Category Archives: Crop Updates
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!
Heat and Pollination: With last week’s heat and anticipated heat later this week, we were receiving questions regarding the impacts of heat and humidity on pollination. You can view the entire article in this week’s CropWatch at https://cropwatch.unl.edu. Key points include: Heat over 95°F depresses pollen production and prolonged periods of heat can reduce pollen production and viability. When soil moisture is sufficient, one day of 95-98°F has little or no impact on yields. After four consecutive days, there can be a 1% loss in yield for each day above that temperature. Greater yield loss potential occurs after the fifth or sixth day. High humidity, without a drop in humidity during the day, can delay pollination or prevent pollen from leaving anther sacs. We’ve been blessed we only had days of extended high heat around pollination, received a break in the heat in addition to weekend moisture.
Insect Pests: From light trap reports, peak western bean cutworm (WBC) flight appears
to have occurred last week, so scout for egg masses and live larvae with a 5-8% treatment threshold. Thistle caterpillars grew rapidly last week. Others are with me in considering spraying closer to 15% (instead of 20% threshold) with stressed fields from flash drought and/or off-target dicamba injury that don’t have canopy cover yet. In CropWatch, check out the articles regarding scouting for grasshoppers in field borders and what to expect for insects depending on crop growth stages yet this year.
Cattle Losses from High Heat: If the recent heat/humidity conditions are determined to be an extreme weather disaster event, then livestock losses would be covered by the Livestock Indemnity Program (LIP). Livestock producers who lost livestock should document losses in the expectation that they may be covered by LIP and contact your local Farm Service Agency (FSA) to report those losses.
South Central Ag Lab Field Day Aug. 1: View current field trials on improving crop production and profitability at UNL’s South Central Ag Lab (SCAL) on August 1 near Harvard. Guests can customize their day to select the tours they’re most interested in. Presentation topics include: Cover crops, pollinators and weed management; European corn borer, corn rootworm, and cover crop insect control; Herbicide-resistant weed management; Assessing injury and management decisions in corn and soybeans; Corn and soybean disease updates; Sensor-based nitrogen management in irrigated corn; Corn stover harvest management and impacts; mobile beef lab and hail machine demonstrations. Registration is at 8:30 a.m. followed by tours through 4 p.m. Lunch and refreshments are included. CCA credits have been applied for. For more info. see the program brochure and register at: https://go.unl.edu/2019scalfieldday.
Silage Webinar Aug. 2: With this year’s challenging weather and the need for forage, there may be more opportunities for harvesting corn for silage. Aimed at feedlot, cow-calf, and dairy producers, a silage webinar on August 2 at Noon CST will focus on moisture at chopping, chop length, inoculants, proper packing, silage covers and more. Pre-registration for the webinar is necessary and can be done at: https://go.unl.edu/vau7.
Trees Losing Leaves: The wet spring and humidity allowed for fungal diseases on leaves of shade trees with flowering pears and crabapples in particular dropping leaves early. I’ve also had a number of questions regarding red maple leaves (Autumn Blaze and Sunset) suddenly turning brown on trees. These symptoms may also be experienced on ash, tuliptree, and other maples. We think it’s environmental stress from having so much cool and wet early to almost a ‘flash drought’ situation in eastern Nebraska prior to this weekend’s rains. Sarah Browning has been recommending watering and mulch as the best ways to reduce stress and to prevent additional root death and tree decline. I’ve been seeing new growth starting to occur on trees so my hope is if your tree is experiencing this, that 10-14 days from now you will also see new growth occurring on your trees.
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
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
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.
Crop Updates: I really appreciate all those in ag industry who share what you’re seeing in the fields; it’s a blessing to have a great network of people looking at fields in different areas of the state and sharing what we’re all seeing!
