Corn: Corn plants are rapidly growing and at or nearing tasseling soon. One sign of rapid
growth is to look at the new leaf edges. Sometimes there will be a white margin, more transparent look, wrinkles, or notches in them. All of those are signs of rapid growth which take place during cell division.
Fertigation and Irrigation: Some fertilizer is occurring now before tassel. I also recommend 30 lbs of N at brown silk if needed. This is based on research from Purdue University sharing today’s hybrids use 30-40% of their total Nitrogen from flowering through maturity. In the past, some have asked about applying fertilizer during pollination. The following information is from Dr. Tom Hoegemeyer, Plant Breeder and UNL Professor of Practice Emeritus, “Pollination mostly occurs between 8:30 a.m. and Noon. Thus, as a precaution, I would not run a pivot on pollinating corn from 6 a.m. to Noon. When the temperature is 90°F to 95°F, the pollen is killed by heat and is seldom viable past 2 p.m. That leaves lots of time to run pivots, apply N, etc. when it won’t harm pollination. Silks tend to be viable for three or four days at these temperatures, so if a plant isn’t pollinated one day, generally the next day will work just fine. (If nitrogen is needed), I’d recommend that nitrogen go on as soon as practical. Corn nitrogen use is very high during the pre-tassel growth phase and again at kernel growth, from one to three weeks post pollination. About seven to ten days post pollination (before brown silk) lower N will start causing kernel abortion and serious yield loss in corn.” The UNL recommendation for fertigation is to use 30 lb of N with 0.25″ of water or 50-60 lb of N with 0.50″ of water.
Insects and Diseases: Thus far, insects and diseases have been pretty minimal in corn. Seeing some spidermites in low numbers. Japanese beetles are showing up in areas where they’ve traditionally been more of a problem. In corn, the threshold is 3 or more beetles per plant, clipping silks to ½” or less, with pollination less than 50% complete. The hard thing about the beetles is they have a long emergence of 3-4 weeks where they don’t all emerge at the same time…and they live as an adult for 3-4 weeks. The threshold for corn rootworm beetles for silk clipping is similar. Light trap data for western bean cutworm is showing moths are beginning to appear in low numbers. They prefer laying eggs on upper leaf surfaces of corn in late whorl stage to early tassel (however, I’ve seen them lay eggs on the underside of leaves and on leaves closer to developing ears in high heat). The current UNL economic threshold for treatment is 5-8% corn plants with eggs or larvae.
And, often there’s discussion about fungicide applications at tassel time or throwing in a
fungicide with an insecticide (or vice versa) to save an application cost. I shared a great deal about this a few weeks ago; please be very careful with growth stages and what is applied in the tassel time. With uneven emergence, not all plants in the field will be tasseling at the same time, which allows for corn ear abnormalities when NIS in particular is added to the tank (or is in the product formulations) and applied just prior to tasseling. That’s why I prefer to see fungicide applications delayed to at least full brown silk and preferably later if there’s no disease pressure to warrant the application.
Research at UNL South Central Ag Lab showed we can still apply fungicide to dough stage with no yield difference, particularly in low disease pressure years. The research also didn’t show an automatic yield increase with tassel applications. This allows us to account for southern rust which has occurred at some point all but two years of my Extension career. With tight economics, it just makes more sense to me to delay fungicide applications to when disease warrants it vs. applying too early as some have had to repeat applications (when southern rust occurred after applying too early). It’s also just good resistance management to not apply when disease and insect pressure doesn’t warrant it. Also be aware that we can see corn leaf aphids flare after fungicide applications as the fungicide kills a natural fungus that keeps their numbers in check. Aphids also can interfere with pollination by covering tassels.
Soybeans: As soybeans approach R3 (beginning pod), that’s the critical time to avoid
water stress in soybean (similar to tassel for corn). We recommend avoiding irrigating during flowering whenever possible to reduce disease pressure (such as white mold and SDS). Don’t pull insecticide triggers too early for soybean defoliators. UNL recommends 20% defoliation at reproductive stages from all defoliators.
