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JenREES 9/4/22
Crop Updates: Weed control has been a challenge in these hail-damaged fields. If needing a harvest aid for corn, 2,4-D or Aim can be used after beginning dent. Glyphosate and Gramoxone can’t be used till black layer. All need to be applied at least 7 days prior to corn harvest. For soybean, don’t go too early. Sharpen is the most commonly used with a 3 day pre-harvest interval and we say to apply at the combination of these things: 65% of pods are brown, there’s more than 70% leaf drop, and seed moisture is less than 30%.
For a few weeks many have observed corn plants rapidly dying in the area, both in irrigated and non-irrigated fields. There has been some Goss’s wilt (leaf version) out there, but I’ve seen more instances of dying leaves being called Goss’s when it’s not. And, that’s an important diagnosis as you think about hybrids for the future. For Goss, look for a shiny, almost varnished appearance on the lesions. In the very edges where the lesion is more ‘water-soaked’ and light-green in color, you should often see the presence of black specks that look like pepper. Some lesions being confused with Goss’ are actually northern corn leaf blight, but it doesn’t have a shiny varnished appearance and will have cigar-shaped lesions usually between the midrib and leaf edge. These lesions can eventually blight entire leaves and may be what’s occurring in some hybrids.
I have seen some anthracnose top die-back in some fields (look for top leaves flagging bright yellow and senescing from top towards middle of plant). I’ve also seen a lot of crown rot in fields…since early this growing season. At that time, it wasn’t something we considered for replant because it doesn’t usually kill plants then. It does hinder water and nutrient uptake at this point in the season, and I think that’s the greater issue combined with higher soil temperatures (up to 8F higher than normal) and water stress. There’s nothing we can do about any of these problems, but you can take note of hybrid differences right now. If you want to see if crown rot is playing a role, dig up a plant with leaves that are rapidly dying and slice the stalk open. For crown rot, you will notice a browning in the crown area and sometimes even up higher on the internodes. Fields that received hail damage and weren’t replanted are also showing greater rot into the stalks where you can see the original hail stone damage that penetrated.
Irrigation: I know you’re weary of irrigating. The blessing of this slow fill period is packing on weight with deeper kernels. We’ve known for some time that we will most likely be irrigating replant crops while harvesting. Some need this replant crop to fill contracts while others are trying to get by without many additional inputs. For several weeks I’ve thought about ‘how much yield do we give up if we stop irrigating at X’. Was thinking about this for those who get tired and are ready to shut off early and for the replant corn if shutting off early can move it along/get it to dry down faster. Wasn’t sure how relevant this thinking was till two farmers asked me. So, the following is combined from ISU’s ‘How a Corn Plant Develops’, ‘Last irrigation of the season’ NebGuide, and info. from some plant breeders if it can be helpful for your decision making going forward. The caveat is that hybrids differ, thus the range, so perhaps also talk with your seed dealer. For corn:
- Beginning dent needs 5.0” water, around 24 days to maturity, 25-55% yield loss potential.
- ¼ milk needs 3.75” water, about 19 days to maturity, 15-35% yield loss potential.
- ½ milk needs 2.25” water, about 13 days to maturity, 5-10% yield loss potential.
- ¾ milk needs 1.0” water, about 7 days to maturity, around 3% yield loss potential.
I don’t have the same numbers for soybean, but in much of the soybean replant, I’m seeing beans that either caught up to the old stand development stage or are up to 3 stages behind it. The biggest thing I’ve seen in replant soybean in the past is having beans at a variety of development stages at harvest…from lima beans to dry bbs, particularly when later maturity groups were planted as replant compared to the original maturity group. Regarding all who ask me if this replant corn crop will make it, for now, let’s just leave it that I genuinely hope and pray it does! Each day is one more day closer!
Crown Rot: Was seeing this early on in the growing season in the below-ground nodes (left triangle area) and seeing quite a bit now as well (right). Regardless of the specific pathogen causing this, what we observe this time of year is leaves rapidly dying and rotted crowns on plants such as what you see in the plant on the right. This plant is actually rotted to the vascular bundles in the crown area with rot progressing up the plant into subsequent internodes and nodes.
JenREES 8/1/21
Reminder of the Seward and York County Fairs this week! August also brings the season of field days! Soybean Management Field Days will be held next week at various locations in the State from Aug. 10 to Aug. 13. The closest to this part of the State is Aug. 12th near Rising City at the Bart & Geoff Ruth Farm. More info. at: enrec.unl.edu/soydays.
Corn Update: I realize this week’s column shares lots of problems seen in the field last week. My goal is always to increase awareness, but sometimes it feels ‘heavy’ hearing about the problems. Grateful we’ve had few problems overall this season till now! The high humidity has allowed non-irrigated crops to hang on and crops in general to not use as much water as anticipated for crops at this stage. In general, fungal disease is still low in fields. I’m starting to see baby lesions that will most likely become gray leaf spot around mid-canopy, so that will be something to watch in coming weeks. Spidermites have also been flaring above the ear in some fields, particularly non-irrigated.