Western bean cutworm (WBC) moths were seen in corn whorls the past week. They’re
also showing up in UNL light traps in addition to industry ones. To view the UNL light trap reports near Clay Center, please go to: https://scal.unl.edu/ltr2019.pdf. The light trap near Mead is currently having black light issues, but the report can be viewed at: https://go.unl.edu/2usz and the light trap report from North Platte is at: https://go.unl.edu/a56b. WBC moths prefer laying eggs on upper leaf surfaces in corn that is in the late whorl to early tassel stage. UNL entomologists recommend scouting at 25% of moth flight. It’s unknown how larval survival will be impacted by corn growth stage at this time. Larvae survival is highest when they have fresh tassel tissue and pollen to feed on before moving down to developing ears and silks. Larval survival is lowest when only vegetative tissue is available to feed on. So, the delayed planting and growth in some fields may allow for less western bean cutworm damage in 2019. However, our entomologists say that air and soil temperature can also impact insect development leading to slower development of the insects. UNL Entomologists Tom Hunt and Bob Wright, along with University of Minnesota researchers, developed a degree-day model to predict when WBC moths will emerge to begin mating and laying eggs. In a recent CropWatch article, they were predicting 25% moth flight to occur for the following dates/locations: July 7th in Lincoln; July 11 in Hastings and Ithaca; July 12 in Grand Island and York; July 13 in Clay Center; July 15 in Holdrege, and July 23 in North Platte. Corn expressing VIP3A proteins are highly effective for WBC control. Corn expressing Cry1F (Herculex) proteins may provide some WBC feeding suppression but shouldn’t be relied upon for control. The current UNL economic threshold for treatment is 5-8% of corn plants with eggs or larvae.
Common Rust in Corn: The rainfall, humidity, and wet canopies have allowed for
increased common rust to be seen in corn this past week. I was seeing larger numbers of pustules on lower leaves of plants, but this week could also see pustules occurring in upper canopies. Pustules of common rust are typically brick red in color, larger, more separate, and can appear on both the upper and lower leaf surfaces. Southern rust typically has smaller, orange to tan colored pustules occurring in tight clusters on upper surfaces of leaves. However, the past few years, we’ve seen common rust looking more orange in color, including this year. The best way to confirm for sure if it’s common or southern rust is to check the spores under the microscope, and I’m happy to do that. The spores of common rust will be circular in shape whereas southern rust spores are more oval to football shaped. Samples can also be submitted to the UNL Plant and Pest Diagnostic lab. So far, every sample I’ve looked at has been common rust. Southern rust hasn’t been found further than Georgia and Louisiana to my knowledge right now. We don’t typically recommend fungicides for common rust. It will be important to continue scouting for diseases with the humidity and leaf wetness we’re experiencing this year.
Lawn and Garden Questions: The wet weather has allowed slime mold (gray-black fungal growth on leaves) in patches in lawns in addition to mushrooms in lawns and landscapes. They are harmless and fungicides aren’t effective. They will go away upon drying out and with warmer weather.
Bagworms are out and it’s time to control them if you have them. The following gives more detailed info on their life cycle: https://go.unl.edu/rgju and this YouTube video shows what you’re looking for this time of year on your trees: https://jenreesources.com/2015/06/27/bagworms-in-evergreens/.
Japanese Beetles may be causing holes in Linden trees or rose leaves. They are
green/brown beetles with white hairs that look like rows of white spots near each wing. Kelly Feehan in Platte County shares that “applying insecticides to lawns to control grubs will not prevent beetles from feeding on landscape plants. The product ‘Milky Spore’ sold to kill them, does not work. On landscape plants, hand picking or knocking beetles into a bucket of soapy water around 7 PM is the best time of day to do this as it prevents plants producing a distress pheromone that attracts more beetles. Japanese beetle traps work very well – IF you want to attract them to your yard – so traps are best NOT used. If a Linden tree has Japanese beetles, know these trees CANNOT be treated with Imidacloprid or other Neonicotinoid insecticides.” Carbaryl (Sevin) is effective to use for Lindens and landscape plants where it’s not feasible to remove beetles by hand.
Prevent Planting and Herbicides for Cover Crops: This past week, corn for silage was approved as a cover crop in prevent plant situations, primarily because of the herbicide restrictions on cover crops for forage. A team of us wrote an article about how to understand herbicide rotation restrictions and also shared the information from NRCS regarding corn as a cover crop in this week’s CropWatch. You can see these and more articles about soybean gall midge and Japanese beetles at http://cropwatch.unl.edu.
