Category: Weed Management

Glyphosate-Resistant Annual Ryegrass in New York State: The Case of a Cover Crop Becoming a Problematic Weed

Vipan Kumar1, Mike Stanyard2, Antonio DiTommaso1

1Cornell University, School of Integrative Plant Science, Soil and Crop Sciences, Ithaca, NY; 2Cornell Cooperative Extension Northwest New York Dairy, Livestock & Field Crops, Newark, NY

Introduction

clump of mature ryegrass with seedheads
Annual ryegrass at heading stage

Annual ryegrass [Lolium perenne L. spp. multiflorum], also known as Italian rye, is commonly grown as a winter annual cover crop in New York State. Annual ryegrass was originally introduced from Europe to the United States during colonial times. About 3 million acres of annual ryegrass are currently grown as a cover crop in the United States. Annual ryegrass is often confused with perennial ryegrass (Lolium perenne L.) and rigid ryegrass (Lolium rigidum Gaud.), therefore close attention to identification characteristics between these species should be considered when distinguishing them. Annual ryegrass is generally taller than perennial ryegrass. For instance, annual ryegrass can grow 2 to 4 feet tall at full maturity, whereas perennial ryegrass can only grow 1 to 2 feet tall. Additionally, the red-tinged base of annual ryegrass also helps to distinguish annual ryegrass from perennial ryegrass, which is quite similar in growth habit and appearance. Annual ryegrass establishes quickly and grows vigorously and could become a weed if not properly managed. Annual ryegrass has been established as one of most problematic weeds in small grain cereals, row and vegetable crops as well as along roadsides in the United States.  A recent survey conducted by the Weed Science Society of America (WSSA) has ranked annual ryegrass as the most troublesome and difficult to control weed in winter cereal grains. In the U.S., annual ryegrass populations have developed resistance to five different herbicide sites of action (WSSA groups: 1 2, 9, 10, and 15).

Problem of Annual Ryegrass Termination with Glyphosate

Mature annual ryegrass is generally difficult to kill with glyphosate if it is applied under suboptimal weather conditions (for instance, air temperature below 50˚ F). However, in spring of 2023, a grower in Livingston County in western New York State reported an inadequate kill during the termination of an annual ryegrass cover crop with two sequential applications of glyphosate (Roundup® or similar brands) at field-use rates (32 fl oz/a of Roundup®) (Figure 1). Similarly, in spring of 2024 and 2025, two separate field crop producers from Ontario and Genessee Counties reported termination failure of annual ryegrass cover crops with glyphosate (Figure 1). Annual ryegrass plants surviving glyphosate applications from these three fields in Livingston, Ontario, and Genesse Counties recovered, fully head out, pollinated and produced viable seeds.

Three fields with clumps of ryegrass undeterred by the herbicides applied to them
Figure 1. Annual ryegrass cover crop plants surviving glyphosate applications in Livingston (A), Genesse (B), and Ontario (C) counties of western NY State (Photo credits: Mike Stanyard, CCE).

Glyphosate-Resistant Annual Ryegrass in New York

Greenhouse experiments were conducted at Cornell University Guterman Bioclimatic Laboratory in 2023 through 2024 to investigate if the annual ryegrass population from Livingston County, NY was resistant to glyphosate. Seeds of annual ryegrass plants surviving glyphosate applications from Livingston County, NY were tested along with a previously known glyphosate susceptible annual ryegrass population from Arkansas (Courtesy: Dr. Jason Norsworthy, University of Arkansas). Seedlings from both annual ryegrass populations (one from New York and the other from Arkansas) were grown separately in 4-inch plastic pots containing commercial potting mixture under greenhouse conditions. Seedlings of annual ryegrass from both populations were sprayed across a range of glyphosate doses (0, 3.3, 6.75, 13.5, 27, 54, 108, 216, and 432 fl oz/a of Durango®) along with 2% w/v ammonium sulfate (AMS) using a cabinet spray chamber when seedlings were at the 5- to- 6-leaf stage. Results indicated that Durango® applied at the field-use rate (27 fl oz/a) did not provide any control of the annual ryegrass population from Livingston County, NY at 21 days after application (DAA) (Figure 2). In contrast, plants from the Arkansas annual ryegrass population were all killed with this field-use rate of Durango® at 21 DAA. Furthermore, the annual ryegrass population from Livingston County, NY was not completely killed at the highest tested dose (432 fl oz/a) of Durango® at 21 DAA (Figure 2). Results further revealed that the annual ryegrass from Livingston, County had a 22-fold level resistance to glyphosate compared with the annual ryegrass population from Arkansas.

Pots showing green and healthy NY herbicide resistant ryegrass in pots next to dead Arkansas ryegrass
Figure 2. Response of annual ryegrass populations from Arkansas and New York State 21 days after treatment with Durango® (glyphosate) applied at 27 fl oz/a (field-use rate) and 432 fl oz/a (16 times the field-use rate) in greenhouse experiments at Cornell University (Photo credit: Vipan Kumar, Cornell University).

