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Ohio State University Extension

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C.O.R.N. Newsletter 2013-22

Dates Covered: 
July 16, 2013 - July 23, 2013
Editor: 
Rob Leeds
Wind Damage to Corn and Prognosis for Recovery

Wind Damage to Corn and Prognosis for Recovery

Strong winds associated with thunderstorms on Wednesday last week caused widespread crop injury across Ohio. Most of the wind damage I’m seeing and hearing about is root lodging with many fields nearly “flattened” by the winds.

Photos of plants goose necking (2), green snap at ground level (3), reduction in plant stand (4), and green snap below the ear (5) are available in the Agronomic Crops Team on-line photo library.

Strong winds can pull corn roots part way out of the soil. The problem is more pronounced when soil is saturated by heavy rains accompanying winds. The past two to three weeks of persistent rains we’ve experienced may have inhibited root development resulting in shallow root systems more vulnerable to wind lodging. The magnitude of the wind damage is influenced various other factors including crop stage of development and hybrid genetics. Prospects for recovery of “downed corn” are usually good, especially when the injury occurs early before the mid-late vegetative stages (V13-VT).  If root lodging occurs before grain fill, plants usually recover at least partly by "kneeing up." This response results in the characteristic gooseneck bend in the lower stalk with brace roots providing above ground support. If this stalk bending takes place before pollination, there may be little effect on yield. When root lodging occurs later in the season, some yield decrease due to partial loss of root activity and reduced light interception may occur. If root lodging occurs shortly before or during pollen shed and pollination, it may interfere with effective fertilization thereby reducing kernel set.

Hybrids differ in their ability to resist root lodging. Moreover, a hybrid may exhibit outstanding stalk lodging resistance but may be very susceptible to root lodging. Some popcorn hybrids appear especially susceptible to root lodging cause by wind. Plant population also affects root lodging with higher populations generally more susceptible to wind damage.

This is the third consecutive year we’ve experienced major wind storms and root lodging across a widespread area of Ohio at this stage of the growing season (last year high winds occurred at the end of June and in 2011 about mid-July).  It has been remarkable how quickly root lodged corn recovered, in most cases.

Several university studies have been performed to assess the impact of wind lodging on corn growth and grain yield. At the University of Wisconsin study, root lodging was simulated by saturating soil with water and manually pushing corn plants over at the base, perpendicular to row direction. Wind damage was simulated at various vegetative stages through silking (V10 to R1). Compared to hand harvested grain yields of control plants, grain yield decreased by 2 to 6%, 5 to 15% and 13 to 31% when the lodging occurred at early (V10-V12), mid (V13-V15) and late (V17-R1) stages, respectively. Iowa State University researchers forced V10 corn to “root lodge” at a 45 degree angle in plots with and without rootworms. Grain yield of root lodged corn without rootworms yielded 11 and 40 percent less than the control in the two years of the study while root lodged corn with rootworms yielded 12 and 28 percent of the control. Years were a major factor affecting the yield response. The ISU researchers concluded that “root lodging was more detrimental to biomass accumulation and grain yield than corn rootworm injury caused by larval feeding.” In another ISU study that evaluated natural root lodging, root lodged plants intercepted 28 percent less light than plants that were not root lodged.

Root lodging and downed corn can also be directly related to severe feeding by rootworm larvae that results in poor root development.  Remember that Bt rootworm resistance alone will not prevent root lodging. However, before assuming downed corn is a result of rootworm feeding, roots should be examined and rated for signs of significant larval feeding.  With the soil conditions that we have experienced the past month, the shallow roots we are seeing are probably NOT from rootworms but from the excess moisture.  Also make note on whether your corn is continuous or rotated corn.  Most rootworm injury should be in continuous corn, and be lacking if the corn was rotated (unless of course you are in a high rootworm variant area which we have seen little of the past few years). If significant rootworm injury is observed on your downed corn, and especially if injury is observed in corn with Bt rootworm protection, please contact your extension educator or us at hammond.5@osu.edu. 

