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June 2010 Archives

Feekes 10.51: A Pictorial

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The recommended timing for fungicide applications to suppress Fusarium head blight or scab is Feekes 10.5 in barley and Feekes 10.51 in wheat. At growth stage Feekes 10.5 the inflorescence or spike is completely emerged from the boot. Photo 1 shows the progress of the heading procres in barley. The third kulm is at Feekes 10.5 and the correct growth stage to receive a fungicide to suppress FHB. Photo 2 shows the progressing of the pollen shed in durum wheat; in the first kulm no anthers are visible on the outside of the individual florets, while in the second kulm the anthers are only visible in the center section of the spike. As these anthers are still yellow, they likely shed pollen earlier that day. In the third pollen shed is complete as anthers are visible across the length of the spike and are bleached and desiccated. The second photo closely approximates Feekes 10.51. The progression in spring and winter wheat is identical to the progression in durum wheat.

Note that not all varieties will extrude the anthers in which case anthers may not become visible on the outside despite the fact that pollen shed is complete. It is always a good idea to peel back the glumes in the center of the kulm and inspect the color or the anthers as you scout fields. If the anthers are yellow, pollen shed will likely commence that day.

Barley heading stages.JPG
Photo 1: The progression of the heading in six-row spring barley (photo courtesy of Joel Ransom, NDSU).

Durum stage for fungicide control.JPG
Photo 2: The progression of anthesis (pollenshed) in durum wheat (photo courtesy of Joel Ransom, NDSU).

Purple Auricles in Wheat

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The auricles in wheat are defined as the clasping appendages or the claw-like projections that are located at the junction of a leaf sheath and the leaf blade. Auricles in combination with the shape of the ligules are two anatomical features used to distinguish grassy species from another, such has in this identification key.

The auricles on most of our wheat and barley varieties are pale green. A few recent releases have purple auricles. Below is a close-up picture of the auricles on the cv. 'Faller'. This coloring is the result of the presence of anthocyanins and is a heritable trait. Expression of the trait is, however, not stable and you may find different levels of coloring from year to year. There is no reason to be concerned about this coloring.

10 Purple Auricle.JPG
Photo 1: Purple auricles on the cv 'Faller'.

Late Season N in Wheat - The Cliff Notes Edition

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Based on the number of phone calls I received in just the last few days there is a considerable amount of interest in late season application of nitrogen with the goal to improve the grain protein content of spring and winter wheat. This interest isn't surprising given the extremely low grain protein concentrations of last year's crop and the crippling discounts that followed. Foliar applications of N during the onset of kernel fill have shown to be able to increase grain protein. A review article and decision guide were published in 2006 and can be found here.

The key points of foliar applications of N on wheat to improve gran protein content are:

  • Apply up to 10 gpa of 28-0-0 with an equal amount of water - the water is needed to reduce leafburn; more water is advantageous
  • DO NOT apply during the heat of the day - early evening application reduce leafburn considerably
  • DO NOT tankmix this N with any fungicides at Feekes 10.51, but rather apply the additional N 5 to 7 days after anthesis
  • The probability of a response by the crop is about 80%
  • Only expect an increase of 0.5 to 1.0 full point in grain protein with the additional 30 lbs N/A
  • All varieties respond equally well to the additional N
  • Use the decision guide in the above mentioned link to determine whether an economic return is possibly in relationship to the price of the 28-0-0


Risk of Fusarium Head Blight in Wheat on the Rise

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Wheat crops in the flowering stage are now at risk for FHB infection across most of the state, with highest risk in the NW region of MN. Winter wheat either already flowered or is flowering now, while some of the first planted spring wheat is close to flowering.

Risk is highest for susceptible to very susceptible cultivars. The 24-72 hour forecast indicates that the risk will remain or even get higher in the next few days.

When considering the application of a fungicide to suppress FHB, assume that all winter wheat varieties are susceptible to very susceptible to FHB (http://www.ag.ndsu.edu/pubs/plantsci/smgrains/a1196_08.pdf). The spring wheat varieties rate from moderately resistant to very susceptible. The ratings can be found in the Minnesota Variety Trials Bulletin (http://www.maes.umn.edu/10varietaltrials/redspringwheat.pdf)

Disease pressure of other diseases is high for tan spot but low for leaf rust as it appears that little leaf rust inoculum has made it this far north to date. Powdery mildew can readily be found in Lake of the Woods and Roseau counties and central Minnesota.

Fungicides labeled for an application at Feekes 10.51 include Folicur, several generic versions of Folicur, Caramba, and Prosaro. Extensive university studies comparing Prosaro and Caramba fungicides with Folicur show that Prosaro and Caramba provide a 20% better reduction of FHB and a 30% better reduction of vomitoxin than Folicur, when tested on moderately susceptible to susceptible cultivars.

The risk maps of the different diseases, including FHB, for Minnesota can be found at the Minnesota Association of Wheat Grower's Fusarium Heab Blight Forecasting website (http://mawg.cropdisease.com). The website also creates risk maps for tan spot, Septoria leaf blotch, and leaf rust. Access to the national risk map may be found at www.wheatscab.psu.edu/. The NDSU disease forecasting site can be found at www.ag.ndsu.nodak.edu/cropdisease.