POST Herbicides for Termination of Glyphosate-Resistant Annual Ryegrass

An on-farm field study was conducted in spring of 2025 to test the effectiveness of alternative postemergence (POST) herbicides for termination of glyphosate-resistant annual ryegrass. A total of nine POST herbicide programs, including Select Max® (clethodim) at 16 fl oz/a, Assure II® (quizalofop) at 12 fl oz/a, Roundup PowerMAX® 3 (glyphosate) at 32 fl oz/a alone and in combination with Select Max® or Assure II®, Liberty® 280 SL (glufosinate) at 43 fl oz/a alone and in combination with Select Max® or Assure II®, and Gramoxone® SL 3.0 (paraquat) at 32 fl oz/a alone and in combination with Metribuzin 75 DF (metribuzin) at 4 oz/a were tested at their field-use rates for termination of glyphosate-resistant annual ryegrass. All herbicides were applied with appropriate adjuvants as recommended by each herbicide label using a CO2-operated backpack sprayer fitted with six AIXR110015 nozzles at 15 Gallons per acre, when annual ryegrass was headed out. Among all tested programs, Gramoxone® SL 3.0 alone or in combination with metribuzin, Liberty® 280 SL alone and in combination with Assure II® or Select Max® provided 92% to 100% control/kill of mature glyphosate-resistant annual ryegrass at 21 days after treatment (DAT) (Figure 3). In contrast, poor kill (10 to 25%) of glyphosate-resistant annual ryegrass was observed with Select Max or Assure II at 21 DAT.

Field plots with greenish ryegrass in nontreated and roundup plots and killed brown ryegrass in the other treatment
Figure 3. Visual response of glyphosate-resistant annual ryegrass terminated with nontreated (A), Liberty® 280 SL at 43 fl oz/a (B), Gramoxone® at 32 fl oz/a (C), and Roundup PowerMAX®

Conclusions and Ongoing Research

Findings from this research confirm the first case of glyphosate resistance in annual ryegrass in New York State. Alternative POST herbicide burndown chemistries (including Liberty® 280 SL and Gramoxone® SL 3.0) can be used to terminate glyphosate-resistant annual ryegrass at or prior to planting of cash crops. We are currently investigating the status of these annual ryegrass populations for multiple herbicide resistance and underlying mechanism(s) of glyphosate resistance. We are planning to conduct on-farm field studies at multiple locations in New York State and in the northeastern region for developing cost-effective integrated strategies to manage the seedbank of glyphosate-resistant annual ryegrass in various field crops, including small grain cereals, soybean, and corn.        

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Profitability of contrasting organic management systems from 2018-2021 in the Cornell Organic Cropping Systems Experiment

Kristen Loria1, Allan Pinto Padilla2, Jake Allen1, Christopher Pelzer1, Sandra Wayman1, Miguel I. Gómez2, Matthew Ryan1

1School of Integrative Plant Science, 2Charles H. Dyson School of Applied Economics and Management, Cornell University, Ithaca, NY 14853.

About the Cornell Organic Cropping Systems Experiment

The Cornell Organic Cropping Systems (OCS) experiment was established in 2005 at the Musgrave Research Farm in Aurora, New York to serve as a living laboratory for organic field crop management systems and provide practical insights to farmers. This ongoing long-term experiment compares four management systems along a dual spectrum of external inputs and soil disturbance over a multi-year crop rotation. An advisory board consisting of a dedicated group of organic farmers provides guidance on management decisions. The four systems are compared in terms of several sustainability indicators including yield, profitability, soil health and greenhouse gas emissions.

Both external input and soil disturbance gradients of the four treatment systems range from an extensive approach (low input) aimed at maximizing profitability by reducing costs via efficient resource use, to an intensive approach (high input), aimed at maximizing profitability by maximizing yield. Risk associated with low input management includes reduced crop production from inadequate soil fertility or weed competition, which can lead to decreased returns despite low input costs. Risk associated with high input management include diminishing returns where productivity increases are insufficient to justify additional cost.

The four management systems of OCS are: 1) High Fertility (HF), 2) Low Fertility (LF), 3) Enhanced Weed Management (EWM), and 4) Reduced Tillage (RT). In 2018, the crop rotation was modified from a three-year rotation to a  four-year rotation based on advisor input.: This article includes an economic analysis of the complete four-year crop rotation cycle from 2018-2021, which consisted of: 1) triticale / red clover, 2) corn / interseeded cover crop mix, 3) summer annual forage mix / cereal rye cover crop, 4) soybean (Figure 1).

Figure 1. Four-year crop rotation for the OCS phase 2018-2021.

Looking back: key takeaways from past OCS cycles

Caldwell et al. (2014) compared the yields and the profitability during and after the initial phase of organic transition in OCS following two three-year rotation cycles (corn-soybean-winter spelt/red clover) from 2005-2010. The first three years were considered as transitional production years in which crops could not be sold as certified organic, while crops produced from 2008 to 2010 could be sold as such. They used flexible interactive crop budgets to calculate relative net returns based on crop yields, tillage, weed management and fertility practices and, after the three-year transition period, compared relative net returns of organic production with concurrent organic price premiums to Cayuga County yield averages with conventional crop production inputs and prices. With a 30% organic price premium, the relative net return of organic production in all systems except RT was positive. The RT system was excluded from most analyses due to major challenges with experimental ridge-till practices resulting in decreased crop competitiveness. For both corn and soybean phases averaged across entry points, relative net return in the HF system was significantly lower than LF or EWM, due to higher input costs without corresponding higher yields in the HF system. For the spelt phase averaged across entry points, relative net return was higher in HF than LF and EWM (though not significantly so), with increased input cost in the HF system corresponding with a yield increase. The HF system led to higher weed biomass over time than the EWM and LF systems.

Trial design and system differences

The Cornell Organic Cropping Systems experiment uses a split-plot randomized complete block design with four blocks. The main plot treatments are the four management systems, whereas subplot treatments are two crop rotation entry points (A and B) . Entry points A and B represent different phases of the crop rotation. For example, in 2018 entry point A was planted to triticale while entry point B was planted to soybean.

