Category Archives: Diseases
System’s Approach to Soybean White Mold
Grateful for seasons, for fall, and that we have such beautiful fall colors this year! For whatever reason, it just doesn’t seem like we’ve seen colors like this for a few years and several have commented about the beauty this year. May we take time to notice the beauty around us each day! Also grateful for harvest being completed or nearing completion for many! Each day is one day closer to the end!
White Mold in Soybean: Sclerotinia sclerotiorum (the pathogen that causes white mold) impacts over 400 plant species from 75 families including soybean, dry bean, potato, sunflower, peas. Host weed species include: pigweeds, velvetleaf, henbit, lambsquarters, ragweeds, nightshades, mustards, sunflower. Cover crop hosts include: peas, lentils, turnips, radishes, collards, common vetch, (alfalfa and clover to a lesser extent). Just reading all that is discouraging. The fungus survives in a hard, black structure called a sclerotia that looks like mouse/rat droppings and can survive in the soil for 5 years (3 years in no-till fields). Frequent irrigation, plant wetness/fog/cool conditions at flowering (like we had in 2023), narrow rows, high plant populations, and cooler weather conditions of 46-75F allow the sclerotia to develop apothecia (look like circular tan mushrooms). Under a specific pressure, the apothecia shoot spores into the canopy where they infect the soybean plants whenever they land on senescing soybean flowers.
Flowering occurs from R1-R5 in indeterminant soybeans. Thus, why white mold is difficult to control and why we can see it develop so late into the year. The fungal infection moves from the flower into the stem, disrupting water transport. Thus, why you will often see plants that look wilted as an early symptom even before you see the signs of the white fungal growth. Wilting of plants leads to premature death impacting yields like we saw with large yield hits this past year. New sclerotia are formed within and also stick out of the plant stem and pods. They fall to the ground and the cycle continues when a susceptible host is grown.
So, what do we do about it? The following information is for fields that have a history of white mold. I’d suggest looking at this from a system’s approach. One piece is to consider varieties with disease resistance. I won’t argue that’s important. However, I’m honestly hesitant to start there as I’m unsure we have strong disease packages. And some defensive varieties give up too much yield. This is my perspective and I don’t expect people to agree. For now, I suggest finding the strongest yielding genetics first because there’s large yield variation in soybean.
From there, it becomes managing the other factors that can aid in disease. Manage weeds and avoid susceptible cover crops in the field. Crop rotation is not effective if it’s only a 2 year corn/soy rotation. While I realize they won’t work for everyone’s operation and they take more management, using small grains like cereal rye before soybeans is a tool that can help with both weed and disease suppression and doing so adds another crop to a 2 year rotation. Avoid irrigation at flowering (I realize 2023 was tough) and seek to irrigate deeper and less frequent.
There’s also tradeoffs within the system regarding row spacing for weed or disease control. Results from 18 site-years of research from Wisconsin, Michigan, Ohio, Indiana, and Iowa showed:
- If planting in row spacings of 15 inches or less and in fields with a history of white mold, use a seeding rate no greater than 110,000 seeds/ac.
- If planting in fields with a history of severe white mold, widen the row spacing to 30 inches and use a seeding rate no greater than 110,000 seeds/ac. UNL research shows you don’t give up yield with final plant stands at 100,000 plants/ac.
- Fungicide applications remain an effective tool for reducing white mold levels if applied between the R1 (most effective) and R3 (less effective) growth stages. Fungicides provide 0-60% control. They’re most effective if sprayed below the canopy.
- Not all fungicide products are equally effective at controlling white mold, with Endura® remaining the most effective product if applied between the correct growth stages.
- Consider downloading the Sporecaster app for white mold to better time fungicide apps based on weather conditions (found to be 81.8% accurate).
Most biological control agents should be applied at least 3 months before flowering for fungal colonization. Biological control agents and seed treatments such as Heads Up® were shown as effective tools to reduce severity of white mold and SDS based on Iowa State research. Plant nutrition is also showing promise and that’s something I’d like to try next year with a few growers; please let me know if you’re interested. Hydrogen peroxide products had little to no success in Wisconsin research (provided only 4 hours of activity killing spores). None of the things mentioned here are exclusive, but a combination of many of these factors as a system’s approach can help in the battle against white mold.
