Monthly Archives: July 2020
Crop Update: Grateful to see how corn ears in wind damaged fields were able to expand and expose silks to pollen! Noticing on the primary ear node one normal ear and another 1-2 small ears on the same node in some hybrids-more common this year than I’ve noticed before. Unsure what to think of it; just an observation. Southern rust has been confirmed in 19 Nebraska counties at low incidence and severity; levels not necessary for fungicide applications yet (in my opinion). Last week I shared UNL data that showed no yield differences between a check treatment vs. various growth development timings (through 100% dent) and various fungicides in two low and moderate disease years. For those dealing with spidermites, it’s important to determine whether the plants have two-spotted or banks grass mites as they differ in control. For more information, check out this information: https://go.unl.edu/idsm.
Virtual Field Days: As someone who enjoys field days and meetings to see and catch up with people, it’s been hard to not have field days this year! Thankfully we can share information via technology. The following are resources for weed management and wheat production/variety info:
- South Central Ag Lab Weed Science Field Day: https://go.unl.edu/2020weedfieldday
- Glyphosate Resistant Palmer Amaranth Field Day: https://go.unl.edu/palmer-amaranth2020
- Wheat Field Days (Part 1 Production background): https://mediahub.unl.edu/media/13563
- Wheat Field Days (Part 2 Varieties): https://mediahub.unl.edu/media/13564
Tree Problems: Trees are important to any landscape, whether in town or on the farm!
Often, there’s stories behind their planting and it’s always hard to see them decline/die. The #1 killer I’ve found of cedar windbreaks is landscape fabric used as a weed barrier when trees are planted. No matter what the product says or who tells you it will tear as the tree grows, it rarely does. It does a great job with weed control! And, 5-15 years down the road, it’s understandably forgotten. Once the tree trunk expands to where the original edge of the hole is, the trunk often can’t tear the fabric right at the soil line while the trunk above and below it tries to expand. Sometimes a tree can survive for awhile with the choking. However, if you ever see a tree that dies quickly with no other apparent reason, it usually
is due to something with the root system or choking somehow on the tree. I realize it’s a pain, but with as much work and money that goes into windbreaks, it’s a really good idea to take some time and pull weed barrier away from the tree trunks. A long-handled tool with tines can help but just make sure to carefully get all the way to the trunk to release any potential choking (I often have to get under the tree and cut the fabric next to the trunk to accomplish this). This goes for weed barrier used for any trees and shrubs. Weed barrier with rock is one of the biggest killers of plants I see in landscapes.
Bagworms are also impacting cedars, spruce, and various shrubs. Right now I recommend using Bifenthrin as it irritates the bagworms and makes them leave bags to be better exposed to the product. It has a two week residual and is used as an insecticide for many plant situations. Get really good coverage of the trees/plants when applying.
A number of fungal diseases are impacting evergreen trees. Many started the past few springs due to wet, humid weather. They are showing up worse now with recent humidity. The good news is trees can be treated with various fungicide products next spring that can be obtained from local hardware, farm, and landscape stores. PLEASE read and follow the label (can pull the label back in the store) regarding if the tree/plant is labeled for the product. I’ve been called out to disasters this year when the wrong products were applied to trees for which they weren’t labeled.
Japanese beetles continue to be a problem. Hopefully they’ll be finished in the next few weeks. Apply products at dusk to reduce harm to pollinators. Natural products include Neem and Pyola oil that can be applied every week. Conventional insecticides can provide 2 weeks of control: pyrethroid products like Tempo and Bayer Advanced Lawn & Garden Multi-Insect Killer (cyfluthrin) or Ortho Bug B Gone (bifenthrin).
York County Fair Open Class: Quick note for those exhibiting in York County Fair’s Open Class, we ask that you have entry tags completely filled out including mailing address PRIOR TO fair this year. Entry tags can be obtained from the York Co. Extension Office and Wagner Decorating. All rules same as last year except Needlework is limited to 3 entries per exhibitor. Exhibits can be dropped off on the WEST side of Ag Hall Tues. Aug. 4th from 6-8 p.m. and Wed. Aug. 5th from 8-11 a.m. Volunteers will take items into buildings as much as possible.
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!
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!
Wind-damaged Corn: The evening/early morning hours of July 8-9 caused quite a bit of damage to corn fields for some of you reading this. It’s always hard to see crop damage. For field corn, it came at a critical time prior to pollination. The severity and amount of recovery for every field situation will vary depending on the soil moisture at time of the wind, root mass structure, hybrid planted, severity of leaning/bent/snapped plants, and growth stage of the plants. It will also depend on where the bending and snapping of those plants occurred. ‘Recovery’ encompasses the plants righting themselves, re-establishing roots, and re-orienting leaves as they have the ability to bend and grow up towards the sunlight in areas of the plant where plant tissues were not yet lignified (hardened). We know hybrids have been bred to better withstand greensnap. We know that plants that are leaning due to root lodging may have better ability to upright themselves (and have seen this in some fields since the storm). We also know that it is harder for plants near tasseling to upright themselves compared to plants at earlier vegetative stages.
What to expect? It really depends on the conditions outlined above. We all will learn a lot and I encourage us to share what we are observing. For fields very close to tassel with severe bending near ears, we may see pollination, possibly even ear formation issues. There may be fields that were leaning and will have minimal impacts after uprighting themselves. The main research I can find regarding corn lodging yield impacts comes from the University of Wisconsin in 1988. In the study, they manually lodged corn at various growth stages over 2 years to determine yield impacts. Corn lodged at V10-V12 resulted in a yield reduction of 2-6%. Corn lodged at V13-15 resulted in a yield reduction of 5-15%. Corn lodged after V17 resulted in a 12-31% yield reduction.
