What's Cropping Up? A NEWSLETTER FOR NEW YORK FIELD CROPS & SOILS
Burndown Herbicide Options in No Till Soybeans Mike Hunter CCE North Country Regional Ag Team Glyphosate resistant and multiple resistant (Group 9 and Group 2) marestail is spreading across New York State and may already be on your farm. If you don’t have it on your farm today the chances are you will at some point in the future. The presence of herbicide resistant marestail, tall waterhemp and palmer amaranth in New York is changing the way we manage weeds. We need to use burndown herbicide programs Figure 1. Resistant marestail in a field with more than one of soybeans in Jefferson County, NY. effective site of action to delay the development of resistant weeds and provide the best control. The use of glyphosate alone should no longer be considered a viable burndown herbicide program. In no-till, strip-till and very minimum till (i.e. one pass with a vertical tillage tool) situations burndown herbicides will be necessary to control emerged weeds prior to planting. Marestail can be either a summer annual or winter annual. The winter annual marestail rosettes are present right now and as it warms up these will begin to bolt and grow tall quickly. Once resistant marestail gets any taller than 6 inches it becomes very
VOLUME 30, NUMBER 3 May/Jun. 2020
difficult to control. Xtend, Enlist and Liberty Link traited soybeans are the choices that allow for effective postemergence control of multiple resistant marestail. In Roundup Ready or conventional soybean fields we have no effective herbicides for the postemergent control of multiple resistant marestail. Burndown herbicide programs for no till soybeans will include either glyphosate, glufosinate or paraquat tank mixed with 2,4-D and/or Sharpen (saflufenacil). The addition of metribuzin or Valor SX (flumioxazin) or both to the burndown program will provide residual control of marestail. If dandelions are also a problem in the field, consider using one of the listed programs that include 2,4-D ester. Don’t substitute 2,4-D amine formulations for the ester formulation. Apply 1 pint per acre of 2,4-D ester (4 lb gal formulations) to keep the preplant interval to 7 days, rates higher than that will lengthen the planting interval. If using a burndown option that includes Sharpen, apply 1 oz/acre for no preplant restrictions (except for coarse soils with 2% or less organic matter where the preplant restriction is 30 days). If Sharpen (used at 1 oz/ac) is included in the burndown program and tank mixed with a flumioxazin product the preplant restrictions will Weed Management
Burndown Herbicide Options in No Till Soybeans ............................................... 35 - 37
Disease Management
Wheat spindle streak mosaic in spring: A reminder to plant a resistant wheat variety in fall ....................... 38
Forage Management
Meadow Fescue -Alfalfa Mixtures in Nor thern New York ................................................................. 39 - 41
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Weed Management be a minimum of 14 days in no till (except for coarse soils with 2% or less organic matter where the preplant restriction is 30 days) and 30 days in conventional till regardless of the soil texture and organic matter.
+ s-metolachlor)) In Roundup Ready 2 Xtend (dicamba tolerant) soybeans only
Here are choices that include more than one effective site of action for the control of resistant marestail in soybeans:
Resistant tall waterhemp has been found in 12 counties in NYS. If resistant tall waterhemp is present on your farm the herbicide program will be slightly different from a multiple resistant marestail program. It is highly unlikely that a one pass, preemergence herbicide application will provide adequate control of resistant tall waterhemp in soybeans. It will require a two pass (Pre and Post) herbicide program to provide season long control to minimize the spread of seed.