Crop Update: So grateful for some rain for much of the area last week! Updated soil moisture status at http://jenreesources.com. The crops are rapidly growing now as are the weeds. Some were seeing Palmer shooting heads at soil level already…last year we
didn’t see that till late July. Many have been in the process of postemergence herbicide applications. We revisited a CropWatch article regarding best management practice considerations for postemergence dicamba-based applications to corn based on the research that is available. Please see the full article with more explanation at http://cropwatch.unl.edu. Briefly, those practices include:
- Consider a quick irrigation (rainfast/irrigation timing based on label requirements for the product you’re applying) of only 1000 gal/ac to help reduce any potential volatility.
- Don’t use dicamba products in both corn and soybean to reduce selection pressure and resistance.
- Check for temperature inversions and wind speed. Temperature inversions can be tested by using Innoquest SpotOn® inversion tester and testing the temperature at 1 meter and 3 meters. If the temp is cooler at 1 meter than 3 meters, a temperature inversion is occurring and spraying is not recommended.
- Consider using the more restrictive RUP dicamba requirements regarding wind speed, boom height, etc. Also consider not using AMS with any dicamba product even though it is labeled for use in some of the corn dicamba products. This may result in you needing to increase the glyphosate rate to the highest labeled rate to increase efficacy. Amit Jhala will showcase research on efficacy of dicamba products with and without AMS at the South Central Ag Lab Weed Science Field Day on June 27.
Volunteer corn is also a major issue in many corn and soybean fields in the area and there’s two articles in CropWatch at http://cropwatch.unl.edu addressing this topic. A number of grass herbicides are available for control in soybean. The challenge is in the continuous corn fields. If you had glyphosate resistant corn last year and used a different technology such as Liberty or Enlist, you have some other options this year. For Liberty Link corn this year, two applications, each of 32 to 43 fl oz/acre, could be made. Remember that Liberty will NOT be effective if Roundup Ready + Liberty Link hybrid corn was planted last year. Regarding Enlist corn, Assure® II is the only grass herbicide labeled to control volunteer corn with this technology. It can be applied at 5 to 12 fl oz/acre in Enlist Corn for selective control of volunteer corn. Please be sure to read and follow all label requirements. A few farmers have also discussed their past experiences with cultivation, using either one or two passes and their concern about the soil moisture situation this year.
So how much yield loss can be anticipated from volunteer corn? Perhaps more than one would think with more loss occurring in soybean! Studies were conducted in several mid-western states at various densities including 3500, 5000, 7000 and greater volunteer corn plants per acre. To envision this, imagine 3.5, 5, and 7 volunteer corn plants respectively in 1/1000 of an acre (17’5” in 30” rows). Some fields this year have much higher densities than this! Clumps of corn impact yield more than individual plants.
UNL research found a volunteer corn density of 3500 plants/acre led to 10% yield reduction in soybean. Doubling the density to 7000 plants/acre led to a 27% yield reduction. South Dakota State University data revealed similar trends. A volunteer corn density of 5000 plants/acre resulted in a 20% yield reduction (12 bu/acre yield loss in 60 bu/ac soybean).
Clumps of volunteer corn in soybean led to greater yield loss as they were more competitive than individual plants. In the UNL study a density of 3500 clumps of corn/acre resulted in a 40% yield reduction. Researchers in Minnesota and Illinois also found increased competition with clumps of volunteer corn versus individual plants. Clumps of corn (7-10 plants/clump) were established at different densities. Depending on the location and year, soybean yield was reduced 1% for every 75-115 clumps/acre.
A recent UNL research study found highest yield reduction occurred when volunteer corn was left uncontrolled or when it was controlled too late at the R2 (full flower) soybean growth stage. The combined density at this greatest yield reduction was at 24,710 volunteer corn plants per acre plus 1,235 volunteer corn clumps per acre.
In corn, UNL research found a volunteer corn population of 3500 plants/acre resulted in a 2% yield reduction in corn. Doubling the density to 7000 plants/acre caused a 5% yield reduction. Clumps of volunteer corn led to greater yield loss as they were more competitive than individual plants. A density of 7000 clumps of corn/acre resulted in a 14% yield loss compared to a 5% yield loss with individual plants. So volunteer corn in general can be fairly competitive especially to our legume crops. It can also be a problem regarding harboring corn rootworm in soybean fields, reducing the advantage of the rotation from that perspective.