To view tables of the fungicide research results for white mold go to: https://cropprotectionnetwork.org/publications/modern-integrated-management-practices-for-controlling-white-mold-of-soybean
JenREES 10/8/23
Soybean Cyst Nematode: 2023 was a year for soybean diseases. I’ve been thinking about the soybean disease problems we’ve had and am planning a series of columns to talk through thoughts on management. Will focus on soybean cyst nematode for this week.
After soybean harvest is a prime time to sample for soybean cyst nematode as they’ll be at their highest levels in the soil. Soybean cyst nematode (SCN) is considered the #1 soybean disease in the U.S. as it can rob yield (up to 40%) with or without the presence of symptoms on soybean plants. When symptoms are present, they can include patchy areas of fields that may contain chlorotic and/or stunted plants. Digging up plants and carefully looking around the roots, one may observe tiny white specks that look like sand grains. With closer observation, if it is SCN, the specks will appear lemon-shaped as the female soybean cyst nematode. Technically, when the female body turns brown and dies is when it is called a ‘cyst’. Each cyst protects and contains up to 400 eggs each. When soybean is planted, juvenile nematodes hatch from eggs within the cysts during the right moisture and temperature conditions. The nematodes migrate to soybean roots where they infect, feed, breed, and then females produce new cysts full of eggs. This lifecycle occurs 3-4 times during the summer, thus, SCN populations can rapidly increase in a field in one year.
I saw that this year, a handful of times. Most field situations didn’t only have SCN as the problem, but I saw SCN populations rapidly increase from the first time fields were sampled to the next time. As you or agronomists are taking soil fertility samples this fall, split part of the 0-8” (or 0-6”) sample for testing for SCN. Or, take the soil sample in areas where the yield monitor showed yields were very low, patches where you saw disease, or field entryways. It’s also wise to take a sample from a good portion of the field for comparison. In soybean fields, take the sample a few inches off the old soybean row. However, SCN samples can also be taken from corn or other crop fields to help inform decisions if rotating to soybean next year. Place the sample cores (12-20 in total) in a plastic bucket, mix, then place in your sampling bag. I use quart-sized ziplock type bags, but there’s also SCN sampling bags available at local Extension Offices or directly from the UNL Plant and Pest Diagnostic clinic (402-472-2559). Label the bag with your contact info., field name, and that you want SCN analysis. Also be sure to fill out a completed sample submission form requesting SCN analysis and mail the samples to the UNL Plant & Pest Diagnostic Clinic (1875 North 38th Street, 448 Plant Science Hall, Lincoln, NE 68583-0722). There’s no charge for the sample analysis thanks to the Nebraska Soybean Board and your checkoff dollars. Knowing if you have SCN is the first step in management. Will share more on management in future columns.
Caring for Drought-stressed trees/shrubs: With the continuing dry conditions, this is a critical time to prepare woody plants for winter and prevent winter injury, especially to evergreens. Dry fall conditions can reduce the number of leaves, blooms and fruits trees produce the next season. Trees often delay the appearance of drought-stress-sometimes months or years after the stress occurs. Drought-stressed trees are more susceptible to secondary attack by insect pests and disease problems, such as borers and canker diseases, which can cause tree death. When watering, moisten the soil around trees and shrubs, up to just beyond the dripline (outside edge of tree leaf/needle canopy), to a depth of 8 to 12”. Avoid overwatering; but continue to water until the ground freezes as long as dry conditions persist. Use a screwdriver pushed into the soil to gauge the depth of watering.
Cedar beetles (Cicada parasite beetles): Have gotten a few calls about numerous beetles on ash and other trees that were crawling on them and flying around. The ones I’ve received samples of are cedar beetles, also known as cicada parasite beetles, which were new for me to learn about. They are about one inch long, and dark brown or black. The males have short, comb-like antennae. The beetles are harmless to trees and are laying eggs in the bark cracks. Larvae hatch, travel down tree cracks and burrow through soil looking for cicada nymphs to feed on their blood. So, they’re considered a parasite of cicadas, not of trees, and no control is needed.