Treatment systems are arranged along a fertility gradient as well as a soil disturbance gradient (Figure 3). For triticale, summer forage, and corn, the HF system had a 50% higher fertilization rate than RT and EWM. LF received fertilizer rates 50% lower than RT and EWM on the same crops. Intermediate fertilizer rates were applied to both EWM and RT. With respect to soil disturbance, EWM received additional weed management operations in several crops, while RT and LF incorporated an organic no-till soybean phase. Overall number of primary tillage events was not substantially different between systems, though mechanical cultivation was reduced in the soybean phase for RT and LF.

Figure 2. Contrasting management approaches in four systems.

Crop yields across management systems

No matter the management system, crop yield is a key component of profitability. Yields across all four years of the cycle comprising five harvested crops are summarized below. Ryelage was only harvested in EWM and HF systems as the cereal rye cover crop was rolled-crimped for no-till soybean in LF and RT systems. Triticale was grown as a grain crop in EWM and HF and taken for forage in the LF and RT systems. Organic no-till practices were implemented in RT and LF systems only, with soybean planted into tilled soil in HF and EWM. In entry point A soybean yields were comparable across systems, but in entry point B organic no-till soybean yields were nearly half of cultivated yields, likely due to dry conditions in the soybean phase in 2018.

Table 1. Mean yields for all harvested crops across four management systems and crop rotation entry point from 2018-2021. Within an entry point, systems sharing a letter were not significantly different (p < 0.05). Means were not compared between entry points. Triticale in RT and LF systems was harvested as forage (lbs DM/ac) while in HF and EWM it was harvested as grain (lbs/ac). Means were not compared.

Net return of management systems

Net return subtracts total variable costs (TVC) of production (inputs + labor + equipment-associated costs) from gross income (crop yield x price). Prices for corn and soybean were obtained from the USDA organic grain report (USDA National Organic Grain and Feedstuffs Report, February 4, 2022). As commodity price references for triticale grain, cereal rye forage and summer annual forage were unavailable, prices were based those typically fetched for organic forage in NY (MH Martens and P Martens, personal communications, 2022). All operation-related costs were taken from Pennsylvania’s 2022 Custom Machinery Rates (USDA NASS 2023). To correct the absence of an inflation adjustment, crop prices and input costs used in this study were converted to real values using the U.S. Consumer Price Index (CPI), with 2016 as the reference year.

All values are denominated in U.S. dollars and represent the average annual revenue, production costs, and net return over four years. In the case of crop rotation entry point A, the LF cropping system exhibited the lowest Total Variable Cost (TVC). Conversely, the HF system had the highest TVC, which despite higher grain and forage yields, resulted in lower net return than LF, EWM and RT systems (Figure 4).

Overall, across four years of the crop rotation and in both crop rotation entry points (i.e., temporal replications of the trial) the EWM system maximized net return via intermediate fertility rates and relatively high yields, though the HF system yielded higher in both entry points Net return for RT and LF systems was more variable between crops and entry points, possibly indicating higher weather-related risk associated with those system approaches, i.e. reliance on cover crops for fertility in LF, and use of organic no-till management for LF and RT (Figure 4).

Figure 4. Comparison of net return and components across four systems in entry point A.

In entry point A, LF demonstrated higher net return than both HF and RT despite lower yields due to reduced input costs. Net return in RT narrowly surpassed HF due to lower input costs as well. In entry point B, LF ranked lowest in net return due to low grain yields across the rotation. HF ranked second and RT ranked third, with RT characterized by intermediate to low yields with intermediate input costs.

Figure 5: Comparison of net return and components across four systems in entry point B.

When net return of each management system is summarized by entry point, high variability in profitability was observed across entry points, largely due to yield differences between growing seasons of the same crop. Because management was nearly identical for each crop within each system across entry points, temporal variation in net return can be attributed to yield response from seasonal environmental or climatic factors either directly or in interaction with management. This highlights the complexity of systems experiments given year-to-year variation (Figure 6).

Figure 6: Net return comparison of all four cropping systems and two entry points.

Conclusions

Differences in yield and subsequent net return between systems varied significantly across entry points, making it difficult to draw conclusions on the most profitable system overall. However, the HF system had the lowest net return across entry points, indicating that input levels were likely higher than optimum and yield gains to justify increased inputs were not realized. EWM had the highest net return across entry points, indicating that intermediate levels of fertility combined with additional cultivation passes in the row crop phases and full tillage soybean production “paid off” as a management strategy, with increased labor or fuel costs outweighed by increased yields. Of course, this assumes availability of labor required which may be out of reach for some farms, and can be challenged by finite weather-related windows conducive to field operations.

Variability in net return between entry points was particularly high for the LF and RT systems, largely driven by yield variation in the soybean phase between temporal replications. For entry point B, intermediate corn yields and low organic no-till soybean yields drove low profitability in LF, while relatively high corn yield in RT partially made up for low organic no-till soybean yield. This variation in soybean yield highlights a challenge with an organic no-till management approach that dry conditions can reduce yields to a greater extent compared to a tillage-based approach. However, in an extremely wet year where adequate weed control was not possible, no-till management may pay off.

By accounting for system profitability only, this article does not consider other tradeoffs between systems such as soil health outcomes or greenhouse gas emissions from contrasting management, additional sustainability metrics to evaluate organic production system success.

References

Caldwell, B; Mohler, CL; Ketterings, QM; and DiTommaso, A. (2014). Yields and profitability during and after transition in organic grain cropping systems. Agronomy Journal, 106(3):871–880.

Gianforte, L personal communication. 2022.

Jernigan, A. B., Wickings, K., Mohler, C. L., Caldwell, B. A., Pelzer, C. J., Wayman, S., and Ryan, M. R. (2020). Legacy effects of contrasting organic grain cropping systems on soil health indicators, soil invertebrates, weeds, and crop yield. Agricultural Systems, 177:102719.

