C.O.R.N. Newsletter: 2021-19
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Corn Rootworms and Fireflies
Most of us remember a connection between fireflies and corn rootworm hatch. This connection may not be absolute and could have changed since we’re now using different production practices than in the past.
We also know a lot more about corn rootworm biology. In Ohio, western corn rootworms are by far the most common (although you may see some northern corn rootworms). Adult rootworms lay eggs in the late summer and these eggs typically hatch the following June. We also know that peak egg hatch (i.e., 50% of the total hatch) occurs between 684 to 767 accumulated growing degree days (base 52oF). Our map below shows that much of Ohio has reached or exceed these GDD. If rootworms are in your field, chances are they have hatched and begun their feeding.
Over the next few weeks, corn should be inspected for damage. Prioritize your scouting in non-rotated corn (i.e. 2nd, 3rd-year corn, or more), and corn without below-ground Bt traits or insecticidal seed treatments. However, some rootworm populations have also adapted to infest 1st-year corn, as well as to overcome virtually all Bt traits (important note—we have NOT detected any Bt-resistant rootworms in Ohio yet). See our corn rootworm fact sheet (https://aginsects.osu.edu/sites/aginsects/files/imce/ENT_16_14%20CRW.pdf) for more information on inspecting corn roots for damage. If any damage is detected on Bt roots, please contact us or your local extension educator, because it might be an early indication of resistance in Ohio.
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Rye can be a pesky weed.
In recent years Ohio has seen a huge resurgence of rye usage as a cover crop. While rye can be a good option as a cover crop, it is also a persistent threat as a weed in subsequent crops and neighboring fields. In parts of Ohio this season, volunteer rye is obvious in many crop fields. This is usually a minor threat to the crop, but in certain circumstances, it does create big problems.
The problem of volunteer rye tends to become a more serious issue when seed drifts into a neighboring field belonging to another producer. Neighbors often resent seeing what is in effect a weed that was scattered (all be it accidentally) on their field. The issue can grow exponentially if the neighboring field happens to be a seed production field of wheat where any rye (even one plant) is unacceptable.
Even in regular fields of wheat, volunteer rye can become an economic problem if the concentration is high enough. If rye is found in a sample of wheat, it will typically be treated as foreign material. As such, any foreign material above 1% is typically subtracted from the gross weight and can be subject to other discounts as well.
Any crop growing in the wrong place can become a weed. Rye has many properties that make it a good cover crop, but its ability to germinate with little cover and its persistence makes it a formattable weed as well. Keep that in mind when seeding cover crops and avoid seeding rye by aircraft in sensitive areas such as seed production fields.
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June 24th CORN Live Webinar Focuses on Weeds in Soybeans and Wheat Harvest
The next session of CORN Live is this Thursday, June 24th from 8:00 – 9:00 am. This week’s webinar will touch on a variety of issues, starting with a crop progress report and field updates from Jason Hartschuh, Extension Educator in Crawford County, and a review of weed management in soybeans with Mark Loux, Professor and Extension Specialist in Weed Science at OSU.
In many parts of Ohio, wind or rain have reduced spray days allowing weeds to grow to a size that is tougher to control. Loux will be available to answer questions about adjustments to weed control programs.
Brad Moffitt, Director of Market Development and Membership at Ohio Corn and Wheat, and John Hoffman, Pickaway County farmer, will also be online to review this year’s growing season for wheat and talk about getting started with wheat harvest.
1 hour of CCA CEUs will be offered (0.5 PM + 0.5 CM). The webinar is free to attend. Register at www.go.osu.edu/cornlive.
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Weather Update: First of the Season Tornadoes Strike Ohio
Though not in the heart of Tornado Alley, Ohio certainly deals with its fair share of severe weather. The season typically ramps up during May and June, but severe weather so far in 2021 has been rather benign.
