Sudden Death Syndrome and Corn Residue
Symptoms of Sudden Death Syndrome (SDS) on leaves show green veins with discoloration between the veins (left photo). Signs of the blue/gray/white Fusarium fungus causing SDS on a rotted soybean root (right photo).
Grazing corn residue provides many benefits to both livestock and grain farmers, yet many corn stalks in our area are not grazed for various reasons. With as much hail as we’ve had this fall, grazing is also an option to remove ears and kernels that were lost, preventing volunteer corn next season. Normally there is less than a bushel of ear drop per acre, but we most likely have more than that in some of our fields this year. Two kernels per square foot or one ¾ pound ear in 1/100 of an acre is the equivalent of 1 bu/ac yield loss. In 30” rows, 1/100 of an acre is 174’ long if you count in one row or 87’ if you count in two rows.
Soil samples (0-8″) for soybean cyst nematode (SCN) can be taken at any time but always good to sample areas that were affected with SDS to determine if SCN is also present.
What may also be of interest to you is a recent finding between corn grain loss pre-and during harvest and sudden death syndrome (SDS) of soybean. Many asked me this this year, “Why did I see SDS this year when we’ve never had it in this field before?” It’s a great question and I often responded by saying we need to sample the areas affected with SDS for soybean cyst nematode (SCN) as the two diseases are synergistic. Sampling for SCN still remains free through your Nebraska Soybean Board Checkoff dollars and you can stop by the Extension Office for free sampling bags. Crop consultants should contact the UNL Plant and Pest Diagnostic lab directly at (402) 472-2559 if you are requesting 10 or more sampling bags.
Anything that moves soil can transport the fungal soil-borne pathogens causing these diseases. But recent research from Iowa State University also suggests that the fungal pathogen causing SDS (Fusarium virguliforme) survives on grain lost during the harvest process in fields and that SDS management in soybean actually needs to begin at corn harvest.
Studies were conducted for two years in greenhouse and in field plots with nine treatments to determine the survivability of Fusarium virguliforme (Fv) on corn and soybean residue. The treatments were: 1-Corn kernels + Fv; 2-Corn roots + Fv; 3-Corn stem/leaves/husk + Fv; 4-No residue + Fv; 5-Soybean seeds + Fv; 6-Soybean stem/leaves/pods + Fv; 7-Soybean roots +Fv; 8-Corn stalk on soil surface + Fv; 9-Corn kernels and stalk on soil surface + Fv. The researchers consistently found in both the greenhouse and field experiments that Treatment 1 of corn kernels at average harvest loss resulted in the most SDS. Treatment 2 consistently resulted in the second most SDS.
From Iowa State University, September 2010, “Good Harvest in Corn Should Help Manage SDS“.
This helps to explain why some farmers are finding SDS in fields that have been continuous corn for a period of years, are finding SDS in corn and soybean rotation when little or no SDS was previously observed, and why SDS has increased in seed corn fields that may have higher harvest losses. They did not experiment with tillage systems and their recommendation is to reduce harvest losses to reduce the risk of SDS.
Grazing residues can reduce your risk from these harvest losses and for those losses which were incurred with the hail/wind storms we’ve experienced since Labor Day. When grazing corn residue, cattle are selective. They will eat the grain first followed by the husk and leaf followed by the cob and stalk.
It’s also important to be aware of grazing restrictions from herbicides applied to row crops; you can read more about that in this post.
Forage, Feed, and Grazing Restrictions for Row Crop Herbicides
It’s nice seeing cattle being turned out into corn stalks! 
One point that I haven’t mentioned recently is that we all need to be checking the herbicide label for any grazing restrictions of crop residues.
So check the labels from in-season applied herbicides to row crops and fall-applied herbicides to crop residue for any potential grazing restrictions…and any restrictions on grazing cover crops planted into crop residues following application of those chemicals to a row crop. If the label doesn’t specify any restrictions, then it should be ok. If you want to be on the safe side, a rule of thumb many chemical reps use is to use the pre-harvest interval for the amount of time to wait before grazing stalks.
