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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter: 2017-27

  1. Late-Season Scouting for Palmer Amaranth

    Palmer amaranth seedhead
    Author(s): Mark Loux

    Palmer amaranth has shown up in a few more places in Ohio this summer at a range of infestation levels, and waterhemp has also become more prevalent. Newly discovered Palmer infestations in some fields were too high to be remediated by walking fields and removing plants, although there is still some potential to mow down weeds and soybeans to prevent seed production and even bigger problems next year. Infestation level in a few other fields was low enough to allow removal of Palmer amaranth plants by a crew of concerned people. Credit is especially given to the entire staff of one dealership in western Ohio who took the time to walk an 80-acre infested field for one of their customers. Palmer was found in several other fields in that area at low levels, and the source appeared to be manure from a dairy operation that had brought in hay from Kansas. It was reassuring to see an immediate coming together of growers and dairy operators and agbusiness to determine how to deal with the developing Palmer problems, without trying to place blame. The attitude of at least one person organizing the meeting was “we need to have a zero tolerance for Palmer amaranth”, and we could not agree more. Remediation will require use of aggressive herbicide programs in infested fields along with continued frequent observation and removal of plants by hand. Essentially all of the Palmer amaranth that we have screened for resistance has been resistant to both glyphosate and ALS inhibitors (site 2), but we have not yet found resistance to PPO inhibitors (site 14). Resistance characteristics of waterhemp populations are more variable. They are all resistant to ALS inhibitors. Resistance to glyphosate is now fairly common in the western half of the state, and PPO resistance is getting a foothold as well. Waterhemp populations in eastern Ohio are more likely to be still sensitive to both glyphosate and PPO inhibitors.

    Neither one of these weeds is a picnic to deal with, and both can cause substantial increases in the cost of herbicide programs. The trend across the country is for them to develop resistance to any new herbicide sites of action that are used in POST treatments. So preventing new infestations of them should be of high priority for Ohio growers. When not adequately controlled, Palmer amaranth can take over a field faster than any other annual weed we deal with. Taking the time to remove any Palmer and waterhemp plants from fields now will go a long way toward maintaining the profitability of farm operations. There is information on Palmer amaranth and waterhemp identification on most university websites, including ours – (go to “weeds” and then “Palmer amaranth”). An excellent brief video on identification can be found there, along with a fact sheet. The dead giveaway for Palmer amaranth as we move into late summer is the long seedhead, and those on female seed-bearing plants are extremely rough to the touch. We recommend the following as we progress from now through crop harvest:

    - Take some time now into late summer to scout fields, even if it’s from the road or field edge with a pair of binoculars. This would be a good time to have a friend with a drone that provides real-time video, or your own personal satellite. Scouting from the road is applicable mostly to soybean fields, since corn will often hide weed infestations.

    - Walk into the field to check out any weeds that could be Palmer amaranth, waterhemp, or are otherwise mysterious. If you need help with identification, send photos to us or pull plants and take them to someone who can identify them.

    - Where the presence of Palmer amaranth or waterhemp is confirmed, check to see whether plants have mature seed (the Palmer plants with the rough seedheads), by shaking/crushing parts of the seedhead into your hand or other surface that will provide contrast. Mature seed will be small and very dark.

    - Plants without mature seed should be cut off just below the soil surface, and ideally removed from the field and burned or composted. Plants with mature seed should be cut off and bagged and removed from the field, or removed via any other method that prevents seed dispersal through the field.

    - If the Palmer amaranth or waterhemp population is too dense to remove from the field, some decisions need to be made about whether or how to mow or harvest. Harvesting through patches or infested fields will result in further spread throughout the field and also contamination of the combine with weed seed that can then be dispersed in other fields. So consider: 1) not harvesting areas of the field infested with Palmer amaranth or waterhemp, and instead mowing several times to prevent seed production, and 2) harvesting the infested field(s) after all other fields have been harvested, and cleaning the combine thoroughly before further use. This also applies to any infestations that are discovered while harvesting.

    - Scout field borders and adjacent roadsides, and also CREP/wildlife area seedings, which can be infested due to contaminated seed produced in states where Palmer amaranth is endemic and not considered noxious. Reminder - ODA will test any seed used for these purposes for the presence of Palmer amaranth.