This changed in a big way this past weekend, with numerous reports of damaging winds and large hail. According to the National Weather Service, two tornadoes (first of the year) hit western and southwestern Ohio on Friday, June 18. An EF2 tornado, with winds to 115 mph and up to 200 yards wide, struck just north of Ft. Recovery in Mercer County, causing extensive damage to barns, livestock, and fields. Another, weaker EF1 tornado moved from southwest Montgomery County into northeast Butler County.
A large swath of straight-line winds brought down numerous trees and lodged corn and wheat, while hail as big as 2.50” in diameter (tennis ball) combined with wind to shred some young crops across southwest Ohio. Much of southwest Ohio picked up 2-7” of rainfall, some of this occurring in less than one hour, leaving this area of the state in need of some drying weather to get back to cutting hay, wheat, and side dressing corn.
Calmer, cooler, and drier weather will filter in for Tuesday and Wednesday, with highs in the 60s and 70s and overnight lows in the mid-40s to low 50s. Heat and humidity will return late week through the weekend with numerous opportunities for showers and thunderstorms.
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Canada thistle rebounds?
It can be nice to see old friends. Except when they cause crop and yield loss, refuse to leave after a few days, and don’t respond to chemicals. A while back we wrote about what appeared to be an increase in populations of dandelions and other winter weeds and made some guesses about why this was happening. Canada thistle has once again become a problem in some fields in a big way, probably for some of the same reasons that dandelion has. Our history with thistle during the past 30+ years is that it was a major problem before the widespread adoption of RoundupReady soybeans in the late 1990s. Back then we had to take advantage of specific windows in the cropping cycle to try to get control with glyphosate, and the rest of the time we just tried to keep it from getting worse. The “all glyphosate, all the time” strategy during the first decade of RoundupReady soybeans handled thistle and other perennials such as milkweed and hemp dogbane well, and we didn’t hear much about them. Now we are though, and increases in thistle could be due to the following:
- lack of herbicide treatments in fall, when thistle is most effectively controlled
- lack of wheat in the rotation. Including wheat allows a period after harvest for thistle to regrow to a large enough size in fall (compared with cutting it off during corn and soybean harvest)
- nonGMO soybeans, where options for control are ineffective/expensive and thistle gets a better foothold
- switch to the use of Liberty Link soybeans and the use of glufosinate in POST treatments. Glufosinate is a contact herbicide that can burn down the top-growth but will not reduce populations
- applying POST glyphosate treatments too early, before thistle is large enough to respond well
- failure to use effective POST treatments in corn
The initial slow increases in the population of any weed are often ignored since populations are too low to cause a loss in stand or yield or interfere with harvest. At some point though, the current year’s infestation will be substantial enough to provide the source for a much denser infestation the following year. In this steeper part of a population’s growth curve, things can get out of control fast. Canada thistle reproduces via windblown seed, and also spreads via a deep, dense network of creeping roots. Left uncontrolled for a while, the patch of thistle that results from this can be thick enough to reduce crop stands and vigor considerably, literally sucking the life out of corn and soybeans. Some suggestions for controlling thistle for those experiencing a rebound:
- Apply herbicides in the fall when the thistle plants are at least 10 to 12 inches tall. This can occur into November as long as plants are still green, before freezes. Our experience is that it’s probably not worth treating in fall when plants do not regrow to at least this size unless there are other weeds requiring fall application anyway.
- Use effective POST herbicides in corn, especially where wheat is not in the rotation and glyphosate is not being used POST in soybeans.
- if using glufosinate POST in soybeans that are resistant to glyphosate also (LLGT27, Enlist), add glyphosate to the mixture.
- use effective burndown and residual herbicides in soybeans, to try to delay the POST glyphosate application until later in June when thistle are larger (ideally in the bud to flower stage).
- Herbicides applied to small thistle plants in late spring only reduce the top-growth, without herbicide getting to the roots. At small sizes, thistle plants are primed to just regrow again. We have heard from several clients who observed ineffective activity on thistle from burndown applications and then resprayed as soon as the thistle plants had a few inches of regrowth. While the basis for this approach in dense stands is to try to prevent suppression of the crop, it largely won’t work. Steps need to be taken the previous years to prevent the development of dense thistle stands.