Some labels will say that residue should not be grazed or baled and fed to livestock. Sometimes studies were actually conducted to know there is a safety concern. In other cases, the chemical company may not choose to conduct all the studies the Environmental Protection Agency (EPA) required for labeling due to high costs. If that’s the case, the EPA requires the strongest restrictive language be placed on the label.
Hail/rain/wind caused for soybean shatter and harvest loss. Volunteer beans have created green fields in the area. For those considering grazing, one needs to look at any herbicide grazing restrictions from herbicides applied in-season to soybeans as well. Dr. Bruce Anderson says, “Soybeans can cause bloat, but the incidence is low. The young green ones may be more risky. Founder would be possible problem with a sudden diet change. Too many unsprouted beans in the diet could cause excess fat; I think maximum is about 3 lbs beans per cow. I’d try to limit amount of grazing for a few days, maybe feeding a very palatable supplement like a ground forage/distillers mix and reduce the amount of this supplement each day for a week or so. And keep a dry, palatable hay always available free choice.” Additional information from the University of Missouri.
Regardless, if it says there’s a grazing restriction on the label, the label needs to be followed as it is a legal document and the law. Your cattle may/may not be affected by grazing stalks or cover crops where a chemical with a grazing restriction is on the label, but there may be other concerns such as problems with the chemical affecting the calf or being retained in the cow’s milk.
For quick references, the 2015 UNL Guide for Weed Management shows Forage, Feed, Grazing Restrictions for Row Crop Herbicides on pages 174-177. A new weed guide will be released January 2016. These pages just provide a reference; it’s truly best to read and follow the label.
Wind-Hail Crop Damage Meeting
Recent wind and hail storms have created damage across our area counties in Nebraska and Kansas. This brief meeting to be held on Monday near Gladstone, NE is designed to answer farmers’ questions regarding harvest, crop insurance expectations, and what to expect regarding crop maturity and future damage. Please click on the image to enlarge.
Corn Disease July 2015
Radio advertisements, email blasts, and other media are warning of corn diseases and the need for fungicides. Two months of humid, wet weather has allowed for disease development. It’s important to know what diseases truly are in your field before spraying a fungicide, particularly with today’s economics. Here’s what we’re seeing in fields right now in the Clay, Nuckolls, Thayer, Adams county area. Based on the diseases we’re seeing, we would recommend you scout your fields to know whether you have mostly bacterial or fungal diseases present. Consider disease pressure, where on the plant the disease is occurring, growth stage, and economics. We have had southern rust show up in 10 of the last 11 years I’ve been serving in this area. If you spray a fungicide at tassel, you may not have enough residual to ward off southern rust when it appears later, potentially resulting in the need for a second application. In our area thus far, I’m not seeing enough disease pressure in many fields to warrant a fungicide at tassel; consider delaying an application till later for economic and resistance-management reasons. Ultimately this decision needs to be done on a field by field basis. Please also see this UNL CropWatch article regarding fungicide application and corn growth stage. Although I don’t have a photo of it, I’ve also seen common rust in the mid and lower portions of corn canopies thus far.
Anthracnose has been observed in fields for a good month now. It is mostly seen on lower leaves of plants, particularly in fields where we’ve had high amounts of rainfall, standing water, and/or hail. Lesions are tan in the center and have a wavy yellow colored margin. I haven’t seen it moving up the plant very far yet. There are fungicides labeled for this, but we don’t often recommend fungicide treatment for anthracnose.