USDA National Organic Grain and Feedstuffs Report, February 4 2022. Agricultural Marketing Service.

Martens, MH personal communication. 2022.

Martens, P personal communication. 2022.

Pennsylvania’s 2022 Machinery Custom Rates. USDA NASS.

For more results from the Cornell Organic Systems Experiment visit the Sustainable Cropping Systems Lab website.

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PRE and POST Herbicide Options for Weed Control in NY Field Corn

Vipan Kumar1, Mike Hunter2, Mike Stanyard3

1School of Integrative Plant Sciences -Soil and Crop Sciences Section, Cornell University, Ithaca, NY 14853, 2Field Crops IPM Coordinator, New York State Integrated Pest Management Program (NYSIPM), Redwood, NY, 3Cornell Cooperative Extension Northwest New York Dairy, Livestock, and Field Crops Program

As the spring weather is warming up in the New York (NY), some producers have started planting their field corn in various parts of the state. Planting is an important time to make decisions regarding herbicide selection for effective weed control throughout the field corn growing season. This article provides an overview and discuss some major herbicide options labelled in the NYS field corn.

Preplant burndown options

If no tillage is practiced, burndown herbicides such as glyphosate (Roundup PowerMax), glufosinate (Liberty), paraquat (Gramoxone), 2,4-D (2,4-D LV4) and saflufenacil (Sharpen) can be helpful to control winter annual weeds prior to corn planting. If glyphosate-resistant horseweed is present in the field, paraquat or combination of Sharpen + 2,4-D can be an effective burndown option. Make sure to use appropriate adjuvants as per each herbicide label to maximize the effectiveness of these burndown treatments. Burndown treatments should be made on actively growing winter annual weeds under optimum weather conditions (sunny conditions with air temperature above 55 F with no forecast of cold weather after applications).

Preemergence (PRE) herbicide options

Preemergence or soil-applied herbicides are generally applied after crop planting but prior to its emergence. However, sometimes these preemergence herbicides can also be tank-mixed with preplant burndown treatments. Several preemergence options are available to use in field corn in the NY. Majority of these preemergence herbicides belong to Group 5, 14, 15, and 27 although there are few options from Group 2, 3, and 4 as well. Major preemergence herbicide options (not a complete list) along with their active ingredients and sites of action (SOA) labelled in NYS field corn are listed in Table 1. Several of these preemergence options are available in premixtures with two or three active ingredients from different groups (multiple SOA) and generally provide longer soil residual activity on summer annual weeds. For example, Harness Extra and FulTime NXT are premixtures of atrazine (Group 5) and acetochlor (Group 15) whereas Lumax EZ and Lexar EZ are premixtures of atrazine (Group 5), s-metolachlor (Group 15), and mesotrione (Group 27). Premixtures containing active ingredients from Group 5, 15 and 27 are most commonly used in field corn for grass and broadleaf weed control. While selecting appropriate preemergence option and its application rate, producers should thoroughly read the herbicide label for target weed species, rotational restrictions on the subsequent crops, cover crops or intercrops as well as consider the soil type, texture, and other soil properties (organic matter, soil pH, etc.).

Table 1.  Preemergence herbicide options labelled in NY field corn.

Herbicides Active Ingredients SOA
Prowl Pendimethalin 3
Aatrex*¥ Atrazine 5
Outlook*¥ Dimethenamid 15
Surpass NXT*¥ Acetochlor 15
Dual Magnum*¥ S-metolachlor 15
Harness Xtra*¥, FulTime NXT*¥ Atrazine + Acetochlor 5, 15
Bicep Lite II Magnum*¥, Cinch ATZ Lite*¥ Atrazine + S-metolachlor 5, 15
Verdict*¥ Saflufenacil + Dimethenamid 14, 15
Harness Max*¥ Acetochlor + Mesotrione 15, 27
Acuron Flexi*¥ S-metolachlor + Bicyclopyrone + Mesotrione 15, 27
Acuron*¥ Atrazine + S-metolachlor + Bicyclopyrone + Mesotrione 5, 15, 27
SureStart II*¥ Flumetsulam + Clopyralid + Acetochlor 2, 4, 15
Lumax EZ*¥, Lexar EZ*¥ Atrazine + S-metolachlor + Mesotrione 5, 15, 27
Resicore*¥, Resicore XL*¥ Clopyralid + Acetochlor + Mesotrione 4, 15, 27

*Restricted Use Pesticides      ¥Not for use in Nassau and Suffolk Counties

Postemergence (POST) herbicide options

Postemergence herbicides are applied after emergence of corn and weeds. Redroot pigweed, Powell amaranth, common lambsquarters, common ragweed, horseweed, common waterhemp, velvetleaf, foxtails (yellow, green, and giant), fall panicum, etc. are most common spring/summer annual weeds in NY corn. In addition, Palmer amaranth populations have also been recently found from six counties. In addition, field bindweeds, horsenettle, milkweed, yellow nutsedge, Canada thistle, hemp dogbane, quackgrass, etc. are most common perennial weeds. Johnsongrass populations have also been reported from corn fields in some southern counties of NY. Several postemergence herbicides are available to use in NY field corn to control these annual and perennial weed species. Majority of these labelled postemergence herbicides belong to Group 2, 4, 5, 6, 9, 10, 15, and 27.