Hail Damage: For a ‘slight chance’ of rain, it was interesting to have the hail and 4” of rain in the gauge Wednesday morning! It appears we had hail from the York area through Cordova area and I heard there was also hail in Butler and Platte counties. The larger hail appeared to have damaged crops into Kansas through Superior, south and west of Lawrence through Blue Hill and Holstein. What was encouraging was not even 24 hours after the storm, signs of recovery could be seen in corn and soybean. Warm temps, no rain, and sunshine make all the difference in recovery after hail compared to cool, wet, cloudy conditions. I went back to look at fields in the southern tier of counties into Kansas and in York area southeast on Friday and was further encouraged by the regrowth. You can view photos on my blog at https://jenreesources.com. The bruising on stalks and stems can allow stalk rot to set in on corn and soybean stems to become brittle and break off with wind…so keep this in mind towards harvest and plan to get these fields out first if possible. What’s hardest is wheat fields that were nearing harvest that shattered or were totaled due to hail. Also difficult is the fact we’ve lost so much canopy in crops at the peak of palmer growth for those who have fields with palmer problems. And speaking of palmer, a reminder of the palmer amaranth field day near Carleton on July 10th. View herbicide options for palmer control and listen to keynote speaker Dr. Jason Norsworthy from the University of Arkansas. Registration at: http://agronomy.unl.edu/palmer.
So, this may sound crazy, but I was curious about the potential of interseeding a cover in these corn fields with extreme canopy missing right now. I was standing in one field of V11-12 corn with all the leaves gone listening to the growers tell me how much of a palmer problem this field has, even though it is clean right now. We know from research that interseeding at this growth stage typically doesn’t work due to canopy closure, but I’m wondering if it could help with weed pressure since the remaining leaves may be more upright and may not completely shade the rows? The keys to this consideration would be the herbicides used and considering rotation restrictions if you plan on using the stalks and cover for forage after harvest. If you don’t plan to use the cover for forage, there wouldn’t be restrictions as you’d assume planting at your own risk. We can’t predict if it will keep raining for non-irrigated fields. It would also be wise to talk with your crop insurance agent about this.
Fungicides in Hail Damaged Crops: Several have asked about fungicide use on hail damaged crops. There’s no good research to support this and fungicides only control fungal diseases. Bacterial diseases such as bacterial leaf streak and Goss’ wilt are favored after hail events. We’ve already seen both of these diseases in this part of the State due to heavy rains. Fungicides at some point may help with stalk strength with all the bruising and we may need fungicides later this season for disease if the humidity and rains continue.
The available research had fungicides applied at tassel instead of the earlier growth stages we’re currently at. ISU did a one-year 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 yield increase in 12 of the 20 fields). A study was also conducted by Carl Bradley at the University of Illinois in 2007-2008 to evaluate the effects of fungicide applications at tassel in simulated hail-injured corn on gray leaf spot severity and yield. In that study, fungicide applications did not statistically increase yield when applied on corn that was damaged to simulate hail injury.
If you’re considering a fungicide now, you could consider an on-farm research study depending on equipment, ability to get in the field, and crop height. 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. View: Fungicide Protocol for Hailed Corn and Soybean. Some talking about this wondered about aerial applications. If we had enough people who left a check, we could look at combining the data to make up for lack of reps in one field. Please let me know if you’re interested in either of these options.
Butterflies and Soybean Defoliators: Painted lady butterflies and others like sulfur butterflies can be seen flying around as they’re emerging from soybean fields. I really wish they’d move on but I’m seeing butterflies in my gardens now too, so we’re just going to have to keep scouting fields. There’s also a lot of yellow striped armyworms out there of various larval stages. If your soybeans don’t seem to be growing or you seem to be losing canopy beyond hail damage and ‘burner’ herbicides, be looking for various larvae. In this heat, if you have a lot of residue in the field, they may be hiding under it, so be sure to look there too if you have a spot in the field especially affected.
NOTE: End of News Column. Photos below to document recovery.
Soybeans with new growth seen in axillary buds and/or main shoot within 24 hours of June 26 hail storm (first two photos) and 3 days after hail storm (last two photos). Soybeans were V4 to R1. Note, temperatures were hot with sun and dry conditions post-hail.
Wheat grain shelled from heads and broken heads in both early and later planted wheat. Warm season forages may be a good option to consider in totaled out wheat fields.
