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JenREES 7-22-18

Crop Update: This past week was fairly interesting with southern rust being confirmed in a few Fillmore, Thayer, and Saunders County fields.  We would recommend to continue scouting fields as the disease was low incidence at all these sites. There also were a number of questions regarding fungicide applications.

For those asking about chemigating fungicides, it’s important to ensure the fungicide

On-farm chemigation

On-Farm Research design for those considering chemigation vs. none of fungicide (could also use this for 2 different irrigation amounts instead). Can have more pies than this for smaller area if desired-we would just need at least 4-5 pies of each of same area. Data can be collected throughout field normally during harvest via yield monitor and we can use software to determine yields within the pies as long as we know the angle degrees you used.

product label allows for chemigation and to follow the recommended irrigation amount if specified on the label. If an irrigation amount isn’t specified, Tamra Jackson-Ziems and I were talking about trying to apply with as small amount as possible (perhaps like 0.25″). She has chemigation data at 0.25″ vs. 0.50″ vs. ground application from 2005-2007, but not vs. aerial application. The data had a high degree of variability numerically in the yield data in spite of non-statistical differences. The only other info I could find was the University of Georgia recommends only 0.10″ on chemigation using fungicides, but they didn’t show any data. I encourage those who can to please consider doing this as an on-farm research study where chemigation occurs in pies throughout the field with other pies left untreated. I realize it’s not popular to leave areas untreated, but it may be of interest to you.  For those asking about comparing aerial vs. chemigation for corn, that would be very difficult with one pivot with true research involving replication. Perhaps it could be done if a producer had a couple of quarters side by side, planted the same day with same hybrid and crop rotation where we could truly compare via research. If you do and that’s of interest to you, please contact either Tamra or myself. A couple have also discussed maybe applying half a pivot aerially and the other half via chemigation and just taking observations, which may also be beneficial to you.

We also released a few CropWatch articles this week on differentiating growth regulator herbicide injury in soybean and using a forensic method to diagnose off-target dicamba

dicamba injury-Purdue

Dicamba on Soybean: Because dicamba negatively affects leaflet margin cell division, direct dicamba exposure to nearly fully developed leaflets results in in a “draw-string” injury symptom at the leaflet tips, thus shortening the leaflet length. Keep in mind, however, that the translocation of dicamba from directly exposed leaflets to very young leaf primordia developing at new nodes at the main stem apex will also induce leaf cupping in those yet to emerge leaflets, even though these very young leaflet primordia were not directly exposed to dicamba. The same can be true for new trifoliolates occurring from additional stem branching at lower nodes. Photo via Purdue University.

injury in soybean. Please check them out at http://cropwatch.unl.edu. I hadn’t heard anyone really explain the difference between 2,4-D and dicamba in how they work in plants so felt that information was important in addition to the fact dicamba is highly translocateable and 2,4-D isn’t. That also has been important in home-owner discussions regarding off-target movement to garden produce. And, a reminder to all home-owners that weed control products used in lawns and empty lots often contain dicamba and/or 2,4-D…so it’s important to read those labels regarding environmental conditions in applying them and also when you can/can’t use grass clippings as mulch.

Buzzing Beetles: This past week, several people came to the office or called

2-4D injury Purdue

2,4-D on Soybean: 2,4-D impacts cell division in the more central (major vascular) portion of the leaflet. Low-dose 2,4-D exposure induces injury that results in a “narrowed, strap-shaped” leaflet in which the leaflet veins are made more parallel. This 2,4-D-induced injury is often accompanied by a rugose leaf surface ― a botanical term describing a rough leaf surface of irregularly spaced bumps/wrinkles and prominent ridged/corrugated leaf veins. Low-dose 2,4-D exposure will also lessen leaflet area, but differently, by narrowing/elongating the leaflet. 2,4-D is also not highly translocatable, wheras dicamba is. Photo via Purdue University.

regarding large green beetles flying around that sounded like bumble bees. These are called Green June beetles. They only fly during the day. There are also smaller green beetles with white spots (tufts of hair) around the abdomen; those are Japanese beetles. Japanese beetles feed on crops in addition to favorites such as Linden trees and knockout roses.  Both have larval forms that are white grubs and both have a one year life cycle. In the beetle form, both adult beetles are fond of ripe fruit such as grapes, berries, plums, and peaches. As larvae, the grubs feed on decaying organic matter and grass roots in the soil. However, the June beetle larvae can reach 2″ long creating larger tunnels in lawns and pastures as they move in the soil.