    - Feel free to contact OSU weed science for help with identification or management of Palmer amaranth. Mark Loux – 614-292-9081,

  2. Late Season Soybean Insects

    Bean leaf beetle variation

   Soybean pod-feeding (photo by Ron Hammond); examples of resulting seed damage (photo by NCSU Cooperative Extension); bean leaf beetle adult


    As the season winds down, soybean growers need to continue scouting their fields, especially later-planted fields that will remain green well into September. As other fields in the area begin maturing and yellowing, some insects will migrate to soybeans that are still green and continue their feeding there. Two of those insects are second generation bean leaf beetles and the stink bug complex consisting of several species. These insects feed on the pods and seeds of the plant, causing direct damage to the harvestable part of the soybean. to prevent pod damage from bean leaf beetle is based on the level of insect injury observed on the pods. Select 10 plants at random, spread around the field, and examine all the pods on each plant. Count the number of total pods and the number of pods exhibiting pod scar injury, and then determine the percent pod injury based on the 10 plants inspected. It is important to estimate percent pod injury on inspection of the entire plant. Treatment is justified if the percent pod injury is approaching 10-15%, and bean leaf adults are still present and still active. Beetles will start to leave the field as beans mature, so it is important to verify they are still there. A sweep net is an efficient way to sample for the presence of adults. Take 10-sweep sets in several locations in the field to determine presence or absence. Stink bug life stages, and damage to beans.

    Stink bug damage to soybean pods is not apparent from the outside since they don’t feed on the pod surface. Instead, they pierce directly into the seed with a straw-like mouthpart. Scouting for stink bugs is based on numbers of adults and nymphs (immatures). Scout by by walking into the field at least 100 ft from the field’s edge (numbers tend to be higher on the edges and are not representative of the whole field). Use a sweep net to take sets of 10 sweeps at 3 to 5 locations in a field. Both adults and nymphs should be counted together. Experience suggests that the brown marmorated stink bug is difficult to sample using sweep nets, so you might need to walk slowly through the soybeans and attempt to count the bugs directly on the plants. Insecticide treatments should be considered when an average of 4 or more adults or nymphs of all species are collected per 10 sweeps in regular soybeans. When grown for seed or are food grade soybeans, we suggest lowering the threshold to only 2 adult or nymphs per sample. For brown marmorated stink bug, control is suggested if you see 1-2 per row ft through at least the R4 stage.

    When the decision to make a rescue treatment is made to prevent pod and seed injury to later maturing soybeans, there are numerous foliar insecticides to use for bean leaf beetle and stink bug control. Growers should also be aware of pre-harvest intervals for the insecticides, which range from 14 days to 60 days. The time period left before anticipated harvesting of a field might dictate the insecticide chosen.

  3. Frogeye at R5 on Indeterminant Soybean - Not to Worry

    Frogeye leaf spot
    Author(s): Anne Dorrance

    I must admit that I am a bit surprised at how slow frogeye leaf spot, a foliar leaf spot of soybean, was to show up in fields this summer. Early indications were that it was going to get a good early start. But scouting of fields throughout the state – it was hard to find. It took me 90 minutes before a crop walk in western Ohio in July to find 2 spots! Last week a couple of calls came in, where folks found large round gray lesions on the new leaves. Based on the size of the lesions – it was clear that this was a susceptible cultivar. These lesions were also only on the new leaves on plants in the midst of pod fill. This is actually more typical of when we would see frogeye, late in the season and at these late growth stages at these low inoculum levels, it does no damage. A few spots on a few leaves on the top of the plant, scattered throughout the field will not cause yield loss. More importantly, the disease cycle for 2017 is finished as no more new leaves or very few new leaves will develop on the plant, and these are the susceptible parts of the plant. So no fungicide is warranted at these late growth stages. Where we have measured substantial yield losses is when there are lesions, throughout the canopy, mid-to-upper canopy leaves all have many leaf spots.

    We are still monitoring these fields to measure the amount of fungicide resistance to the strobilurins we have in Ohio populations of the fungus, Cercospora sojina, which causes this disease on soybean. So if you do come across some lesions, please send them to the lab. These lab tests are paid for by the soybean check-off through Ohio Soybean Council.

  4. Western Bean Cutworm Monitoring Update for Week Ending August 18, 2017

    Western bean cutworm adult

    We are nearing the end of WBCW trap monitoring in Ohio as trap counts continue to decrease across the state. A total of 71 traps were monitored in 23 counties. Overall, 138 WBCW adults were captured, with 11 counties reporting a “zero” for their trap count. The state average also continues to decrease from 5 WBCW (week ending August 11) to 2 WBCW (week ending August 18).

    Amy Raudenbush, Kelley Tilmon, Andy Michel, Mark Badertscher, Lee Beers, Amanda Bennett, JD Bethel, Bruce Clevenger, Sam Custer, Thomas Dehaas, Allen Gahler, Jason Hartschuh, Cecelia Lokai-Minnich, David Marrison, Sarah Noggle, Les Ober, Adrian Pekarcik, Eric Richer, Garth Ruff, John Schoenhals, Jeff Stachler, Alan Sundermeier, Curtis Young, and Chris Zoller monitored the moth traps.