Last week’s winds also caused green snap damage ("brittle snap") which is pre-tassel stalk brakeage caused by wind. Based on preliminary reports, it appears that most of the wind damage was caused by root lodging not green snap – which is good.  Green snap has the potential to cause major yield losses. Corn plants are more prone to green snap during the rapid elongation stage of growth between V8 and tasseling, especially during the two week period prior to tasseling. Breaks in the stalk usually occur at nodes (along nodal plates) below the ear. When soil moisture and temperature conditions are favorable for growth during this stage of plant development, plants elongate rapidly but stalks are unusually brittle. Stalk brittleness is greatest in rapidly growing corn under high temperature, high soil moisture conditions. There is speculation that rapidly growing plants are more susceptible to snapping-off for several days during the few weeks before tasseling because there has been little time for plants to develop lignified tissues at the nodes.

Although we encounter green snap problems in Ohio, it's usually a more serious problem in the western Corn Belt. Vulnerability to green snap damage varies among hybrids. However, all hybrids are at risk from such wind injury when they are growing rapidly prior to tasseling. Once the crop tassels, susceptibility to green snap generally disappears. Back in the 1990’s, Nebraska researchers observed that it was often the most productive fields with the highest yield potential that experienced the greatest green snap injury. They concluded that factors promoting rapid growth early in the growing season also predisposed corn to greater green snap injury.

If growers are hearing about or observing wind damage in fields near their farm, they should investigate a little farther than the edge of fields to assess crop conditions, especially if they think that they have an insurance claim to file. Wind damage may be hidden within fields that appear to be perfectly fine from the road edge. 

 

Sources:
Carter, P.R. and K.D. Hudelson. 1988. Influence of simulated wind lodging on corn growth and grain yield. J. Production Agriculture. 1:295-299.

Elmore, R. 2005.Mid-to-late season lodging. Iowa State University Integrated Crop Management Newsletter IC-494(21)161-162. (http://www.agronext.iastate.edu/corn/production/management/mid/silking.html)

 

Midseason soybean diseases: brown spot, frogeye leafspot, white mold, and Phytophthora.

Midseason soybean diseases: brown spot, frogeye leafspot, white mold, and Phytophthora.

The water has hopefully found its way off of the fields.  Flooding for greater than 2 days may reduce soybean yield by as much 20% compared to 1 day flooding events on soils with higher clay content.  If I do some quick math here – 20% from a field that typically produces 50bu/A soybeans – is 10 bu.  Matt Roberts may have some issues with my math but this is approximately a $120 loss ($12/bu, estimated price for fall soybean).  It is time to check the costs of your inputs to determine if you can put additional inputs into this crop.  Fields where soybeans were submerged, covered with silt etc, will not recover, and those should be forgotten about.  I think I have said this several times this year, work on the drainage issues for that field, that will be money better spent. 

For those fields with less flooding, we have several issues that are “brewing”. Here is the link that has a nice set of pictures to help in the identification diseases discussed below.  (There are also additional diseases to the ones listed) http://www.oardc.ohio-state.edu/ohiofieldcropdisease/t01_pageview3/Soybean_images.htm

1.      White mold.  Plants with symptoms caused by Sclerotinia sclerotiorum, stem rot were found in NE Ohio.  This is unusually early.  In a previous article, several fungicides were listed.  These were listed for preventative spraying at R1 growth stage.  I don’t have any data on spraying fungicides once infections have developed to the point of symptoms.  But we can tell you that Approach (DuPont) is not recommended for these situations. If your fields are at R2, have a susceptible variety and no symptoms, and this field is a historic white mold field, Approach may still be used.  If your soybeans are at R2, symptoms are visible then one of the triazole fungicides, Domark (Valent) or Proline (Bayer), are alternative choices;  we do not have any data from these situations so leave untreated strips.  If you have a variety that has a good score for resistance to Sclerotinia.  It is best to leave it alone, double check with your seedsman to see what they are saying about that varieties genetics. 

2.      Frogeye leafspot:  It is time to scout.  If you find frogeye lesions in the field, conditions are expected to continue to favor repeat infections.  Applications should begin at R3 followed by a second application at R5.  So this would be a good year to protect your crop.  Again, if the variety has a good score for resistance, a fungicide is not needed.

