C.O.R.N. Newsletter 2011-13

Dates Covered: 
May 17, 2011 - May 23, 2011
Editor: 
Glen Arnold

The period from 1895-1964 had 11/69 times with a state average of 12+ inches (16% of the time) while since 1964 we had none from 1965-2007 (0/42). We have had two since 2008 - 2/46 (4%). The mean over the period of record is 11%.

We are regressing to the mean!

 http://www.ncdc.noaa.gov/temp-and-precip/time-series/index.php?parameter=pcp&month=04&year=2011&filter=3&state=33&div=0

 First, let's review April final numbers. The link below is for the official statistics,

http://www.ncdc.noaa.gov/sotc/national/2011/4

The following is the outlook for the next two weeks which is not much different than the outlook issued last week:

May 16-22 - Temperatures will average 2 degrees below normal. However, temperatures will average 10 degrees below normal the first half of the week and 6 degrees above normal for late week into the weekend. It will be a tail of two-halves. Rainfall will be near normal around an inch but will be highly variable. Some areas especially southwest may see 0.50 inches or less while some places in the northeast and east could exceed 1.5-2 inches. Most of the rain will be through Wednesday or early Thursday before we dry out for the second half of the week into much of the weekend.

 May 23-29 - Temperatures will be 5-10 degrees above normal. Confidence on temperatures is rather high. As for rainfall, confidence is low to moderate as there is uncertainty in how strong the high pressure will be over the Southeast extending north into the Ohio Valley. Rainfall will likely be at least normal (an inch) but will be highly variable, 0.5 to 2+ inches. It looks like the heaviest rain will fall in the western corn/soybean belt. There is a chance we will return to above normal rainfall for the second half of next week.

May 30-June 5 - Temperatures will remain above normal with rainfall normal or above normal. Heaviest rain will likely continue to shift to the western corn/soybean belt. 

Statewide, wheat growth stage ranges from Feekes 7 to Feekes 10.5. Concerns about wheat diseases, especially head scab, continue to increase. Some fields in southern Ohio are at Feekes 10.5, heading, and will likely reach flowering later this week. The scab risk tool now shows a few areas of moderate risk in southern Ohio and these risk predictions will likely increase if it does indeed continue to rain and temperatures increase over the next few days.

Fields in the southern third of the state are, or will be, at risk during this week (May 16-21). Be prepared to apply a fungicide at flowering to suppress scab and vomitoxin. Application by air may be the only option if it is too wet to get into the field. For the best results in terms of scab control, THESE AERIAL APPLICATIONS NEED TO BE MADE AT FLOWERING, USING A VOLUME OF 5 GAL/ACRE AND GETTING AS CLOSE AS POSSIBLE TO THE WHEAT CANOPY. Applications made at flowering will also help to control foliar diseases. However, applications made before flowering to manage foliar diseases will not provide adequate control of scab or vomitoxin.

2 - The head scab fungus infects when the wheat crop is flowering i.e., when anthers are seen sticking out of the heads, causing scab to develop and producing vomitoxin. 

3 - Therefore, fungicides need to be applied to protect the flowering head to reduce infection, scab development, and vomitoxin production.

4 - Between flag leaf emergence and boot, the head is in the leaf sheath of the flag leaf where it is protected from the head scab fungus, so scab will not cause a problem while the head is hidden, even during these constant rains.

5 - Between flag leaf emergence and boot, the head is in the leaf sheath of the flag leaf where the fungicide will not reach it. These fungicides need to be applied like a protectant – ON THE PLANT PART just prior to infection. THIS PLANT PART FOR SCAB control is the WHEAT HEAD WITH ANTHERS HANGING OUT. So, if it becomes wet and humid after the heads emerge when the crop is at greatest risk for scab, applications made before flowering WILL NOT PROVIDE PROTECTION.

6 - Fungicide application between flag leaf emergence and boot will provide EXCELLENT CONTROL OF LEAF DISEASES BUT NOT SCAB.

7 - Fungicide applications made at heading (when the heads are fully emerged) will provide some suppression of scab, but are much less effective than applications made at flowering.

8 - For scab and vomitoxin control, application by air may be the only option if it is too wet to get into the field, but THESE APPLICATIONS NEED TO BE MADE AT FLOWERING, USING A VOLUME OF 5 GALLONS/ACRE AND GETTING AS CLOSE AS POSSIBLE TO THE WHEAT CANOPY. 

9 - APPLICATION BY AIR BEFORE FLOWERING is even LESS EFFECTIVE FOR SCAB control; quite frankly IT DOES NOT STOP SCAB.