Some have said, “I thought June beetles were golden/tan!” And you would be correct! There’s several types of “June” beetles. The most common and perhaps most damaging is known as the June beetle or masked chafer which is golden/tan in color and has a one year life cycle. There’s also a May/June beetle (also known as the 3 year grub) which tends to do more damage in range/pasture ground. Those beetles are tan to brown/near black in color.

When it comes to damage, start looking for browning areas of turf occurring late July, throughout August, and early September. The turf may look like drought stress or fungal disease; however, if you can gently roll the turf back like a carpet, it’s most likely grubs (and you should also find the presence of grubs). Other signs of grubs can include birds, skunks, etc. tearing up your lawn. White grubs in general feed on decaying organic matter, lawn and ornamental roots in the soil. Grubs don’t tend to be an issue in fescue lawns or lawns that are low maintenance or newly established. They tend to prefer Kentucky bluegrass lawns that are highly maintained with fertilizer and irrigation. They also may be spotty in their feeding such as under yard lights or on irrigated slopes. The threshold level for turfgrass damage by masked chafer larvae is 8-10 white grubs per square foot of lawn…so I would assume that to be the case for all grub species. One or two grubs per square foot is normal and does not require control. If grub control is needed, products like Sevin or Dylox provide the best control for mature grubs and should be watered in after application.

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.  I haven't seen it moving up the plant very far yet.  There are fungicides labeled for this, but we rarely recommend fungicide treatment for anthracnose.

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.  We have informally called it

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.

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.

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.

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 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.

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).

Corn Disease Look-Alikes

Physoderma brown spot

Physoderma brown spot on corn. While the small, speckled lesions may look like southern rust, under hand lens or microscopic observation, there are no raised pustules as would be the case with southern rust. Also notice the brown/purple discoloration on the midrib which is also noticed on the stalk as well where the leaf color meets the stalk.

Fair week tends to be time for tasseling in corn and considerations for watering and fungicide application are being made.  Regarding diseases in corn, there has been confusion about a few diseases, particularly about a disease called physoderma brown spot which some have confused for southern rust.  The fungus causing physoderma brown spot feeds on pollen and debris on leaves and does not cause harm to the corn plants themselves.  Because the spores of this fungus move via water (it’s closely related to oomycetes), numerous lesions can appear on leaves in bands or areas where water collects.  While the lesions may look like early southern rust, there will be no pustules present and often purple colored lesions will also be observed in the midrib, leaf sheath, stalk, and outer husks.

Differentiating Rusts:

2013-07-30 09.31.26

Southern rust in corn. We currently have not seen southern rust in Nebraska in 2014. Notice how you can see raised pustules in this picture compared to the photo of physoderma brown spot above.

When differentiating between southern rust vs. common rust, there are several criteria to consider and this NebGuide is a great resource.  Typically common rust will have brick-red pustules randomly scattered on the upper and lower leaf surfaces that are larger in size.  It is common rust that we are currently seeing in our fields.

Bacterial leaf blight showing up heavily in some hybrids.  The UNL Plant and Pest Diagnostic Lab is determining species and we will share more information in the future.  There is no control for this disease at this point.

Bacterial leaf blight showing up heavily in some hybrids. The lesions are red-brown in color, long and skinny and mostly vein-limited.  Older lesions spread outside the veins and are buff in color-sometimes they are being confused as gray leaf spot.  The UNL Plant and Pest Diagnostic Lab is determining species and we will share more information in the future. There is no control for this disease at this time of the season.

Southern rust in our area tends to have very small, raised, tan-orange pustules on the upper leaf surface of leaves in localized areas on mid-upper leaves.  These pustules are tightly clustered on the leaves. However, color and size are relative as sometimes the two diseases can look alike.  Microscopic observation is the best way to differentiate the two diseases.  Fungal spores from Puccinia sorghi causing common rust will be near perfect round circles whereas fungal spores fromPuccinia polysora will be oblong in shape.

We do have some gray leaf spot in the lower canopies and I haven’t seen much northern corn leaf blight in the fields.  But we do

have a bacterial leaf blight that is affecting quite a bit of leaf tissue on some hybrids.  These lesions are long and skinny appearing at first to be limited to the veins.  There’s been concern about these lesions being severe gray leaf spot but it’s not and there’s nothing you can do about the bacterial disease.  Please don’t mistake this bacterial disease as a fungal one and trigger a fungicide application too early.