Table 2 highlights major postemergence herbicide options (not a complete list) along with their active ingredients and sites of action (SOA) labelled in conventional, Roundup Ready and Liberty Link corn hybrids. Several of these postemergence herbicides are broad-spectrum and can control both grass and broadleaf weed species. For instance, Postemergence applications of Capreno, Realm Q, Impact Core, Roundup PowerMax, Liberty can all help controlling grass and broadleaf weeds. In contrast, postemergence applied Aatrex, Banvel, Clarity, Callisto, Yukon are most effective controlling broadleaf weeds only. Producers should thoroughly read each herbicide label for target weed species, rotational restrictions on the subsequent crops, cover crops or intercrops during selection of appropriate postemergence option and its rate. Make sure to use appropriate adjuvants as per each herbicide label to maximize the effectiveness of these postemergence herbicides. If glyphosate- or triazine-resistant weeds are present, producers should select alternative effective two-pass herbicide program (preemergence followed by postemergence).

Table 2. Postemergence herbicide options labelled in NY field corn.

Herbicides Active Ingredients SOA
For Conventional Corn Hybrids
Accent Q, Steadfast Q Nicosulfuron, Nicosulfuron + Rimsulfuron 2
Permit, Resolve Q Halosulfuron, Rimsulfuron + Thifensulfuron 2
Banvel, Clarity, DiFlexx Dicamba 4
Aatrex*¥ Atrazine 5
Basagran; Moxy 2EC Bentazone; Bromoxynil 6
Callisto; Armezone/Impact; Laudis Mesotrione; Topramezone; Tembotrione 27
Yukon Halosulfuron + Dicamba 2, 4
Capreno*¥ Thiencarbazon + Tembotrione 2, 27
Realm Q Rimsulfuron + Mesotrione 2, 27
Impact Core*¥ Acetochlor + Topramezone 15, 27
Kyro*¥ Clopyralid + Acetochlor + Topramezone 4, 15, 27
For Roundup Ready Corn Hybrids
Roundup PowerMax; Durango DM Glyphosate 9
Halex GT Glyphosate + S-metolachlor+ Mesotrione 9, 15, 27
For Liberty Link Corn Hybrids
Liberty Glufosinate 10

*Restricted Use Pesticides      ¥Not for use in Nassau and Suffolk Counties

Note: For further information on currently labelled PRE and POST herbicide options in NY field corn, check the 2024 Cornell Guide for Integrated Field Crop Management (available online).

Field Study in 2023

A field study was conducted in Franklin and Jefferson counties, NY, in 2023 growing season to determine the effectiveness of various preemergence herbicides (Table 3) with and without atrazine (42 fl oz/a) for weed control in field corn. Both field sites had natural infestation of common lambsquarters. Field corn was planted around May 20 at both sites and selected preemergence herbicides were applied immediately after planting. Small plots (10 feet wide by 30 feet long) were used to test each herbicide program. Test plots were laid arranged in Randomized Complete Block Design (RCBD) with 4 replications. All PRE herbicides were applied using CO2-operated backpack sprayer equipped with handheld boom with four nozzles (AIXR 110015). Results indicated no significant differences in common lambsquarters control among all tested preemergence herbicides at 35 days after treatments. Across both sites in Franklin and Jefferson counties, preemergence applied Acuron Flexi, Harness Max, Resicore XL, and Verdict + Outlook alone or with atrazine provided 94 to 100% control of common lambsquarters (Table 3; Figure 1)). In 2024, we plan to evaluate these preemergence applied herbicides (with or without atrazine) across multi-locations again to validate these results.

Table 3. Percent common lambsquarters control at 35 days after applications of various preemergence herbicide premixes alone or in combination with atrazine in field corn during 2023 growing season in Franklin and Jefferson Counties, NY.

 

Herbicide Active Ingredient (s) Site of action (SOA) Rate (oz/a) Franklin Jefferson
% control
Acuron Flexi S-metolachlor/bicyclopyrone/mesotrione 15, 27 72 98 97
Aatrex 4L + Acuron Flexi Atrazine + S-metolachlor/bicyclopyrone/mesotrione 5,15,27 42 + 72 99 94
Harness Max Acetochlor/mesotrione 15,27 64 100 97
Aatrex 4L + Harness Max Atrazine + acetochlor/mesotrione 5,15,27 42 + 64 99 97
Resicore XL Clopyralid/acetochlor/mesotrione 4,15,27 96 99 98
Aatrex 4L + Resicore XL Atrazine + clopyralid/acetochlor/mesotrione 5,4,15,27 42 + 96 100 99
Verdict + Outlook Saflufenacil/dimethenamid-P + dimethenamid-P 14,15,15 16 + 4.6 99 94
Aatrex 4L + Verdict + Outlook Atrazine + saflufenacil/dimethenamid-P + dimethenamid-P 5,14,15,15 16 + 4.6 + 42 99 98
corn rows showing amount of weeds with different treatments
Figure 1. Side-by-side comparison of PRE applied Acuron Flexi and Harness Max with and without atrazine for common lambsquarters control at 35 days after application in Jefferson County, NY during 2023 growing season.

Disclaimer: Brand names appearing in this publication are for product identification purposes only. Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.

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2024 Updates on XtendiMax, Engenia and Tavium Registrations and Use in Dicamba-Tolerant Soybeans for NY Producers

Vipan Kumar1, Michael Helms2, Mike Hunter3, Mike Stanyard4

1School of Integrative Plant Sciences -Soil and Crop Sciences Section, Cornell  University, Ithaca, NY 14853, 2Cornell Pesticide Safety Education Program, 3Field Crops IPM Coordinator, New York State Integrated Pest Management Program (NYSIPM), Redwood, NY, 4Cornell Cooperative Extension Northwest New York Dairy, Livestock, and Field Crops Program

soybeanOn February 06, 2024, the U.S. district court in Arizona vacated 2020 registrations of three dicamba containing products (XtendiMax, Engenia and Tavium) for over-the-top (OTT) applications in dicamba-tolerant (Xtend and XtendFlex) soybean. In response to the U.S. district court ruling, the EPA issued an Existing Stock Order on February 14, 2024, that allows limited sale, distribution, and use of these dicamba OTT products that were already in the possession of growers, distributors or in the channels of trade and outside the control of pesticide companies as of February 06, 2024.

