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.
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 firstname.lastname@example.org. 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.