Posts Tagged ‘small grain weed control’

Fall Can Be a Good Opportunity for Getting a Jump on Next Year’s Weed Problems

Friday, September 21st, 2012

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Fall herbicide treatments have a nice fit for many situations such as small grain weed control, assisting with cover crop management, and reducing the severity of weed infestations for no till corn or soybeans.

Let’s look at each of these situations. Treating small grain fields with a late fall herbicide application has worked well in our trials. As discussed in earlier newsletters there are no herbicides labeled for applications at planting (a preemergence application). As a result we have lots of winter annuals that emerge with or shortly after the crop. Waiting until spring to control these weeds often results in poor control because the weeds are large, and often stressed from the winter weather. On the other hand, an application in the late fall is made while the weeds are relatively small and actively growing. Remember these weeds are winter annual and will continue to grow after a few hard frosts, and the soil temperatures allow for significant growth through the month of November. If there is a lot of spring emergence, then those weeds can be controlled with a herbicide applied in combination with spring nitrogen applications.

Controlling weeds in cover crops that will be used for early-season vegetables can be challenging in some springs (particularly henbit and chickweed). One way around this with a grass cover crop is using a herbicide in the fall to “clean up the cover crop”. Using a broadleaf herbicide such as Harmony Extra or 2,4-D in the fall will control many of the broadleaf weeds and not limit crop rotation in the spring (replant intervals are 1.5 to 3 months). Then when burning down the grass cover crop in the spring, the concern is killing the cover crop, and not worrying about the winter annual broadleaves that can be tough to control that time of year.

Finally, fall treatments for fields that will be planted to no-till corn or soybeans next spring. We have looked at a number of products that could be tankmixed with glyphosate or paraquat with the idea they would provide residual control for spring emerging plants and these fields will not need a burndown herbicide. UD Weed Science Research has not found a consistent herbicide program for this approach. Furthermore, for effective weed control in corn or soybean most fields need a residual herbicide applied prior to or at planting, so a trip across the field for a herbicide application is needed in the spring. Fall herbicide applications of glyphosate or paraquat with 2,4-D are an excellent way to limit the amount of weed biomass in the spring, which in turn allows the soil to warm up faster and possibly conserve moisture. In our experiences, the addition of residual herbicides to the tankmixture of glyphosate, paraquat, and/or 2,4-D has limited utility in most situations.

Considerations for Small Grains Weed Control

Friday, September 7th, 2012

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

For no-till fields, a non-selective herbicide needs to be used prior to planting. If grasses are present glyphosate is a better choice than paraquat. Fields worked with a vertical tillage implement for residue management still need a non-selective herbicide. These implements are not weed control tools.

There are few effective herbicides labeled for preemergence applications. Sharpen is labeled but we have limited data in the region to recommend it for either residual weed control or crop safety. Valor can be used at 1 to 2 oz with the burndown application, but there must be a 30 day period between application and planting wheat due to concerns with crop safety.

A few products can be used shortly after the crop has emerged. Axiom and Prowl H2O can be used at crop emergence (Axiom at the spike stage and Prowl H2O at 1 leaf stage); however they need to be tankmixed with other herbicides or followed by postemergence herbicides to provide a broad spectrum of control.

Products that provide postemergence control include: Harmony, Harmony Extra, Starane Ultra, Osprey, PowerFlex, Axial XL, 2,4-D, or dicamba. Others labeled with a limited fit include metribuzin, Finesse, and Maverick.

Cleaning Equipment to Prevent Spreading Weed Problems Around

Thursday, August 2nd, 2012

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

This summer has been very challenging for weed control so I want to remind you to not spread the problems around the farm or from farm to farm. I believe that a lot of our new weed infestations are due to transporting seed on equipment, whether the equipment is mowers, combines, or vegetable harvesters. I have seen a number of fields with heavy weed pressure due to escapes. Some of these are suspected to be resistant biotypes, others just hard to control weeds. If a particular weed is giving you headaches, wouldn’t you rather deal with it in only one field rather than all of your fields? Ask yourself, what you would do if you could no longer use the best herbicide for a problem weed. In vegetables, where we only have one or two broadleaf herbicides, what are your options when they are no longer effective?