First photo is corn west of Lawrence on July 26 and showing regrowth in second photo 3 days later. Third photo is corn near York on July 26 showing growth in whorl not damaged. Last photo is worst hail damaged area I saw near Webber, KS. There was nothing left of soybean in the nearby fields.
Hail damage on stems may be only on the outer surface of leaves with no bruising below that (as in first two photos). Or, it can be more severe where bruising is leading to rot setting into the stem (as in last two photos).
Crop Update: This past week’s top question was about yellow looking and/or buggy whipped corn and weed control. Much of what we’re seeing can be attributed to cool, wet conditions this spring. Yellow striping on leaves is often due to sulfur deficiency but could be combined with other nutrient deficiencies depending on conditions. Purdue University has a nice guide with pics if you’d like to check it out: https://www.agry.purdue.edu/ext/soilfertility/news/Striped_Corn.pdf.
Most of what I looked at or received questions about was yellow and/or buggy whipped corn due to herbicide injury. This isn’t uncommon for pre-plant residual herbicides to impact corn more in years where we have wet conditions, cooler temps, and plants that are slower to emerge/grow. Yes, some of these products are considered ‘safe’ for corn, and they shouldn’t kill it. It’s just we’re experiencing a strange year with cool, wet conditions and the corn is metabolizing the chemical but not growing fast enough, thus the injury. Situations which may be extra sensitive are ones in which corn was planted too wet with slots not closing or if corn was planted too shallow. Soil applied grass herbicides and those with pre-mixes containing atrazine may be experiencing more of the buggy whipping or yellowing from Group 15 growth inhibitor herbicides. Yellow/purple leaves and sometimes ‘bottlebrush’ looking roots can be exhibited from Group 2 ALS-inhibitor herbicides. Herbicides in Group 27 with ‘bleacher’ chemistry are re-activated with rain events and we’re seeing some yellow/white corn and milo due to that. Dr. Kevin Bradley, University of Missouri, wrote an article that shares photos and trade names if you’re interested in checking that out: https://ipm.missouri.edu/IPCM/2009/4/Cool-Wet-Soils-Can-result-in-More-Corn-Injury-from-Preemergence-Residual-Herbicides/. I realize it’s frustrating, but overall these are good products and it’s the weather conditions causing the problems. Each day of sunshine and warmer temps are helping corn to grow out of the symptoms and look greener/healthier in most cases.
The other concern is the rain has moved herbicides down into the soil and we’re beginning to see weed flushes of waterhemp and palmer on the soil surface. Chris Proctor, Extension Educator, addressed this in CropWatch and Nebraska Farmer as we think of post-emergence control right now in both corn and soybean. There are additional trade names with similar chemistries mentioned and this isn’t an endorsement of specific products. “There are a number of effective herbicide options in corn such as Acuron, Laudis, or Diflexx Duo. In soybean, herbicide options are much more limited. When coupled with traited seed, Liberty, or Xtendimax can be effective at controlling these weeds postemergence, and in a Roundup Ready system Warrant Ultra or Flexstar GT are good options. It’s not too early to plan how to improve weed control in fields with a history of difficult-to-control weeds. A good preemergence herbicide program, use of narrow row-spacing, and even cover crops, when used as part of an integrated management plan, can improve control of herbicide-resistant weeds.”
Thistle Caterpillars: Painted lady butterflies migrate north from the southern U.S. and
Mexico each spring. The butterflies have been around for a little over a month and thistle caterpillars have been found feeding in soybean the past few weeks. Last week, I was seeing higher populations in early planted soybeans in Clay and Nuckolls counties. Larvae can feed from 2-6 weeks depending on weather. Treatment thresholds for vegetative stages are 30% defoliation. Each field needs to be assessed regarding percent defoliation and larval stage. Some fields I checked had larvae that were pupating or already emerged as adults. Other fields had larval stages that will still feed 2-5 weeks, depending on weather. Much information we read says they stay on field borders, which I’ve seen to be true later in the growing season. But right now, I’m finding situations where they’re fairly consistently infested throughout the field. Some may consider adding an insecticide to your post-herbicide application. If you have dicamba-tolerant soybeans, be sure to check the product’s website regarding approved tank-mix partners.