Also, an update on my soybean planting date demo at the fairgrounds: I wasn’t counting on rabbits! All the soybeans were reduced to stems below the point of recovery. So there is no demo but the groundskeeper preferred they took out my soybeans instead of his petunias 🙂 Will try again next year.
Crop Update: So grateful for rain and truly hope those who wanted and needed rain received it! An update to soil moisture profile as of 5/17/18 can be found at http://jenreesources.com.
A number of crop issues surfaced this week. One being root burn and wilted-looking corn seedlings from anhydrous ammonia applications with the dry winter/spring we’ve had thus far. Anhydrous ammonia can expand in soils 2.5-3” in all directions and potentially more in dry soils. Pivots were running to help with that and hopefully rain events will help non-irrigated fields that were suffering in this way. Another problem observed in some non-irrigated corn fields has been fomesafen carryover injury from products such as Flexstar, Reflex, Prefix, etc. These products have a 10 month planting window back to corn which is fine in most years, but dry conditions didn’t allow for the herbicide to break down in all situations from applications last June. This active ingredient is in Group 14 (PPO inhibitors) and the injury from this particular active ingredient is unique in that it causes yellow/brown striping of the veins themselves instead of interveinal chlorosis/necrosis. Seedlings most affected right now are found on field edges or wherever there was overlap of application. Hopefully corn should grow out of this injury in time. Herbicide carryover may be a something to watch for in soybean as well from other active ingredients. We also saw regrowth occurring on plants affected by wind/dust/debris damage but there are situations where replanting will be needed on endrows, etc. Roger Elmore has a photo gallery explaining regrowth in this week’s CropWatch at http://cropwatch.unl.edu.
Another situation that surprised me this year was finding seed corn maggot damage in
soybean. At first I was puzzled as the beans were clearly treated but then learned the beans didn’t have an insecticide added to the seed treatment. In scouting a number of fields, I’ve actually seen quite a bit of seed corn maggot damage, particularly in tilled fields and those with manure applied or those with cover crops that were green or where termination included tillage. I’ve also been surprised how many have told me they don’t use an insecticide seed treatment on early planted beans. We didn’t have any research in our early soybean planting studies without insecticide + fungicide seed treatment so we just automatically recommend both. Unfortunately this year we’re seeing what can happen without it with higher insect pressure in some fields. For seedlings with the insecticide seed treatment, I’m seeing light scarring on the cotyledons and hypocotyls but no maggot penetration. In fields without the seed treatment, I’m actually seeing penetration of the cotyledons and hypocotyls. The good news is that most of the maggots were also pupated, pupating or will be soon. But it is something to watch for, particularly in fields that have been tilled and especially if manure was applied or they were tilled and had a cover crop on them. They are not as attracted to no-till fields. Regarding stands, from my experience with soybean pops and stand loss due to crusting, hail, herbicide injury, etc., I keep stands of 60,000 plants/acre or more. It really stinks to talk about replanting anything right now with guys still trying to finish planting. If you choose to replant soybeans, consider proving it to yourself by planting strips and leaving strips. If you’re interested in that, I’d be happy to work with you. You can learn more about seed corn maggots here: https://crops.extension.iastate.edu/cropnews/2016/04/look-seedcorn-maggot-corn-and-soybean.
Wheat in the area ranges from boot to flowering. A couple of wheat fields I know of
were taken for hay. For those still considering silage, check out the CropWatch article this week where Todd Whitney shares data on wheatlage (wheat silage): https://go.unl.edu/qkbr. The rainfall will greatly help our wheat right now. And, rainfall at heading to flowering makes me think about the potential for Fusarium Head Blight (scab). The wheat scab prediction monitor http://www.wheatscab.psu.edu/ is predicting medium to high risk for scab in Nebraska for the next 48-72 hours. Some years I feel the model is delayed in prediction, but I still feel it’s a good tool and resource. Scab is caused by Fusarium graminearum and is favored by warm (70-80°F temps), humidity, and rain events before and during flowering. Once wheat begins flowering (Feekes 10.5.1), many foliar wheat fungicides are off-label. In fact, recent research presented at the 2017 Fusarium Head Blight meetings shows that in general, strobilurin products can actually increase the presence of deoxynivalenol (DON) in wheat if applied at full heading (Feekes 10 or 10.5). Thus, your better fungicide options for preventing scab are Caramba and Prosaro and these products can also kill any fungal diseases present on leaves (such as powdery mildew, tan spot, and rust). These products aren’t 100% for scab prevention due to the variation of heading and flowering that occurs in so many fields. Better efficacy is obtained with more uniform plants which begins at seeding time. So I would recommend watching the growth stage in your fields, the weather, and the prediction tool regarding if you feel you need to treat any fields this year to prevent scab. Research has shown best efficacy to be obtained when at least 50% of the plants are at 1/3 flowering. Flowering begins with yellow anther sacs in the middle of the head with flowering continuing throughout the head from there. Once the pollen is released, the anther sacs turn white.