    Figure 1. Average western baen cutworm (WBCW) trap counts within participating counties for week ending August 18, 2017.  Number represents the average WBCW per trap in each county.


    Figure 1. Overall average number of western bean cutworm adults captured in traps in Ohio.

  5. Fertilizer Certification Training

    Fertilizer Spreader

    September 30th is the deadline to receive your Fertilizer Certification. Anyone applying fertilizer to greater than 50 acres must obtain this certification, unless the crop will be feed to livestock or you are only applying start-up fertilizer with the planter.

    The Top of Ohio EERA will be holding one of its last Fertilizer Certification Trainings on August 28, 2017. The Fertilizer Certification meeting will take place at the Palazzo (309 S. Main St.) in Botkins, Ohio. There are two classes, one from 2:00 to 5:00 PM and a second from 6:15 to 9:15 PM. There will be a free meal at 5:00 PM.

    To get registered call the Auglaize County Extension office at 419-739-6580.

  6. One Last Chance to get Fertilizer Certification in North Central Ohio

    Anhydrous Ammonia Application

    The Erie Basin EERA of OSU Extension will offer Ohio Fertilizer Applicator Certification training at 1:30 pm on August 30, 2017 at Independent Ag located at 4341 Sandhill Rd in Bellevue, OH 44811. The store is visible from US Route 20 between Bellevue and Monroeville. No registration is required and there is no charge for this training. For information call the Huron County Extension Office at 419-668-8219.

    Independent Ag will also be having Field Day in the morning, prior to this training. Although this event is separate from the training, they graciously invite anyone coming to the training to join in their Field Day events. To RSVP for the Independent Ag Field Day please call 419-483-1515.

    This will be the last opportunity in North Central Ohio to receive Fertilizer Applicator Certification before the September 31, 2017 deadline set by the Ohio Department of Agriculture. After the September deadline, any applicator of commercial fertilizer applying 50 acres or more in any 12-month period, is required to have Fertilizer Applicator Certification. Don’t miss this opportunity.

  7. Join Us for a Workshop: ROI of Digital Tools for Soybean Production

    Digital maps
    Author(s): , John Fulton

    The Ohio State Precision Ag Team will be hosting a free workshop for tech savvy soybean growers on Friday, September 8, 2017 from 9a-4p at Beck’s Hybrids in London, Ohio. Topics of discussion will include data warehousing, production benchmarking, analysis, in-season monitoring, crop modeling, and recommendations.

    The day’s discussions will focus on understanding potential value of digital tools for soybean production and how growers are utilizing these tools and services. The value and use will be examined and key outcomes will focus on key outcomes centered around:

    • Different types of benefits that individual technologies provide to soybean farmers.
    • Direct value propositions realized by a soybean farmer using a digital technology.
    • The value of sharing data with trusted advisors or companies providing digital technologies while simultaneously considering data privacy and control.
    • Identifying key educational needs of soybean farmers relative to digital technologies.

    Confirmed speakers include Jeremy Wilson of MyAgData, Mike Hannewald of Beck’s Hybrids, and Dr. Laura Lindsey from The Ohio State University. Industry professionals will also be presenting. The day will end with a panel discussion comprised of producers, retailers, an independent agronomist and a commodity representative.

    Please consider bringing a tablet, laptop or other smart device with you to the workshop. Space is limited to the first 75 registrations, so act quickly! To register for the free workshop that includes lunch and breaks, visit or follow the QR code!

Upcoming Events

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.


Beth Scheckelhoff (Educator, Agriculture and Natural Resources)
Chris Zoller (Educator, Agriculture and Natural Resources)
Dean Kreager (Educator, Agriculture and Natural Resources)
Ed Lentz, CCA (Educator, Agriculture and Natural Resources)
Elizabeth Hawkins (Field Specialist, Agronomic Systems)
Eric Richer, CCA (Field Specialist, Farm Management)
Garth Ruff (Educator, Agriculture and Natural Resources)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
Greg LaBarge, CPAg/CCA (Field Specialist, Agronomic Systems)
Lee Beers, CCA (Educator, Agriculture and Natural Resources)
Les Ober, CCA (Educator, Agriculture and Natural Resources)
Mark Badertscher (Educator, Agriculture and Natural Resources)
Mike Estadt (Educator, Agriculture and Natural Resources)
Sarah Noggle (Educator, Agriculture and Natural Resources)
Steve Culman (State Specialist, Soil Fertility)
Ted Wiseman (Educator, Agriculture and Natural Resources)


The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

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