Cedar beetles/Cicada parasite beetles
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 3/14/21
March is a month where I spend some time planning on-farm research and other experiments. One topic that surfaced during our on-farm research meetings in February was potentially testing the fungicide product Xyway™. This product is unique in that it is applied in furrow and can be applied with starter fertilizer at planting. It moves systemically in the plant through the water carrying vessels (xylem). For growers who are near towns or locations where aerial applications are restricted, a product like this is intriguing and could have a unique fit.
There’s limited university research with the product, but the findings have been intriguing thus far. The LFR® and 3D versions (in furrow at planting) were tested in Kentucky compared to untreated check and foliar fungicide products (Lucento® and Headline AMP®) applied at R1 in corn. In 2019, Xyway™ LFR® and sometimes the 3D version also showed the same efficacy for northern corn leaf blight (NCLB) and even gray leaf spot (GLS) compared to products applied at R1. All the products had less disease severity compared to the untreated check. Xyway™ did not reduce southern rust disease severity. In 2020, low disease pressure in general was observed in the Kentucky locations. The Xyway™ still provided the same disease reduction to GLS as foliar products applied at R1, which were all significantly less than the check.
In 2020, Dr. Tamra Jackson-Ziems also had a study at UNL South Central Ag Lab near Clay Center. The study compared different application timings (at planting, R1 and R3) of different products compared to an untreated check. Xyway™ LFR® was applied with starter at 15.2 oz/ac at planting. This was compared to Xyway™ at planting + 5 oz/ac Lucento® applied at R1. A number of foliar fungicide products were applied at R1 and R3. The Xyway™ LFR® applied at planting showed no disease difference compared to the untreated check for southern rust. All the other products and timings reduced the amount of southern rust compared to the untreated check. Traditionally, we’ve seen fungicides provide improved standability. In 2020, there were no differences in lodging for any of the products or timings compared to the untreated check. Regarding yield, the Xyway™ LFR® at planting yielded better than the check, whereas there was no yield difference with the Xyway™ + Lucento® at R1. Looking at the data, there were no yield differences between applying foliar fungicide at R1 vs. R3 for any of the products except Miravis® Neo. And, sometimes a product didn’t show a difference between other products or even the untreated check. I show a picture of the data on my website jenreesources.com. With last year being a heavy southern rust year, being able to wait till R3 to apply a fungicide provided some additional time for the residual to work when southern really came on. I know some had to apply a second fungicide application when they automatically applied at R1; that’s just tough from an economic and resistance management perspective.
Because I’ve got nearly a handful of growers interested in testing Xyway™, I put together protocols at jenreesources.com if you’d also like to check them out. If you’re interested in testing any study via on-farm research, please contact me or your local Extension educator.
Solar Energy Webinars: These webinars are free and for anyone who is interested in solar. What is the payback for Solar PV systems? A common question with not such as easy answer. Farmers and businesses are receiving marketing materials to invest in solar, yet the economic feasibility of solar is not always clear. This webinar series will cover how solar electric systems work, how to determine the value of energy and how the complexity of subsidies and policy make general statements about feasibility more complex. This workshop will cover these issues in detail and provide participants with the information they need to speak confidently with farmers about solar electric systems. All webinars are held from 9:00-10:30 a.m. on March 30, Apr. 1, Apr. 6, Apr. 8. Registration at: https://unl.zoom.us/meeting/register/tJEod-qhrz0sHdYkpW9nRnfdsv0wlk78bW99. Those with specific questions can reach out to John Hay, Nebraska Extension Educator at 402-472-0408 or jhay2@unl.edu.
JenREES 7-19-20
Crop Update: The smell of pollen is in the air! Did you know each tassel contains around 6000 pollen-producing anthers? Two good articles from Dr. Bob Nielsen, Purdue University at https://go.unl.edu/x5tv.
