will soon be moving to corn), and bean leaf beetle on soybean.  As we mentioned in previous articles in this newsletter, these are insects that should be scouted for potential problems that might need management.  See past C.O.R.N. newsletter articles from this spring, or the field crop insect web site, http://entomology.osu.edu/ag/, for information on these insects along with a list of insecticides that will offer control. 

Feeding Wheat to Beef Cattle

As we anticipate the probability of wheat quality being less than ideal and in some cases below quality standards for milling you may want to look at alternative markets. Steve Boyles, OSU Extension Beef Specialist has provided some guidence on wheat as a feedstuff.

Wheat can be used to replace a part of the grain ration when protein prices are high and wheat is relatively cheap compared to other grains. As a general rule, limit mold-free wheat to 50% of the grain portion in finishing diets. However, some experienced feeders have used larger amounts of wheat. I tend to recommend lower levels to people not familiar with feeding wheat though (fast fermentation). Lower quality wheat: Limit wheat to 40% of dry matter or 50% of corn, whichever is highest. Take a longer time to build up to full feed than you would with corn. I would not recommend using wheat in high grain diets on self feeders or in creep rations. Salt (7-12%) might be used as an intake inhibitor for cattle on grass using a self-feeder. However, producers need to monitor consumption.

Wheat can range form 9-17% protein. Full value can be given to the protein in wheat. Since cattle can use nonprotein nitrogen to meet protein needs, beef feeder probably should not pay much premium for high protein wheats.

Processing Wheat: Although the kernel must be cracked or broken, over processing will result in the production of many fines that are undesirable since the rate of wheat starch digestion in the rumen is very rapid. Therefore, an excessive amount of fine particles will cause generally low and erratic intakes, digestive upsets and poor performance. If wheat is dry-rolled, it should be rolled or ground as coarsely as possible while still breaking all the kernels. Rolling rather than grinding generally results in fewer fines. Steam flaking wheat can improve animal performance. Mixing grains should occur after grain processing rather than before. Mix wheat with silage, haylage or corn grain to reduce the risk of animals eating too much at one time.

Problems of Feeding Wheat: Once on full feed, feed should be kept before the cattle at all times. It is not advisable to change back and forth from wheat to other feed grains when feeding high concentrate rations. Wheat is a fast fermenting grain in the rumen. Problems of depressed feed intake, acidosis and abscessed livers have been reported. They are the basis for recommendations on limiting the amount of wheat in the ration, mixing it with other grains, and for feeding at least 15% roughage. In general keep fiber levels above 6%. Wheat rations that have 6-10% fiber can work well. The addition of ionophores has made it possible to reduce some of these digestive problems and feed the higher levels of wheat.

Buffers: Buffering agents have been added to overcome the problems of reduced feed intake when high-wheat rations are feed to cattle. Adding 3.5 ounces of sodium bicarbonate (baking soda) per head daily gives a slight improvement in performance of steers on wheat rations. A finely ground feed-grade limestone can also serve as a buffer. Adding an additional 1.0 to 1.3% (dry matter basis) finely ground feed grade limestone to wheat rations may give a slight improvement to performance of cattle. However, avoid increasing the calcium levels of the ration above 0.9 (dry matter basis).

Sprouting: Wheat showing more than 2% percent sprouted kernels is classified as sprouted wheat. The nutritional value of grain protein does not appear to be depressed, providing the sprout is not lost. The value of sprouted wheat for ruminant feed is apparently only slightly affected, if at all by moderate sprouting. One aspect of the feeding of field sprouted grains that must be mentioned is the fact that mold and fungal infestations are more likely with sprouted grain. Care must be taken to avoid feeding moldy wheat to livestock to prevent mycotoxin poisoning. If you suspect toxins, have it tested.

Scab: The occurrence of scab in wheat does not automatically mean vomotoxin but high levels of scabby kernels in harvested grain should be suspect. If you suspect mold/toxins have it tested. Here is a link from the OSU Beef Team Library on what to do if aflotoxins are present. http://beef.osu.edu/library/mycotoxins.html

DON (vomotoxin): New FDA limits for "beef" cattle are indicated in Dr. Shulaw's response in the previous article. Research conducted in North Dakota and Minnesota has suggested growing and finishing cattle can tolerate higher levels (up to 18 ppm) based on research at the Carrington Research Extension Center). Assume all other classes of livestock (including horses) have much lower levels of tolerance. Molds/mycotoxins can be higher in screenings than the grain.

Agronomic Performance of Modified Relay Intercropping

Agronomic Performance of Modified Relay Intercropping

Modified Relay Intercropping (MRI) is the planting of soybeans into standing wheat.  MRI planting occurs in late May or early June.  Soybeans in the MRI system are generally sown into wheat around the pollination time period, with a planter or grain drill.  The wheat has a tramline to facilitate soybean planting.  Light or the lack of it, has a profound effect on the growth of intercropped soybeans.  Soybeans planted too early into well tillered wheat often may become tall and spindly, be clipped by the combine and take longer to recover after wheat harvest.  The wheat plant, by virtue of its wide adaptability, is able to tolerate slightly wider row spacing  (10 to 16 inches) and the stress of soybean planting with minimal yield loss.  In 12 years of replicated trials on the MRI system, soybean and wheat yields have averaged the following over all trials: 74 bu/acre for wheat and 31 bu/acre for soybeans.  Wheat yields in good years have exceeded 80 bushels per acre and soybean yields over 40 bushels per acre.

Among the trials conducted the include the follow:

  1. Effect of intercropping on wheat yield.
  2. Effect of intercropping in wide row wheat yield (15 inches)
  3. Effect of wheat nitrogen rate on wheat and soybean yield in a MRI system.
  4. Effect of USDA inoculate on soybean yield in a MRI system.
  5. Effect of fungicide yield of Roundup Ready soybeans in a MRI system.
  6. Effect of seed treatment insecticide on soybean yield in a MRI system.

Modified Relay Intercropping Wheat and Soybean Yields (Crawford County, Ohio)

Year

MRI Wheat Yields (bu/ac)

MRI Soybean Yield (bu/ac)

1994

65

41

1995

72

27

1997

70

28

1998

73

41

1999

83

5

2000

76

37

2003

67

29

2004

65

47

2007

84

0

2008

82

37

2009

88

30

2010

61

45

Grand Mean

74

31

For more information on MRI go to http://crawford.osu.edu .

 

Weather Outlook through July 3

The outlook is as follows:

A cooler pattern for much of this week will give way to a more summer pattern again this weekend into most of next week. An area of showers can be expected the middle and end of this week on a warm front followed by another warm front and some rain activity late weekend. More organized activity will follow in a warm and humid air-mass for the second half of next week.

Overall, temperatures the next few week will average near to slightly above normal and precipitation near to slightly above normal.

June 13-19 - Temperatures normal to -2F. Rainfall 0.50" to 1.50" on average.

June 20-26 - Temperatures +2 to +5F.  Rainfall 0.50" to 2.00" on average.

June 27-July 3 - Temperatures near normal. Rainfall 0.50" to 1.00" on average.

Three week average: Temperatures 0 to +1F. Rainfall 1.5-4.5 inches. Normal is 3 inches.

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Crop Observation and Recommendation Network

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.