Irrigation Scheduling Workshops for wet years will be held Wednesday June 19th, 12 noon, at The Leadership Center, 211 Q St (E Hwy 34) in Aurora and Tuesday June 25th, 12 noon, at the Chances R Restaurant, 124 West Fifth Street, York. The program will start with lunch at 12:00 pm, followed by the speakers and wrap up around 1:30 pm. The Upper Big Blue NRD will provide the lunch. RSVP is not required but appreciated for a meal count. Call the Hamilton County Extension office at 402-694-6174 or email Steve Melvin at email@example.com. Dan Leininger with the Upper Big Blue NRD will speak on installing sensors and Steve Melvin will speak on deciding when and how much water to apply using watermark sensor readings.
Crop Updates: It’s been interesting seeing growers sharing pics comparing crops on the same dates in 2018 to 2019. They are behind in many cases compared to last year. Yet, we can be thankful for every field that we’ve been able to plant in Nebraska this year! Weed control is something on many minds right now. On corn, please be sure to count collars to determine growth stages. First leaves are sloughing off on V5-V7 plants right now, so slitting open stalks to aid in counting collars is important as we think of herbicide applications. Bob Nielsen from Purdue has a nice recent article with photos to help you with this: http://www.kingcorn.org/news/timeless/VStageMethods.html. When it comes to beans, I’m concerned how much longer the PRE’s will hold. I share this every year in pesticide training to have the POST with residual on a week before you think you need it, even if you don’t see weeds in the field yet. So assess each field as to when your PRE went on, current weed emergence, and plan on your POST a week earlier to overlap when your PRE residual should be running out. Also, with palmer amaranth on people’s minds, consider attending a glyphosate resistant palmer amaranth field day July 10th near Carleton, NE. Dr. Jason Norsworthy from the University of Arkansas will be the featured speaker. For those who’ve heard me speak on palmer or at my pesticide trainings, much of what I share has been what I’ve learned from his presentations and research papers. You can learn more and register at: http://agronomy.unl.edu/palmer. Adding a small grain and diversifying our cropping systems is one way to aid in palmer/waterhemp management. There are several upcoming wheat and pulse crop field days occurring throughout Nebraska in the next two weeks and you can read more about them at: https://go.unl.edu/b65e.
At some point, irrigation may be needed again. Installing irrigation scheduling equipment now allows you to watch your soil moisture profile as your crops grow, gain better confidence in your readings, and it’s just easier to install them at earlier growth stages when there’s moisture in the profile. Here’s some tips for those using watermark sensors. (As I walk through this, I’m using kilopascals (kpa) for the sensor readings but the same numbers apply to centibars (cb)). First, be sure to prime the sensors to ensure they’re working correctly. Do this by soaking the sensors for at least 24 hours in water. If you still have mud on the sensors, gently remove with your fingers, not with a brush. Then check the readings to ensure they read 10 or less. If they don’t, I allow them to soak another 24 hours and recheck; replace any that don’t read 10 kpa or less. Allow the sensors to dry out to 199 kpa again by setting out in the sun/wind/blowing fans. (Note that water will move into the PVC tube during soaking, so you’ll need to remove the cap and dump the water out if you don’t have a hole drilled at the bottom of the PVC tube. This is also true during the installation process.) When you’re ready to install the sensors, they need to be soaked again, but it should only take them 1-5 minutes to read 10 kpa or less prior to installation. There’s a couple things I’ve learned with installations that help me. First, use an ag consultant’s tube on soil probe to dig the foot wherever the sensor is installed. This allows for a better fit with no air gaps along the sensor. I use a regular soil tube to dig the hole the foot/feet above that to aid in pushing the sensors. In wet, clayey soils, it can be difficult to push the PVC pipe into the ground, so digging the upper holes with a bigger tube helps me with that. The other thing I do is carry my bucket with water for the sensors to the field with me with the sensors. To aid with pushing the sensors in the ground, I wet the PVC tube with water from the bucket prior to installing it. NEVER pour water into the holes and don’t make a slurry mix. I’m hearing several were taught to do this, but it’s not what Nebraska Extension teaches based on Dr. Suat Irmak’s research as it will change the soil moisture of the holes compared to the surrounding soils. Make sure the sensors hit the bottom of the hole and fill in soil where the PVC pipe meets the soil line. Suat shared how he used rubber washers around the top of the PVC pipe at the soil line to aid in water not running down the PVC tube when soil cracks at the surface. For those installing ET gages, a reminder to remove the stopper from the ceramic top and fill the ceramic top with distilled water in addition to the main tube of the ET gage. I fill the ceramic top, allow it to soak into the ceramic plate a little and refill it. Then prime the inner tube with stopper ensuring there’s no air bubbles in the small tube after placing it into the ceramic top. You can also double check for air bubbles by gently removing the glass site gage (by pressing down on the rubber tubing at the base of the site gage), allowing some water to cycle through, and then replacing it.
