Dicamba Approved for Over-the-Top Use 2021 and Beyond

Source: Agweb.com

Tuesday, Oct. 27, 2020, the Environmental Protection Agency (EPA) announced it will approve three of the new dicamba formulations for over-the-top use for five years, according to EPA Administrator Andrew Wheeler. The herbicide is labeled for use in soybeans and cotton with the trait that confers tolerance to dicamba.

The specific formulations include Xtendimax VaporGrip Xtra, Engenia and Tavium. The registration starts next year (2021) and runs through 2025. The administrator said they opted for a five-year registration, which is typical for pesticides, instead of a two-year like dicamba has experienced in the past because they had more data to base this decision upon.

“EPA will register dicamba for over-the-top use on dicamba tolerant cotton and soybeans, this decision provides a five-year registration to provide certainty to growers,” Wheeler says. “EPA. has determined that these registrations address the concerns outlined in the June 9th Circuit Court of Appeals decision.”

The administration said it reviewed 65 new studies when making this decision, reviewed all literature and consulted with experts before making this decision.

In approving the herbicide for use in cotton and soybeans, EPA provided the following changes to the herbicide labels. These changes, and all label instructions, must be followed for legal use:

  • Downwind buffer of 240′ is required and a buffer of 310′ required where listed species are located.
  • Over-the-top application of dicamba of soybeans prohibited nationwide after June 30, and after July 30 in cotton.
  • An approved pH buffering agent will be required to be mixed for application to lower volatility. Buffering agents are registered with the EPA and must be documented each use.
  • Opportunities for growers to use hooded sprayers to reduce buffers.
  • States can expand over-the-top use to meet local needs by working with EPA.

“All of these efforts will help ensure there are not negative impacts on other farmers’ lands,” Wheeler continued. “States can further restrict, but they have to work with us and file the appropriate requests with EPA. We’re trying to have a national program here, we’re responding the the court’s concerns with a national cutoff.”

Dicamba’s use was hotly contested earlier this year. An appeals court vacated the product’s use in early June, which was followed by an exemption for use of stocks on-hand for farmers by EPA. The announcement brough confusion and brought dicamba’s compliance with the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) under the microscope. EPA took those concerns into consideration while making this decision.

“The economic damage that would result from not being able to use dicamba herbicides would be tremendous,” said Ken Fountain, National Cotton Council chairman. “We greatly appreciate EPA’s timely issuance of a new five-year label for the critical crop protection product for cotton farmers.”

Some have already expressed concerns about EPA’s most recent announcement.

“Rather than evaluating the significant costs of dicamba drift as the 9th Circuit told them the law required, EPA rushed re-approval as a political prop just before the election, sentencing farmers and the environment to another five years of unacceptable damage,” said George Kimbrell, legal director at the Center for Food Safety. “Center for Food Safety will most certainly challenge these unlawful approvals.”

This story will be updated with quotes and information as it becomes available.

Noxious weeds on your property: what is your responsibility?

Source: Ellen Essman, OSU

Despite the fact that “pumpkin spice” everything is back in stores, it is still summer, and if you’re anything like me, you’re still dealing with weeds. In fact, we have been receiving many questions about noxious weeds lately.  This blog post is meant to be a refresher about what you should do if noxious weeds sprout up on your property.

What are noxious weeds?

The Ohio Department of Agriculture (ODA) is in charge of designating “prohibited noxious weeds.”  The list may change from time to time, but currently, noxious weeds include:

  • Shatter cane (Sorghum bicolor)
  •  Russian thistle (Salsola Kali var. tenuifolia).
  • Johnsongrass (Sorghum halepense ).
  •  Wild parsnip (Pastinaca sativa).
  • Grapevines (Vitis spp.), when growing in groups of one hundred or more and not pruned, sprayed, cultivated, or otherwise maintained for two consecutive years.
  • Canada thistle (Cirsium arvense ).
  • Poison hemlock (Conium maculatum).
  •  Cressleaf groundsel (Senecio glabellus).
  • Musk thistle (Carduus nutans).
  • Purple loosestrife (Lythrum salicaria).
  • Mile-A-Minute Weed (Polygonum perfoliatum).
  • Giant Hogweed (Heracleum mantegazzianum).
  • Apple of Peru (Nicandra physalodes).
  • Marestail (Conyza canadensis)
  • Kochia (Bassia scoparia).
  • Palmer amaranth (Amaranthus palmeri).
  • Kudzu (Pueraria montana var. lobata).
  • Japanese knotweed (Polygonum cuspidatum).
  • Yellow Groove Bamboo (Phyllostachys aureasculata), when the plant has spread from its original premise of planting and is not being maintained.
  • Field bindweed (Convolvulus arvensis).
  • Heart-podded hoary cress (Lepidium draba sub. draba).
  • Hairy whitetop or ballcress Lepidium appelianum).
  • Perennial sowthistle (Sonchus arvensis).
  • Russian knapweed (Acroptilon repens).
  • Leafy spurge (Euphorbia esula).
  • Hedge bindweed (Calystegia sepium).
  • Serrated tussock (Nassella trichotoma).
  • Columbus grass (Sorghum x almum).
  • Musk thistle (Carduus nutans).
  • Forage Kochia (Bassia prostrata).
  • Water Hemp (Amaranthus tuberculatus).

The list of noxious weeds can be found in the Ohio Administrative Code section 901:5-37-01. In addition to this list, Ohio State has a guidebook that will help you identify noxious weeds in Ohio, which is available here.  It may be helpful to familiarize yourself with the weeds in the book, so you can be on the lookout for noxious weeds on your property.

When am I responsible for noxious weeds?

The Ohio Revised Code addresses noxious weeds in different parts of the code. When it comes to noxious weeds on the property of private individuals, there are two scenarios that may apply: noxious weeds on private property, and noxious weeds in line fence rows.

Noxious weeds on your property

If your property is located outside of a municipality, a neighbor or another member of the public can inform the township trustees in writing that there are noxious weeds on your property. If this happens, the township trustees must then turn around and notify you about the existence of noxious weeds. After receiving a letter from the trustees, you must either destroy the weeds or show the township trustees why there is no need for doing so. If you do not take one of these actions within five days of the trustees’ notice, the township trustees must cause the weeds to be cut or destroyed, and the county auditor will assess the costs for destroying the weeds against your real property taxes.  If your land is in a municipality, similar laws apply, but you would be dealing with the legislative authority, like the city council, instead of township trustees.

What if you rent out your land out to be farmed or otherwise?  Are you responsible for noxious weeds on your property in that situation?  The answer is probably.  The law states that the board of township trustees “shall notify the owner, lessee, agent, or tenant having charge of the land” that they have received information about noxious weeds on the property (emphasis added).  Furthermore, the law says that the “person notified” shall cut or destroy the weeds (or have them cut or destroyed).  In all likelihood, if you own the land, you are going to be the person who is notified by the trustees about the presence of weeds.  If you rent out your property to be farmed or otherwise, you may want to include who is responsible for noxious weeds in the language of the lease.

Noxious weeds in the fence row

The “line fence law” or “partition fence law” in Ohio requires landowners in unincorporated areas to cut all noxious weeds, brush, briers and thistles within four feet and in the corners of a line fence. A line fence (or partition fence) is a fence that is on the boundary line between two properties. If you fail to keep your side of the fence row clear of noxious weeds and other vegetation, Ohio law provides a route for adjacent landowners concerned about the weeds. First, an adjacent landowner must request that you clear the fence row of weeds and must allow you ten days to do so. If the weeds still remain after ten days, the complaining landowner may notify the township trustees of the situation. Then, the township trustees must view the property and determine whether there is sufficient reason to remove weeds and vegetation from the fence row. If they determine that the weeds should be removed, the township trustees may hire someone to clear the fence row.  Once again, if this occurs, the county auditor will assess the costs of destruction on your property taxes.

Being aware of noxious weeds is key. 

As a landowner, it is really important for you to keep an eye out for noxious weeds on your property.  If you keep on top of the weeds, cutting them or otherwise destroying them as they grow, it will certainly make your life a lot easier. You will avoid awkward conversations with neighbors, letters from your township trustees, and extra charges on your property taxes. Additionally, you will help to prevent the harm that noxious weeds may cause to crops, livestock, and ecosystems in general.