According to this Existing Stock Order, the manufacturers/registrants are no longer allowed to distribute these dicamba products in the US other than for disposal or lawful export. However, any dealer with an existing stock may sell these dicamba products until May 31, 2024 (cutoff date in New York (NY)). If soybean producers and applicators in NY are planning to grow Xtend or XtendFlex soybean and thinking to use these dicamba products in 2024 growing season, they should consider the following important points:

  • Only three dicamba containing products (XtendiMax, Engenia and Tavium) are labelled for OTT applications in Xtend or XtendFlex soybean.
  • Only certified applicators (private or commercial) are allowed to use XtendiMax, Engenia and Tavium herbicides for OTT applications in Xtend or XtendFlex soybean.
  • NY growers and applicators must read and understand the EPA’s Existing Stocks Order on the use of XtendiMax, Engenia and Tavium herbicides for OTT applications in Xtend or XtendFlex soybean.
  • Product that dealers had on hand prior to February 06, 2024 can be sold or distributed in NY through May 31, 2024 (the cutoff date for NY).
  • Applicators are allowed to use existing stocks of these dicamba products for OTT applications in Xtend or XtendFlex soybeans until June 30, 2024 (cutoff application date for NY).
  • The NY registrations for XtendiMax, Engenia and Tavium herbicides are set to expire on July 31, 2024. Unfortunately, there are no CleanSweepNY programs currently scheduled for 2024, so alternative disposal options may need to be found.
  • Mandatory dicamba training: Applicators must take mandatory annual dicamba training before applying XtendiMax, Engenia and Tavium herbicides in Xtend or XtendFlex soybean. These online dicamba trainings are offered by following manufacturers/registrants:

Training is reciprocal across brands and applicators only need to take one dicamba-specific training each year (i.e. only one training session either from BASF, Bayer or Syngenta). Contact your local dealer for further information.

  • Note that other dicamba-containing products (e.g. Banvel, Clarity and the many generics) are not labelled for OTT applications in Xtend or XtendFlex soybeans. However, some glyphosate products (Roundup PowerMax, Durango, etc.) can be used in OTT applications in Xtend or XtendFlex soybeans. Some glufosinate (Liberty) products can only be used for OTT applications in XtendFlex soybean, not in Xtend soybean.

Disclaimer: Brand names appearing in this publication are for product identification purposes only. Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.

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Cut-Off Date and Other Considerations for Xtendimax, Engenia and Tavium Applications in Dicamba-Tolerant Soybeans

Vipan Kumar1, Lynn Sosnoskie2, Mike Hunter3, Mike Stanyard4

1School of Integrative Plant Sciences -Soil and Crop Sciences Section, Cornell University, Ithaca, NY 14853, 2School of Integrative Plant Sciences – Horticulture Section, Cornell AgriTech, Geneva, NY 14456, 3Cornell Cooperative Extension North County Regional Ag Team, 4Cornell Cooperative Extension Northwest New York Dairy, Livestock, and Field Crops Program

With recent rainfall events and a new flush of summer annual weeds, NY producers are busy applying postemergence herbicide applications in row crops. If you have planted dicamba-tolerant soybeans and are planning for postemergence applications of dicamba-containing products (Xtendimax, Engenia, or Tavium), the following points need to be considered.

    • Xtendimax, Engenia and Tavium are the only dicamba-containing products that are labelled in dicamba-tolerant soybeans (Roundup Ready 2 Xtend or XtendFlex soybeans).
    • Be sure of your trait technology! Do not confuse Xtend traits with Enlist traits. Enlist traits provide crop resistance to 2,4-D but not to dicamba.
    • As per the revised labels in 2021, the legal last day of postemergence applications of Xtendimax, Engenia and Tavium in dicamba-tolerant soybeans is June 30.
    • Only certified applicators with dicamba training are allowed to apply these products.
    • Spray records need to be created within 3 days of applications of these products and should be maintained for 2 years. (Note: In New York State all applications of restricted use pesticides must be maintained for at least three years)
    • An approved drift reduction agent (DRA) and volatility reduction agent (VRA) should be included.
    • Only approved nozzles and tank-mix partners should be used for these products.
    • Wind speed at boom height should range from 3 to 10 miles per hour at the time of application.
    • As per the labels, maximum ground speed of sprayer should not exceed 15 miles per hour and maximum boom height above target pest or crop canopy should not exceed 24 inches.
    • Survey surrounding fields ahead of dicamba applications for sensitive crops (e.g., grapes, fruit trees, snap beans, fruiting vegetables (e.g., tomatoes, peppers), soybeans without dicamba-tolerance trait technology, etc…).
    • DO NOT apply these products if sensitive crops are in a downwind field or a run-off producing rain event is in the forecast in the next 48 hours.
    • After determining no adjacent sensitive crops are downwind, maintain a 240-feet downwind buffer.
    • Stop spraying if winds change direction towards sensitive crops.
    • DO NOT apply dicamba products during temperature inversions. Only spray between one hour after sunrise and two hours before sunset.
    • Ensure the entire sprayer system is properly cleaned before and after dicamba applications are made.
    • Applicator should consult Bulletins Live Two website to make sure no endangered species will be affected by these dicamba applications.