How does heat impact pollination? Dr. Tom Hoegemeyer, former UNL Professor of Practice, shared that high humidity, without a drop in humidity during the day, can delay pollination or prevent pollen from leaving anther sacs. While heat over 95°F depresses pollen production, one day of 95-98°F has no or little yield impact when soil moisture is sufficient. After 4 consecutive days, there can be a 1% loss in yield for each day above that temperature. Greater yield loss occurs after the fifth or sixth day. Thankfully we’re not in a high heat pattern during this critical time of pollination!
My concerns regarding pollination: bent ear leaves covering silks in wind-damaged fields. Seeing a great deal of this. Also seeing silks continuing to elongate and grow through broken mid-ribs to increase exposure to pollen. Will continue to observe impacts.
Preliminary storm prediction center weather data showed a total of 93 wind, 11 hail, and 13 tornado damage reports on July 8th in Nebraska. Univ. of Wisconsin found lodged plants had yield reductions of 2-6% (V10-12 stage), 5-15% (V13-15 stage), and 12-31% (V17 and after stages). For greensnapped plants (below ear), Iowa State found in the worst case situation, yield reduction may range up to a 1:1 percent broken:yield loss. It’s possible these losses will be as low as 1:0.73 or even 1:0.50. We have an article in this week’s CropWatch (https://go.unl.edu/cwy2) with more detailed information. Recovery pics also at https://jenreesources.com.
Southern Rust was confirmed at low incidence and severity in Fillmore, Nuckolls, and Jefferson county fields this past week (probable for Thayer). Received questions on fungicide applications. In conversations, it seems like there’s fear of making the wrong decision and ultimately pressure to apply them. I realize economically it’s easier to justify adding a fungicide with insecticide when insect thresholds are met to save application costs. Most fungicide studies focus on VT applications; however, yield increases with automatic VT applications aren’t consistently proven in Nebraska.
In fact, in 2008-2009, a UNL fungicide timing trial was conducted near Clay Center on 2 hybrids (GLS ratings ‘fair’ and ‘(very) good’) with a high clearance applicator. Timing over the two years included: Tassel, Milk, Dough, 25%, 33%, 50%, and 100% Dent comparing the fungicides Headline, Headline AMP, Quilt and Stratego YLD.
- 2008: No yield difference on GLS hybrids rated ‘good’ at any of the timings (Tassel, Milk, 33% and 100% Dent) nor the check when Headline or Stratego YLD were applied. For the ‘fair’ hybrid, no yield difference for any application timing nor the check for the April 30th planting except for Headline applied at milk stage (increased yield). Low gray leaf spot pressure.
- 2009: No yield difference on GLS hybrids rated ‘very good’ or ‘fair’ nor the check on any timings (Tassel, Milk, and Dough) using Headline, Headline AMP, or Quilt. Moderate gray leaf spot disease pressure.
Thus I’ve recommended waiting till disease pressure warrants the application (have personally recommended apps as late as hard dough in previous years). Hybrids vary in disease susceptibility (thus response to fungicide application). The main ‘plant health’ benefit observed in Nebraska when disease pressure was low (ex. 2012) was stalk strength and that may be something to consider again in this lower disease year. Regarding any improved water use efficiency for drought-stressed plants, the peer-reviewed research published on this was in 2007. The researchers found slightly increased efficiency in well-watered plants, but it was reduced in water-stressed plants. They suggested fungicide use in water-stressed plants could potentially negatively influence water use efficiency and photosynthesis.
Same area of a York County Field taken morning of July 9th (left photo) and morning of July 13th (right photo). Grateful to see how plants are re-orienting themselves in many impacted lodged fields!
Plants re-orienting themselves by ‘pushing’ and establishing more brace roots on the leeward (leaned side) helping roots reconnect with soil on the windward side. Notice the additional brace root development within the circled area of this photo.
Plants reorienting themselves at each node at various angles and bends. Nodes become thicker to aid in reorientation.
Splitting open of thickened node. Additional cell division and/or elongation occurring at these nodes appears to help ‘push’ the stalk upward (geotrophic response).
Consistently seeing bent ear leaves covering silks in wind-damaged fields. Will have to watch any impacts to pollination.
Also seeing how either the ear or silks are working their way through tears in leaves or silks elongating to the side of the plant to try to pollinate.
Severely greensnapped field of later-planted corn.