- In soybeans resistant to glyphosate, scout later in the season following the initial POST application for thistle regrowth and treat again as necessary.
- POST options in nonGMO soybeans are generally not good or are just expensive. From the Weed Control Guide: “Postemergence applications of Basagran (2 pt/A) will control above-ground parts of the plant or suppress the growth of Canada thistle. Regrowth usually occurs, but this treatment will reduce competition from Canada thistle in soybeans and help prevent the production of more rootstock. Apply when thistle plants are from 8 inches tall to the bud stage. COC should be included in the spray mixture. A second application at the same rate may be made 7 to 10 days later, if necessary. Other products and mixtures with activity on thistle include fomesafen and mixtures of Basagran with fomesafen, Ultra Blazer, or Cobra. Postemergence application of Pursuit (1.44 oz/A), Classic (0.66 to 0.75 oz/A), FirstRate (0.3 oz/A), and Synchrony XP (0.75 oz/A) may also suppress thistle growth, but results have been variable.”
A reminder that the first page of the “Control of Problem Weeds” section of the “Weed Control Guide for Ohio, Indiana, and Illinois” contains a list of strategies for managing perennials. This was first written before the availability of RR soybeans, so it can have some useful information for this type of situation where the use of glyphosate is being deemphasized.
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Putting poison hemlock in perspective
Poison hemlock seems to be on everyone’s radar more than usual this year, especially in northern Ohio. We know that while hemlock has been all over southern Ohio for years, it is continuing to spread northward, where new occurrences and observations of it may be engendering concern in the general public and local government. There have also been comments that it seems “worse than usual” this year in some areas, and we don’t have a ready explanation for what would cause this. For any plant that reproduces by seed, an abundance of seed in one season can lead to much higher populations the following season. Seed-based population increase tends to be exponential. When left uncontrolled for several years, the populations may stay low for a few years until seed production reaches a certain level, and that amount of seed can cause a large and very observable increase in population. 
Poison hemlock in Ohio has made the news over the past month, in articles such as this one. From a frequency of poisoning standpoint, some of these articles can make it seem worse than it is. Hemlock is in the Apiaceae or parsley plant family, which also includes wild carrot (Queen Anne’s lace), wild parsnip, cow parsnip, and giant hogweed. Giant hogweed is the truly bad actor in this group but has not become established in Ohio. All of these species share some of the same characteristics with poison hemlock to varying degrees. This comprehensive article in the OSU BYGL newsletter does a nice job of presenting information on the various species, including identification. 
Poison hemlock has been in Ohio for a long time, and there are many areas it is never subject to any control measures – abandoned fields, forest borders, etc. And there are other areas hemlock grows well where it should be controlled because it reduces the quality and safety of these areas or can be seen by people. These areas include parks, roadsides, ditches, hayfields, pastures, etc. Poison hemlock is poisonous to humans and livestock, but only when ingested. Poisoning seems to be extremely rare because: 1) it’s not a plant that smells or tastes good, so animals avoid it; and 2) humans are not prone to wandering down roadsides eating plants, especially the ones that do not appear appealing. Contact with hemlock can also cause skin and eye problems which are way more likely than internal poisoning. The severity of this response varies depending upon the sensitivity of the individual and the degree of contact. This does not happen from a distance though – only with direct contact with plant parts or fluids from the plants. Anyone mowing or removing hemlock by hand should keep this in mind and protect themselves from skin and eye contact. Mowing large populations with open station tractors is not recommended.
