Earlier this week I posted links to BASF’s online dicamba training module. Here is another online training option from Monsanto. Again, Michael and myself encourage applicators to attend face-to-face trainings, but know that extenuating circumstance exist. You can access the training at the link below.
http://www.roundupreadyxtend.com/stewardship/education
As always, feel free to contact us with any questions or concerns.
BASF’s dicamba training module is now live! To access the training visit engeniastewardship.com and click on the training tab.
This online training module satisfies the US EPA requirement for mandatory dicamba training. It should be utilized as an alternative training opportunity for individuals who are unable to attend in-person trainings. BASF and Virginia Cooperative Extension strongly encourages in person training because it offers opportunities for dialogue and questions. Individuals can request in person trainings on engeniastewardship.com.
This online training module will NOT fulfill the Engenia® herbicide label requirement for training in the following states:
Charlie Cahoon and Michael Flessner, Extension Weed Specialists at Virginia Tech
Horseweed or Marestail
Horseweed is a winter or summer annual and a member of the asteraceae family. In the winter annual cycle, horseweed germinates in the fall and overwinters as a basal rosette. The following spring, the rosette bolts, reaching 1.5 to 6 feet in height. While most populations of horseweed in the region emerge in the fall, significant spring emergence can occur under certain conditions. Spring germinating horseweed does not form a rosette. Leaves are alternate, simple, linear to oblanceolate in shape, and lack petioles. Leaf margins are either entire or toothed. Flowers consist of numerous small heads arranged in a panicle with many white ray flowers and 20 to 40 yellow disk flowers. Seed are small and have a pappus of tan to white bristles (resemble dandelion seed). Seed are easily dispersed by the wind, allowing it to quickly spread to nearby fields and within fields.
Bolted horseweed. Virginia Tech Weed ID Guide.
Herbicide resistance: Regionally, glyphosate- and ALS-resistant horseweed are widespread. If you are unsure of the resistance status in your fields, assume resistance to glyphosate and ALS herbicides. Resistance to Gramoxone (PS I-inhibitor) has been reported in Delaware.
Management: Horseweed is more prevalent in no-till fields compared to fields prepared conventionally. Tillage can be useful in the long-term management of horseweed. Chemical control of horseweed is more consistent when the weed is in the seedling or rosette stage compared to bolting plants. Traditionally, glyphosate and ALS-inhibiting herbicides effectively controlled horseweed, however, biotypes resistant to these herbicides are wide-spread. Chemical control of glyphosate- and ALS-resistant horseweed requires a postemergence herbicide to control emerged horseweed and depending on application timing a residual herbicide for horseweed yet to emerge. Due to the prolonged germination period, horseweed seedlings can emerge 5 to 6 weeks after residual herbicide application, thus fall applications of residual herbicides often have limited effectiveness for spring emergence.
Herbicides used for emerged plants include 2,4-D (1 pt in the fall or 1 qt in the spring), dicamba, Liberty, Sharpen, or Gramoxone plus a triazine herbicide (atrazine or metribuzin). Preliminary research from Virginia and North Carolina suggest Elevore (a new auxin herbicide from Dow) also controls horseweed well. Fourteen days are required between Elevore application and corn or soybean planting and 30 days prior to cotton planting. Herbicides providing residual control include Valor SX, triazine herbicides (atrazine, simazine, and metribuzin), and ALS-inhibiting herbicides (if horseweed is not ALS-resistant).
Horseweed seedlings do not tolerate shade. Thus a well-established cover crop, or dense crop canopy can be very effective to manage horseweed infested fields.
Horseweed rosette. Virginia Tech Weed ID Guide.