What to do? Recommend waiting, observing, call your crop insurance adjuster. Don’t apply products right now. Economically, we need to see how each field recovers before putting more into the crop. Plants are already stressed so give them time to try to recover. A respected agronomist shared another point with me-that adding heavy amounts of water right now can add weight onto the plants and keep them sticking together when they’re trying to separate. For those who were planning on fertigation, I’ve seen soil sample results and heard from several people that we’re seeing increased mineralization this year in fields due to the heat. It may be worth a tissue and/or soil test to see if you really need additional nitrogen (final application at brown silk). Regarding fungicides, my recommendation prior to the storm was to wait till at least brown silk (or after) due to low disease pressure, uneven growth stages in fields, waiting for southern rust, and economics; I stand by that after this storm. Fungicides can’t help much with the plant stress being experienced.
Spidermites have been found in low levels in corn, but in some cases, fairly high levels in soybean. Higher levels have been observed in stressed fields (due to off-target herbicide damage and/or beans stressed due to drought). If you’re noticing pockets in fields that appear to be yellow/brown/dying and spreading, check the top side of the leaf for stippling (yellow needle-like pin-pricks) and undersides for webbing and mites. Seeing them in non-stressed beans at low levels as well. Check out this information from Illinois for guidelines on when and how to control: http://bulletin.ipm.illinois.edu/?p=5080.
Gardening Resources: Nebraska Extension is hosting a series of 12 virtual learning sessions for home gardeners to discuss timely issues around vegetable gardening and trees. Each session will include a short (15-20 minute) presentation on the specified topic and opportunities for participants to chat about their issues and “ask the expert”. Sessions will be each Tuesday through September at 7 p.m. CST. Participants can register via go.unl.edu/grobigredvirtual – you can register for all the sessions you’re interested in at one time. You can also view the series via this Facebook post: https://www.facebook.com/events/1195072680839800.
Japanese Beetles: Areas of the State have seen Japanese beetles for a few weeks. They’ve shown up strong in the York/Seward county area this past week with the number of calls I’ve received.
Unfortunately they cause two problems. The larvae are grubs that can impact our lawns. The adult beetle is ½” in length with a metallic green head and white ‘tufts’ that look like spots on its abdomen. Adults emerge from grassy areas like lawns, ditches, and even fields; however, they don’t emerge at the same time. They emerge over a 4-6 week period beginning in late June and last for around 4-6 weeks. There’s one generation per year. Adult beetles feed, mate, and lay eggs in lawns and grassy areas. The eggs hatch 10-14 days later into grub larvae and feed on turf and grassy areas in the August time-frame. They also over-winter in turf and grassy areas.
Adults feed on 300 plant species, but their favorites are ones that are in many of our
landscapes (roses, cannas, marigolds, grapes, Virginia creeper, and trees such as lindens, birch, Japanese and Norway maples, cherry, plum, peach, American elm). They also feed on soybean and corn crops. They love hot weather and full sun and feed on leaf tissue during the day (leaf tissue will look skeletonized or lacy and turn brown). Trees may be severely impacted with browning occurring from the top to bottom. Thankfully healthy trees will re-leaf next year since the underlying twigs and branches aren’t damaged-even if the entire canopy is impacted this year. It’s not recommended to remove branches or trees.
DO NOT use Japanese beetle traps!!! Research shows they attract beetles to the landscape and many homeowners I’ve talked with will attest to this!
Beetle Control: Wait till dusk (7-9 p.m.) before trying to control beetles as they are less
active then and to reduce impact to pollinators. Organic means include hand-removing beetles by knocking them into soapy water. You can also spray trees with water to knock them down to the ground and then drown in soapy water. This takes diligence over many days. With heavy beetle infestations, it’s not uncommon to literally have scoop shovels full of the beetles when removing from trees. Neem and Pyola are two organic sprays that will protect for 3-7 days. Applying these products regularly (once per week) can also be effective as a repellent.
Japanese beetles often impact the same flowering plants that other pollinators visit. Use insecticide products correctly to avoid damage to pollinators. Avoid spraying insecticides on windy days or when pollinators are present (best to spray late in day near dusk) and be sure to read and follow all label instructions and harvest intervals (for cherries, plums, etc.). Conventional insecticides can provide 2 weeks of control: pyrethroid products like Tempo and Bayer Advanced Lawn & Garden Multi-Insect Killer (cyfluthrin) or Ortho Bug B Gone (bifenthrin). Sevin (carbaryl) is another option although more dangerous for bees.
Grub Control: Turf damage can be evident in Aug./Sept. Products that control common white grub can also provide control of Japanese beetle grubs and should be applied mid-to-late June. Dylox can be used as a rescue treatment if grub control is needed later on and no grub products were applied in the spring.
Next Year: Systemic products like imidacloprid can be used as a soil drench around plants (apply around Mother’s Day). These products can’t be used on Linden trees. You may also wish to swap out more susceptible plants for those less susceptible as you observe which plants they tend to impact most in your backyard.
Also seeing green June beetles and this shows the difference between them and Japanese beetles. Green June beetles don’t have the same impact on leaf damage. They do lay eggs in turf which become grubs as well.
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.