For our area of the State, southern rust has been confirmed in Adams, Nuckolls, Thayer, Gage, Saline, Clay, and Fillmore counties. There are probable samples at time of writing this for Seward and Jefferson counties (https://corn.ipmpipe.org/southerncornrust/). In all the samples, incidence and severity were very low. Many are being found around waist-high in the canopy. Three samples I confirmed last week were from fields that had already been sprayed and the pustules were found mid-canopy. This happens every year, regardless of the residual applied in the first application. I know a couple farmers who have paid a little extra to have the aerial applicator increase gallonage from 2 gal/ac to 3 gal/ac. They felt that aided in coverage a little further into the canopy. For those with chemigation certification, I also know several growers who chemigate their insecticide and/or fungicide effectively, which allows for better plant coverage into the canopy (as long as pivot doesn’t have drop nozzles below canopy).
I really enjoy observing what occurs with plants, yet I honestly don’t know anyone who wishes to see abnormal corn ears, especially after wind events such as July 9. I feel it’s important to observe and document what occurs on these plants that bent and didn’t break. The goal is awareness to know what type of ear development exists so there’s not such a surprise at harvest if yields are off, and to be aware when working with your crop insurance agent. There’s unfortunately some ugly looking ears out there. Some similar stress events occurred this year comparable to 2016, minus the drop in temperature prior to the wind event. I’m not seeing anything yet to the level like what we saw in 2016, which is encouraging. What I’m seeing ranges from row abortion above where the ear stress occurred to torpedo and banana shaped ears to pinched areas on ears including various forms of ‘barbells’. Finding greater damage in fields where the plants were within a week of tasseling when the wind event occurred. It also appears like those fields that were 2 weeks or more from tasseling at the time of the wind event aren’t as impacted. For growers that had plants that blew down or leaned and then righted themselves but didn’t break, it’s wise that you and/or your agronomist are checking ear development on them. Each field can be unique depending on stage of development the particular hybrid was in at the time of the wind event. Pictures of what is being observed are at jenreesources.com.
Soybean Update: Received a number of calls regarding poor-looking patches in soybean fields this week. Drought stress is showing up in non-irrigated fields. Be checking those areas for spidermites as well. If they’re present, I tend to find them towards the edge of the patch between the impacted area and what appears to be healthier beans. White mold in soybeans is something that’s becoming more common in counties such as Butler. It can have patterns such as several plants in a row impacted and/or a patchy area in the field. The plants will have a white cottony fungal growth on them and eventually the stem (upon splitting) has black fungal structures that look like mouse droppings in them.
Sudden death syndrome (SDS) and/or brown stem rot are also showing up in small patches of fields where the leaves have a chlorotic/necrotic look between the veins. The humidity has allowed the blue/gray fungal growth characteristic of SDS on the rotted taproots to be observed even mid-day. If you split the stem and the pith is brown, the culprit is most likely brown stem rot; if it’s not but the taproot is rotted and you can easily pull it from the soil, it’s probably SDS. Plants can sometimes have both diseases. All of these are soil-borne fungal diseases and there’s no control measures for this time of year. It would be wise to pull 0-8” soil samples to check for soybean cyst nematode in areas of fields you’re finding SDS and brown stem rot in. Dectes (soybean) stem borer tunneling can be confusing when determining dectes vs. brown stem rot. At this time of year, I don’t typically see dectes moving far (more than 1-2″ either direction) from the initial point of hatching near the petiole. This is in comparison to brown stem rot which would have browning of pith from soil line. Dectes also will not kill plants (just create conditions for lodging and breaking off near harvest). This is because the vascular bundles of soybeans are found on the outside edge and not in the center of the stem. Thus, death of plants this time of year are due to another cause.
Two examples of shortened husks on developing ears. Husking back these ears often shows a pinch point that occurred during the windstorm resulting in jumbled kernels.
JenREES 8-25-19
Crop Updates: An increase in disease pressure has been the theme the past few weeks. 
Sudden death syndrome is increasing in soybeans, but there’s also brown stem rot (BSR) and frogeye leaf spot in some fields. The foliar discoloration is the same for SDS and BSR with the yellow/brown discoloration between leaf veins. You can tell the difference by pulling a plant out of the ground. SDS is usually easy to pull as the taproot is rotted. Splitting the stem open, the root will show rot at the soil line but the stem pith will be white and healthy. With brown stem rot, the pith will have brown discoloration. The addition of stem borer can make it more difficult to tell the difference sometimes. Unfortunately there’s nothing one can do for SDS or brown stem rot now as both are caused by soil borne fungi. I would recommend taking soil samples for soybean cyst nematode (SCN) in areas currently impacted by SDS as the combination of diseases is synergistic in impacting yield loss. You only need 0-8” samples and they can be taken during soil fertility samples if you don’t want to take them now. The samples are free via your checkoff dollars and they can be sent to the Plant and Pest Diagnostic Lab at UNL in Lincoln.