Soybeans: The key to managing horseweed in in soybeans is to control it prior to planting. Horseweed needs to be controlled prior to bolting (grow upright); this may require an application weeks prior to planting. Glyphosate plus 2,4-D (1 qt/A), glyphosate plus dicamba or glyphosate plus Sharpen will effectively control glyphosate- and ALS-resistant horseweed when they are small. Pay attention to rotational restrictions of preplant burndown herbicides when planning burndown applications and planting. If horseweed are susceptible to the ALS-inhibiting herbicides, Classic-containing herbicides (i.e. Canopy, Valor XLT, Envive, Surveil) are effective. If applications are made early pre-plant, herbicides containing Valor SX or metribuzin or the Authority products can be included to provide residual control, or a second application of a non-selective herbicide may be needed at planting. Liberty or Gramoxone also control small horseweed and can be used as a part of the burndown application. If horseweed is present at planting, Gramoxone plus a residual product (Valor SX, Authority products, metribuzin, or Sharpen) is suggested in regions with later emerging horseweed. Foliar applied PPO-inhibiting herbicides (Blazer, Reflex or Flextar, Resource, and Cobra) DO NOT control emerged horseweed. For Liberty Link varieties, Liberty applied postemergence controls small horseweed. Classic and FirstRate are postemergence options where horseweed are susceptible to the ALS-inhibiting herbicides and are small.
Cotton: Like soybean, horseweed needs to be controlled prior to cotton planting. Burndown combinations of glyphosate plus 2,4-D/dicamba plus Valor SX is normally in order. Again, pay attention to plant-back restrictions when timing burndown applications. Glyphosate plus Sharpen is also effective, but requires a long waiting period between application and cotton planting.
Corn: In no-till corn, Gramoxone plus triazine, glyphosate plus atrazine plus 2,4-D or dicamba, and Liberty plus atrazine applied burndown of emerged seedlings and residual control of glyphosate- and ALS-resistant horseweed. Consult labels for waiting interval prior to planting corn. Atrazine alone will provide good residual control of horseweed. Dicamba and 2,4-D are the most effective postemergence herbicides. For small emerged horseweed, foliar applied HPPD-inhibitors or Liberty plus atrazine are effective.
Sorghum: Glyphosate plus Sharpen or Gramoxone plus a triazine applied burndown. Atrazine alone or in combination with Gramoxone applied preemergence for residual control and control of small emerged horseweed. Atrazine can be used postemergence for control of small horseweed. However, similar to corn, 2,4-D and dicamba are the most effective postemergence options.
Small grains: 2,4-D, dicamba, Quelex, or Huskie will provide effective postemergence control of horseweed in small grains. Harmony Extra is also very effective on small horseweed that is susceptible to ALS-inhibiting herbicides.
Fall fallow application: In fields with a history of horseweed, fall applied herbicides can be helpful in managing the weed. However, a fall herbicide application will not substitute for a spring burndown application. Target applications for emerged horseweed plants in the late fall after one to two killing frosts. 2,4-D or dicamba should serve as the base for these applications. Glyphosate is often suggested in combination with 2,4-D and dicamba to control other winter annual weeds.
To see similar information on other problematic weeds consult the Virginia Pest Management Guide: Field Crops at http://pubs.ext.vt.edu/456/456-016/456-016.html or the Mid-Atlantic Field Crop Weed Management Guide at https://extension.psu.edu/mid-atlantic-field-crop-weed-management-guide.
As always, don’t hesitate to contact Michael or myself with any questions or concerns.
The federal labels for XtendiMax® herbicide with VaporGrip® Technology (Monsanto), Dow DuPont ® FeXapan® herbicide Plus VaporGrip® Technology, and Engenia® Herbicide (BASF) now require additional training beyond a Pesticide Applicator’s License prior to use of these products “over the top” of dicamba-tolerant soybean or cotton. Training for 2018 will be provided by the registrants of the products (BASF, Monsanto, and Dow DuPont).
Agents/dealers interested in scheduling a training in their area or having a company representative deliver the training at an already scheduled meeting should contact the following company representatives:
|
Company |
Area |
Name |
|
Phone |
|
BASF |
Eastern Shore |
Gar Thomas |
NA |
|
|
BASF |
Rest of Virginia |
Kelly Liberator |
NA |
|
|
Monsanto |
Virginia |
Jeff Phillips |
||
|
Monsanto |
Southeast Virginia |
Ken Lampkin |
If you schedule a training with either BASF, Dow DuPont, or Monsanto, I would encourage you to make the other companies aware of the training planned in your area. That way, the companies can better coordinate their efforts to reach as many applicators as possible. Also, training by any of the three registrants will cover all dicamba products labeled for in-crop use to dicamba-tolerant soybean or cotton (applicators do not need to take training from the registrant of the specific dicamba product they intend to use).