Granted weeds that get blown around (like marestail or thistle) or spread (by birds like pokeweed) are difficult to prevent. Nevertheless, many of our problems are due to moving seeds from field to field on equipment; pigweed and lambsquarters are two that come to mind. Take the time to clean the equipment in the field before it gets moved and isolate where those infestations are located. This is true for all fields. A new weed or a resistant biotype does not just take over a field in one year. A few plants get started and they produce seeds which next year leads to more plants and more seeds (see where this is going?). Prevent the problems from developing and spreading. Clean the equipment thoroughly, before it leaves the field, and leave the weed seed where you found it.

Small Grain Weed Control

Friday, March 2nd, 2012

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

With the mild winter that we have had, small grain fields should be scouted for weeds, and applications should be made before the weeds get too large.

Be sure to read the herbicide label carefully because some products can be tankmixed with nitrogen but only if the nitrogen is no more than 50% of the spray solution (nitrogen is mixed 1:1 with water). A few specifics:

    · Osprey cannot be applied within 14 days of nitrogen application.
    · Harmony Extra can be applied with nitrogen, but use of surfactant differs depending on concentration of nitrogen and targeted weed species.
    · Axial XL and PowerFlex can only be applied with nitrogen if it is mixed 1:1 with water; also PowerFlex cannot be applied with nitrogen if the amount is more than 30 lbs of N/A.

Be sure to consider your rotation after small grains when you select your herbicides. Harmony Extra is very flexible for vegetable rotations; and Starane Ultra and Axial may require up to 120 days; while Osprey and PowerFlex cannot be rotated to vegetables for 9 to 12 mos. The most restrictive are Finesse and Maverick, which cannot be rotated to vegetables and require use of STS soybeans.


Cleaning Equipment to Prevent Spreading Weed Problems Around

Friday, September 9th, 2011

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

This summer has been very challenging for weed control so I want to remind you to not spread the problems around the farm. I have seen a number of fields with heavy weed pressure due to escapes. Some of these are suspected to be resistant biotypes, others just hard to control weeds and others are due to poor herbicide performance as a result of the summer drought. If a particular weed is giving you headaches, wouldn’t you rather deal with it in only one field rather than all of your fields? Ask yourself, what you would do if you could no longer use the best herbicide for a problem weed. In vegetables, where we only have one or two broadleaf herbicides, what are your options when they are no longer effective?

Granted weeds that get blown around (like marestail or thistle) or spread (by birds like pokeweed) are difficult to prevent. Nevertheless, many of our problems are due to moving seeds from field to field on equipment; pigweed and lambsquarters are two that come to mind. Take the time to clean the equipment in the field before it gets moved and isolate where those infestations are located. A new weed species or a resistant biotype does not just take over a field in one year. A few plants get started and they produce seeds which next year leads to more plants and more seeds (see where this is going). Prevent the problems from developing and spreading. Clean the equipment and leave the seeds where you found them.

Fall Control of Perennial Weeds

Friday, September 9th, 2011

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Fall is the best time to treat most perennial weeds because it is the time that plants are best able to move the herbicide to the roots where it will do the most good. When considering fall weed control the emphasis should be on what the patch of weeds will look like next spring or summer not the amount of dead stems this fall. Also, it is important to consider that a fall application will not eradicate a stand of perennial weeds; the fall application will reduce the stand size or the stand vigor. Fall applications of glyphosate is the most flexible treatment for most perennial weeds such as artichoke, bermudagrass, Canada thistle, common milkweed, common pokeweed, dock, hemp dogbane, horsenettle and johnsongrass. Rates of 1 to 1.25 lb acid per acre are consistently the most economical (or about 1.5X the normal use rate for annual weeds). Allow at least 7 days after treatment before tilling, mowing, or planting through the treated area. Dicamba (Banvel) at 2 to 4 pints is also labeled for artichoke, bindweeds, dock, hemp dogbane, horsenettle, milkweeds, pokeweed or Canada thistle. Allow 10 days after treatment before disturbing the treated plants. Planting small grains must be delayed after dicamba application 20 days per pint of dicamba applied. Fall herbicide applications should be made to actively growing plants. Allow plants to recover after harvest before treating them. Consider keeping the combine header as high as possible so the weeds are quicker to recover; or combining around the weed patches and then spraying those patches immediately after harvesting. Weed species differ in their sensitivity to frost; some are easily killed by frost (i.e. horsenettle) others can withstand relatively heavy frosts. Check the weeds prior to application to be sure they are actively growing.