• Sharpen (1 oz) + glyphosate + metribuzin
• 2,4-D ester (1 pint) + glyphosate + metribuzin (7 days prior to planting) o Can include a flumioxazin product (Valor SX, Valor XLT, Envive, Surveil o Or a premix containing metribuzin + flumioxazin (Trivence WDG or Panther Pro) • 2,4-D ester (1 pint) + Sharpen (1 oz) + glyphosate + metribuzin (7 days prior to planting) • Sharpen (1 oz) + glufosinate (Liberty) • Sharpen (1 oz) + glufosinate + metribuzin • 2,4-D ester (1 pint) + Sharpen (1 oz) + glufosinate + metribuzin (7 days prior to planting) • paraquat (Gramoxone) + metribuzin • 2,4-D ester (1 pint) + paraquat (Gramoxone) + metribuzin (7 days prior to planting) • Sharpen (1 oz) + glyphosate + dicamba (must use one of these: XtendiMax, Engenia, FeXapan, Tavium (dicamba + s-metolachlor)) In Roundup Ready 2 Xtend (dicamba tolerant) soybeans only
• Enlist One + glyphosate or Enlist Duo In Enlist soybeans only
If Roundup Ready or conventional soybeans are planted, make a preemergence application of a Group 15 herbicide (Dual II Magnum, Warrant, Outlook, EverpreX) + metribuzin and consider including flumioxazin in this tank mix as well. The postemergence herbicide choices will be limited to Reflex, Flexstar, Flexstar GT (if RR soybeans), Prefix (Dual Magnum + Reflex) or Warrant Ultra (Warrant + Reflex). If necessary, a late postemergence rescue treatment of Cobra can be used. If Xtend, Enlist or Liberty Link traited soybeans are planted, make a preemergence application of a Group 15 herbicide (Dual II Magnum, Warrant, Outlook, EverpreX) + metribuzin and consider including flumioxazin in this tank mix as well. In Roundup Ready 2 Xtend (dicamba tolerant) soybeans apply a postemergence application of XtendiMax, Engenia, FeXapan, Tavium. If Enlist soybeans are planted, apply Enlist or Enlist Duo. If Liberty Link soybeans are planted apply Liberty.
• Sharpen (1oz) + Enlist One + glyphosate (or Enlist Duo (2,4-D choline + glyphosate)) In Enlist soybeans only Always read and follow label directions prior to using
Here are choices that include only one effective site of action for the control of resistant marestail in soybean:
• 2,4-D ester (1 pint) + glyphosate (7 days prior to planting) • Sharpen (1 oz) + glyphosate
• glyphosate + dicamba (must use one of these: XtendiMax, Engenia, FeXapan, Tavium (dicamba
any herbicide. If you have any questions or would like more information regarding burndown herbicide programs for soybeans contact your local Cornell Cooperative Extension office.
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;
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Weed Management 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
Editor’s note: as of the publication date, three dicamba products have been given a cancellation order by the United States Court of Appeals for the Ninth Circuit. Read the EPA letter regarding the cancellation order. Also read the follow-up article Dicamba tolerant soybeans without dicamba.
What’s Cropping Up? Vol. 30 No. 3 Pg. 37
Disease Management
Wheat spindle streak mosaic in spring: A reminder to plant a resistant wheat variety in fall Gary C. Bergstrom Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell University
The Disease Wheat spindle streak mosaic (WSSM), caused by wheat spindle streak mosaic virus (WSSMV), is a disease that attracts little attention today because most of our widely grown, winter wheat varieties have significant levels of resistance to it. Yet WSSMV persists in New York soils in its protozoan vector ready to infect the roots of susceptible winter wheat varieties soon after planting. Swimming spores (zoospores) of the vector move through films of water in the soil and thus root infection is favored by moist conditions in fall. Plants remain infected over the winter dormant period but do not develop typical leaf symptoms until spring following a number of weeks of cool weather which favors virus replication and virus movement from roots into shoots. Temperature, not moisture, is what drives symptom development in spring since plants were already infected in the fall. Only winter wheats, not spring wheats, are affected by WSSMV because of the time it takes to build up virus levels in the roots and then the shoots. Symptoms Symptoms of WSSM first appear in late April or early May and are characterized by long, light green, spindle-shaped streaks with dark centers (Fig. 1). As leaves age, these streaks can become necrotic and resemble lesions of Septoria tritici blotch but without
dark fruiting bodies, i.e., pycnidia of Zymoseptoria, in evidence under a hand lens. Symptoms of WSSM fail to develop on new leaves that emerge when average daily temperatures exceed 60 F, though symptoms can reinitiate at later growth stages if persistent cool conditions occur during stem elongation, head emergence, and even grain-filling. Conditions have been ideal in April and May 2020 for development of WSSM. Symptom development is extremely sensitive to warm temperatures such that we have seen very little WSSM in years with high temperatures in early spring. Management What should a wheat producer do if she/he observes characteristic symptoms of WSSM this spring? There is no action that can be taken to mitigate WSSM in a growing crop – the yield damage, which can exceed 30% of the crop’s potential, has already occurred. However, diagnosis of the disease is a sure reminder that the variety they are currently growing is susceptible to WSSMV, and they need to choose a variety with at least moderate resistance for planting in the coming fall. This should elicit a conversation with your seed supplier about varieties resistant to WSSMV; some companies include that information on their website and in their seed catalogs but others do not. While the majority of available varieties express resistance to WSSMV, susceptible varieties appear in the seed market from time to time. Scores for WSSM also are included in winter wheat variety trial tabular results (https://blogs.cornell.edu/varietytrials/small-grainswheat-oats-barley-triticale/small-grains-cultivar-trialresults/) from Cornell’s Small Grains Breeding Program in years when symptoms are observed.