Sign-up for Fusarium Head Blight Alerts

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Producers and ag professionals that are interested in the potential risk for Fusarium head blight in wheat and barley can sign-up for a national alert system. These alerts are delivered either short text messages (SMS) on mobile phones or as e-mail messages.

Go to the National Scab Initiative website (http://scabusa.org/fhb_alert.php) and chose which way you would like the alerts to reach you and from which state or states and regions you would like to receive the alerts.

These alerts are made possible through the collaborative effort of teh US Wheat and Barley Scab Initiative and the national FHB Prediction Center at the Pennsylvania State University.

The alerts for Minnesota will be provided in collaboration with Marcia McMullen, NDSU's extension plant pathologist, and others in the region.

By Dave Nicolai, IAP Program Coordinator

The 2010 Field School for Ag Professionals will be held on July 20th - 21st. The University of Minnesota Southwest Research and Outreach Center at Lamberton, MN will be the host site for the Field School.

Participants may choose to attend either day or both days of the field school. The first day's program

on July 20 will consist of four disciplines - weed science, soil science, entomology, and a crop

diagnostics session.

Control of Volunteer Soybean in Corn

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By Jeff Gunsolus


This week I have received several inquires about the presence and potential impact of volunteer soybean in corn and cost-effective control procedures.  The scenario of volunteer soybean in corn is a fairly recent phenomenon due to the wide-spread use of the glyphosate-resistant technology in corn and soybean.  As a result, to my knowledge, data on corn yield loss potential as a function of volunteer soybean density is not available.  However, I do know of one NDSU study conducted by Dr. Richard Zollinger that does evaluate several herbicide options to control volunteer soybean in corn. You can find a general summary titled Control of Volunteer Roundup Ready Crops at:

http://z.umn.edu/ndweedguide and click on Weed Control Ratings.

Yellow Wheat

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History repeats itself ever so often and unfortunately excess precipitation in many part of the Red River Valley has caused once again overland flooding and saturated field conditions. Wheat and barley can handle some flooding but it is not without a cost. As the water recedes and the soils drain you will likely notice that the wheat crop (and barley for that matter) has turned pale green or even yellow. In 2008 Doug Holen, Dan Kaiser and I wrote a short a summary of the causes of this yellowing and the possible solutions. Below is a nearly complete reprint is that article:

Some of the common reasons for early season yellowing are:

- Temporary nitrogen deficiency
- Temporary herbicide injury
- Early tan spot infection

Other possible causes include Barley Yellow Dwarf virus or temporary micro nutrient deficiencies.

The nitrogen deficiencies can readily be indentified as the symptoms are worst on the oldest leaves and start at the tip of the leaves, progressing towards the base as the deficiency gets worse. The causes of the N deficiencies are several, all which have common denominator, namely excess precipitation. Excessive rainfall causes:

- Leaching
- Denitrification
- Inability of the plants to take up available N

Leaching is a potential problem in coarser textured soils. Saturated soils/standing water will cause both denitrification and inability to take up available N. Denitrification is a microbial process and speeds up considerably as soil temperature increase. According to Univ. of Illinois data (Hoeft, 2004), denitrification losses are 1-2% if soil temperatures are less than 55°F, 2-3% when soil temperatures are between 55 and 65°F, and 4 -5% once soil temperatures exceed 65°F. As soils are saturated, the plant's roots also are unable to take up N - even if available. Often the crop recovers quickly if the growing conditions improve and the excess water has drained.

If the N deficiency is severe, a supplemental application of N as either urea (46-0-0) or urea ammonium nitrate solution (28-0-0) can be advantageous. Research by Russ Severson in 2002 showed that 40 lbs of supplemental N at the 4 leaf stage yielded 7 bu/A extra over the untreated check. As excess rain saturated soils and yellowed the wheat crop that spring, he designed a small, replicated trial in which he looked at the impact of timing of supplemental nitrogen. The wheat followed corn. Prior to the supplemental N, the field had received 80 lb. N per acre as 82-0-0 and 50 lb. 18-46-0 per acre. The supplemental N was applied at either Zadoks growth stage 14 or Zadoks growth stage 60.

The early application of fertilizer N increased yield by 7 bu/A when compared to the wheat that did not receive supplemental N. The later application did not increase grain yield compared to the untreated check. Even at today's N prices that would be an economic return.

The cool and wet conditions have made some of the micro nutrients also less available to the plant. These symptoms are often first noted on the coarser textured soils. George Rehm has chased this problem in the past and found that no single culprit was to blame. As soon as growing conditions improved, the symptomology would disappear.

The cool growing conditions have also made a number of our common small grain herbicides more prone to cause temporary injury. Especially the ACCase class of grass herbicides is more active with cool(er) growing conditions. This temporary yellowing will dissipate in one to two weeks after application with no effect on grain yield.

Early season tan spot infection can also cause the young wheat crop to turn a bright yellow. Especially young seedlings up to the 3 to 4 leaf are very sensitive to a toxin that is produced by the fungus. This yellowing affects the whole seedling. If tan spot is identified as the cause of the yellowing, an early season fungicide treatment is warranted. Half a labeled rate of any of our labeled fungicides - e.g. Tilt, Quilt, Stratego, and Headline - can be used to halt the development of the tan spot and allow the crop to recover.

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