3.      Brown spot.  Brown spot caused by Septoria glycines, is very prevalent in many fields this summer.  But is still in the lower canopy and we have very thick canopies early this year.  From previous studies, we documented that in the worst case scenario, brown caused no more than 5 bu/A and most times it was between 2 to 3 bu/A, @ the projected price of $12/bu that is only $24 to $36/Acre.  Our studies showed that applications at R3 of a strobilurin were the most effective at reducing brown spot.  However, the variety resistance package should keep this from moving up the plant.  Going after the 2 to 3 bu will be dependent on what your input costs are for this field right now coupled with the amount of flooding injury that occurred.  Visit the Enterprise worksheets on the AgManager Website to determine if this is a worthwhile decision.  http://aede.osu.edu/research/osu-farm-management/enterprise-budgets . This is determining the economic threshold for this disease in this type of year. 

4.      Soybean Rust.  We have been scouting this year due to the weather patterns – but everything is negative to date.  Soybean rust was found in central Alabama and in western Mississippi, which are both a long way off, and levels are still low.  From the scouting that occurred in previous years, it takes at least 3 cycles of infection at 7 to 10 days each, prior to rust being detectable.  

5.      Phytophthora stem rot.  You can definitely tell this year where the Rps genes are not working and where the partial resistance levels are too low for Ohio conditions.  The fields have a choppy appearance with holes randomly spaced in the field.  And the plants will keep dying now throughout the summer, especially if we hit a dry spell.  Go back and look at the seed catalogues and see what you bought for resistance to this disease – make a note to buy something with more resistance in the future.

Weather Outlook: Expect Above Normal Temperatures Through The End Of July

The core of a hot high pressure dome will be centered in the Rockies the next 2 weeks. At times, there will be pieces of this high pressure that extends across the corn and soybean region including Ohio.

Overall, expect above normal temperatures the through the end of July. The week of July 15 will be hot with highs in the 90s and lows in the 70s. A cool down will come later this weekend into early the week of July 22. This will be the start of the pattern of several hot days followed by a few warm days followed by several hot days again. Due to soil moisture being good, we do not see temperatures above 95. However, lots of very warm overnight lows in the 70s are expected in the next 2 weeks.

As for rainfall, little rainfall is forecast the week of July 15. As a front moves across the area this weekend expect some showers and storms with the best chances in the north and east sections which will linger into early next week. This will be followed by some hotter and drier weather again.

Rainfall averages 1.5 - 2.0 inches for the rest of July. We are forecasting about 1 inch west and south up to 2-3 inches in the north and east for the rest of July on average.
 

Western Bean Cutworms Counts on the Rise

Western Bean Cutworms Counts on the Rise

Our OSU Extension WBC trapping network has shown a sharp increase in the number of adults caught.  This indicates that oviposition is imminent and will occur over the next few weeks.  We recommend that scouting corn for egg masses should begin.  We know that females prefer to lay eggs in corn that has not tasseled, so those fields should take priority.  Egg masses are laid on the uppermost 1-2 leaves, especially those that remain in the vertical position. Scout 10 plants in 10 locations. Egg masses contain 25-75 eggs and start out white then tan and then turn purple.  Once eggs turn purple egg hatch will occur within 24 hours.  Treatment is recommended when 5% or more plants have egg masses.  Although we have yet to see economic populations of WBC, we do have a fair amount of pre-tassel corn that is at risk.  See fact sheet http://ohioline.osu.edu/ent-fact/pdf/0040.pdf for more information.

 

 

Soybean Aphids

Soybean Aphids

 

 

Soybean aphids appear to have begun making their appearance in the Midwest, including Ohio.  We found aphids in fields near Toledo this past week.  Although they were at very low numbers, they were present and easy to find with a little searching.  At this time, areas to the north of us in Michigan and Ontario are already reporting thresholds of 250 aphids per plant being reached.  Fields in Ohio though are far from that.