Maple seedlings: Maple trees have now leafed out and the rain has allowed the abundance of seeds to produce seedlings in people’s lawns and gardens. I know they look bad because they do at my place too. Mowing is the best way to take care of them in your lawn and it will take several mowings to do so. Don’t lower your mowing height as you want to maintain a healthy grass canopy. Eventually the seedlings will continue to grow to where the mower blade cuts off below the growing point and the seedlings will die. In the flower beds, they are very easy to pull right now. It takes some extra time, but that’s the best way to rid them there.
Flooded Gardens: This was my top question last week. For those of you with flooded gardens due to ponding of rain water, it will be fine to use your produce and the following information won’t pertain to you. However, most of the calls I received were from those with creeks or rivers that flooded their gardens. In that case, it’s difficult to know what contaminants may be in the water. It’s recommended by our Extension horticulturalists to wait 90 days to use any produce that does not have contact with the soil and 120 days to use any produce that does have contact with the soil. For example, tomatoes, peppers, eggplant, green beans could be harvested and eaten after 90 days. Fruit from trees and shrubs could be harvested and used after 90 days. However, rhubarb, potatoes, asparagus, squash and melon crops would need 120 days before harvesting to eat. Vegetables/fruits that are produced prior to the 90 and 120 day waiting period should be removed from plants and discarded. If the actual plants such as tomatoes, peppers, beans, etc. survive flooding, they do not need to be removed or replaced. You can allow them to continue to grow, just don’t use the fruit till 90 days post-flooding. Additional information can be found at: https://grobigred.com/2019/03/22/gardenflood/amp/?. Also, don’t harvest the morel mushrooms that are abundant this year due to the contaminants they’ve potentially been in contact with.
Crop Considerations: If you’d like more in-depth information regarding flooded/ponded corn/soybean, please check out this week’s CropWatch at http://cropwatch.unl.edu. We also shared a replant considerations article for corn in CropWatch. The tables in that article will be helpful as one assesses stands. Check corn, soybean, and milo for new regrowth 3-5 days after water recedes to determine potential survival. When it comes to assessing soybean stands for replant considerations, most UNL agronomists would say to leave stands of non-irrigated at 60,000 plants per acre and irrigated at 75,000 plants per acre. Honestly, my cutoff is 50,000 plants/acre for both irrigated and non-irrigated based more off of observation. A few on-farm research studies with lower actual stand counts include the following examples. 1-A non-irrigated field in Nuckolls County in 2006 was hailed at the cotyledon stage, so planted populations of 100K, 130K, and 160K became average actual stands of 74,417; 89,417; and 97,917 plants per acre with a 4 bu/ac yield difference between highest and lowest plant populations. 2-An irrigated field in Hamilton County in 2010 showed a 3 bu/ac yield difference between planted stand of 80K vs. 120K seeds/acre. 3-A York County irrigated field in 2018 comparing 90K, 120K, and 150K became final plant stands of 60,875; 88,125; and 121,750 plants/acre with yields of 93; 94; and 97 bu/ac respectively. So soybeans greatly compensate for reduced populations. Weed control may be another factor, depending on time of year, for soybean replant consideration. When in doubt, leaving some strips with the original stand and others with replant to test is also an option. I’ve also received questions regarding how much nitrogen to expect in the flooded/ponded soils. I don’t have a good answer other than soil samples will be helpful in determining this.