LBNRD Open House Public Hearing: The Little Blue Natural Resources District (LBNRD) is hosting a public hearing on May 29th from 6:30-9:00 p.m. at the Davenport Community Center in Davenport, NE. The purpose of the hearing is to provide information and receive testimony on proposed amendments to Groundwater Management Rules and Regulations. The hearing will be an open house format allowing individuals to ask questions of the NRD staff, look at exhibits, and offer testimony. The proposed rule changes and additional information can be found on the LBNRD website at: http://www.littlebluenrd.org/. Please contact the NRD with any questions at (402) 364-2145.
Not part of my news column: on a more positive note after mentioning all the crop problems, the lilacs in general were beautiful and smelled amazing!!!
It was great to see so many fields of corn and even soybean emerging throughout the
area this past week! Also grateful for the rain we received in York and for those who received some in other areas. There are still areas who continue to miss rains and I remain concerned about the soil moisture situation. I have another soil moisture update this week at http://jenreesources.com if you’re interested in checking that out.
Thursday night/Friday morning’s high winds caused some damage with overturned pivots/corner systems and tree damage. We also saw newly emerged corn and even soybean cut off or
buried due to blowing debris/soil, particularly in soybean stubble. It will be important to watch the plants in these fields the next several days. By late Friday afternoon, I was already seeing new growth occur, which is good. Typically, that has been the response in the past-new regrowth in corn as the growing point is still below ground. However, it will be important to watch the corn plants for any bacterial issues that may kill seedlings. One can also split open a few plants and look for a healthy growing point. Regarding the soybean, I have seen soybean lose cotyledons due to hail, crusting, freeze, and wind damage, and still produce a plumule at the top of the soybean stem. It’s just hard to know for sure what will happen so it’s best to watch the plants in the fields.
Wheat in Nuckolls, Thayer, and Webster counties ranges from elongation to near boot and is turning blue-gray from moisture stress. Wheat is a crop that I’m always learning about-it can look really bad (or really good) and then end up surprising a person regarding yield either way. Lower leaves
in fields are turning yellow-brown. Some of this is due to moisture stress while there’s also powdery mildew pretty thick in lower canopies of wheat that had more tillers. A few have talked with me about using the wheat for hay or silage and then potentially going in with short season corn, sorghum, or a forage crop. Our forage specialists would recommend that if the wheat variety has awns, it’s best to either take for hay or silage at the boot stage so the awns don’t cause issues with livestock feeding. Todd Whitney, Extension Educator in Phelps/Gosper counties, had worked with a feedlot using an awnless wheat variety. Because of the additional growth that occurs in wheat (and other small grains) from boot to full head elongation, they found biomass production may be increased 25% if the forage was harvested during the later pollination period.
Evergreen Trees: There’s also been a lot of evergreen tree questions. For those noticing spruce trees looking kind of yellow with early morning sunlight, spruce spidermites have been working hard with the cooler, dry weather. They tend to build populations in spring and fall. You can check for spidermites by taking a white piece of paper and banging the needles on it. Then look for the presence of tiny dark green to nearly black spidermites crawling on it. Rainfall is a great way to wash them off of trees as are strong streams of water (easier done with smaller trees). There are also a number of miticides available that homeowners can purchase from lawn and garden stores (look for products that say they can be applied to trees for control of spidermites). A great brochure on insect pests of evergreen trees can be found at: https://nfs.unl.edu/documents/foresthealth/insectevergreen.pdf.