10 - So, if you are targeting leaf diseases, applying a fungicide at this time may be an excellent idea, given the wet weather that we have had.

11 - However, if you are truly concerned about scab and vomitoxin, which is understandable after last year’s problems and the weather we have had so far, applying a fungicide now (before flowering), is both a waste of time and money. You will need to make another application at flowering to control scab.

12 - Read product labels for proper timing, since not all fungicides can be applied as late as flowering.

Long term research by universities and seed companies across the Corn Belt gives us a pretty good idea of planting date effects on relative yield potential. Estimated yield loss per day varies from about one bushel per acre after the first week of May to nearly two bushels per acre by the end of May (Nielsen, 2011). These yield losses can be attributed to a number of factors including a shorter growing season, greater disease and insect pressure and drought stress during pollination and grain fill.

Given these planting date effects, do yield losses associated with late plantings translate into lower statewide yields? Not necessarily. Let’s consider some previous growing seasons that were characterized by a “late start” and what impact this had on crop production. (For the purposes of this discussion I’ll consider “late start” years as those in which 40% or more of the corn acreage was not planted by May 20). Since 1980, there have been significant planting delays associated with wet spring weather in eight years – 1981, 1983, 1989, 1995, 1996, 2002, 2008, and 2009. Table 1 shows the percentage of corn acreage planted by May 20 and May 30, the 50% planting date (the date by which 50% of the corn acreage was planted), yield, the state average yield for the previous five years, and the departure from the yield trend in each of those years. Of these eight years, the greatest delays in crop planting occurred in 1989 when only 40% of the corn acreage was planted by May 30. In five of the eight years (1981, 1983, 1996, 2002, 2008, and 2009) average state yields were markedly lower than the state average yield of the previous five years (In six of the  eight years, average yields were five bushels per acre or more below the yield trendline for Ohio). In one of these years, 2002, the average corn yield dropped to 88 bushels per acre (nearly comparable to the record low of 86 bushels per acre in 1988). However in three of the eight years, yields were similar or higher than the than the statewide average yield of the previous five years, and in one of these years, 2009, a record high corn yield, 174 per acre, was achieved .

Table 1.  Performance of Ohio’s “Late” Planted Corn Crop– Yield

 

% of Crop Planted by

       

Year

 

 

May 20

 

 

May 30

 

50%

Planting Date

 

Yield (Bu/A)

 

Avg. Yield of

Previous 5 Years

   Departure from Yield Trend (Bu/A)

1981

 

30

 

55

 

May 26

 

96

 

108

 

-10

1983

 

45

 

65

 

May 22

 

80

 

109

 

-36

1989

 

22

 

40

 

June 4

 

118

 

116

 

0

1995

 

60

 

77

 

May 19

 

121

 

122

 

-5

1996

 

10

 

54

 

June 1

 

111

 

122

 

-15

2002

 

22

 

58

 

May 28

 

88

 

138

 

-56

2008

 

50

 

66

 

May 20

 

135

 

153

 

-7

2009

 

42

 

95

 

May 22

 

174

 

149

 

15

Data Source: National Agricultural Statistics Service USDA/NASS (http://www.nass.usda.gov/)

This comparison of statewide average corn yields from past years does not suggest that lower grain yields are a certainty with late plantings. While delayed planting may cause yield loss relative to early planting, planting date is one of many factors that influence corn yield. Figure 1 shows grain yields associated with dates by which 50% of the corn acreage was planted in Ohio, 1980-2010, and it does not suggest an especially strong relationship between planting date and yield. There are other factors that are of greater importance than planting date in determining grain yield. Weather conditions (rainfall and temperature) in July and August are probably the most important yield determining factors. Favorable weather conditions subsequent to planting may result in late planted crops producing above average yields as was case in 2009. However if late planted crops experience severe moisture stress during pollination and grain fill, then corn yields may be significantly lower than average, with 2002 being the most notable example in addition to 1981, 1983 and 1996.

Historic corn yield

Do late plantings delay corn harvests? Not necessarily. Table 2 shows calendar dates by which 50% of the corn crop was harvested in each of these” late planting” years.  In four of these late planting years (1981, 1989, 1996, and 2009), the 50% harvest date was eight to fifteen days later than the previous five year average. However, in two of the late planting years (2002 and 2008), 50% harvest dates were the same as the previous five year average 50% harvest date, and in two years (1983 and 1995), it was three to nine days earlier than the previous  five year average 50% harvest date.