Wheat Diseases: I didn’t find any pustules looking at wheat in Nuckolls and Clay this past week. Stripe rust was confirmed in Perkins County and it was also found in Hamilton County by a crop consultant. While the model wasn’t showing as high of a risk, I’ve been concerned about our potential for wheat scab this year with all the rain. There are early planted wheat fields in which the flowering process has been completed. But there are a number of fields that are just fully headed now with beginning flowering to start soon. Upon flowering, your options for controlling any fungal diseases present on leaves as well as preventing scab are Prosaro, Caramba, and Miravis Ace. Research has found best timing to prevent scab is when 30% of the heads are at 15% flowering…basically early flowering. Flowering in wheat begins in the middle of the head.
South Central Ag Lab Weed Science Field Day: June 26th will be the South Central Ag Lab Weed Science Field Day near Clay Center. The field day will run from 8:30 a.m. to 1 p.m. with registration beginning at 8 a.m. Tours include: New Technology/Herbicides for Weed Control in Soybean; Herbicides for Weed Control in Corn; and a presentation by Bob Klein on “What Works and Doesn’t Work in Managing Spray Drift”. There is no cost to attend and CCA credits are available. Please pre-register at: http://agronomy.unl.edu/fieldday.
Keeping Rural Worksites Strong: This is a workshop for those who work in human resources, leadership and wellness roles, agriculture, and safety to create a mental health friendly workplace. It will be held on Tuesday, June 25 from 9 a.m.-4 p.m. (Registration 8:30 a.m.) at the Seward Medical Center in Seward. Topics include: stress and employee health; substance use issues in the workplace; identifying risk for violence in the workplace; employer’s role in preventing suicide; caring for employees; and being a mental health friendly worksite. Cost is $20 and includes light breakfast, lunch, and materials. Please RSVP to Four Corners Health Dept. at: http://www.fourcorners.ne.gov or (877) 337-3573.
Driving through Nebraska towns around Memorial Day, I find the streets lined with flags such a beautiful site. Grateful to live in our Country with our freedoms. I’m also grateful for those who paid the ultimate price for our freedom and for their families left behind.
Flooding/Ponding and Crop Effects: With the rain, some may be experiencing ponding/flooding of crops. Emerged corn prior to 6 leaves can survive from two to four days depending on temperatures and if entire plants are submerged or not. Cooler air temperatures (60’s and cooler) allows for longer survival than temperatures in the mid-70’s and warmer. Little data exists for germinated seeds and seedlings prior to emergence, but they most likely would experience soil oxygen depletion within 48 hours. Once emerged, soybean may handle a fair amount of flooding due to the growing point being above ground (depending on if they’re submerged or not). Four or more days of flooding may result in shorter plants due to shorter internodes and/or perhaps fewer nodes. Stand reductions may be observed after seven days of flooding (depending on size and if completely submerged or not).
Prevent plant may be another topic on some growers’ minds in addition to considerations after the May 25 corn planting date for crop insurance. These are addressed in this week’s CropWatch at http://cropwatch.unl.edu.
Interseeding Cover Crops: In a previous news column, I touched on the topic of interseeding cover crops into corn or soybean. For this week’s CropWatch at http://cropwatch.unl.edu, we provide more information based on the research available. For those considering this as an on-farm research study, please contact me or your local Extension Educator soon to work out details.
Wheat: Michael Sindelar and I looked at wheat in Clay and Nuckolls counties last week. For diseases we’re mostly seeing powdery mildew and septoria leaf blotch. Backlighting revealing yellow specks on upper leaves in some fields will most likely develop into leaf rust. Wheat ranges from nearing flag leaf to beginning flowering. My concern for wheat in the heading to flowering stage is risk of fusarium head blight (scab) with the rain we’ve been receiving at heading/flowering. The scab risk tool (http://www.wheatscab.psu.edu/) is showing a low to medium risk for our part of the State right now. If you do consider a fungicide, your best options include Prosaro, Caramba, or Miravis Ace as these products will help protect against scab in addition to kill any fungal diseases on your wheat leaves. Other products are off-label once flowering begins or are not as effective preventing scab based on research. Best application timing to prevent scab is when 30% of the plants in the field are at 15% flowering (early flowering stages).
