Month: April 2020

Burndown Herbicide Options in No Till Soybeans

Mike Hunter, CCE North Country Regional Ag Team

plants in field
Resistant marestail in a field of soybeans in Jefferson County

Glyphosate resistant and multiple resistant (Group 9 and Group2) 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 with more than one 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 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 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.

Here are choices that include more than one effective site of action for the control of resistant marestail in soybeans:

    • Sharpen (1 oz) + glyphosate + metribuzin
    • 2,4-D ester (1 pint) + glyphosate + metribuzin (7 days prior to planting)
      • Can include a flumioxazin product (Valor SX, Valor XLT, Envive, Surveil)
      • 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
    • Sharpen (1oz) + Enlist One + glyphosate (or Enlist Duo (2,4-D choline + glyphosate)) In Enlist soybeans only

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 + s-metolachlor)) In Roundup Ready 2 Xtend (dicamba tolerant) soybeans only
    • Enlist One + glyphosate or Enlist Duo In Enlist soybeans only

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.

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.

Always read and follow label directions prior to using 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.

NYS IPM Field Corn Pheromone Trapping Network for 2020 Caught Moths in Mid-April!

Ken Wise and Jaime Cummings – NYS IPM Program

The NYS IPM Field Corn Pheromone Trapping Network has started trapping black cutworm (BCW) Agrotis ipsilon and true armyworm (TAW) Mythimna unipuncta moth flights in NYS. While it seems like it might be early, we have caught BCW and TAW moths this week in Western, NY in pheromone bucket traps. These moths migrate north on weather fronts from the southern US every year. Both BCW and TAW prefer feeding on grasses, such as grassy weeds, hay fields, small grains and corn.

Even though the number of moths caught this week were low, it indicates that they have arrived. From this point forward, we can set the “Biofix Date”. The biofix date is the point where we start to calculate the number of BCW and TAM degree-days. We can predict when the eggs that were laid by moths will hatch. Degree-days are calculated by taking the high and low temperature each day and averaging them from the biofix date. Next, subtract the base temperature of 50 degrees Fahrenheit, and this will give you the daily degree-days. Each day, add the number of BCW degree days and this will give you a total. When this reaches 90 BCW degree-days and 113 TAW degree-days, the eggs will start to hatch.

High Temperature + Low Temperature/2 – 500 F = daily BCW degree days

The easy way to calculate this is to use the NEWA Degree Day Calculator. This will calculate the degree-days from a weather station near your farm. Below is the information on degree-days for the lifecycle of BCW and TAW.

Black Cutworm Degree Days (Base 500 F)

Degree Days               Stage                           Feeding Activity

0                                  Moth Capture              Egg Laying

90                                Eggs Hatch

91-311 1st to               3rd Instar                     Leaf Feeding

312-364                       4th Instar                     Cutting Begins

365-430                       5th Instar                     Cutting Begins

431-640                       6th Instar                     Cutting Slows

641-989                       Pupa                            No feeding

Source: University of Minnesota Insect Pest of Corn-Stand Reducers Black Cutworm

True Armyworm Degree Days (Base 500 F)

Degree Days               Stage                           Feeding Activity

0                                  Moth Capture              Egg Laying

113                              Eggs Hatch

612                              Larval stages               Leaf Feeding

909                              Pupa                            No feeding

Source: Scouting for True Armyworms Is Highly Recommended in Small Grains and Early Corn-University of Kentucky

A large number of moths in a trap does not necessarily mean there is going to be damage in your corn. It will depends on where the moths lay eggs. If a trap near your farm has a large number of moths, it would suggest it is time to scout for larvae and signs of feeding damage.

A good time to start scouting is when you take plant population counts. BCW damage is easy to identify. The larvae will cut the plant near the base at the soil surface, while TAW will feed from the edge of the leaf to the mid rib.

black cutworm armyworm control tableBCW and TAW larvae are primarily nocturnal or night feeders. Normally, you will not see them during the day. BCW larvae are ½ inch to 2 inches. They appear as greasy gray with darker raised spots on each segment. They normally hide in the soil near the base of the corn or under residue that might be on the surface.

Black Cutworm
Photo by Ken Wise, NYS IPM

TAW larvae range from ½ to 1.5 inches long. They have orange and white strips running along the side. They also have a white strip running down the back. TAW will hide under surface residue, in the whorl of the plant or in cracks in the soil.

True Armyworm
Photo by Keith Waldron, NYS IPM

If you are at threshold, and the larvae are still small, try to treat only the infected corn and a 20 to 40 foot border around the area. When the larvae are large (1.25 inches +) they are harder to kill with an insecticide, and they will pupate soon. When pupating, they will stop feeding.

One of the issues with BCW and TAW is that there can be multiple flights on different weather fronts throughout the spring. This can cause multiple infestations with different sizes of larvae in a field. Still follow the economic threshold, and manage if needed.

Our pheromone-trapping network has 25 traps of each BCW and TAW placed in 19 counties across the state. The counts and degree-days for many locations across NY will be published weekly starting later in April in the NYS IPM Field Crops Pest Report .

References:

University of Missouri-True Armyworm

University of Minnesota Insect Pest of Corn-Stand Reducers Black Cutworm

Cornell University Field Crop-Armyworm

Purdue University-Armyworm

Purdue University-Black Cutworm

Cornell University Guide for Integrated Field Crop Management

Scouting for True Armyworms Is Highly Recommended in Small Grains and Early Corn-University of Kentucky

This work is funded by the NYS Corn and Soybean Growers Association.
NY Corn & Soybean Growers Association logo