Table 2.  Performance of Ohio’s “Late” Planted Corn Crop – 50% Harvest Date

Year

 

      50% Planted Date

 

     50% Harvest Date

        50% Harvest Date

         Previous 5 Years

1981

 

May 26

 

Nov 5

 

Oct 28

1983

 

May 22

 

Oct 22

 

Oct 25

1989

 

June 4

 

Nov 10

 

Oct 30

1995

 

May 19

 

Oct 23

 

Nov 1

1996

 

June 1

 

Nov 10

 

Nov 1

2002

 

May 28

 

Oct 25

 

Oct 25

2008

 

May 20

 

Oct 24

 

Oct 24

2009

 

May 22

 

Nov 11

 

Oct 27

Data Source: National Agricultural Statistics Service USDA/NASS (http://www.nass.usda.gov/)

 References

Nielsen, R.L. 2011. Corn planting is important, but…. Corny News Network, Purdue Univ. [online] http://www.agry.purdue.edu/ext/corn/news/timeless/PltDateCornYld.html [URL accessed May16, 2011]

Winter annuals that have flowered and gone to seed are dying anyway, and therefore may be not an essential target for burndown treatments.  Control of emerged marestail continues to be a primary concern.  In our experience, soybean burndown herbicide mixtures that can adequately control herbicide-resistant marestail are likely to be effective on most of the other emerged weeds in a field.

We did ignore corn burndown situations somewhat in the April 26 article.  Effective burndown is generally easier to achieve in corn than soybeans, due to the burndown activity of atrazine, higher rates of saflufenacil, dicamba, SureStart, Hornet, Lumax/Lexar, etc.  Application of 2,4-D too close to corn planting does occasionally cause crop injury, and most labels advise applying either at least 7 days before or 7 days after planting.  Dicamba products can be used at the time of planting.  Dicamba product labels allow the use of up to 1 pint/A on medium to fine-textured soils with at least 2% organic matter, but state that corn should be planted at least 1 ½ inches deep with adequate seed furrow closure to reduce risk of injury.  Gramoxone can have more utility in corn than in soybeans, because it works well in combination with atrazine and a growth regulator herbicide.

We have received questions about whether PRE herbicide rates in PRE+POST programs can be reduced when planting is delayed into late May or June.  The answer is – maybe.  The result of crop planting in late May or early June is an overall compression of the period of time for which weed control is needed.  Crops planted in late April often grow extremely slowly for a while, and a late April planting will be subject to the full season of summer annual weed emergence.  The result is that the crop can require 8 weeks or so of weed control.  Crops planted in late May typically emerge and grow faster than those planted in April.  A late May planting occurs well into the period of summer annual weed emergence, so the weeds that emerge after planted is lower.

The net result of these factors is that only about 4 weeks of weed control may be needed.  So, it may be possible to reduce PRE herbicide rates where a POST herbicide will be applied.  Keep in mind that reducing PRE herbicide rates reduces the longevity of weed control, but it also reduces the initial active rate of herbicide.  This can mean a reduction in control in tougher broadleaf weeds that require a higher herbicide rate to be controlled, such as giant ragweed, cocklebur, and morningglory.  For these weeds, reducing the PRE herbicide rate could result in a higher population of weeds, and larger weeds, at the time of the POST application. 

Scouting is done by examining 10 stems from at least 5 locations within the field.  The small, yellowish larvae should be counted and an average obtained of the number of larvae per stem, or flag leaf.  The threshold for taking action is 1 larva per stem or flag leaf.  It should be pointed out that this threshold is a reduction from that used in the past.  Research by colleagues in Mid-Atlantic States showed that the threshold should be reduced from the previous threshold of 2 larvae per stem.  While the threshold of 1 larva per stem is given in the face sheet currently in use, http://ohioline.osu.edu/ent-fact/pdf/0038.pdf , the old threshold in the Field Guide is still at the higher level.  That field guide had been written and published prior to us getting the needed information that allowed us to reduce the threshold.  Thus, to repeat, the current threshold for cereal leaf beetle IS 1 LARVA PER STEM OR FLAG LEAF.

Last week we discussed the need to take an IPM approach when applying insecticides in wheat, and the problem with automatically adding insecticides when applying fungicides.  We would point out that if fields have cereal leaf beetle populations nearing or are at the threshold of 1 larva per flag leaf, it would be appropriate to add an insecticide to the fungicide spray.  But fields should be scouted first!  There are numerous insecticides available for control of cereal leaf beetle.  One insecticide of note is Entrust, a product from Dow AgroSciences, containing spinosad.  We make mention of this material because it is OMRI listed, making it available for use by organic growers.  However, as with most other insecticides, this material is somewhat toxic to bees and thus, care should be taken when spraying, especially for potential drift problems.  It is also toxic to aquatic invertebrates.  For conventional growers, this same material is available as Tracer.  For more information on cereal leaf beetle, see the fact sheet whose address is given above.

