Conditions Affecting PRE Herbicide Activation
October 30, 2023
Introduction
During this last season, many regions throughout the Midwest experienced drier soil conditions due to reduced rainfall. This has led to a lot of questions about performance issues across many preemergence herbicide products, regardless of brand name or chemical manufacturer. To help answer these questions, a summary on herbicide activation is provided below.
Activation of Soil-applied Residual Herbicide
- For most residual herbicides to work, the active ingredient must move from the soil surface into the rooting zone where weed seeds are present (usually approximately the top 0.25 to 0.75 in of soil).
- This process requires water to occur, usually via rainfall or irrigation. Producers who opt to use pre-plant incorporation (PPI) tillage systems can mechanically move the herbicide to the right soil depth but will still need adequate soil moisture (rain or irrigation water) to ensure the herbicide enters into soil solution.
- Once a herbicide is within the soil solution (e.g. soil water) it is available to be taken up by the germinating weed seedlings’ roots.
Because of the importance of water in these processes, the timing of rainfall and amount of rain (e.g. X in of rain within 7 to 14 days) have the largest impact on herbicide activation.
Other Factors to Consider:
Several other factors that can also influence the performance of soil-applied residual herbicides include:
1.SOIL:
- Soil texture
- Soil organic matter (SOM) percentage
- Soil moisture present at application
2.WEED SPECIES:
- Seed size
- Seed sensitivity to a given herbicide
3.HERBICIDE:
- Starting dose of the herbicide available
- Reactivation potential
- For example: herbicide products containing isoxaflutole (e.g. Balance Flexx® Herbicide, Trivolt™ Herbicide) can reactivate with approximately 0.50 in of rain to control later-emerging weeds.
- How well a herbicide moves into soil solution (water solubility)
- How likely, or strongly, a herbicide will bind to soil particles (soil mobility)
Why It Matters:
- Water solubility measures how likely a herbicide is to dissolve into a water solution.
- Herbicides which have higher water solubility tend to need less rainfall to fully activate than herbicides which have a low water solubility.
- Soil mobility measures how strongly a herbicide binds to soil particles.
- Soil particles are negatively charged and can adsorb herbicides to their surfaces. The strength of this binding depends primarily on the herbicide, and soil type/texture.
- A herbicide will not be readily available to detach and reenter soil solution if it binds too tightly to a soil particle, therefore limiting its soil movement and bioavailability.
- Inversely, a herbicide can enter or re-enter soil solution more readily if it binds weakly to soil, increasing its bioavailability.
Comparing Herbicides:
- A summary of common soil-residual herbicides is provided on the following page. Herbicide active ingredients were classified based on their water solubility and soil mobility using published classification guides within academic literature. An estimation of rainfall requirements is also provided using a modified scale published by PennState Extension in 2021.
- It’s worth noting that in general, the higher the water solubility and soil mobility, the more likely a product is to move within the soil profile. While this can aid in activation, it can also result in performance issues if too much rain is received.
- For example, dicamba is highly soil-mobile and water-soluble. In the Midwest, dicamba can provide residual control for up to 14 days of or until the first significant rainfall event is received.
- As a good rule of thumb, rainfall events totaling approximately 0.75 in within 7 to 10 days of application will provide ideal conditions for most herbicide products.
- If you have any questions or concerns about your herbicide selection, or the contents of this handout, please contact your local Bayer Crop Science Crop Protection representative.
Table 1. Water solubility and rainfall requirement estimates for common soil-residual herbicides used in either Corn or Soybeans.a
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- always read and follow pesticide label directions, insect resistance management requirements (where applicable), and grain marketing and all other stewardship practices. to review additional important information, click to open the menu below.expand_more
No dicamba may be used in-crop with seed with Roundup Ready® Xtend Technology, unless and until approved or specifically permitted, and no dicamba formulations are currently registered for such use in the 2024 season. Please follow www.roundupreadyxtend.com/xtendimaxupdates for status updates
Based on Court ruling and EPA Existing Stocks Order* on XtendiMax® Herbicide registration, Bayer has stopped its sale and distribution of XtendiMax® Herbicide. Visit our XtendiMax herbicide updates page to learn the latest www.roundupreadyxtend.com/xtendimaxupdates.
*Low-volatility dicamba products subject to the ruling include XtendiMax® herbicide with VaporGrip® Technology, Engenia® herbicide and Tavium® Plus VaporGrip® Technology herbicide.
The Preceon™ Smart Corn System, including short stature corn developed through traditional breeding, is expected to be available, subject to final commercialization decisions, for planting in the 2024 growing season.
Short stature corn developed through biotechnology is not currently available for commercial sale or commercial planting. Commercialization is dependent on multiple factors, including successful conclusion of the regulatory process.
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*Commercialization is dependent on multiple factors, including successful conclusion of the regulatory process. The information presented herein is provided for educational purposes only, and is not and shall not be construed as an offer to sell, or a recommendation to use, any unregistered pesticide for any purpose whatsoever. It is a violation of federal law to promote or offer to sell an unregistered pesticide.
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XtendiMax® herbicide with VaporGrip® Technology has been classified as pesticide and must be used with VaporGrip® Xtra Agent (or an equivalent volatility reduction adjuvant). For approved tank-mix products (including VRAs and DRAs), nozzles and other important label information visit XtendiMaxApplicationRequirements.com. Applicators must check XtendiMaxApplicationRequirements.com no more than 7 days before application of this product for additional labeling, including state restrictions. Where applicable, users must comply with additional requirements found on this website.