Disclaimer: Brand names appearing in this publication are for product identification purposes only. Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.

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Controlling Herbicide Resistant Waterhemp in Soybeans: 2020 Trials

Project Leaders

Bryan Brown, NYS IPM Program
Venancio Fernandez, Bayer Crop Sciences
Mike Hunter, Cornell Cooperative Extension
Jeff Miller, Oneida County Cooperative Extension
Mike Stanyard, Cornell Cooperative Extension

Cooperators

Derek Conway, Conway Farms
Jaime Cummings, formerly NYS IPM Program
Quentin Good, Quentin Good Farms
Antonio DiTommaso, Cornell University
Michael Durant, Lewis County Soil and Water Conservation District
Scott Morris, Cornell University
Ali Nafchi, Cornell Cooperative Extension
Ryan Parker, NYS IPM Program
Jodi Putman, Cornell Cooperative Extension
Joshua Putman, Cornell Cooperative Extension
Matthew Ryan, Cornell University
Lynn Sosnoskie, Cornell University
Ken Wise, NYS IPM Program

Funding Sources

New York Farm Viability Institute

Project Location

Trial locations in Seneca County but results are likely applicable statewide.

Abstract

Herbicide resistant tall waterhemp (Amaranthus tuberculatus) continues to be one of the most problematic weeds in US field crops. Thus far, it has primarily established in western and central New York. Our second year of trial results generally followed our first-year results. Herbicides in WSSA groups 2, 5, and 9 should not be relied on for waterhemp control. However, programs that included at least two non-chemical tactics or herbicides from groups 4, 14, or 15 were very effective. Seedbank modelling showed that control at 95%, 98%, or 100% would cause waterhemp emergence to increase, maintain, or decrease over time, respectively. Our partial budget analysis showed that profitability generally reflected yields. We also found that cereal rye (Secale cereale) residue can provide up to 87% control of waterhemp, which, if used in conjunction with a moderately effective herbicide program, could provide excellent control.

Background and Justification

Herbicide resistant waterhemp has been reported in many western and central NY counties. Soybean farmers have reported yield losses of 50% due to this weed, even after herbicide applications. Our greenhouse spray chamber tests and field trials from 2019 suggest resistance to WSSA herbicide groups 2, 5, and 9 (ALS inhibitors, photosystem II inhibitors, and EPSPS inhibitors, respectively). Our most effective control programs in 2019 relied on herbicides from other groups as well as additional physical or cultural tactics.

Waterhemp in other states has also developed resistance to different herbicide classes, including WSSA groups 4 and 14 (http://www.weedscience.org/Pages/Species.aspx). These groups include dicamba, 2,4-D, Valor, and Cobra. Resistance to these additional herbicides would make successful waterhemp control even more challenging.

Overwintering cover crops such as cereal rye can be sprayed or rolled-down to provide a weed suppressive mulch prior to soybean planting. In NY, Pethybridge et al (2019) showed that rolled rye achieved very effective suppression not only for weeds, but also for white mold. Furthermore, waterhemp and another problematic herbicide resistant weed in NY, called horseweed or marestail (Conyza canadensis), both have very small seeds that lack the stored energy to emerge through deep soil or mulch.

Objectives

Objective 1. Continue to evaluate the effectiveness of several different programs in controlling waterhemp in soybeans.

Objective 2. Assess the potential for rye cover crop mulch to suppress waterhemp emergence.

Procedures

Objective 1.

The trial site was in Seneca County, NY on a field of Odessa silt loam soil where waterhemp had survived various herbicide applications and produced seed in 2018 and was moderately controlled in 2019 in corn. In 2020, the ground was prepared for planting with a field cultivator on May 5 and planted on May 6. Pre-emergence applications were made after planting on May 8. Cultivation occurred on June 16 while the other post-emergence treatments were applied on June 18. All treatments are listed in Table 1. For fertilizer, DAP (10-46-0, 20 lbs N/A, 92 lbs P2O2/A) and muriate of potash (0-0-60, 125 lbs K2O/A) were applied prior to tillage and UAN (32-0-0, 30 lbs N/A) was applied at planting.

Plots were 25’ long and 10’ wide. Each treatment was replicated four times in a randomized complete block design. Spraying was conducted using a backpack CO2 sprayer with a 10’ boom. Spray volume was 20 gal/A applied at 40 psi. Row cultivation was achieved using a Double Wheel Hoe (Hoss Tools) with two staggered 6” sweeps (12” effective width). Two passes were made per row so that 24” of the 30” rows were cultivated.

Weed control was assessed August 15-22 by collecting all aboveground weed biomass within a 2 ft2 quadrat. The quadrat was used four times per plot, placed randomly in the two middle rows of each plot. Weeds were placed in paper bags and dried at 113 degrees F for 7 days, then weighed. Control was calculated by subtracting the biomass of each treated plot from biomass of the untreated plots, dividing by the biomass of the untreated plots, and multiplying by 100. Waterhemp was the dominant species present in this trial. Other species did not provide enough data for comparison. All waterhemp was manually removed immediately after the weed control assessments in order to prevent seed production.

Soybean yield was measured in mid-October by hand harvesting 20-row-feet from the two middle rows of each plot. In our partial budget analysis, gross income was calculated by multiplying the average yield per treatment across all sites for 2019 and 2020 by a soybean price of $10.05 per bushel (Langemeier 2018). Weed treatment costs were estimated based on personal communications with several local custom applicators.