Lawn Care: I know some are getting tired of mowing already! Just a reminder to keep mowing heights at 3″. Spring is an important time for deeper root establishment before the summer heat sets in and maintaining a higher lawn height allows the grass to develop that root system. I’m seeing several lawns being scalped in an effort to reduce amount of mowing. Mowing too short stresses the grass impacting its ability to set deeper roots for later. It will also allow for more weeds to germinate in the lawn.
What a blessing last week was for many to be in the fields to either finish or start planting! And, while some may not want it, we could also use some rain to help with the crusting issues that have been developing in various fields due to the warm temperatures and wind. As you assess stands, the following article provides some guidelines on what to look for and any replant considerations for corn: https://go.unl.edu/j727.
For those who planted soybean earlier into cooler soil conditions, Dr. Jim Specht also did so on different dates this year and monitored air/soil temperatures at the former ARDC near Mead. Air temperature daily lows were less than 36°F on eight days (five of which were 32°F or lower), were less than 40°F on 17 days, were less than 44°F on 23 days; and notably, were less than 48°F on 31 of the 37 days. I’ve talked about desiring a 24 hour window of near 50F temps for avoiding potential seed chilling of soybean. It’s based off some Canadian research that showed soybean completing the imbibitional (water uptake) phase in as little as 8-24 hours. Jim had a demo study this year in which he placed water into furrows and planted soybean seed 1.25” deep into the furrows on various days in April at 2:30 p.m. Adding water to the furrow was to hasten the imbibitional phase. There’s a slideshow with the full article in this week’s CropWatch at: https://go.unl.edu/yu2m. The article shows the seeds in this demonstration did not appear to be impacted by chilling injury in spite of low air/soil temperatures on some of the days including within a 24 hour period. The hypothesis is that planting in a warmer part of the day with good soil moisture allowed the imbibitional phase to complete more rapidly before the cold snaps occurred in the evening/following day. While this was only a demo, it spurs many questions. Further research to better document chilling injury and imbibitional period for different soil temps/moisture contents would hopefully help growers planting soybean in April.
Silver and Red Maple Trees: While back home helping with planting, I was also receiving numerous tree questions. For those with malformed leaves or various leaf coloration, I’m thinking that’s mostly due to the cool temperatures we’ve experienced. Malformed leaves can also be due to growth regulator herbicides such as 2,4-D (from weed and feed products or sprays) being applied to lawns when trees are beginning to leaf out.
For the past few weeks, I was observing the slow leaf-out of silver maples in town…even where portions of trees were leafing out and other portions seeming bare. Now, if your maples look like mine, they look brown and bare with huge seed production and minimal leaves. This can also be seen in red maple varieties such as the popular ‘Autumn Blaze’ maples from my observation. For everyone who called or texted, I told you I was assuming it was due to the cold snaps and frosts affecting trees leafing out. It also could be a result of the hard winter. Trees are interesting as stresses from previous years can also affect them several years down the road. While all that’s true, what I didn’t realize is that based on information from Ohio and Michigan State, frost at specific times trigger whether a tree goes into seed or leaf production. Maple trees produce very small flowers that turn into seeds every spring. Frost will kill some of the blossoms if received at the right time which leads to less seeds and more leaves. Even though it was a cold spring, perhaps fewer blossoms were killed than normal at the right time? It could also just be the natural cycle of heavy seed production this year? Regardless, the trees can’t support both massive seed production and leaf production, so many opted for seed production. The good news is that shade trees in general have an ability to shoot new leaves after being stressed. I see this every year after trees lose leaves due to herbicide damage, insects, diseases, or environmental conditions. So, give the trees a couple of weeks and you should begin to see new leaves developing. Don’t add fertilizer or other products to them as it’s not necessary and can actually stress trees that are stressed even more. By summer, the trees should look fairly normal. If they don’t, perhaps there’s another stressor occurring with your tree? The biggest culprits I see are roots that girdle (choke) the tree by wrapping themselves around the trunk or damage to the trunk from weed whackers.
What about those seeds in lawns and gardens? Some pre-emergent lawn herbicides will keep them from sprouting. Pulling them is time consuming, yet a valid option that’s best done as soon as seedlings emerge. Mowing may help keep some of them at bay. Weed and feed products for lawns often contain 2,4-D so using that or lawn care products with 2,4-D can be an option (just be sure to read the pesticide labels). Products like Preen can be pre-emergent options for flower beds/gardens.