Within this plant family, poison hemlock and wild parsnip present the most risk to livestock, based on the level of infestation in Ohio and toxicity. Livestock seldom eats these plants due to strong odor and taste, and most problems occur when no other forages/desirable plants are available, often during droughts. It is also possible for these weeds to inadvertently end up in hay bales where they retain toxicity. Many other plants that can have toxic effects on livestock will see those toxins dissipate during the hay drying process, or the during fermentation process if hay is ensiled or wrapped. This is not the case with poison hemlock – toxins will remain viable and lethal regardless of the curing and storage methods. All parts of the plants are poisonous with the seed heads being the most toxic. Poison hemlock contains eight piperidine alkaloids, with coniine (mature plants) and g-coniceine (young plants) being the two predominant toxic compounds. Experimental hemlock poisoning in livestock has shown a wide range of clinical signs suggesting variation in the toxic alkaloid content in the plant. Cattle eating as little as 300 grams up to 0.5 percent of body weight has shown to be fatal. Bluish discoloration of the skin from poor circulation, respiratory paralysis, and coma without convulsions are common signs before death which usually occurs within 2-3 hours after consuming a lethal dose. Wild Parsnip contains chemicals called furanocoumarins which cause severe sunburns. Housing infected livestock in shade may help reduce its effects. Other clinical signs may include acute disorders to the central nervous system or digestive tract without a fever but weakness and rapid weight loss. Other symptoms may include suddenly accelerated heartbeat, stomach, and intestinal irritation, general distress, or repeated attempts to void feces.
Poison hemlock and wild parsnip are on the Ohio noxious weed list, and therefore need to be controlled before becoming large enough to present a threat, and before seed production to prevent spread. Information on the Ohio noxious weed law can be found in this bulletin and on the OSU Farm Office page. At this time of the year when these plants are flowering, producing seed, and dying, it’s not always possible to use chemicals to control them. The goal should be getting rid of existing plants through cutting, mowing, or hand removal, and limiting production and spread of seed. The most effective timing for the application of herbicides is fall when plants are low-growing rosettes in their first year of growth, or early the following spring when plants are still small. Herbicide effectiveness ratings in Table 21 of the “Weed Control Guide for Ohio, Indiana, and Illinois”, which lists pasture and CRP herbicides. Additional products labeled for roadsides, industrial areas, etc but not shown in this guide are also effective.
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Double Crop Soybean Recommendations for 2021
Wheat harvest is rapidly approaching, and with relatively high soybean prices, we anticipate many growers will be interested in double cropping soybean after wheat. According to the U.S. drought monitor (https://droughtmonitor.unl.edu/), areas bordering Michigan are abnormally dry, but throughout the rest of the state, soil moisture is good. Early wheat harvest, high soybean prices, and adequate soil moisture make double-crop soybean an attractive option in 2021.
The two primary requirements for successful double cropping are: 1) adequate time to produce the soybean crop and 2) adequate water. In Ohio south of I-70, double-crop soybean production is common as there is generally adequate time to produce soybean; however, yield can be variable depending on soil moisture and rainfall. In Clark County Ohio, we’ve had double-crop soybean yield averages of 50 bu/acre, but as low as 21 bu/acre when water was limiting. North of I-70, double-crop soybean is less common but occurs when the wheat harvest is early and/or when soybean prices are high. Table 1 shows full-season soybean yield compared to double-crop soybean yield in a three-year study conducted at the Northwest Agricultural Research Station in Wood County. In Wood County, we’ve had double-crop soybean yield as high as 57 bu/acre in 2018 and as low as 12 bu/acre in 2016. (2016 was a hot and dry year.)
Table 1. Full-season soybean yield compared to double-crop soybean yield at the Northwest Agricultural Research Station in Wood County.
Full-season soybean yield
Double crop soybean yield
2016
49 bu/acre
(planted May 25)
12 bu/acre
(planted July 1)
2017
61 bu/acre
(planted May 6)
29 bu/acre
(planted July 6)
2018
62 bu/acre
(planted May 24)
57 bu/acre
(planted July 5)
AVERAGE
57 bu/acre
33 bu/acre
Cultural practices, such as row spacing, seeding rate, and relative maturity, may be adjusted to help maximize soybean yield in the double-crop system.