Seeing some new growth on some greensnapped plants. Dissecting the growth revealed baby corn ears (they won’t amount to anything). Just shows the resiliency in plants regarding how they’re created to survive and reproduce. I never cease to be amazed by their Creator!
Seeing this very minor. Ear trapped within thickened husk/stalk tissue so forcing itself through side of plant. Silks visible first.
Opened this one to see curving of ear and some potential pinching occurring where ear was trapped above where it was forcing out of husk. Will be interesting to see any pollination and ear development impacts on plants like this.
JenREES 9-15-19
Crop Update: Thinking about harvest as we continue to watch corn and soybeans progress toward maturity. And as I write this, my desire is to be honest about what I’m seeing and the concerns growers and other agronomists are seeing too. Perhaps part of my perspective is the fact that I’m typically called out to problem situations! But hopefully that perspective helps you in some way know what to watch for in your own fields. So before harvest occurs, would encourage growers to get out in your fields and see for yourself how your crops look. It’s just a great way to estimate what your true harvest potential is prior to harvest. And, it’s always easier to diagnose yield potential problems now vs. post-harvest. There are some tremendous looking fields out there, especially non-irrigated ones! Yet sometimes (once we hit canopy closure) we forget about the early season challenges and the variability that can occur. Variability such as plant stands and plant emergence based on variable seed depth that can be seen now with variable ear sizes. There’s misshapen ears due to various stresses based on specific field practices/situations as well.
The warm, drier weather this week allowed for some noticeable changes. Perhaps the biggest one is the concern regarding tops of corn plants rapidly senescing. This could be due to either anthracnose top dieback or another disorder called ‘top leaf death or dieback in corn‘. Anthracnose can cause leaf lesions, top dieback, or stalk rot. To diagnose if anthracnose is the culprit, you can look for black fungal anthracnose lesions which may be blotchy in appearance on the stalk underneath the leaf sheaths. You can also split the upper or lower stalk looking for any discoloration in the pith or nodes. If you don’t see the lesions or pith/node discoloration, the discoloration in the top of the plant may be due to top leaf death or dieback. A Canadian researcher documented greater top leaf senescence during a period of warm, dry weather during grain fill. Another researcher documented this tends to be more common during good grain fill years. We have experienced that type of weather with a good grain fill period, so top leaf death/dieback may be the bigger culprit.
Yet, be sure to check for stalk rot in these fields. I’m finding stalk rot increasing with each week especially where there’s nitrogen deficiency, areas where water ponded, high plant populations, higher disease pressure, and areas with hail damage. There’s also something interesting happening where in specific hybrids, it appears the refuge in a bag plants are dying early (and have stalk rot) in comparison to the primary hybrid planted (I’m unsure exactly why).
The other thing noticeable this week was husk tissue turning color and ears turning 
down as hybrids mature. We’ve had a long grain fill period creating large ears with deep kernels. There are specific hybrids where I’m concerned about large ears and small shank diameters. Shanks appear firmly attached for now, but it’s still something to watch. Been recommending growers get those fields out earlier if possible.
To evaluate percent stalk rot, at least 100 plants throughout the field should be assessed. I prefer the ‘pinch test’ and do this by taking my thumb and first finger and pinching the stalk internode that occurs between the lower nodes above the soil line. Do this for 20 plants in an area and get a percentage for those that crush. Then do this for several areas of the field. This YouTube video helps show how to do this: https://www.youtube.com/watch?v=7z75VN1c51Q. Fields that have the greatest percentages of stalk rot prior to harvest may be prioritized over others. Where it worked in their operations, some growers in 2018 chose to harvest at a higher moisture content in order to get at fields in a more timely manner.
Some soybean harvest has started. Taking my final on-farm research notes in fields, I’m 
noticing dead plants next to green ones. The dead plants often have anthracnose and/or pod and stem blight. In some fields early death is due to sudden death syndrome. Also noticing red/purple leaves on some varieties indicative of cercospora leaf blight. Thus, we have potential for discolored, chalky seed and also purple seed stain again; hopefully nothing to the extent of 2018.
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.