We saw this disease in the Saronville/Sutton area last year. This year, we are seeing it throughout Nuckolls, Thayer, Clay, and Adams counties…and most likely others too. Some hybrids (and have seen this across companies) are highly affected by this bacterial disease. Neither last year, nor this year, has the pathogen causing this disease been confirmed. Plants will have vein-limited lesions in streaks on the leaves. It is often confused with gray leaf spot early on. Take a hand-lens and looking closely, you will see wavy margins on the lesions which doesn’t usually occur with gray leaf spot. Over time, these lesions become elongated and can coalesce with other lesions. Also looking closely with a handlens or microscope, one finds the leaf tissue eventually becomes transparent. While other diseases can look similar to it, under the microscope, no fungal spores are found other than secondary ones. Putting an infected leaf in water reveals cytoplasmic streaming in which the bacteria is escaping the leaf tissue. (The pathogen causing Goss’ wilt also does this, but this disease is not the same as Goss’ wilt). Fungicides will not cure bacterial diseases and the products advertised for targeting bacterial diseases haven’t been researched for this disease. This is the primary disease we are seeing in our area right now-and it looks nasty in some fields! Unfortunately there’s nothing we can do about it. If you are considering testing one of the products for bacterial diseases, please let me know as I’d appreciate testing it with you via on-farm research.
Goss’ wilt (bacterial disease) has been observed in fields as well. I typically notice it along field edges, pivot tracks, pivot/well roads or hail-damaged fields as plant wounds in general allow an entry for bacterial pathogens. However, research has shown that the bacterial pathogen causing Goss’ wilt can enter through the leaf stomates as well. Leaf miner damage can be observed at the top of this photo, and often, but not always, I notice this occurring together in fields. There is nothing we can do for Goss’s wilt if you have this disease in your fields right now. There are products targeting bacterial diseases on the market. If you’re interested in trying these, please consider an on-farm research experiment to prove the efficacy to yourself and help us obtain data.
Physoderma brown spot typically doesn’t occur in our area until tasseling (which is where we are at now in some fields). However, I was seeing this as early as two weeks ago on some hybrids. The pathogen causing this disease is a fungal-like pathogen that moves with water. You will notice a purple/brown color on midribs of leaves, leaf sheaths, stalks, and tiny yellow/brown/purple spots on leaves. This disease isn’t considered yield-limiting or of significance to us in Nebraska. Some confuse this disease with southern rust, but there are no pustules produced with Physoderma brown spot.
The larger, rectangular lesion is typical of gray leaf spot found in some lower leaf canopies right now. It is easy to confuse with anthracnose as both diseases appear a little different on various hybrids. Gray leaf spot will be vein-limited while anthracnose is more blotchy in appearance. Comparing gray leaf spot with the unknown bacterial disease, the lesion edge will be straight for gray leaf spot and wavy for the bacterial disease.
Northern corn leaf blight is a disease we’re hearing a lot about but I have yet to see it in our area. Most have been mistakingly calling the unknown bacterial disease shown above and even Goss’ wilt, northern corn leaf blight, but there’s truly a difference as you see these photos. Compared to gray leaf spot, northern corn leaf blight will be more cigar-shaped instead of forming a rectangle. As this photo taken from the Mead, NE area shows, lesions are often forming in close proximity to each other on the leaves in Nebraska right now. This disease is one to watch as it has been expanding on certain hybrids in some fields, particularly in eastern, Nebraska. However, I still haven’t seen it in our area and haven’t received any confirmations of it being found in our area at this time. (Photo courtesy of Aaron Nelson, Nelson Precision Agronomics).
It’s Fair Time!
This week is the Clay County Fair! We hope you will come out to view the 4-H and Open Class exhibits, 4-H/FFA youth showing their animals, family fun night, 4-H Council Bar-B-Q, cattle sorting, mutton busting, Amanda Winter concert, mud drags, and much more! I absolutely love our fair for the focus on youth and families! I also enjoy watching the fairgrounds come alive with excitement from youth and families as they bring their projects and show them. It’s such a blessing to work with wonderful people who desire what’s best for the youth! A full schedule of events can be found at http://clay.unl.edu. See you at the fair! (photo is of those wearing “orange out” t-shirts the last day of the fair in 2014-Photo courtesy of Tory Duncan, Clay County News).