We have also received reports of alfalfa weevil showing up on alfalfa (http://ohioline.osu.edu/ent-fact/pdf/0032.pdf ).  While there are numerous insecticides available to control this insect, we would mention that if the alfalfa is at least 16 inches tall, a preferable management technique to consider is early cutting.  However, we do note that with the wet conditions and the need to get corn and soybean planted when it finally dries up, it might be just as difficult to make an early cutting.

We have written articles regarding this subject in the past (here), and the one thing we stress is to use your knowledge of the soil/plant system to determine if the claim being made makes any agronomic sense.  While I will not go so far as to say that the university is the all-knowing entity regarding every product, products marketed without independent testing should automatically be viewed with caution.  Some practices (regardless how weird) may have some legitimacy to them, but the question is – will the observed benefit occur frequently enough to be a viable option for your operation?  Extension researchers generally do not recommend products or practices that do not have a high probability of predictability and or repeatability.

When approached with a practice or product to adopt, first ask for data to substantiate the claim.  Anecdotal data should be viewed with caution, if not disregarded completely.  Most can tell a good story about what the practice or product does, but without some solid scientific data you should be skeptical.  If it does not make agronomic sense, then you will know not to proceed.   Solid scientific data refers to a study completed by a respected researcher with a properly designed experiment.  A properly designed experiment would contain replications, necessary control treatments (checks), and statistical analysis of the data. Often product literature shows marketing data and not research data (marketing data is slanted to sell a product or concept and conveniently leaves out research that would diminish interest in the product or concept).  Marketing data is generally correct but does not tell the whole story and often leaves out important research observations. In addition, marketing data may have a university name associated with it but not the researcher’s name.

We have contacted some of the institutions listed with the marketing data to talk with the researcher and have often found out that it was a study in progress, or an unfunded proposal (no research completed) or the marketing benefit does not match the data (for example, product works but only when rates are above a certain value). If a company has a legitimate product, they should be able to fund a study with a respected researcher in one of the land grant institutions of the 12 Corn Belt States growing corn, soybeans or wheat.

Let’s look at an example of a product and practice being discussed in many parts of Ohio. Sugar is being promoted for a myriad of benefits for a crop.  It is claimed that the sugar is a source of carbon and that it will stabilize nitrogen.  First think of this from a plant physiological standpoint, how do crops take up carbon?  Unlike animals, plants do not get carbon from ingesting other carbon sources.  Plants take carbon right out of the atmosphere in the form of carbon dioxide, so supplementing a crop with a sugar based carbon source does not make physiological sense. Will the carbon in the sugar stabilize nitrogen?  Actually it can, but you may not get the desired effect.  Application of such an easily mineralized carbon source can actually result in a short-term tie up of soil solution nitrogen (called immobilization).  Since the sugar application rate is quite small, this will likely be a very short-term effect, but there will also be very little in the way of long-term effects.  The previous example tells a good story that appears logical, but when we think about it, it does not make agronomic sense. And the main caution flag, no solid scientific data. Thus a producer should not expect a benefit from using sugar to stabilize nitrogen.

To inform producers about various non-traditional products, university research and extension soil fertility specialists in the Corn Belt also maintain a data base on non-traditional ag products (Ohio State University participates with this committee). The criteria to be included in the data base follows these guidelines: 1) at least two site-years of research, with multiple crops or varieties substituting for a site-year; 2) authors listed; 3) replicated with statistical analysis; 4) reasonably applicable to north central USA crop production; 5) reference source available; and 6) author permission. These are also good guidelines for a producer to consider for legitimacy of a non-traditional product. The web site is located at http://extension.agron.iastate.edu/compendium/index.aspx . Please contact Ed Lentz or Robert Mullen for more information about this committee. If you would like to evaluate a non-traditional product, contact your county Extension Agriculture Educator to set up an on-farm experiment.

In summary consider these three points with non-traditional products:

1. If it sounds too good to be true, it probably is. This old adage is almost always true. So if something is promising tremendous yield improvements by supplying adequate nutrition, suppressing weeds, improving soil health with a small application rate, it is most likely not going to deliver the desired benefits.

2. Look for unbiased research results. Many products are vetted through land-grant universities to determine their potential usefulness. Just because a product works at some remote location does not necessarily mean it will work on your farm (this is why land-grant universities conduct field research). If the individual selling you the product is also the individual conducting the research be wary.  

3. Before completely adopting an alternative product to be used on the entire farm, evaluate the product on a limited basis and make simple comparisons to current practices. If you see no yield advantages, you have your answer.

 

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About the C.O.R.N. Newsletter

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.