In corn, foliar disease is increasing in mid-canopies. Most concerning are the number of stalk rot samples/situations I was called to the past week. They all appear to be bacterial stalk rot thus far. Symptoms include watersoaked nodes and below the nodes with plants breaking off/falling over. Damaged nodes are from the soil line to upper canopy. The bacteria disintegrates these stalks creating a stringy appearance within them where the nodes break and when slitting open stalks. It also has a distinct foul smell. This is more of a problem in wet years such as this and hybrid susceptibility varies. The bacteria doesn’t typically transfer from plant to plant. I have photos of what I’m seeing on my blog at https://jenreesources.com.
There have been multiple late-season hail events in the area. For those fields hit by the 
August 6th storm, the rainy, cool conditions have allowed for increase in mold on the hail damaged side since many of those damaged ears were at milk stage. However, I’m also seeing mold damage on some back-side of ears in hybrids with tighter husks. The white/pink fluffy growth on the hail damaged side is caused by Fusarium/Gibberella fungi. The presence of these fungi does not automatically mean mycotoxins are present; they do have the potential to produce mycotoxins. The green fungal growth in ears are caused by secondary and minor fungal pathogens that don’t produce mycotoxins. The white fungus overtaking ears on some tight-husked hybrids is diplodia which can cause for light test weight but does not produce a mycotoxin. It will be important to continue to watch grain quality over time prior to harvest.
Wild and Burcucumber on Trees has also been a huge question. Do Not apply 2,4-D to trees for
Thanks to Randy Pryor for demonstrating how easy these are to pull while we were on a field call together!
control as that has been the most common question! The simplest way to kill wild and burcucumber is pull or hoe the plant at its base below the tree. There’s not much to the plant root and the vines will then die on the tree!
It’s been a hard year for our growers and livestock producers with continued challenges. Seeking to end this column on a positive note, this year is the 10th year of the Nebraska State Fair in Grand Island and the 150th Fairabration. I’m grateful for the focus on agriculture, families and youth! And, it’s encouraging to me to see youth learning life skills whether competing in public speaking, 
working with and showing livestock, or studying and competing in contests such as weed and grass ID at the State Fair. 4-H is where I got my start and it’s exciting for me to wonder at the futures these 4-H and FFA youth have ahead of them as they continue to work hard and put into practice the life skills they are learning! Hope you can make it out to the State Fair at some point!
*End of News Column. Bacterial stalk rot photos below.
Plants still standing showing various symptoms of dying and death
Some plants exhibiting bacterial stalk rot are already lodged or broke off at or around plant nodes.
Plant nodes show discoloration with watersoaking around the nodes (notice the soaked appearance on internode where I removed the outside sheath).
Majorly impacted nodes and internodes by bacterial stalk rot. There’s a distinct foul odor. Notice how wet and watersoaked nodes and internodes are and there’s even bacterial ooze in this case on the stalk.
Plants break at nodes. Also notice the stringy appearance of stalk pith.
Commonly seeing this with impacted nodes from the soil line through upper canopy…stringy appearance of pith tissue.
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).
Ag Reflections from 2014
Happy New Year! Wishing all of you and your families a wonderful 2015! As I look back at 2014, there are several ag-related observations that I noted throughout the year.
Cleanup after the tornado in Sutton on Mother’s Day 2014.
The first observation continues to be the way communities and people in this County/area pull together in difficult times. Whether after tornadoes/wind storms or helping other farm families who had an injured family member or had lost a family member, it’s just a blessing to see the way people pull together to help each other in time of need. It was also a blessing for many who were unable to harvest in 2013 due to the August 1st storm, to harvest fields in 2014, and for many in the area to experience really good irrigated and dryland yields this year.
The dry winter of 2013/14 allowed for very mellow ground during planting time. Often seeding depth ended up ½-1” deeper than intended. The dry winter also didn’t allow for good residue decomposition leading to problems during planting and ensuing stand emergence. Cutting off residue and high rains in May led to unintended consequences of replant situations when residue was moved off of farmers’ fields onto neighboring fields, suffocating emerged plants in portions of fields. I’m not sure what the solution is for the future other than it really needs to be something worked out with neighboring farmers, but perhaps mentioning it here opens an opportunity for future conversations.
Cover crops have been incorporated into more operations in recent years, yet the ultimate goal for using them remains important in determining what species/crops are used in the fields. We also realized the importance of determining amount grazed prior to turning cattle into fields (whether for grazing cover crops or crop residue), as high winds in winter 2013/14 in overgrazed fields led to soil blowing throughout the winter.