If you find more pronounced mosaic and fewer distinct streak symptoms in a variety designated to be WSSMV-resistant, your wheat could be infected by another soilborne, protozoan-transmitted virus called soilborne wheat mosaic virus (SBWMV), which we have diagnosed occasionally in isolated fields in southern areas of the Finger Lakes Region. Resistance to SBWMV is independent from resistance to WSSMV, though it is also available from wheat seed suppliers in Figure 1. Characteristic symptoms of wheat spindle streak mosaic on a choice of adapted varieties. wheat flag leaves at boot stage (A) and close-up of spindle streaks (B).
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Meadow Fescue-Alfalfa Mixtures in Northern New York J.H. Cherney1 and D.J.R. Cherney2 1 Soil and Crop Sciences Section, School of Integrative Plant Science; 2Animal Science Department; Cornell University
Over 90% of the alfalfa acreage in northern NY is seeded with a perennial grass. Meadow fescue is becoming increasingly popular for mixtures with alfalfa in New York. Most meadow fescue varieties were developed in northern Europe or at higher elevations in southern Europe. Meadow fescues are very winter hardy and tolerant of wet soils, they have been popular for both grazing and hay in Canada for decades. They have also been shown in NY and WI trials to be higher in fiber digestibility than other grasses more commonly used in mixture with alfalfa in the northern USA. One concern in the Northeast has been the seeding rate for meadow fescue with alfalfa. This grass is very aggressive when grown with alfalfa, particularly if soil conditions are not optimal for alfalfa production. We evaluated one diploid (SW Minto) and one tetraploid (Tetrax) meadow fescue at 5 seeding rates with either a reduced-lignin alfalfa (HarvXtra) or a conventional high-quality alfalfa (Hi-Gest 360). Procedure In May, 2018, we planted field trials on farms near Copenhagen in Jefferson County, NY (Site 1) and near Lowville in Lewis County, NY (Site 2). HarvXtra and HiGest 360 were seeded at approximately 15 lbs/a, with the same number of pure live seeds per sq. ft. for both alfalfa varieties. Tetrax meadow fescue was seeded at 0.5, 1, 2, 3, and 4 lbs/a, with the same number of pure
Forage Management
live seeds per sq. ft. for SW Minto. Tetraploid meadow fescue seed is up to three times greater in weight per seed compared to most diploid varieties. Plots at both sites were mowed to control weeds during the seeding year, and no data was collected. In 2019, three photographs were taken per plot (covering >70% of the plot area) prior to each harvest and were visually evaluated for grass percentage. Site 1 was harvested four times in 2019, on 6 June, 10 July, 12 August, and 18 September. Site 2 was harvested three times on 31 May, 15 July, and 14 August. At each harvest, forage quality and dry matter samples were collected prior to harvest, and forage quality samples were separated into alfalfa and grass components for laboratory analysis. Forage Yield Dry matter yield for Site 1 averaged 5.1 dry tons/acre and was 67% greater than Site 2. Site 2 had a soil pH of 6.4 at spring harvest in 2019 and had been adequately fertilized, but alfalfa never looked reasonably healthy and had a stunted appearance throughout the season. There was insufficient regrowth to justify a fourth harvest at Site 2. Yield at both sites was primarily attributed to spring growth. Site 1 yield distribution was 41%, 29%, 18%, and 12% for four cuts, while Site 2 yield distribution was 61%, 28%, and 10% for three cuts. Yield at both sites was influenced by grass seeding rate (Fig. 1).
Grass Percentage in Mixtures Struggling alfalfa resulted in very high grass percentages at Site 2 (Fig. 2). Although alfalfa was normal in appearance at Site 1, grass percentage was also high for the year after seeding. SW Minto was considerably higher in grass percentage of mixtures than Tetrax at both sites (Fig. 3). Grass percentage consistently agreed with grass seeding rate, but plots with the 0.5 lb/acre grass seeding rate were less uniform than at higher seeding rates. Visual estimation of a majority of the plot area provided more consistent results than calculating a grass percentage estimation based on a small, separated sample of alfalfa-grass Figure 1. Yield of alfalfa-meadow fescue as related to grass seedthat may or may not be representative of the entire plot. ing rate. What’s Cropping Up? Vol. 30 No. 3 Pg. 39
Forage Management
Figure 2. Grass percentage in mixtures for Tetrax meadow fescue in 2019 at two sites, averaged over harvests, weighted for dry matter yield.