Many of us also noticed our spruce trees turning red/brown/purple/yellow in color last fall. This is most likely a disease called needle cast of spruce and can be prevented by spraying trees now (mid-May) with a product containing copper sulfate. Regarding Ponderosa or Austrian pines, if you look closely at the needles and observe dark bands or rings on them followed by death of the needle either direction from the band, the tree problem is most likely due to a fungal needle blight like dothistroma or brown spot in Scotch pines. They can all be prevented by spraying a fungicide containing copper sulfate now. The following brochure on diseases of evergreen trees is really helpful: https://nfs.unl.edu/documents/foresthealth/diseasesevergreen.pdf. Sometimes the problem is finding the products listed on these brochures in our smaller towns as these brochures were developed in Lincoln. If these specific products aren’t available from your local lawn/garden store, box store, or coop, I would recommend looking at the products available and look for a product that says it is effective against needle blights on trees. Not all the products I’m seeing have copper as an active ingredient, but other fungicides are listed and the key would be the fact that the site (trees) and even better, the site with problem (trees with needle blights), is listed on the label.
We also continue to see pine wilt affecting our Scotch (short needles in groups of 2) and Austrian pines (long needles in groups of 2). Pine wilt disease is caused by the pinewood nematode that is carried within the gut of a long-horned beetle. The beetle is what creates the ‘shotholes’ often seen in bark of infected trees. The nematode is native to Nebraska, as are Ponderosa pines (long needles in groups of 2 and 3). This is why we don’t see the problem in Ponderosa pines but do in Scotch and Austrian, which are non-native to Nebraska. A tip, if you’re trying to distinguish Ponderosa vs. Austrian pines, anytime you see needles with a group of 3 it’s a Ponderosa. Pine wilt is caused by beetles carrying pinewood nematodes vomiting them into the water-carrying vessels of the tree (xylem). The tree senses the nematodes and essentially blocks water to those branches. Often you will observe a branch then perhaps a side of the tree and eventually complete death of the tree within 6-9 months. While I have diagnosed many samples of pine wilt, more often when I visit homeowners the tree problems are due to fungal diseases which occur on the needles.
Lawns: Please remember the importance of sweeping or blowing fertilizer and pesticide products back into the lawn instead of leaving them on sidewalks. Leaving them on the sidewalks puts them in contact with people and pets walking on sidewalks and moves them into storm water systems via rain that can eventually end up in streams. I’m also seeing a number of 2,4-D/dicamba products being sprayed around tree bases to kill weeds which is affecting the new growth emerging on trees. Consider applying a wood mulch layer around the base of trees to help avoid this situation in the future and be sure to read and follow all pesticide labels.
Planting Considerations: This email newsletter reaches a wide area of the State, so soil temps vary quite a bit and some of you may be in better planting conditions than others. We still recommend planting into soil temps as close to 50°F as possible, check weather conditions for next 48 hours to hopefully maintain temps 50°F or higher, and avoid saturated soil conditions. If planting a few degrees less than 50°F, make sure to check with seed dealers on more cold-tolerant seed. This is most likely common sense, but I still feel worth mentioning. Everything we do at planting sets the stage for the rest of the year. We’re blessed to have equipment that can allow for many acres to be planted in a short amount of time. And…we also have the ability to mess up a lot of acres in a short amount of time.
Planting depth is also key. Aim to get corn and soybean in the ground 1.5-2” deep. This is critical for correct root establishment in corn to avoid rootless corn syndrome. Rootless corn syndrome is when the nodal (crown) roots don’t get well established and successive brace roots can’t establish either. This allows the seedling to whip around in the wind, potentially being dislodged, become weak or die. With center-fill planters, when adjusting down-pressure on the go, sometimes the planter ends may not always be seeding as deep as the center. Too often I’ve seen that resulting in seed 1” or less and the field pattern can be observed the entire growing season with potential yield impacts. So don’t just rely on the monitor. Take the time to dig up seed behind the planter and at spots along the whole planter length to ensure the proper seeding depth. And do this with every field, particularly with different tillage/residue situations. I realize this takes time, but you’ll be glad you did to catch any issues before too many acres are planted incorrectly.