Determining Your Needs
In the Clay County Fair Open Class flyer printed in the Clay County News, you will find the middle page pulls out and is a survey. Nebraska Extension in Clay County and our Clay County Extension Board have launched a survey to determine programming/information needs you deem critical to you and your families. We know that we provide crop, 4-H, and some horticulture programming and information, but there is much more that Nebraska Extension as a whole provides that we haven’t necessarily offered as much as we could in Clay County.
The survey is meant for those of you in Clay County, if you’d be willing to take less than 5 minutes to fill it out, we’d greatly appreciate it! You can also fill it out online at: https://www.surveymonkey.com/r/clayext. The survey will remain open till the conclusion of the Clay County Fair on July 12 this year. Please pass this information along to Clay County constituents as we’re trying to reach as many people as possible. It really is important that we receive as much feedback as possible. It’s important as the goal is to better serve you-and we can’t do that without your input! Please do take a few minutes and complete this for us as we’ve only had a handful complete it thus far. Thank you and please encourage others to complete it as well!
Bagworms in Evergreens
I’ve been receiving questions regarding when to spray for bagworms. Bagworms overwinter as eggs in these up to 2″ bags which are formed throughout the summer with silk and evergreen needles by larvae. Larvae feed until late August or early September. Males then emerge and mate with females through the bag opening in September. 500-1000 eggs are deposited by female moths within their own bags. After depositing eggs, the females drop to the soil and die. Bagworms overwinter as eggs within bags fastened to twigs such as these shown in this photo.
Eggs hatch in mid-May to early June. Some caterpillar larvae remain on the same trees containing the bags from which they hatched. Others are blown by the wind to area trees allowing for new infestations to occur. This photo shows new bags (1/8-1/4″) being formed on trees as they create these bags around themselves. Look closely for these tiny bags on trees right now. The video below shows how to look for bagworms on evergreen trees right now. Study your trees and look for small movements on small bags being formed. If you are seeing this, consider treating your trees for bagworms. Products containing bifenthrin or permethrin irritate caterpillar larvae causing them to come out of the bags and be exposed to the pesticide. There are a number of other management options available. Please see the following publication for more information.
Nebraska Extension Publication: Bagworms
Treating Iron Chlorosis in Trees
Throughout the County, iron chlorosis is appearing in trees and landscapes. It can especially be seen in the silver maples (shown in this photo) and pin oaks. Iron chlorosis symptoms appear as yellowing of leaves while the leaf veins remain a dark green color. Eventually the leaves become so chlorotic that leaf tissue begins to turn brown/black and die. Severely affected leaves often drop from the tree and new leaves emerge in 7-14 days. Alkaline soils (pH above 7) reduce the availability of iron and manganese; two important nutrients found in tree leaves. It’s not necessarily that these nutrients are deficient in the soil. The high pH just makes these nutrients less soluble and unavailable to the trees. Adding iron to the trees or the landscape around the trees won’t correct the problem as the pH ultimately needs to be corrected.
Early in my Extension career, I inherited the job of injecting trees with a solution of iron sulfate. There would often be a waiting list of people to help, particularly in Sutton, when they’d see the jugs hanging from trees. As a plant pathologist, I was concerned about how much damage we were doing to the trees with repeated injections every five years or so…if secondary pathogens would affect these areas we were drilling in the trees. I was also concerned about providing a free service that took a great deal of time and if we were competing with industry by doing so. Eventually we stopped providing the service but we do rent out the equipment and can provide the recommendations on how much iron sulfate to add based on tree diameter if you are interested. But you may be interested in another less invasive method instead.