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Product Use Statement: Enlist E3® soybeans contain the Enlist E3 trait that provides crop safety for use of labeled over-the-top applications of glyphosate, glufosinate and 2,4-D herbicides featuring Colex-D® technology when applied according to label directions. Following burndown, the only 2,4-D containing herbicide products that may be used with Enlist® crops are products that feature Colex-D technology and are expressly labeled for use on Enlist crops. 2,4-D products that do not contain Colex-D technology are not authorized for use in conjunction with Enlist E3 soybeans. Warning: Enlist E3 soybeans are tolerant of over-the top applications of glyphosate, glufosinate, and 2,4-D. Accidental application of incompatible herbicides to this variety could result in total crop loss. When using 2,4-D herbicides, grower agrees to only use 2,4-D products that contain Colex-D technology authorized for use in conjunction with Enlist E3 soybeans. Always read and follow herbicide label directions prior to use.
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ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. FOR COTTON TREATED FOR MARKET YEAR 2024, EACH ACCELERON® SEED APPLIED SOLUTIONS OFFERING is a combination of separate individually registered products containing the active ingredients: BASIC Offering: fluoxastrobin, prothioconazole, metalaxyl, myclobutanil, and penflufen. STANDARD Offering: fluoxastrobin, prothioconazole, metalaxyl, myclobutanil, penflufen, and imidacloprid. ELITE plus Copeo® Offering: fluoxastrobin, prothioconazole, metalaxyl, myclobutanil, penflufen, imidacloprid, and fluropyram.
FOR COTTON TREATED FOR MARKET YEAR 2022 OR PRIOR, EACH ACCELERON® SEED APPLIED SOLUTIONS OFFERING is a combination of separate individually registered products containing the active ingredients: BASIC Offering: fluxapyroxad, pyraclostrobin, metalaxyl, and myclobutanil. STANDARD Offering: fluxapyroxad, pyraclostrobin, metalaxyl, myclobutanil, and imidacloprid. ELITE plus Poncho®/VOTiVO® Offering: fluxapyroxad, pyraclostrobin, metalaxyl, myclobutanil, imidacloprid, clothianidin, and Bacillus Firmus I-1582.
Please review each seed tag to determine active ingredients in the product offering on the seed. The distribution, sale, or use of an unregistered pesticide is a violation of federal and/or state law and is strictly prohibited. Not all products are approved in all states.
ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. FOR SOYBEANS SEED TREATMENT PRODUCTS APPLIED DOWNSTREAM, EACH ACCELERON® SEED APPLIED SOLUTIONS OFFERING is a combination of separate individually registered products containing the active ingredients: BASIC Offering: metalaxyl, penflufen and prothioconazole. STANDARD Offering: metalaxyl, penflufen, prothioconazol and imidacloprid. FOR UPSTREAM TREATED SOYBEANS, EACH ACCELERON® SEED APPLIED SOLUTIONS OFFERINGis a combination of separate individually registered products containing the active ingredients: BASIC Offering: metalaxyl, fluxapyroxad, and pyraclostrobin. STANDARD Offering: metalaxyl, fluxapyroxad, pyraclostrobin and imidacloprid. The distribution, sale, or use of an unregistered pesticide is a violation of federal and/or state law and is strictly prohibited. Not all products are approved in all states.
ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. FOR CORN, EACH ACCELERON® SEED APPLIED SOLUTIONS OFFERING is a combination of separate individually registered products containing the active ingredients: BASIC plus Poncho®/VOTiVO® Offering for corn: metalaxyl, ethaboxam, prothioconazole, fluoxastrobin, clothianidin, Bacillus firmus I-1582. ELITE plus Poncho®/VOTiVO® Offering for corn: metalaxyl, ethaboxam, clothianidin, and Bacillus firmus I-1582; prothioconazole and fluoxastrobin at rates that suppress additional diseases. BASIC Offering for corn: metalaxyl, prothioconazole, fluoxastrobin, ethaboxam, and clothianidin. ELITE Offering for corn: metalaxyl, ethaboxam, and clothianidin; and prothioconazole and fluoxastrobin at rates that suppress additional diseases. BioRise® Corn Offering is included seamlessly across offerings on all class of 2017 and newer products. The distribution, sale, or use of an unregistered pesticide is a violation of federal and/or state law and is strictly prohibited. Not all products are approved in all states.
Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.
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ONLY USE FORMULATIONS THAT ARE SPECIFICALLY LABELED FOR SUCH USES AND APPROVED FOR SUCH USE IN THE STATE OF APPLICATION. Contact the U.S. EPA and your state pesticide regulatory agency with any questions about the approval status of dicamba herbicide products for in-crop use with products with XtendFlex® Technology.
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Roundup Ready® Technology contains genes that confer tolerance to glyphosate. Roundup Ready® 2 Technology contains genes that confer tolerance to glyphosate. LibertyLink® Technology contains genes that confer tolerance to glufosinate. Roundup Ready® Flex Technology contains genes that confer tolerance to glyphosate. Roundup Ready technology contains genes that confer tolerance to glyphosate, an active ingredient in Roundup® brand agricultural herbicides. Roundup Ready 2 Xtend® soybeans contain genes that confer tolerance to glyphosate and dicamba. Products with XtendFlex® Technology contains genes that confer tolerance to glyphosate, glufosinate and dicamba. Plants that are not tolerant to glyphosate, dicamba, and/or glufosinate may be damaged or killed if exposed to those herbicides. Contact your seed brand dealer or refer to the Bayer Technology Use Guide for recommended weed control programs.
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