To learn more about Ohio’s noxious weed laws, you can access our law bulletin on the subject here.  While the bulletin addresses the responsibilities of landowners, it also goes beyond the scope of this blog post, addressing weeds on roadways, railroads, and public lands, as well as how to respond if your neighbor has noxious weeds on their property.  Additionally, the bulletin has a helpful section of “frequently asked questions” regarding noxious weeds.

Burndown Herbicides for No-till Wheat

Source:  Mark Loux, OSU

Herbicide options for burndown of existing weeds prior to planting of no-till wheat include glyphosate, Gramoxone, Sharpen, and dicamba.  Among these, the combination of glyphosate and Sharpen probably provides the best combination of efficacy on marestail, flexibility in application timing and residual control.  Dicamba labels have the following restriction on preplant applications – “allow 10 days between application and planting for each 0.25 lb ai/A used”.  A rate of 0.5 lb ai/A would therefore need to be applied at least 20 days before planting.  We do not know of any 2,4-D product labels that support the use of 2,4-D prior to or at the time wheat planting.  There is some risk of stand reduction and injury to wheat from applications of 2,4-D too close to the time of planting.  Liberty and other glufosinate products are also not labeled for use as a burndown treatment for wheat.  Sharpen should provide limited residual control of winter annuals that emerge after herbicide application, and the rate can be increased from 1 to 2 oz/A to improve the length of residual.  Gramoxone should also effectively control small seedlings of marestail and other winter annuals.  Be sure to use the appropriate adjuvants with any of these, and increase spray volume to 15 to 20 gpa to ensure adequate coverage with Sharpen or Gramoxone.

There are several effective postemergence herbicide treatments for wheat that can be applied in November to control these weeds, in fields where preplant burndown treatments are not used.  The most effective postemergence treatments include Huskie, Quelex, or mixtures of dicamba with either Peak, tribenuron (Express etc), or a tribenuron/thifensulfuron premix (Harmony Xtra etc).  We discourage application of 2,4-D to emerged wheat in the fall due to the risk of injury and yield reduction.

Herbicide Residue Considerations for Fall Cover Crop Establishment

Source: Alyssa Essman, Mark Loux, OSU

Herbicides with residual that are used in corn and soybeans can affect the establishment of fall-planted cover crops, and should be taken into account when planning cover crop practices and selecting species. Soil characteristics and weather also play a role in the persistence of residual herbicides, which can vary by field and year. More information is needed on rotational intervals for many cover crop species, and this information is often not included on herbicide labels. University weed scientists have studied the effect of residual herbicides on some of the most popular cover crop species in order to provide this information to growers. In general, residual herbicides that control grass weeds can hinder establishment of grass cover crop species. Broadleaf cover crop species are most impacted by group 2 (ALS inhibitors), 5 (PSII inhibitors), 14 (PPO inhibitors), and 27 (HPPD inhibitors) herbicides (Purdue University).

A multi-state study found that the general order of sensitivity of cover crops to herbicide carryover, from greatest to least sensitive, is:

  • Tillage radish > Austrian winter pea > crimson clover = annual ryegrass > winter wheat = winter oats > hairy vetch = cereal rye.

Soybean herbicides that tended to be most injurious were:

  • Fomesafen, pyroxasulfone, imazethapyr, acetochlor, and sulfentrazone.

Corn herbicide treatments that were most injurious to cover crops were:

  • Topramezone, mesotrione, clopyralid, isoxaflutole, pyroxasulfone, and nicosulfuron

(University of Missouri).

Below is a table of commonly used corn and soybean herbicides, the fall cover crops that are safe to plant in rotation, and cover crop species that may be injured following these herbicides (Adapted from Lingenfelter D. and Curran W., Penn State University).

 

 

Cover crops provide a multitude of benefits and their use is becoming an increasingly popular practice in Ohio. Including cover crops in rotation with agronomic crops to realize these benefits costs time and money. It is important to evaluate the potential risk of herbicide residue on the establishment of cover crops in order to ensure success. Residual herbicides applied at the time of planting typically interfere with cover crop establishment less than those applied POST. Weather can affect the persistence of herbicides also, especially rainfall in summer.  The risk of residual herbicides affecting cover establishment will be higher in areas that have been dry since herbicide application.  Risk will be lower where the herbicide application was followed by some wet weather to get herbicide degradation started, compared with an application during prolonged dry weather.  One of the least problematic cover crop species is cereal rye, which can be successfully established following a late corn or soybean harvest, and is tolerant to a most of the most commonly used corn and soybean herbicides. Weed control should continue to be the priority in selecting herbicides, and cover crop species selection should be based on potential injury and goals for the use of cover crops.  The introductory section of the “Weed Control Guide for Ohio, Indiana, and Illinois” has some of the same information presented here, and OSU weed scientists also summarize this in a video: https://www.youtube.com/watch?v=ylr0zGnXMfs