What does this mean for Ohio?  This summer appears be an “aphid year”, meaning that Ohio growers will need to at least be aware and scouting for them.  There is nothing to suggest that any particular field will have a problem, but they will need to be monitored.  If problems occur, it will most likely happen later this summer when adult winged populations migrate from northern locations as their populations get extremely large.  In previous years, this has usually occurred in very late July and early August.  See the fact sheet http://ohioline.osu.edu/ent-fact/pdf/0037.pdf for more information. 

At this time, the most important thing is to start scouting your fields and become prepared for more intensive sampling later this month and next.  We will have more information in this newsletter as the weeks go on.  Also, we recommend NOT adding insecticides to fungicide or herbicide sprays that might go over your soybeans in the next few weeks (see other articles in this week’s newsletter) unless aphids reach threshold.  Applying insecticides as an insurance or prophylactic spray is not an appropriate IPM approach, and could cause a greater problem when the winged aphids arrive later in the summer.  Observations the past decade indicate that early, unnecessary sprays will often kill off predators that help to slow aphid population growth and perhaps allow for even greater aphid numbers in August, including in situations that might never have had a problem.  And as discussed in previous newsletters, applying insecticides to flowering soybeans could lead to mortality to honey bees and other pollinators.  We urge growers NOT to make these insurance insecticide applications and wait until thresholds are actually reached.  As an added benefit, you might just save some money.

 

Soybean Defoliators

Soybean Defoliators

Various foliar feeding insects are starting to show up on soybeans, including the first generation bean leaf beetles, adult Japanese beetles, green cloverworm, and in parts of Ohio, Mexican bean beetle.  These insects will continue to feed throughout the next month or so.  See the fact sheet at http://ohioline.osu.edu/ent-fact/pdf/0039.pdf on how to scout and manage for them.  Remember that as flowering begins, the thresholds go down to 15-20%.  However, with the good moisture in many parts of the state, note how much foliage and heavy canopy is in much of the soybeans, and remember to take into account the entire plant canopy when determining percent defoliation.

Falling Number as a Measure of Pre-Harvest Sprouting: What Does It mean?

As was explained in last week’s newsletter article (http://corn.osu.edu/c.o.r.n.-newsletter#1), delayed harvest in association with repeated wetting of the wheat heads often leads to pre-harvest sprouting. This is characterized by the swelling of kernels, splitting of seed coats, and germination of seeds (emergence of roots and shoots) within the wheat heads. Once wheat starts to sprout (or even before it actually sprouts), enzymes are produced to break down sugars that provide the energy needed for sprouting (germination). Burning us these sugars while the grain is still in the head reduces the milling and baking quality of the flour produced from this grain, since the emerging plant ends up using up much of what is needed to produce good quality flour. This leads to down-grading or even rejection of the grain.

Falling Number provides an indirect measure of the activity of the enzymes responsible for breaking down the sugar during sprouting. Consequently, it provides a measure of sprouting and grain quality. Remember, the greater the activity of these enzymes, the worse will likely be the quality of the grain. Falling Number is reported in seconds (click on the link below for details). As enzyme activity increases, the Falling Number decreases, therefore a Falling Number of 350 seconds or greater indicates low enzyme activity and good wheat quality (low sprouting). On the other hand, values below 200 seconds are usually associated with severe sprouting and low grain quality. For more information on the actual test used to measure the Falling Number, please refer to the article below published by the University of Delaware.

http://www.udel.edu/FREC/PUBS/ER06-02.pdf

Update Corn Fungicide Efficacy Chart

An updated version of the corn foliar fungicide efficacy chart is now available on the Field Crops Diseases website (click on the link below). The information presented in the chart is based on multiple years of fungicide efficacy trials conducted by university scientist across the Corn Belt and organized by the Corn Disease Working Group (with Dr. Wise at Purdue as the lead). This is not a complete list of all the fungicides labeled for use in corn nor is it a complete list of all the diseases managed with foliar fungicides; it is a list of some on the most marketed products, with ratings of their efficacy against some of the most common and economically important foliar diseases.