JenREES 7-28-19
Southern Rust in Nebraska was confirmed in Nuckolls, Thayer, and Fillmore counties last week. The lesions were typically on one leaf in an isolated portion of fields at low incidence and severity. I was recommending to watch the fields instead of spraying right away. Greatly appreciate everyone who has gotten samples to me this month and to neighboring Extension offices serving as drop off points for samples. I’ve been looking at samples since early July and honestly, common rust at times has exhibited signs similar to southern rust. At my blog site (https://jenreesources.com), I’ve posted photos showing the differences of common vs. southern rust that we’re seeing this year. Southern rust typically is orange to tan colored with tiny, clustered pustules on the upper leaf surface. Common rust has had an orange appearance to it at times with smaller lesions than the ‘typical’ brick red larger ones. However, in every southern rust sample I’ve confirmed, the pustules have not gone through the back of the leaf…there’s been indentations but nothing has produced pustules on the backside. That doesn’t mean that the fungus can’t; it just rarely does. Also, these leaves have all occurred in the mid-canopy. I realize lowest leaves of plants often have a great deal of rust on them, but it’s been common rust in leaf samples I’ve pulled and received to date. I’ve also posted photos of another disease called Physoderma brown spot on my blog. Physoderma is the disease that has purple/brown on the midribs, around leaf axils and sheaths and it also can have tiny yellow-brown spots without pustules that look a lot like southern rust on leaves of plants. It’s one that we tend to see around pollination as the fungus-like pathogen swims in water on the leaf surface and feeds off of decaying pollen.
Confirming southern rust in a few Nebraska counties thus far doesn’t mean that every field has it and we don’t know how it will progress. So our recommendation is to continue scouting and if you have a suspect sample, you can get it to me (if you’re in the area) or to our Plant and Pest Diagnostic Lab in Lincoln. You can keep updated with counties that are confirmed by checking out the Southern Rust tracking site at: https://corn.ipmpipe.org/southerncornrust/. The wide range of planting dates across Nebraska this year has resulted in a wide range of corn growth and reproductive stages in fields, some of which are still in the vegetative growth stages. Keep in mind that late planted fields are at particular risk for southern rust if it increases in development. Right now corn disease pressure in general is low. I’m anticipating that to soon change for gray leaf spot susceptible hybrids. Some growers added a fungicide in with an insecticide treatment for western bean cutworm, which made sense to save an application cost. However, in general, automatic fungicide applications when one treats before disease develops may lead to loss of full product efficacy before critical disease levels. This can also result in the need for reapplication later if the disease worsens after the previous fungicide application and residual has worn off. And, always in my mind is eventual potential for pathogen resistance…so utilizing fungicides when we need them vs. automatically applying is wise for maintaining these fungicide chemistries.
York County Fair: This week is the York County Fair! All events and details can be found at: http://www.yorkcountyfair.com/. One special addition this year is “Brownies for Bergen” on Saturday, August 3 from 5:30-7:00 p.m. The late Gene Bergen was a 4-H icon and was planning on celebrating 50 years as a York County Ag Society Member at this year’s fair before retiring. While he won’t be with us in person, the York County Ag Society, 4-H Council, and Extension Office would like to honor him and his original plans to celebrate. So please join us for brownies and ice cream and share your favorite memories and stories of Gene!
Lower corn leaf that is dying early and has a great deal of rust on it. So far, this has all been common rust as pictured here in spite of smaller, clustered pustules or even orange colored pustules.
Common rust spores are circular in shape.
Southern rust was confirmed on this leaf in 2019. Small, clustered, tan-orange colored pustules can be seen on this leaf.
Southern rust spores are brown and oval in shape. Sharing this photo as the clear structures are spores (condia) and spore-holding structures (conidiophores) of Cercospora zeae-maydis which causes gray leaf spot (gls) in corn. Was seeing these spores/structures with only ‘specks’ of gls lesions on this leaf. With humid weather and longer leaf wetness from dews, we may see an increase in appearance of gls lesions in the next 7-10 days.
Physoderma brown spot. Symptoms include both the purple/brown midrib in addition to the yellow-brown lesions on the leaf. These lesions are flat in comparison to southern rust which would have raised pustules.