With cold temps or higher soil moisture conditions, it’s still important to get that seed at least 1.5-2” in the ground. Planting 1.5-2” deep helps both corn and soybean to have that seed in even soil temperature and moisture conditions. You may be surprised on that recommendation for soybean, but I think it’s even more critical with planting early. In fact, UNL research near Mead compared planting depths of 1.0, 1.25, 1.5, 1.75, 2.0, 2.25, and 2.5 inches in 2011 and an additional planting depth of 2.75 inches was added in 2012 and 2013. The study found lowest yields when soybean was planted 1.25” or less or 2.25” or greater with the highest yield at 1.75” deep. One of that study’s hypotheses was that planting deeper would buffer soil temperature and moisture and protect newly emerged seedlings from frost and freeze damage, particularly when planting early in the season.
Hopefully planting soybean early is still something you’re considering for this year! We wrote a CropWatch article this week at http://cropwatch.unl.edu to provide some updated research on amplifying the effects of planting early. There’s so much research regarding how early soybean planting increases yield that we wanted to share new research regarding maturity groups, etc. Essentially, what it appears from the research thus far, is that it’s more important to choose a consistent, high-yielding soybean for your area, regardless of specific maturity group. We’d like to get more specific data and have on-farm research protocols available to compare MG2.4-2.5 vs. MG3.0-3.5 and Dr. Jim Specht would also like to collaborate with us on documenting various factors. Please let me know if you’re interested in this! There’s also a protocol for comparing early vs. late planting of soybean.
Soil moisture conditions didn’t improve this week at the six sites I’m monitoring in Webster, Nuckolls, Thayer, and Clay counties. You can find the chart comparisons on my blog at http://jenreesources.com. Last weekend’s bizzard didn’t provide significant moisture in this area. With pastures slow with growth and drought increasing in Kansas, discussions with farmers have included cover crop termination, grazing rye that’s had anhydrous ammonia applied to it (with the original intention of termination and planting to corn), and grazing wheat. Most of these topics are included in this week’s UNL CropWatch at http://cropwatch.unl.edu. The articles are too long with too many considerations for me to add them in this news column, so please do check them out if you’re interested in these topics. Another topic I’ve had several questions about is regarding how temperature and rain affect burndown herbicide applications. Dr. Amit Jhala, Extension Weed Specialist, addresses that in this week’s CropWatch as well, so please check that out. Here’s wishing everyone a safe planting season with conditions to get #plant18 and #grow18 started off well!
On-Farm Research Protocols:
Hail and wind damage occurred throughout the area I serve last week. Overall, I’ve been encouraged by the regrowth observed on corn and soybean plants affected by the June 14th storm. We were blessed with warmer weather and sunshine that allowed for regrowth to occur in many situations other than some fields around the Deweese area.
You can look for regrowth on leaves within the whorl of corn plants and on the axillary buds of soybeans. Even what appeared to be soybean ‘sticks’ may show regrowth by now.
The concerns I have for plants affected by these storms is all the stem bruising on both corn and soybeans and the potential for bacterial diseases to affect corn.
For those of you affected by June 16th storms, we recommend to wait a week to assess damage and any decisions. I realize we’re also at a critical stage for replant decisions as we continue later in the season. Ultimately, decisions need to be made on a field by field basis.
- CropWatch Hail Damage Resources
- Resources from storm damage in 2014
- Fungicide Use After Hail or Wind
There’s no good research to Dr. Tamra Jackson-Ziems or my knowledge to support this. Fungicides only control fungal diseases. Bacterial diseases are favored after hail events and we have already seen bacterial leaf streak in the area prior to the storm. From past-years’ experience of prior wind/rain events, we can expect to see more of it in about a week. Fungicides won’t help that disease nor Goss’s wilt which is another we often see come in after hail events.
However, if you’re considering this, I’d like to have several farmers prove it to yourselves with on-farm research this year so we do have data for the future. It’s this simple. All you do is spray fungicide in enough width to complete 2 combine passes. Then skip an area for 2 combine passes. Then treat again and repeat across the field. Fungicide Protocol for Hailed Corn and Soybean. Please let me know if you’re interested in this!
Timing of fungicide app: ISU did a study to simulate hail damaged corn at tassel stage within an average of 3 or 8 days post-hail. They didn’t find the timing to provide any yield effects. They also didn’t find a statistical yield increase (90% confidence level) in fungicide application to hail damaged plants vs those which weren’t hailed although they also reported a numerical increase in 12 of the 20 fields.