In lieu of the face-to-face trainings, the companies also plan to have a web-based training that will satisfy applicator training requirements. Michael and I feel the face-to-face training will better prepare the applicators for the off-target challenges of dicamba. Web-based training can be used as a last resort if a grower is unable to attend face-to-face training. The following websites offer more information on web-based training:
https://www.roundupreadyxtend.com/Pages/default.aspx
There are a few trainings scheduled for the area. See the link below for an announcement from Monsanto for two training sessions in Suffolk, VA on Wednesday January 31st. BASF will be training applicators at the Virginia Grains & Soybean Conference (http://www.virginiagrains.com/annualconference/). The BASF training for this meeting is schedule for Wednesday February 21st at 12:00pm. I anticipate both companies to have other training; Michael and I will keep you updated as we receive word. Please help spread the word on these trainings, as many growers still do not know that training is required. Also,I would encourage you and your applicators to pre-register for the events so folks can plan accordingly.
With that said, feel free to reach out to Michael or me if you have any questions or concerns.
Charlie Cahoon, Extension Weed Specialist
Eastern Shore AREC-Virginia Tech
Italian ryegrass is one of the most common and troublesome weeds Virginia small grain producers face. The weed competes with wheat for essential nutrients, sunlight, and moisture and also interferes with harvest. In the past, growers have relied upon herbicides, such as Axial XL, Hoelon, PowerFlex, and Osprey, for control of Italian ryegrass. However, herbicide resistant Italian ryegrass biotypes have developed, limiting the herbicide options available to growers.
During the summer of 2016, the weed group at the Eastern Shore AREC traveled Eastern Virginia in search of resistant Italian ryegrass. To broaden the survey, we solicited samples from extension agents and members of the agriculture industry. In total, 82 samples were collected throughout Eastern Virginia (Image 1). The objective of this survey (and subsequent resistance screening) was to determine the distribution of resistant biotypes in Virginia; allowing growers to tailor management strategies specific to biotypes in their area.
Italian ryegrass heads collected during the summer were allowed to dry down and then threshed to separate the seed. Approximately 400 seed from each population were planted in a seed tray. Once Italian ryegrass reached 3.5 to 4 inches in height (1 to 2 leaf), plants were treated with a 1X rate of Axial XL (16.4 oz/A), Hoelon (43 oz/A), PowerFlex HL (2 oz/A), and Osprey (4.75 oz/A). A non-treated check from each sample location was included for comparison purposes. Visual injury was recorded at 28 days after treatment (DAT) for Italian ryegrass treated with Axial XL and Hoelon. PowerFlex HL and Osprey are both ALS-inhibiting herbicides and act much slower than the ACCase-inhibiting herbicides (Axial XL and Hoelon). Therefore, ryegrass treated with these products were evaluated 42 DAT. Also at 42 DAT, Italian ryegrass biomass (and subsequent % biomass reduction) was determined by cutting and weighing the above ground portion of ryegrass.
Image 1. Locations of 2016 Italian ryegrass samples collected.
Overall, approximately 23% of all samples collected were resistant to Axial XL (Image 2) compared to 30% that were resistant to Hoelon (data not shown). Most samples resistant to Hoelon were also resistant to Axial XL. However, for 6 samples, Axial XL remained effective despite poor Hoelon activity. Axial-resistant Italian ryegrass is widespread in two of Virginia’s major wheat producing regions (Eastern Shore and southern Chesapeake/Virginia Beach). Of the 14 samples collected in Northampton Co., 9 were found to be resistant to Axial XL (64%). In contrast, none of the 5 samples collected from Accomack Co. were Axial-resistant. In southern Virginia Beach and Chesapeake, 5 of 6 samples collected were resistant to Axial (83% of samples). Excluding the Eastern Shore and southern Chesapeake/Virginia Beach, only 9% of remaining samples were resistant to Axial XL; 1 samples east of Stony Creek in Sussex Co.; 1 sample south of Waterview in Middlesex Co.; 1 sample northeast of Newtown in King and Queen Co.; 1 sample northwest of Loretto in Essex Co.; and 1 sample south of Somers in Lancaster Co.