JenREES 7-14-19
Interesting, memorable don’t seem to capture this year. While portions of Nebraska are flooding again, many growers in this part of the state and east would like some rain. Dr. Suat Irmak shares on understanding matric potential and water content thresholds on sensors for irrigation scheduling in this CropWatch article: https://go.unl.edu/miym.
Soybean: The large number of painted lady butterflies we experienced in late May/June was due to a wet season in Mexico that allowed for greater vegetative growth and survival for northern migration, according to Bob Wright, Extension Entomologist. The cooler conditions may have caused more to stay here instead of move north. Saw newly hatched to early instars of thistle caterpillar (the larvae of painted lady butterflies) this week. Yet, a tremendous number of butterflies are still laying eggs. A painted lady female can lay up to 500 pale green eggs on plants individually instead of in egg masses. The larvae hatch in around a week and can feed from 2-6 weeks depending on weather conditions. Other defoliators including various worms, grasshoppers, Japanese beetles are also present. Thresholds for damage for all soybean defoliators is 20% defoliation of plants during the reproductive stages. If you’re unsure what 20% defoliation in soybean looks like, check out the graphic in CropWatch at: https://go.unl.edu/v0ts. If your primary defoliator is thistle caterpillars, it’s important to use insecticides that can be effective on them once their ‘tents’ are built. The 2019 Guide for Weed, Disease, Insect Management gives information regarding products that may work better on pages 308-314.
Gall Midge in Seward County: My colleague Aaron Nygren found soybean gall midge in
Gall midge (orange colored worm)
Seward County north of Bee this past week. I was a few miles away so met him at the field. Being a new insect pest, little is known about it. Infected plants show signs of wilting from larvae feeding within the base of the stem. These plants will eventually die. To scout for soybean gall midge, focus on plants that are close to the field edge and adjacent to fields that were planted to soybean in 2018. If you’re seeing wilted/dying plants, particularly in early planted beans this year, please contact your local Extension educator. More information at: https://cropwatch.unl.edu/gallmidge.
Bob Wright is asking for help to understand distribution of the green June beetle, Japanese beetle, and brown marmorated stink bug. If you see these insects, please take a picture and upload it to: inaturalist.org, including information on where the photo was taken. You need to make an account with inaturalist.org before you can upload photos. And, if you’re unsure what these insects look like, you can view them at: https://go.unl.edu/uzd0.
Corn: Looked at numerous corn leaves but so far, only common rust in Nebraska. Southern rust was confirmed in southern Kansas and Missouri this past week. You can view U.S. counties where southern rust has been confirmed at: https://corn.ipmpipe.org/southerncornrust/.
As we approach tasseling: 1-Areas of fields that had water ponded this
Tassels appear leafy in crazy top of corn. Took this pic from flooded waterway area in 2017.
growing season may show crazy top of corn. Crazy top symptoms include when the tassel appears strange and leafy. Plants can be barren, have barren kernels on ears, or have multiple ears at shank. 2-Automatic fungicide applications at tassel: I prefer waiting till disease warrants application & Nebraska research shows fungicide applications later in the season are effective. Be careful if you automatically spray at tassel! Canopy closure covered problems in fields, including uneven growth stages. Plants in the field may have tassels with others several growth stages behind. Arrested ear development primarily occurs on plants from 12-14 leaves when surfactants (particularly non-ionic) are applied with fungicides. So, it’s important to know your growth stages and consider what you’re applying. 3-Japanese beetles in corn threshold: Three or more Japanese beetles per ear with silks clipped to less than ½ inch and pollination is less than 50% complete. 4-It’s OK to fertigate pollinating corn. Avoid running pivot from 6 a.m.-Noon during pollination. Can apply 30 lbs N in 0.25″ water or up to 60 lbs N in 0.50″.
Linden trees and Japanese beetles: Last week I didn’t stress the importance of insecticides and impact to bees when spraying linden trees. ‘Sevin’ is effective but highly toxic to bees. It’s better to use heavy streams of water in late afternoon to knock Japanese beetles down (then drown in soapy water), pyrethroids, or permethrin like ‘Eight’ as those products are not taken back to the hives.
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