Small Grain Herbicides

Friday, September 9th, 2011

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

For the past two weeks I have written about weed control for winter wheat. The concepts and ideas I talked about are the same for barley and other winter grains. The following table is a list of herbicides labeled for the various small grains.

 

Herbicide Form. Active Ingredient MOA /

Grp #

Winter Wheat

Barley

Oats

Rye

   

Broadleaf Weeds

 

 

 

Harmony SG 50 SG Thifensulfuron 2

XX

XX

XX

 

Unity 75 DF Thifensulfuron 2

XX

XX

XX

 

Harmony Extra 50 SG thifensulfuron +

tribenuron

2 + 2

XX

XX

XX

 

TNT Broadleaf 75 DF thifensulfuron +

tribenuron

2 + 2

XX

XX

XX

 

Starane Ultra 2.8 L Fluroxypyr 4

XX

XX

XX

 

2,4-D various 2,4-D 4

XX

XX

XX

XX

dicamba (Banvel) 4 S Dicamba 4

XX

XX

XX

XX

Finesse 75 DF chlorsulfuron +

metsulfuron

2 + 2

XX

POST only

 

 

   

Numerous Grasses / Broadleaves

 

 

 

Osprey 4.5 WG Mesosulfuron** 2

XX

 

 

 

Axiom 68 DF flufenacet + metribuzin 15 + 5

XX

 

 

 

PowerFlex 7.5 WG Pyroxsulam 2

XX

 

 

 

   

Strictly Ryegrass

 

 

 

Hoelon 3 EC Diclofop 1

XX

XX

 

 

Axial XL 0.42 L Penoxaden** 1

XX

XX

 

 

   

Seldom Recommended

 

 

 

Peak 57 WDG prosulfuron 2

XX

XX

XX

 

Stinger 3 L clopyralid 4

XX

XX

XX

 

Buctril 4 EC bromoxynil 6

XX

XX

XX

 

Aim 2 EC carfentrazone 14

XX

XX

XX

 

Prowl H2O 3.8 ACS pendimethalin 3

XX

 

 

 

Maverick 75 WG sulfosulfuron 2

XX

 

 

 

*Finesse is labeled in barley for postemergence applications only
**Also contains a safener

Related Articles:
Considerations for Weed Control in Winter Wheat I
Considerations for Weed Control in Winter Wheat II
Metribuzin Use in Winter Wheat

Weed Control in Winter Wheat

Friday, September 2nd, 2011

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

In last week’s issue of Weekly Crop Update I explained why we need to consider fall herbicide treatments for small grains. When splitting nitrogen applications in the spring, neither one of the timings are a good for herbicide application when trying to achieve spraying small weeds that are actively growing and achieve good coverage.

1. Weeds are more susceptible in the fall.

2. Fall applications match better with weed development.

3. Weed emergence is primarily in fall.

4. Fall herbicide applications are not influenced by temperature as much as spring applications.

5. Coverage is better with fall applications.

6. Spreads out the workload.

For no-till fields, a non-selective herbicide needs to be used prior to planting. However, we do not have effective herbicides labeled for preemergence applications, so it is important that the field be scouted to ensure the crop is at the proper stage for herbicide application.

A few products can be used shortly after the crop has emerged. Axiom and Prowl H2O can be used at crop emergence (Axiom at the spike stage and Prowl H2O at 1 leaf stage); however they need to be tankmixed with other herbicides or followed by postemergence herbicides to provide a broad spectrum control.

Products that provide postemergence control include: Harmony, Harmony Extra, Starane Ultra, Osprey, PowerFlex, Axial XL. Others labeled with a limited fit include metribuzin, Finesse, Maverick, 2,4-D or dicamba.

Control of specific problem weeds:

Annual bluegrass: fall applications of Osprey are the most consistent. Fall application of PowerFlex is also good. Maverick is a last resort type treatment in the spring (Maverick requires use of STS soybeans).

Annual ryegrass: fall applications of Osprey, PowerFlex, or Axial XL work extremely well. Spring applications of PowerFlex and Axial XL are options, but neither can be applied in nitrogen without reducing the amount of nitrogen applied.