Grass Quality Grass crude protein (CP) was related to the proportion of alfalfa in the mixture, as alfalfa provides grass with nitrogen (Fig. 4). Grass quality was very similar between sites. Across sites and harvests, Tetrax averaged 51% NDF, while SW Minto averaged 55%. Tetrax averaged 2.5% greater fiber digestibility (NDFD48h) than SW Minto across sites. NDF, ADF, and lignin tended to
Figure 3. Grass percentage in mixtures in 2019 for two meadow fescues averaged over two sites, and averaged over harvests, weighted for dry matter yield.
Figure 4. Crude protein in meadow fescue as influenced by grass seeding rate in alfalfa-grass mixtures in 2019. Average of two meadow fescue varieties and two sites. Harvests were also averaged, weighted for yield.Research has been conducted on a range of corn silage management topics in NYS over the past few decades. This summary is based on research that has included multiple sites and/or multiple years. Issues can be divided into two basic categories: Concerns prior to planting and concerns after planting. First, we prepare for the season, and then we have a limited number of options to react to the specific weather conditions of each season.
increase with increased grass seeding rate, while in vitro digestibility and NDFD decreased with increasing grass seeding rate. Grasses were harvested prior to heading, so we lack relative maturity information, however, these two grasses had the same spring heading date in Ithaca, NY in 2019. Meadow fescue averaged 82% NDFD over variety, site and harvest, while alfalfa averaged 56%. Alfalfa Quality With less than ideal sites for alfalfa production, grass dominated stands at all but the lowest grass seeding rates. Typical forage quality differences between reduced-lignin alfalfa and conventional alfalfa were not observed at these sites. HarvXtra was significantly lower in lignin (but only 2.7% lower) than Hi-Gest 360 at Site 2, and varieties did not differ for lignin at Site 1. HarvXtra had 4.2% greater NDFD than Hi-Gest 360 at Site 1, while alfalfa varieties did not differ for NDFD at Site 2. Alfalfa composition was not affected by grass seeding rate.
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Forage Management Harvesting grass with reasonably good forage quality in mixtures in the spring in NY often results in alfalfa harvested at relatively immature stages. For example, mixtures were harvested on June 6, 2019 at Site 1, and alfalfa averaged 30% NDF, while grass averaged 58% NDF. A common rule of thumb for alfalfa is harvesting in the spring at approximately 40% NDF after accumulating 750 growing degree days (GDDbase41F). The two sites reached 750 GDD on June 15 and June 17. Summary Meadow fescue is well adapted to colder environments and to somewhat marginal soils. Meadow fescue also is generally high in fiber digestibility compared to other cool-season grasses typically sown with alfalfa in the Northeast. It is very competitive with alfalfa under such conditions. If the goal of a mixed seeding for dairy forage is to produce a stand with 20-30% grass on soil not ideally suited to alfalfa, meadow fescue seeding rate should probably not exceed 1 lb/acre. While seeding rates can be controlled, climatic conditions cannot. Grass percentage in alfalfa-grass mixtures can be greatly affected by soil moisture, particularly for the first month after seeding. Shallow-rooted young grass seedlings are much more susceptible to drought than alfalfa seedlings. Reduced-lignin alfalfa may not perform as well on more marginal soils, as it generally does on good alfalfa soils. In these trials and other studies conducted in NY, Tetrax meadow fescue has been less aggressive with alfalfa than most meadow fescues evaluated and is often higher in fiber digestibility. There are over 120 meadow fescue varieties certified for sale in Europe; few are currently sold in North America. Optimum seeding rate for meadow fescue with alfalfa may vary for different cultivars and for different regions in the Northeast; more research on meadow fescue varieties is warranted. This research was supported by the Northern New York Agricultural Development Program.
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What's Cropping Up? is a bimonthly electronic newsletter distributed by the Soil and Crop Sciences Section at Cornell University. The purpose of the newsletter is to provide timely information on field crop production and environmental issues as it relates to New York agriculture. Articles are regularly contributed by the following Departments/Sections at Cornell University: Soil and Crop Sciences, Plant Breeding, Plant Pathology, Animal Science and Entomology. To get on the email list, send your name and email address to Jenn Thomas-Murphy, jnt3@cornell.edu.
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