Fungicide Application Timing

We tend to see southern rust in our part of the State each year; it’s a matter of time.  Triggering a fungicide application too early may result in no residual for when you need it if/when southern rust occurs.  Every year some producers make more than one fungicide application due to blanket applications at tassel or shortly after followed by another fungicide application when southern rust occurs later in the year.  Consider good fungal resistance management and apply fungicides when disease pressure warrants them in your fields and also consider economics for your situation for proper fungicide application timing.

Storm Damaged Crops

The rain was welcome on Thursday but the wind and hail damage that came were devastating to a good portion of theSeverely damaged corn County.  I’m so sorry to all of you affected….for some of you, this is two years in a row of severely hail damaged or totaled out crops.  We are thankful the damage wasn’t worse.  You can see more pictures here.

So the big question is what do you do now?  Ultimately, each field will need to be assessed on a case by case basis.  The following are our NebGuides for hail damage to corn and soybeans.  For the most part we were in brown-silk to blister for corn and late pod-beginning seed in soybean (R4-R5).  The concerns I have right now are stalk quality, disease, grain filling, and the amount of diseased grain we may have due to mushy areas on hail-damaged cobs right now.   Several years ago, we watched how severely hail-damaged corn a little later in the season turned brown and died.  We also know that southernCorn ears damaged by hail that are turning mushy. rust is in the area and while much of the leaf tissue in the County is damaged, it is still in the County in other fields and south of us.  The Puccinia polysora fungus that causes southern rust, when severe enough, will infect and cause pustules on the stalks.  With the wounding and low leaf area for photosynthesis, stalk strength is a concern and fungicides may be a consideration depending on potential yield loss-again need to assess on a field by field basis.

I talked with a number of people on Friday regarding thoughts on silage, green chop, haying/baling, planting cover crops, etc.  Dr. Bruce Anderson, UNL Extension Forage Specialist, said the most common salvage operation for corn damaged by hail, wind, drought, or other calamities is to chop it for silage.  Don’t be in a hurry, though.  Standing corn currently could be over 80 percent moisture.  The easiest way, and maybe the best way, to lower moisture content is simply wait until some stalks start to turn brown.  Waiting also allows surviving corn to continue to add tonnage.

But in some of our damaged fields, I don’t think we can wait to make silage.  Bruce also shared you can reduce moisture by windowing the crop and allow it to wilt one-half to one full day before chopping.  You also could mix grain or chopped hay to freshly chopped corn to lower the moisture content.  It takes quite a bit of material for mixing though – about 7 bushels of grain or 350 pounds of hay to lower each ton of silage down to 70 percent moisture from an original 80 percent moisture.  That’s 7 bushels grain or 350 pounds of hay for each ton of silage.

Or, you can allow that windrowed corn to dry completely and bale it as hay.  Be sure to test it for nitrates before feeding.   Grazing might be the easiest way to use damaged corn, and this is a good way to extend your grazing season.  You might even plant some corn grain or sorghum-sudangrass or oats and turnips between rows to grow more forage for grazing if you can wait until late fall before grazing.  Be sure to introduce livestock slowly to this new forage by feeding them before turning in to reduce the chances of digestive problems.  Also, strip graze the field to reduce trampling losses and get more grazing from the corn.

Southern Rust

Several of us had been watching the USDA IPM Pipe Map for weeks.  It wasn’t showing southern rust moving and only Georgia2013-07-30 09.31.26 was really lit up.  Yet, I had heard reports in Texas and Oklahoma at one point.  Spots were evident on corn leaves when backlit-so they were bound to develop into something.

That something has showed itself to be southern rust last week as it was confirmed in 11 Nebraska Counties:  Kearney, Adams, Clay, Nuckolls, Thayer, Fillmore, Gage, Platte, Polk, York, and Boone.  I’d like to thank all the crop consultants and ag industry professionals for sharing information on what we all were seeing and for submitting samples.  2013-07-30 11.44.36

So the common question was, why didn’t the map show anything south of us?  Federal funding was no longer available for this site and scouting efforts associated with it.  Many Extension Plant Pathologists weren’t aware that the site was even still online and were sharing information via other means instead.  The map for Nebraska will continue to be updated, but for surrounding states, it is advised to consult with your local Extension Plant Pathologist.

Differentiating Rusts:

When differentiating between southern rust vs. common rust, there are several criteria to consider and this NebGuide is a great resource.  Typically common rust will have brick-red pustules randomly scattered on the upper and lower leaf surfaces that are larger in size.