Image 2. Distribution of Axial-resistant Italian ryegrass in Virginia.
ALS-resistant Italian ryegrass is more widespread throughout eastern Virginia. Of the surveyed populations, 92 and 93% were resistant to Osprey and PowerFlex HL, respectively. Producers should keep in mind the presence of herbicide-resistant Italian ryegrass nearby does not automatically mean they have a resistant biotype on their farm. Fields with escaped Italian ryegrass were purposely chosen for this survey. It is best to rely on field history and performance of herbicides in the past when making management decisions. However, it is always a good idea to rotate modes of action to delay the development of resistant biotypes.
Unfortunately, if ryegrass is resistant to Axial XL and the ALS-inhibiting herbicides (Osprey and PowerFlex HL), there are no postemergence options left. In this situation, a residual product that includes pyroxasulfone (Anthem Flex and Zidua) is suggested delayed-preemergence or early postemergence. These products offer residual control of ryegrass only (they will NOT control emerged ryegrass). It is imperative that these products are applied and activated by a timely rainfall prior to ryegrass emergence. Rotating away from wheat also presents an opportunity to control Italian ryegrass (and prevent seed production) with glyphosate early burndown prior to planting corn or full-season soybean. Be aware that glyphosate-resistant Italian ryegrass is suspected in northeast North Carolina and eastern Virginia. In this situation, paraquat plus a residual herbicide like s-metolachlor applied to fallow ground during the fall would be in order.
Image 3. Axial XL-susceptible Italian ryegrass collected near Nassawadox, VA treated with no herbicide (left), Axial XL at 16.4 fl oz/acre (middle), and Hoelon at 43 fl oz/acre (right).
Image 4. Axial XL-resistant Italian ryegrass collected near Cheriton, VA treated with no herbicide (left), Axial XL at 16.4 fl oz/acre (middle), and Hoelon at 43 fl oz/acre (right).
Please join us for Virginia Tech’s Eastern Shore Agricultural Research and Extension Center (ESAREC) 2017 Research Field Day on Wednesday, September 13th. Registration is free, open to the public and will begin at 8:00 AM at the ESAREC complex located at 33446 Research Drive, Painter, Virginia 23420. The field tour will begin at 9:00 AM and conclude with lunch at 12:30 PM. See the attached flyer for specific projects to be highlighted and more information.
If you would like more information or are interested in sponsoring this event, please contact Lauren Seltzer at 757-414-0724 ext. 11 or email at mlpeyton@vt.edu.
Charlie Cahoon
Extension Weed Specialist, Virginia Tech
Warrant is an encapsulated formulation of the herbicide acetochlor and has widely become a part of our postemergence (POST) herbicide program in cotton. Although Warrant does not control emerged weeds, it does provide excellent residual control of pigweed, other small seeded broadleaves, and annual grasses (with the exception of Texas panicum). This makes it an excellent tank mix partner for glyphosate (Roundup) or glufosinate (Liberty) in our first, second, or both POST sprays, especially in fields heavily infested with glyphosate-resistant Palmer amaranth. However, because of its encapsulated formulation, Warrant can also be applied preemergence (PRE) to cotton. You may remember the days of using the EC formulation of acetochlor, known as Harness, in corn. This formulation was not encapsulated and significant injury would result if applied PRE or POST to cotton. This is not the case with Warrant. The encapsulated version affords much more cotton safety that the old EC formulation. In my experience, PRE applied Warrant has been very safe on cotton. As is the case with all residual herbicides, environmental conditions influence cotton response to PRE applied Warrant. Unfortunately, conditions we are currently experiencing in Virginia and northeast North Carolina; cool, wet soils and overall less than ideal weather for planting cotton are conducive to Warrant injury.