Row spacing. Double crop soybean should be produced in narrow rows at 7.5- or 15-inch row spacing. The later in the growing season soybeans are planted, the greater the yield increase due to narrow rows. Soybeans grown in narrow rows produce more grain because they capture more sunlight energy, which drives photosynthesis.Seeding rate. The harvest population for mid-to-late-June planting should be between 130,000 to 150,000 plants/acre. The harvest population for early-July planting should be greater than 180,000 plants/acre. Harvest plant population is a function of seeding rate, quality of the planter operation, and seed germination percentage and depends on soil moisture conditions, seed-soil contact, and disease pressure. Generally, seeding rates between 200,000 to 250,000 seeds/acre result in these targeted harvest plant populations.
Relative maturity. Relative maturity (RM) has little effect on yield when soybeans are planted during the first three weeks of May. However, the effect of RM can be greater for late planting. When planting soybeans late, the latest maturing variety that will reach physiological maturity before the first killing frost is recommended (Table 2). This selection allows the soybean plants to grow vegetatively as long as possible to produce nodes where pods can form before vegetative growth is slowed due to flowering and pod formation.
Table 2. Recommended relative maturity (RM) ranges for soybean varieties planted in June and July in northern, central, and southern Ohio.
Planting Date
Suitable RM
Northern Ohio
June 1-15
3.2-3.8
June 15-30
3.1-3.5
July 1-10
3.0-3.3
Central Ohio
June 1-15
3.4-4.0
June 15-30
3.3-3.7
July 1-10
3.2-3.5
Southern Ohio
June 1-15
3.6-4.2
June 15-30
3.5-3.9
July 1-10
3.4-3.7
Straw removal. Finally, while straw removal may delay double-crop soybean planting a day or more, it will improve soybean emergence and add value to the wheat enterprise. Removing the straw will improve the planter or drill’s ability to provide good seed-to-soil contact without ‘hair pinning (when straw gets trapped in the seeding trench, increasing air spaces) and improve soybean emergence. Straw yields in Ohio range from 1.2 to 1.8 tons/acre. This tonnage creates additional value for a wheat enterprise but will remove approximately $14-15/acre of phosphorus and potassium value (Ohio Enterprise Budgets).
In summary, factors like an anticipated early wheat harvest and higher than normal soybean prices create a logical opportunity for double cropping soybean in Ohio this year. Producers who chose to double-crop should plant as soon as possible after wheat/straw harvest and are encouraged to follow these cultural practices: use narrow rows, increase seeding rates, use a relative maturity suitable to their region and consider removing straw. Happy double-cropping!
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Do you need to apply sulfur to reach your corn yield goals?
There is a general interest in applying sulfur fertilizer to maximize corn productivity and we’ve heard industry professionals claim that sulfur deficiency this widespread across Ohio. How much truth is there to this? Do we have a widespread sulfur deficiency in Ohio?Since 2013, Ohio State University Extension has run 53 sulfur trials in corn, primarily with spring-applied sulfur (gypsum, ammonium sulfate, or thiosulfate) before planting, at-planting, or soon after planting. Not surprisingly, applying these readily available sulfur sources typically increases sulfur concentrations in leaf tissue and corn grain. However, the impacts on corn grain yield are less consistent, with only 44% of trials showing a positive response to sulfur (Figure 1). Interestingly, only 5 trials showed a statistically significant positive response, and 3 trials where in-furrow applications resulted in significant yield decline, presumably due to high salt content. Our data suggest that sulfur deficiency is not a widespread problem in Ohio, but some corn fields will positively respond to sulfur fertilization. We continue to monitor and evaluate the need through on-farm trials. The Tri-State Fertilizer Recommendations provide more guidance on managing sulfur and provide specifics about when crop response to S is more likely to be seen: https://go.osu.edu/fert-recs
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CORN Live set for June 24 from 8:00 AM - 9:00 AM
CORN Live session focuses on weed management in soybeans and wheat harvest. We will have field updates from Jason Hartschuh, Mark Loux, John Hoffman, and Brad Moffitt. The webinar is on June 24th, 8 am-9 am. Register at www.go.osu.edu/cornlive. The official flyer is located here.
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.
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Disclaimer
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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