For southern rust, we’re seeing very small, raised, tan-orange pustules on the upper leaf surface of leaves in localized areas on mid-upper leaves.  These pustules are tightly clustered on the leaves. Fungal spores of Puccinia sorghi, the pathogen causing common rust. However, color and size are relative as sometimes the two diseases can look alike.

Microscopic observation is the best way to differentiate the two diseases.  Fungal spores from Puccinia sorghi causing common rust will be near perfect round circles whereas fungal spores from Puccinia polysora will be oblong in shape.

Disease Progression:

With the cooler weather last week, we were unsure how the disease would progress. Southern rust likes sustained temperatures in the 80’s-90’sF with humidity and leaf wetness.  So we encourage scouting for it.

We saw how southern rust can be devastating to fields in the past regarding removing photosynthetic tissue leading to cannabalization of the stalk.  In determining a fungicide application, consider Physoderma brown spotdisease pressure in your field, stage of growth, pre-harvest intervals, and length of time for fungicide residual in addition to economics.

Look-A-likes:

Other plant samples brought in contained diseases such as physoderma brown spot (which isn’t a significant yield limiting disease of corn).  Because the spores of this fungus move via water (it’s closely related to oomycetes), numerous lesions can appear on leaves in bands or areas where water collects.  While the lesions may look like early southern rust, there will be no pustules present and often the purple colored lesions will also be observed in the midrib, leaf sheath, stalk, and outer husks.

#Wheat Disease Update

Questions have been rolling in regarding dead leaves in the mid to lower wheat canopy.  Wheat is heading in much of South Central Nebraska and in some cases has begun to flower.  When considering a fungicide application, once your wheat has begun to flower, there are only certain products that are labeled for use.  These include but are not limited to fungicides such as Proline, Folicur, and Prosaro.  All of these have a 30 day pre-harvest restriction and can only be applied up to 50% flowering.  For more information on all fungicides, rates, and pre-harvest restrictions for wheat, please check out this resource from Dr. Stephen Wegulo, UNL Extension Wheat Pathologist.  Below is a short video of me scouting a wheat field so you know what to look for in your fields.  Fungicides will not help leaves affected with barley yellow dwarf as that’s caused by a virus; however, with the amount of stripe rust in our canopies and seeing it on the flag leaves already in addition to the rain and humidity allowing for increased risk of Fusarium Head Blight (scab), I still feel a fungicide is a good option.  

CropUpdate 7-18-11

While it may be strange, I love the smell of corn pollinating and don’t mind walking fields this time of year!  Summer is flying by but it seems like it’s taken a long time to get to tasseling in our fields this year.  Now that corn is tasseling, we can take into account the third foot root zone for irrigation scheduling.  There still is moisture to consider in the third foot so continue to check your readings on your irrigation scheduling tools and now take averages for all three feet.  You may be surprised as some of you won’t need to water till end of July/beginning of August!  If you have any questions about your irrigation scheduling tools, please continue to call any of us Extension educators or the NRD personnel as we want to help you and work with you now to answer them.

Disease just isn’t an issue so far in fields, so for those of you who purchased fungicide, wait till disease is present when you may need it.  UNL research by Dr. Tamra Jackson has proven yields are just as good with delayed fungicide applications as they are at tassel.  The longer you wait to use it for gray leaf spot, the more chances you will have residual for southern rust when it comes in.  While corn prices are high, you want to keep as much of that money as you can!  I don’t recommend fungicides on soybeans as we don’t have the disease to warrant it.  If you did pre-pay fungicide for soybeans as well, the timing of that application should be R3 (beginning pod).

Soybeans are approaching beginning pod for many of you.  For soybeans, this is a critical time for moisture in addition to seed fill at R5.  Many irrigation systems were running on beans last week and I just cringed because the time we don’t want to water soybeans is full flower or (R2).  The reason for that is because it can create disease issues.  We’ve seen a large increase of sudden death syndrome (SDS) the past few years in our county.  Part of that is due to early planting in cold soils, but irrigation during flowering can also play a role.  The major disease that occurs when irrigating during flowering is sclerotinia stem rot (also known as white mold).  While we have very few cases of this in the area, this disease is one that you don’t want to get started in your fields.  Like the fungal pathogen causing SDS, the fungal pathogen causing white mold is soil borne.  Thus, once you have it, you can never get rid of it.  White mold gets started during R2 when flower petals begin to die and the fungus develops on those dead petals. Wet, humid conditions during flowering are key to fungal development, so in the future, avoid irrigating beans during the flowering stages to avoid problems with these two diseases.

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