To illustrate the effects of allowing waterhemp to produce seed, we produced a 10-year model of waterhemp emergence based on the number of seeds in the soil. The model was created based on observed waterhemp emergence and biomass production in 2019 and assumed a preceding three-year period of uncontrolled growth. We also assumed that 8% of the seedbank would emerge each year (Davis et al. 2016) and that for a given cohort, viability was reduced by 81% after one year, reduced by an additional 50% after years two and three (Heneghan and Johnson 2017), and reduced by 32% each subsequent year (Davis et al. 2016). We also assumed waterhemp would produce 441 seeds per gram of biomass (Heneghan and Johnson 2017) with a maximum waterhemp biomass of 386 g/m2 based on our results.

Objective 2.

On separate regions of the field near the plots described in Objective 1, we set up two trials investigating the use of cereal rye residue as a waterhemp suppressive mulch. While a cereal rye cover crop was not available for these trials, we transported rye residue from a nearby field and applied it immediately following planting. We used rates of 0, 3570, and 7140 lbs/A. The high- and mid-rates represent attainable rye biomass production in NY with- and without fertilizer, respectively (Mirsky et al 2013; Pethybridge et al 2019). Plots were 5’ by 10’ and each treatment was replicated four times per trial in a randomized compete block design. Waterhemp control was measured in the same manner as Objective 1.

Results and Discussion

Objective 1.

In 2020, waterhemp control was generally similar as 2019 (Table 2). Soil was dry at the time of pre-emergence application but we received 0.9” rain in the first 10 days after application, which was likely sufficient for activation. ValorSX did not perform as well as in the previous year, possibly related to weeds that had germinated prior to activation. WarrantUltra plus metribuzin remained very effective, providing further evidence that at least two effective modes of action ­– WSSA groups 14 and 15 in this treatment – are necessary for successful control.

In the post-emergence-only treatments, this year the Warrant improved the effectiveness of the Roundup and Xtendimax, probably due to our earlier planting and spray dates in 2020 that likely allowed more waterhemp to germinate after the post-emergence application, making use of the residual activity of the Warrant.

Similar to the previous year, the two-pass programs were generally more effective than the pre- or post-emergence-only programs. Having two passes reduces the burden on each pass. So if conditions are not optimal in one of the passes, the other pass can help ensure successful control is still achieved. They are also generally more expensive, but inclusion of more diverse chemistries and/or non-chemical tactics can reduce the risk of worsening the resistance problem.

In our partial budget analysis, the highest grossing (highest yielding) treatments were generally the most profitable (Table 2). The high yields of the row cultivation treatment may reflect the increase in soil aeration and nutrient release associated with soil disturbance. But also, due to small plot size there was some variability in yield results due to random chance.

Our waterhemp production and emergence model demonstrates that programs that control 100% of the waterhemp can result in greatly reduced emergence in subsequent years, whereas programs achieving 98% control or less will perpetuate the problem (Figure 1). Although 95% control would likely allow farmers to avoid a crop yield loss, the resulting waterhemp seed production and increase in emergence in subsequent years would likely make successful control more difficult over time.

Waterhemp congtrol graph
Figure 1. A model of waterhemp emergence for 95%, 98%, and 100% control (dotted, dashed, and solid lines respectively) over time. In this scenario, the newly established waterhemp population grows uncontrolled (shaded region) until year 4. The model shows that greater than 98% control is required to reduce populations over time.

Objective 2.

Across the two trials, cereal rye cover crop residue at high (7140 lbs/A) and medium rates (3570 lbs/A), representing biomass NY farmers could attain with- or without-fertilizer, provided an average of 87% and 73% waterhemp control compared to the untreated check, respectively. Used alone, these levels of control may be sufficient to avoid soybean yield loss. But this tactic could also be used in conjunction with a herbicide program. In such a system, 99% waterhemp control could be achieved with the high level of rye residue plus a herbicide program that only provides 92% control when used alone.

soybean weed comparison
Figure 2. Suppression of waterhemp by cereal rye residue applied at 0 lbs/A (photo A) and 7140 lbs/A (photo B).

References

Davis AS, Fu X, Schutte BJ, Berhow MA, Dalling JW (2016) Interspecific variation in persistence of buried weed seeds follows trade-offs among physiological, chemical, and physical seed defenses. Ecology and Evolution. 6:6836–6845

Heneghan JM, Johnson WG (2017) The Growth and Development of Five Waterhemp (Amaranthus tuberculatus) Populations in a Common Garden. Weed Science. 65:247–255

Langemeier M (2018) Projected Corn and Soybean Breakeven Prices. Department of Agricultural and Consumer Economics, University of Illinois at Urbana-Champaign. Farmdoc Daily 8:66

Mirsky S, Ryan M, Teasdale J, Curran W, Reberg-Horton C, Spargo J, Wells S, Keene C, Moyer J (2013) Overcoming Weed Management Challenges in Cover Crop–Based Organic Rotational No-Till Soybean Production in the Eastern United States. Weed Technology, 27(1), 193-203. doi:10.1614/WT-D-12-00078.1

Pethybridge S, Brown B, Kikkert J, Ryan MR (2019) Rolled-crimped cereal rye mulch suppresses white mold in no-till soybean and dry bean. Renewable Agriculture and Food Systems. doi:10.1017/S174217051900022X

Acknowledgements

Thank you to the New York Farm Viability Institute for supporting this project.

Disclaimer: Read pesticide labels prior to use. The information contained here is not a substitute for a pesticide label. Trade names used herein are for convenience only; no endorsement of products is intended, nor is criticism of unnamed products implied. Laws and labels change. It is your responsibility to use pesticides legally. Always consult with your local Cooperative Extension office for legal and recommended practices and products. cce.cornell.edu/localoffices

For more information on this project, check out: https://nysipm.cornell.edu/agriculture/weed-ipm/

 

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