I learned of another potential method to consider from John Fech, Extension Educator in Douglass/Sarpy Counties, and we tried it at the Sutton Cemetery for two years and at the Clay County Courthouse last year with decent results. The first step is to double aerate the area from the trunk to the dripline of the trees showing iron chlorosis symptoms. The dripline is the outer leaves of tree. Do so several days after irrigation/rainfall to avoid tearing up the grass in your lawn. Often people aerate their lawn in the spring and/or fall, so if you have a problem with iron chlorosis, you could include the following treatment into your routine.
The second step is to broadcast spread granular sulfur on the soil surface. Then broadcast spread iron sulfate on the soil surface. What was recommended to us by Omaha Master Gardeners was using 3 lbs of sulfur + 3 lbs of iron sulfate for “small” or newly established trees; 4 lbs of sulfur + 4 lbs of iron sulfate for “medium” sized trees; and 5 lbs of sulfur + 5 lbs of iron sulfate for “large” established trees. I realize that’s not very scientific based on sizes so do the best estimation of tree size that you have. We used 5 lbs for everything at the cemetery and courthouse. Here Mike, Clay County Courthouse Custodian, is spreading the product close to the trunk first.
He continued applying around the tree in a circle gradually moving out towards the drip line. The final step is to then water the lawn.
We have numerous silver maples at the courthouse. This is a photo of one of the trees and a close up of these leaves was shown in the first photo. You can see the yellow cast to this tree in this photo and how severely affected many of the leaves were from the first photo.
This is the same tree a year later from the opposite side. The photo doesn’t do it justice as it truly is greener than last year and the leaves are hailed damaged. It didn’t really change during the season last year but all the courthouse trees are greener this year. They could use another application though as they still show symptoms of iron chlorosis. This method may take several years before the soil pH changes enough for symptoms to disappear.
You most likely will not see any changes the first year, although the grass under the tree may appear greener. The goal is to change the soil pH to make the iron more available to the tree in the future. This may be a process that needs repeated for several years in a row and while it doesn’t show instantaneous results, it will most likely aid in the longevity of your trees by reducing the symptoms without additional harm to the tree through injections.
Sugar Application in Crops
Corn is approaching or at V7-V8 growth stage. A few weeks ago, we published research results in our UNL CropWatch website. That information can be found in the links below the video. If you are interested in trying this in your field this year, please see the Nebraska On-Farm Research protocals also shown below.
Weed Science Field Day
July 1 is the upcoming Weed Science Field Day at UNL’s South Central Agricultural Laboratory near Clay Center. The brochure with more information is shown below as photos; please click on the photos to enlarge if they are difficult to read. You may RSVP to Dr. Amit Jhala at (402) 472-1534. Hope to see you there!
Crop Update June 9
Corn that was hail-damaged on June 3rd is starting to regrow. Leaves wrapped up in the whorl are beginning to slough off as wind and warm temperatures cause the damaged tissue to die and break off. For more information on how stand loss impacts yield, please check http://cropwatch.unl.edu.
Some corn plants more severely affected were reduced to stems. Sometimes no new growth is appearing while in other plants new growth can be seen. I split open the stem on this plant since no new growth was apparent and the center looked discolored.
In this corn plant, a bacterial rot has set in as can be seen from the discoloration at the upper portion of this plant and the discoloration at crown area. This plant may not survive. This is typical of what we were seeing in Nuckolls/Thayer counties with the 8-10″ of rain they received there. My concerns for corn at this point are bacterial diseases such as this or Goss’ wilt that may continue to reduce stands through the season. Some growers are considering a fungicide application but fungicides don’t target bacterial diseases. We’d recommend anyone considering this to consider an on-farm research experiment and I’d be happy to help set this up for you.
These soybeans were reduced to stems yet are showing new growth 5 days later. UNL research has shown that soybean stands can be greatly reduced without a significant yield effect. Several growers are considering replanting; we’d recommend taking into account the research or conduct an on-farm research experiment to see any differences for yourself like this farmer did. The other thing we have looked for is bruising on stems and some flooded areas truly did not have plants survive. For more information, please check out http://cropwatch.unl.edu.
JenResources 