Systemic Goss’ wilt showed up in some fields that were hail and/or frost damaged by V6.
The May frost showed us emerged soybeans at the cotyledon stage held up well to the frost compared to the corn. We also again watched Goss’ wilt show up systemically by 6 leaf corn that was injured early by frost or hail in fields where Goss’ wilt had been a problem in the past. We need more research/understanding of this disease. Wheat continues to show us its resiliency as it winterkilled in portions of fields, withstood drought-stress, and then made up yield in the last 4-6 weeks.
Perfect pollination conditions coupled with high solar radiation, low night-time temperatures, and timely rain events were keys to the bountiful corn crop we experienced this year. Soybeans were more of a mixed bag. In walking fields and in conversations with farmers, I think the disappointment in some irrigated yields could be attributed to early/over-irrigation, disease problems, and planting date. UNL on-farm research showed on average a 3 bu/ac yield increase when soybeans were planted in late April to first week of May (regardless if growing season was warm/dry or cold/wet like it was this year) and those I’ve talked to who achieved 80+ bu/ac in the area this year planted in that time-frame. I’m curious if there’s something to planting a 2.4-2.5 maturity early vs. a 3.0+ maturity early as some area producers are seeing strong yields from a shorter season hybrid planted early the past few years. So if you’ve also seen this and/or are interested, that will be an on-farm research project to try next year. Please let me know if you’re interested!
Here’s wishing you a healthy and prosperous 2015!
Crop Update 8/1/14
Southern rust of corn confirmed in Clay County July 31. Very small, tan-brown lesions on upper surface of the leaf, usually in clusters. Spores inside the pustules are typically orange. This was found on one leaf in a field near Trumbull. Just because southern rust has been found in the area, we don’t recommend automatically spraying. Scout your fields and consider disease pressure, growth stage, and economics. Long season corn and late-planted fields have the potential for most damage. Secondary common rust sporulation has also been confused as southern rust as the secondary pustules tend to look like this. It’s important to obtain microscopic confirmation to know for sure if you have southern rust in your fields.
Microscopic Observation: Spores of southern rust appear elongated vs. common rust appear as near perfect circles.
Another common problem is old common rust lesions being confused as gray leaf spot. The color of this lesion is a tan-gray, typical of gray leaf spot. Using backlighting or a handlens, you can see the pustules within this lesion confirming it is common rust and not gray leaf spot. I’ve had many calls that gray leaf spot was up the entire plant in their fields and after looking at fields, have found it to be common rust in most situations. It’s important to know what disease you truly have to make the best decision on fungicide application.
Have also received questions on soybeans, particularly in dryland. This photo is showing drought stressed soybeans-often occurring in pockets within dryland fields right now. Closer observation shows plants aborting pods and losing lowest leaves. Spidermites can also be viewed on leaves in some of these patches.
Dryland corn showing stress as well. June rains were making for dryland crops with potential, but also led to shallow rooting. Crops could use a drink right now….but would prefer no more hail and tornadoes. The storm that hit Clay County so hard occurred one year ago today.
Corn Disease Look-Alikes
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:
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 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.
Southern Rust
Several of us had been watching the USDA IPM Pipe Map for weeks. It wasn’t showing southern rust moving and only Georgia
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. 
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. 
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 
disease 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.
- More information can be found in this article from UNL Extension’s CropWatch.
Southern vs. Common Rust in #Corn
In early July, southern rust caused by the fungal pathogen Puccinia polysora was discovered in Hall, Adams, Clay, Fillmore, 
Thayer, and Burt counties in Nebraska. Most farmers in south-central Nebraska remember the corn season in 2006 walking out of fields orange and the slow harvest due to downed stalks. Since then, southern rust has been a disease of concern and fungicides are used to prevent and also treat it when it’s found in fields.
I promised when we were first discovering southern rust this year that I’d post pics, so while delayed, here they are! It is often confused with common rust which we see earlier every year. Common rust typically has pustules (raised fungal spores) that are brick red in color, larger, and on the upper and lower leaf 
surfaces. The pustules tend to be more spread out.
Southern rust typically has very small pustules that are clustered on predominately the upper leaf surface and are tan to orange in color. This year, southern rust pustules tend to be more tan in color than orange but are still distinctively different with their smaller and clustered appearance. Both fungal rust pathogens arrive in Nebraska each year via wind from the south. Southern rust prefers warm, moist conditions which, in spite of our dry spell, is typical within our pivot and gravity-irrigated fields in the area. At this time we are recommending if you find southern rust in your field to consider treating with a fungicide. Please be sure to read and follow all label directions including paying attention to pre-harvest intervals. A list of corn fungicides and efficacy can be found here by scrolling down to the corn section.
Additional information and pictures of these diseases can be found here.
JenREESources's Extension Blog 