I saw this in my on research trials during the spring of 2016. Our cotton planted at the Tidewater AREC (near Holland, VA) on May 15, 2016 took approximately 9 days to emerge whereas cotton planted May 26, 2016 emerged in roughly 5 days. The weather was mostly to blame for the differences in vigor of the two plantings, but Warrant compounded the problem. So why the difference? We all know that cotton planted into cool wet soils is slow to emerge. Cotton tolerance to Warrant all hinges on the breakdown of the tiny capsules used to encapsulate acetochlor versus the time it takes for cotton to emerge. The key to avoiding injury from PRE applied Warrant is for cotton to emerge prior to the majority of these capsules breaking down and subsequent release of acetochlor.
Nontreated check plot.
Under ideal planting conditions this is not an issue. On the other hand, if cotton is slow to emerge, giving the capsules more time to breakdown and the seedlings have to push through a higher concentration of acetochlor, the potential for injury is greater. This is exactly what I saw in 2016 and have heard complaints about in years prior. Cotton that laid in the ground longer than usual and received Warrant PRE was stunted about 25%.
Weed control by Warrant alone.
My cotton eventually recovered and by the end of the season no yield differences were observed. Cotton that emerged quickly showed no injury in response to PRE applied Warrant and was one of the safest and cleanest treatments.
Weed control by Warrant plus 10 oz/A Reflex.
I routinely recommend Warrant PRE especially where Palmer pigweed is a problem. The fact is that all of our residual herbicides are capable of injuring cotton if the weather does not cooperate. As the planting progresses, I would advise you to factor in the planting conditions when choosing your PRE herbicides. Any conditions delaying emergence of cotton is conducive to injury from Warrant PRE. With that said, it may be wise to leave Warrant out of the tank until planting conditions improve. Do not let this stop you from using a residual herbicide all together. Alternatives to Warrant include Cotoran, Direx, Prowl, Reflex, and fluridone containing products (Brake FX and Brake F16). With all the herbicide resistance issues knocking on our door, it is imperative that we continue to use residual herbicides early burndown, around planting, and in-season. Once cotton land dries out and soil temperatures rise, Warrant will again be one of our best residual options.
Charlie Cahoon and Michael Flessner
Virginia Tech Weed Science
Over the past few days we have had several questions concerning replanting corn behind an already failed corn stand. Our biggest concern in this situation is how to terminate emerged corn from the first planting. The best option for small corn (4-8 inch) is clethodim (Select Max or generics). The label for Select Max (0.97 lb active ingredient/gal) specifies 6 oz/A must be applied at least 6 day prior to replanting. Clethodim products that contain 2 lb active ingredient/gal and are labeled for this situation should be applied at 3 oz/A, while adhering to the same plant-back restriction. As is the case with many weeds, timeliness is critical. Control of larger corn by clethodim is variable (> 8 inches).
Poor corn stand as a result of bird damage. Painter, VA 2017.
Producers not wanting to wait 6 days before replanting should use paraquat (at least 3 pt/A of a 2 lb/gal product or 2 pt/A of a 3 lb/gal product). Paraquat should not be used alone; adding atrazine (1 pt/A) and suggested adjuvants to paraquat will enhance control. Research conducted by Dr. Kevin Bradley (University of Missouri) and Larry Steckel (University of Tennessee) concluded Liberty did not consistently control Roundup Ready corn. Although not listed on the bag, many corn hybrids are tolerant to glufosinate (active ingredient in Liberty). For these reasons, producers should be wary of using Liberty to terminate a failed corn stand.
Another common question when replanting corn is whether to reapply residual herbicides such as atrazine. Atrazine and other residual herbicides should not be reapplied. If additional atrazine is desired in a postemergence application, just note that the cumulative total atrazine for your first and second planting of corn cannot exceed 2.5 lb active ingredient per acre per year. Other products have similar restrictions.
On a normal year, growers are usually asking if soybean can be planted behind corn. And our answer to this is usually no. This is mostly due to the fact that most everyone uses atrazine preemergence and planting soybean following atrazine if very risky. The label of most atrazine products says “Do not rotate to any crop except corn or sorghum until the following year, or injury may occur” and “If applied after June 10, do not rotate with crops other than corn or sorghum the next year, or crop injury may occur”.