Roughstalk bluegrass: Osprey or PowerFlex perform well on this species.

Speedwells: We have had limited trials with the speedwell species, but fall treatments seem to be most consistent. Harmony Extra has little to no effect on this species, PowerFlex in the spring was rated as fair to good; and slightly better than Osprey (fair). Research at Virginia Tech has shown good results with Finesse postemergence, but this treatment requires the use of STS soybeans. Initial results with metribuzin show some utility for speedwells.

Jagged chickweed: This is another species we have limited trials for, but fall applications seem much more effective than spring treatments. Osprey, Harmony Extra, and PowerFlex seem to work well when applied in the fall.

ALS-resistant chickweed: This species is on the move with more reports each year. Harmony Extra, Osprey, and PowerFlex are all ALS herbicides (Group 2) and have no activity on this biotype. Rather, Starane Ultra or metribuzin in the fall have been the best treatments.

ALS-resistant horseweed: Another species with no trials. Starane Ultra lists horseweed as a species it will suppress. We do know that 2,4-D will control horseweed in burn-down situations, but we have not looked at low rates of 2,4-D in wheat for crop safety and effectiveness.

One common weed that is not controlled with fall applications is wild garlic.  But this weed needs to be treated with Harmony Extra (or similar products) in the early spring, about the time we apply the second nitrogen application.  We need to think of wild garlic (a late emerging perennial) separately from the annual weeds mentioned above.

A rotation to vegetables is an issue with many of these herbicides, including Osprey, PowerFlex, Finesse, Maverick, and metribuzin. Starane Ultra is a 4 month rotation to most crops. As you can see there is no one program that will provide control of all of our problem species. In most situations, a fall treatment will outperform a spring application, and you need to select the herbicide(s) based on the problem weeds you have in your field.

Metribuzin Use in Winter Wheat

Friday, September 2nd, 2011

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Metribuzin is a product used for years in soybeans and other crops for broadleaf weed control (formerly called Sencor or Lexone). It has been labeled for use in winter wheat, but the label does not recommend its use in our region. Metribuzin is one of the active ingredients in Axiom, and so it has been used on a limited basis in our region. Since metribuzin is a generic product there are different products available, but most go by the name metribuzin or some close version of this spelling.

After identifying ALS-resistant chickweed and looking for potential control options I began testing metribuzin, along with a number of other weed specialists in the region. We have had good results with control and very little injury with metribuzin.

The label reads, “metribuzin alone or with tank-mixture treatments are recommended for use in the following states” and none of the states in the Mid-Atlantic region are included. On the other hand, the label does not prohibit the use of metribuzin. Metribuzin label does allow for tankmixing herbicides, to broaden the spectrum of control. We have not tested all the possible combinations with newer herbicides (Axial XL, Osprey, or PowerFlex).

Rate is dependent on soil type and growth stage. Application timing is from 2-leaf stage of the wheat until 4 tillers. We have tested metribuzin primarily for ALS resistant common chickweed, and rates of 2 to 4 oz applied with a nonionic surfactant have worked quite well.

Some precautions on the label include: Do not apply to stressed crop (including dormant, drought, frost damage, disease); do not apply with liquid fertilizer; do not use on soils with less than 0.75% organic matter; do not apply more than 0.5 inches of irrigation for the first irrigation after application and do not exceed 1 inch for any subsequent irrigation; wheat varieties differ in sensitivity (some are more sensitive than others).

Metribuzin is also labeled for barley, but we do not have experience with it.

Small Grain Weed Control

Friday, April 22nd, 2011

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

I have looked at a few fields of winter wheat or barley where growers were concerned about lack of weed control. Turns out these fields had jagged chickweed or speedwell in them, which spring applications of Harmony Extra do not control. Based on our observations either Osprey or Harmony Extra applied in the fall did do a good job of controlling jagged chickweed. Speedwells are not controlled with Harmony Extra. We have trials this spring and will have more to share with you by fall, but most of the products that can be sprayed this late in the season do not control speedwell.

For wild garlic control, Harmony Extra is the product of choice and the label allows two applications per season. But, be sure to read the label for the total amount that can be used per season.

Common chickweed

Common chickweed

Jagged chickweed