Herbicide application: I spoke with Dr. Amit Jhala, Extension Weed Specialist for his thoughts regarding this. He said ultimately herbicides shouldn’t be applied to stressed weeds in order to achieve greatest efficacy. The concern for many including me right now is how well the weeds survived the hail and how quickly they are regrowing compared to the damaged corn and soybeans. This again is a field by field assessment regarding how well your corn and soybean regrowth is occurring and how rapidly your weeds are. I watched one palmer plant in one field after June 14 storm: 1 day post hail and 2 days post hail put on two sets of leaves in that time period. I also took pictures of soybeans reduced to sticks while waterhemp in that field was virtually untouched. I think many are trying to wait 5-7 days post-hail to apply herbicides but there were some fields I was suggesting to apply over the weekend with the recovery already occurring and less damage.
Corn replant: The biggest concerns with corn would be stands, eventual stalk rot/downed corn due to stalk bruising, and bacterial diseases. I’ve essentially watched stands reduced over the course of the growing season after early-season hail storms mostly due to bacterial diseases like Goss’ wilt. It will be important to have your crop insurance adjuster look at the field again prior to harvest. Splitting the stems of damaged plants across the field can help you assess any damage to growing points; they should be white/yellow and firm not brown and soft. Tattered leaves that are wrapped around the whorl should eventually turn brown and break off with the wind. They can sometimes impede new growth from the whorl as well though.
Soybean replant: Soybeans can compensate so greatly for reduced stands. From hail at this stage in the past, we’ve said to leave stands of non-irrigated at 60,000 plants per acre and irrigated at 75,000 plants per acre. Some soybeans reduced to sticks are shooting axillary buds. My biggest concern on soybeans is the stem bruising which isn’t accounted for in hail adjustments. If you want to prove replanting or not to yourself, consider slicing in soybeans next to the old row in strips across your field. Be sure to inoculate the soybeans and be sure to take prior stand counts. Soybean Replant Protocol.
There’s nothing like doing these studies and seeing the results on your own ground or from your peers’ farms. In 2006, I worked with a grower in the Lawrence, NE area on a non-irrigated soybean plant population study where he tested seeding rates of 100K, 130K, and 160K seeds/acre. He received hail at the cotyledon stage and because he was non-irrigated, chose to leave the stand. His actual stand counts were 74.4K, 89.4K, and 97.9K plants/acre respectively for the previous mentioned seeding rates which resulted in yields of 38.6, 40.6, 42.7 bu/ac respectively. Another soybean replant study occurred near Columbus, NE where the grower had an average plant stand of 75,000 plants per acre on June 11th. He chose to replant five strips across the field at a diagonal to the existing rows. The replanted soybeans ended up yielding 1 bu/ac less than the original plant stand. I realize it’s hard to want to do these extra steps for on-farm research, but this is why it’s important; it’s the way to answer these questions for yourself! Please contact one of our team members if you’re interested in on-farm research this year!
So two questions:
- Why are we seeing this this year?
- Is there anything we need to do?
The short answer to both is that we really don’t know. Perhaps one hypothesis is our warm winter allowed for an earlier generation of wheat stem maggots to pupate and emerge as flies during corn planting when they would typically do so later in May. Perhaps in fields where wheat or rye wasn’t yet terminated, the flies could lay eggs and the larvae that hatched moved from the wheat or rye to the corn upon emergence and once the cover was terminated.
The larvae we’re finding now are in different stages and some are getting close to pupating. After pupating, they will emerge into flies that will lay eggs in grass crops. We don’t know for certain if the flies will lay eggs in these corn fields again or if they will move to other grassy species. We’re not recommending insecticide applications.
South Dakota State and Kansas State have previously reported rare incidences of this occurring in corn. This is my first time observing this in Nebraska. To date, I’ve seen stand loss range in fields from 5-50%.
This doesn’t mean that all potential stunted plants or stand concerns are due to this particular insect as a number of other factors could be involved. This post is intended to increase awareness of another option to look for with the number of questions I’m receiving right now regarding corn concerns in terminated rye or wheat cover.
Dr.s Justin McMechan and Bob Wright are surveying fields and conducting studies to better understand any potential concerns in future years. We will keep you informed as we continue to learn more.