In Ohio, gray leaf spot (GLS) and northern corn leaf blight (NCLB) are our most important foliar diseases. When susceptible hybrids are planted and conditions are wet and humid, like they have been over the last several weeks, both of these diseases may cause substantial yield reduction. In some parts of the state, the crop is now at VT/R1 (tassel/silk emergence) or will reach this growth stage within the next few days. This is the best time to scout for foliar diseases, especially GLS and NCLB. Examine the ear leaf and the leaves below the ear on multiple plants throughout the field for the presence of lesions. GLS will appear as grayish-brown rectangular lesions, limited by the veins of the leaf, whereas NCLB shows up as greenish-gray cigar-shaped lesions (see the link below). If your hybrid is susceptible, a fungicide is usually recommended when lesions are observed on the ear leaf and the leaves below the ear on 50% of the plants - 50 plants with lesions out of 100 plants examined across the entire field.

Images of Common diseases:

 http://www.oardc.ohio-state.edu/ohiofieldcropdisease/t01_pageview3/Corn_images.htm

Fungicide Efficacy Chart:

http://www.oardc.ohio-state.edu/ohiofieldcropdisease/images/CDWG_Fungicide_Efficacy_Table_2013.pdf

 

Field Crops Day

Field Crops Day

Free and open to the public on July 25, 2013 starting at 9:00 am to 11:30 am at the Northwest Ag Research Station OARDC , 4240 Range Line road, Custar, Ohio 43511.

Program: 

Fungicide in Corn – Pierce Paul, 

Phosphorus and Water Quality Researching the Ag Link – Greg LaBarge,

Soybean Planting Date and Seeding Rate from 10 Years of On-Farm Trails – Laura Lindsey,

Re-examining Corn Seeding Rates How Much is too Much – Peter Thomison.

CCA credits.  Contact Matt Davis at 419-257-2060 for more information.

 

Aug 6th Northwest Ohio Precision Ag Technology Day

Aug 6th Northwest Ohio Precision Ag Technology Day at Fulton Co Fairgrounds in Wauseon.  The day will focus planters including seed, steel and related technology.  In morning sessions, producers will hear from Peter Thomison (OSUE), Jeff Taylor (DuPont Pioneer), Scott Shearer (OSU Ag Engineering), and Greg LaBarge (OSUE) and in the afternoon, Case IH, Horsch, John Deere and Kinze planters will provide live demonstrations.  8:15 am to 3:30 pm.  Event is free to the public but registration to richer.5@osu.edu or 419-337-9210 is needed for accurate lunch count. See www.fulton.osu.edu for flyer and more details.”

Western Ohio Manure Application Technology Field Day July 31st

Western Ohio Manure Application Technology Field Day July 31st

Livestock producers and others interested in learning more about manure application technology are encouraged to attend the Western Ohio Manure Application Technology Field Day being held on Wednesday July 31st (rain date August 1st) at the corner of Stelzer and Olding Roads near Maria Stein in Mercer County.

The newest manure application tool being demonstrated will be the Nutrient Boom. This tool has been developed for the application of dairy manure to standing corn. The toolbar is pulled across the field by a Cadman hose while manure is being pumped through the system. Manure can be applied multiple times during the growing season to increase silage or grain yields while making excellent use of the dairy manure nutrients.

Several farmers in Ohio have started sidedressing corn with livestock manure using a manure tanker and incorporation toolbar. Manure tankers can be adapted for corn rows by utilizing narrow wheels and wheel spacers. At this field day corn will be sidedressed using a tanker and Dietrich toolbar.

The field day will also discuss Cover Crops as a 2nd Forage.  Presenters will discuss cover crops that livestock producers can utilize that make great use of the nutrients in livestock manure and can be also harvested later in the season.

There is no cost to attend the Western Ohio Manure Application Technology Field Day and preregistration is not necessary. For more information contact the Mercer County OSU Extension office at 419-586-2179 or the Mercer County SWCD office at 419-586-3289. A flyer can be found at http://www.oardc.ohio-state.edu/ocamm/images/ManureAppFildDay_flyer_2013.pdf

 

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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.