The following resources contain information on residual herbicides and cove crops also:

https://extension.psu.edu/corn-herbicides-and-rotation-to-cover-crops https://extension.psu.edu/soybean-herbicides-and-rotation-to-cover-crops

https://ipm.missouri.edu/IPCM/2020/3/coverCropTermination-KB/

https://ag.purdue.edu/btny/weedscience/Documents/covercropcarryover.pdf

We Now Turn Our Attention to Autumn Harvest Season

Source: Jim Noel

The cooler than normal blob of water in the eastern Pacific Ocean near the equator tends to push the first autumn freeze later than normal in our region. Therefore, there is no indication of an early freeze in September this year. It appears the first freeze for Ohio will not come until October either on schedule or a bit later than normal.

September looks to have the first half start cooler than normal followed by a return to normal temperatures for second half of the month.  Precipitation will be normal or sightly above normal for September. Normal rainfall is currently 1-1.5 inches per two weeks dropping to about an inch per two weeks for the second half of September. Even though we expect rainfall at or slightly above normal in September, there is a great deal of uncertainty due to the tropics and where those systems will travel. So you will want to pay attention to later outlooks at: https://www.cpc.ncep.noaa.gov

Rainfall for the first half of September will average 0.50-2.00 inches. The heaviest rains will likely surround the state of Ohio in most directions.

October into part of November looks to resume the above normal temperatures which should create an extended autumn this year. Rainfall remains highly uncertain but it appears near normal is the most likely outcome for October and November as we have some climate models showing above normal and some below normal rainfall.

The early outlook for winter calls for above normal temperatures first half and below normal temperatures second half. Precipitation is likely to become above normal with potential influences from the tropical Pacific Ocean.

 

Potential for Nitrate Problems in Drought Stressed Corn

Source: Peter Thomison, Laura Lindsey, OSU

Have very dry soil conditions increase the potential for toxic levels of nitrates in corn harvested for silage? Nitrates absorbed from the soil by plant roots are normally incorporated into plant tissue as amino acids, proteins, and other nitrogenous compounds. Thus, the concentration of nitrate in the plant is usually low. The primary site for converting nitrates to these products is in the growing leaves. Under unfavorable growing conditions, especially drought, this conversion process is slowed, causing nitrate to accumulate in the stalks, stems, and other conductive tissue. The highest concentration of nitrates is in the lower part of the stalk or stem. For example, the bulk of the nitrate in a drought-stricken corn plant can be found in the bottom third of the stalk. If moisture conditions improve, the conversion process accelerates and within a few days, nitrate levels in the plant return to normal.

The highest levels of nitrate accumulate when drought occurs after a period of heavy nitrate uptake by the corn plant. Heavy nitrate uptake begins at the V6 growth stage and continues through the silking stage. Therefore, a drought during or immediately after pollination is often associated with the highest accumulation of nitrates. Extended drought prior to pollination is not necessarily a prelude to high accumulations of nitrate. The resumption of normal plant growth from heavy rainfall will reduce nitrate accumulation in corn plants, and harvest should be delayed for at least 1 to 2 weeks after the rainfall. Not all drought conditions cause high nitrate levels in plant. If the soil nitrate supply is low in the dry soil surface, plant roots will not absorb nitrates. Some soil moisture is necessary for absorption and accumulation of the nitrates.

If growers want to salvage part of their drought damaged corn crop as silage, it’s best to delay harvest to maximize grain filling, if ears have formed. Even though leaves may be dying, the stalk and ear often have enough extra water for good keep. Kernels will continue to fill and the increases in dry matter will more than compensate for leaf loss unless plants are actually dying or dead. Moreover, if nitrate levels are high or questionable, they will decrease as the plant gets older and nitrates are converted to proteins in the ear.

Making Corn Silage in Dry Conditions

Source: Bill Weiss, OSU

The primary goal of making corn silage is to preserve as many nutrients in the corn plant as possible, to produce a feed that is acceptable to cows, and to minimize any risks associated with feeding the silage.  The following are important considerations for making corn silage when growing conditions have been dry.

Chop at the correct dry matter concentration (Editor’s note: see accompanying article “Corn Silage Harvest Timing”). Drought-stressed corn plants are often much wetter than they appear, even if the lower plant leaves are brown and dried up.  Before starting chopping, sample some plants (cut at the same height as they will be with the harvester) and either analyze DM using a Koster tester or microwave or send to a commercial lab (turn-around time may be a few days if you send it to a lab).  If the plants are too wet, delay chopping until the desired plant DM is reached.  The plant may continue to accumulate DM (increase yield), and you will not suffer increased fermentation losses caused by ensiling corn that is too wet.

Use a proven inoculant.  When silage is worth upwards of $80/ton (35% DM) reducing shrink by 2 percentage units has a value of about $2/ton. Homolactic inoculants (these are the ‘standard silage inoculants’) produce lactic acid which reduces fermentation losses but sometimes can increase spoilage during feedout. The buchneri inoculants increase acetic acid which slightly increases fermentation losses but greatly reduce spoilage during feedout.  Severely drought-stressed corn can have a high concentration of sugars because the plant is not depositing starch into the kernels.  High sugar concentrations can increase spoilage at feed out because it is food source for yeasts and molds.  Use of a good (from a reputable company with research showing efficacy) buchneri inoculant may be especially cost-effective with drought-stressed corn.

Check for nitrates.  Drought-stressed corn plants can accumulate nitrates which are toxic (as in fatal) to ruminants.  Silage from drought-stressed fields should be tested before it is fed.  Ideally, corn plants should be sampled and assayed for nitrates prior to chopping (most labs offer very rapid turn-around times for a nitrate assay).  If values are high, raising the cutting height will reduce nitrate concentrations in the silage because the bottom of the stalk usually has the highest nitrate concentrations.  Because forage likely will be very limited this coming year, do not raise the cutting height unless necessary to reduce nitrate concentrations.  Nitrate concentrations are often reduced during silage fermentation so that high nitrates in fresh corn plants may end up as acceptable concentrations in the fermented corn silage.  Silage with more than 1.5% nitrate (0.35% nitrate-N) has a high risk of causing nitrate toxicity in cattle.  See the following University of Wisconsin-Extension fact sheet for more details on nitrate toxicity: https://fyi.extension.wisc.edu/forage/nitrate-poisoning-in-cattle-sheep-and-goats/

Chop at correct particle length.  Do not chop too finely so that the effective fiber concentration of corn silage is reduced.  If the corn plants have limited ear development, fine chopping is not needed for good starch digestibility.  Generally, a theoretical length of cut (TLC) of about ½ inch is acceptable (longer with kernel processing and BMR silage) but this varies greatly between choppers and crop moisture concentration.  If using a Penn State particle size sieve, aim for 5 to 10% on the top screen.

Use a kernel processor.  Kernel processed corn silage tends to pack more densely than unprocessed corn silage which may help increase aerobic stability.  Kernel processing will also increase starch digestibility by breaking the kernel.  Poor starch digestibility is a major problem with dry, mature corn silage.

Reduce Shrink. Fill quickly, pack adequately, cover, and seal the silo as soon as you are done filling.  Practicing good silage-making techniques can reduce shrink by more than 5 percentage units, which can be worth more than $4/ton of corn silage (35% DM).

Preharvest Herbicide Treatments

Source:  Mark Loux, OSU

Information on preharvest herbicide treatments for field corn and soybeans can be found in the “Weed Control Guide for Ohio, Indiana, and Illinois”, at the end of these crop sections (pages 72 and 143 of the 2020 edition).  Products listed for corn include Aim, glyphosate, and paraquat, and for soybeans include Aim, paraquat, glyphosate, and Sharpen.  Some dicamba products are also approved for preharvest use in soybeans, and some 2,4-D products are approved for use in corn, and these are not listed in the guide.  The basic information for these follows:

Dicamba – soybeans:  Apply 8 – 32 oz/A (4 lb/gal products) as a broadcast or spot treatment after soybean pods have reached mature brown color and at least 75% leaf drop has occurred; soybeans may be harvested 14 days or more after a pre-harvest application; do not use preharvest-treated soybean for seed unless a germination test is performed on the seed with an acceptable result of 95% germination or better; do not feed soybean fodder or hay following a preharvest application of this product.

2,4-D – corn:  Labels vary with regard to types of corn that can be treated (some indicate no sweet corn) and based on whether crop is being grown for seed.  Apply after the hard dough (or dent) stage when silks have turned brown.  Weed seed production can be suppressed if applied prior to the flowering stage.  Allow 14 days between application and grain harvest.  Do not forage or feed corn fodder for 7 days after application.

Preharvest herbicide treatments are primarily intended to suppress/kill and dessicate weeds that can make harvest more difficult.  Products with contact activity will cause faster dessication and leaf drop of weeds, but may be less effective at killing weeds compared with systemic products.  Effective dessication with contact herbicides may still require a wait of a week or more following application, and this can can vary by weed.  The maximum paraquat rate is well below the rate required to actually kill large weeds, but it is still probably most effective for dessication of morninglory.  Glyphosate is not likely to be effective on marestail and waterhemp, and many giant ragweed populations, whereas dicamba or 2,4-D may with enough time between application and harvest.  The first frost will usually provide results similar to herbicides, so in a situation where crop maturity is delayed or the infested field can be harvested later in fall, consider whether a herbicide treatment is actually needed.  Preharvest treatments can also be effective for control of warm season perennials, and the systemic herbicides will be most effective where this is the goal.  Keep in mind also that for weeds with fruits that can contaminate harvest, such as black nightshade, the preharvest treatment can dessicate the foliage but will not affect the fruits, except that dessication of weeds may result in fruits closer to the soil.

Preharvest treatments are not intended to be used to speed up crop maturity, and largely do not accomplish this.  The restrictions on preharvest treatments that specify how mature the crop must be at time of application are designed to minimize any effect of herbicides on crop maturation.  Applying earlier than specified could interfere with that process.  The residue tolerances for this use are also based on a certain application timing, and failure to follow label guidelines could result in illegal herbicide residues in grain.  For crops being grown for seed, and for sweet corn and popcorn, be sure to check with the seed company/processor for approval prior to using any preharvest treatments.

Corn Silage Harvest Timing

Source: Mark Sulc, Peter Thomison, Bill Weiss, OSU

Silage harvest has begun in some parts of Ohio. Proper harvest timing is critical because it ensures the proper dry matter (DM) concentration required for high quality preservation, which in turn results in good animal performance and lower feed costs. The proper DM concentration is the same whether it is a beautiful, record breaking corn crop or a severely drought stressed field with short plants containing no ears.

The recommended ranges for silage DM are:

Bunker: 30 to 35%

Upright: 32 to 38%

Sealed upright 35 to 40%

Bag: 32 to 40%

Chopping corn silage at the wrong DM concentration will increase fermentation losses and reduce the nutrient value of the silage.  Harvesting corn too wet (low DM concentration) results in souring, seepage, and storage losses of the silage with reduced animal intake. Harvesting too dry (high DM concentration) promotes mold because the silage cannot be adequately packed to exclude oxygen. Harvesting too dry also results in lower energy concentrations and reduced protein digestibility.

Corn silage that is too dry is almost always worse than corn silage that is slightly too wet. So if you are uncertain about the DM content, it is usually better to err on chopping a little early rather than a little late. Follow the guidelines below to be more confident in your moisture assessment.

Kernel stage not a reliable guide for timing silage harvest

Dry matter content of whole plant corn varies with maturity.  Research has shown that the position of the kernel milk-line is NOT a reliable indicator alone for determining harvest timing. Geographic location, planting date, hybrid selection, and weather conditions affect the relationship between kernel milk-line position and whole plant DM content. In a Wisconsin study, 82% of the hybrids tested exhibited a poor relationship between kernel milk-line stage and whole-plant % DM. In Ohio we have seen considerable variation in plant DM content within a given kernel milk-line stage.

Appearance of the kernels should only be used as a guide of when to begin sampling for DM content, see section below When to Begin Field Sampling.

Determining silage moisture

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