Prowl vs. Sonalan in Peanuts (Prostko)

Recent price increases in Sonalan 3EC (ethalfluralin) have many growers taking a closer look at the cheaper priced pendimethalin formulations (Generic Prowl 3.3EC and Prowl H2O 3.8ASC) for use in peanuts.  With the exception of use in reduced tillage systems (i.e. Prowl is preferred there), there have been no consistent differences in peanut tolerance and weed efficacy between Sonalan and Prowl in peanut (Table 1).  It has always been my position that I have no preference between these two herbicides and that every peanut acre in Georgia should be treated with one of them.  If a grower is trying to save a few bucks on input costs, there is no reason not to use a cheaper formulation.

A couple of other comments about this issue:

1) The Weed Science Group at UGA has not been able to detect any major differences in the performance between Prowl 3.3EC and Prowl H20 3.8ASC.
2) 2016 estimated costs for 1 qt/A are as follows:  Sonalan 3EC = $10.50; Generic Prowl 3.3EC = $6.75; and Prowl H2O 3.8ASC = $8.75.
3) The lb ai/A for each formulation are slightly different at the 1 qt/A typical use rate as follows:  Sonalan 3EC = 0.75 lb ai/A; Generic Prowl 3.3EC = 0.83 lb ai/A; and Prowl H2O 3.8ASC = 0.95 lb ai/A.  This might need to be considered when figuring the true cost differences per acre.  

Indemnified Label Allows Dual Magnum Overtop of Summer Squash – Yellow and Zucchini (Culpepper)

Our new label allowing Dual Magnum over-the-top of emerged seeded and transplant squash grown on bare-ground or in a mulch system has been approved for use in Georgia.  The label should be self-explanatory….if not let me know as I was one of the authors.  

Getting Label: See steps below on obtaining the label (this information has been provided several times).

Grower Must Obtain His/her Label: For years we have stressed the importance of growers having a copy of our state local need (SLN) indemnified labels when making applications. This is getting more serious as the Department of Agriculture has started asking to see these labels doing routine visits; this is simply a response to the sheer volume of state local need labels we now have for Georgia growers.  To drive the point home here is an e-mail from GDA a few weeks ago “Dr. Culpepper, If you talk to any grower groups regarding any SLN approvals, please remind them that they must keep or present the SLN label for our inspectors during an audit or it is a label violation. Our inspectors find many individuals that cannot produce an SLN label during farm inspections.”

Thanks,

Eric Olsen

GDA”

OBTAINING LABELS FOR DUAL MAGNUM OR REFLEX:

Consider helping your growers by asking them to come in and visit with you to get their label. This is a great opportunity for young/new agents to obtain face time with our clientele!!

Agents MUST NOT give growers any indemnified label or make any verbal recommendations until the grower has the label.  Agents can help growers through the process but must make sure the grower clicks the “I ACCEPT” liability waver when obtaining the label.

Obtaining the label for First Time (first time takes a couple minutes, thereafter very simple):

1.  Go to www.farmassist.com

2.  Register the grower (or if you want a label register yourself); “register” is located on the 2nd tool bar in top middle of page.  After filling in information; click I accept at bottom.

3.  The next page that pops up asks about you; you do not have to fill this out if you do not want.

4.  Select products along top bar.

5.  Select indemnified labels (4^th one down).

6.  For state, select Georgia and for product, select Dual Magnum or Reflex (play around and see our other labels) and then submit.

7.  Select the Dual Magnum or Reflex crop of interest and submit.

8.  Accept waiver; this is the process making the label an indemnified label.  GROWER MUST CLICK THE  I ACCEPT KEY TO GET THEIR LABEL!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

9.  Print label and have present during application.

Sweet Potatoes and Cadre (Culpepper and Prostko)

Over the last several years, many county agents have asked about carryover concerns of Cadre applied in a peanut crop to sweet potato the following season.  The Cadre label restricts planting potatoes to 40 months after a Cadre application but the label does not specifically mention sweet potato.  Many have wondered is it really this serious?

According to the 2014 edition of the WSSA's Herbicide Handbook (page 256), the half-life of Cadre or the time in which about half of the Cadre would be gone is approximately 120 days.  In theory then, a June application of Cadre at 4 oz/A in peanut should be down to a rate somewhere between ½-1 oz/A approximately 8-12 months later when one would plant sweet potato.  

During 2015, a study was conducted where we applied ½ and 1 oz/A of Cadre prior to transplanting sweet potato.  Cadre at ½ oz/A caused 55% visual injury (stunting and discoloration) and reduced U.S. Number 1 fruit yield by 59%.  For Cadre at 1 oz/A, sweet potato injury reached 77% and reduced U.S. Number 1 fruit by 96%.  Simply, applications of Cadre in peanut should be avoided if you plan to rotate to sweet potato!!!!!.

Quick Responses (Prostko)

Here are a few answers to some questions that I have been receiving over the last few weeks or so:

1) How long do I have to wait to plant field corn if I use 1 pt/A of 2,4-D amine in my pre-plant burndown?

I usually recommend that growers wait at least 7-10 days after an application of 2,4-D amine to plant field corn.  If they need to plant sooner than that, the 2,4-D should be replaced with atrazine (1 qt/A).  When atrazine is used in a pre-plant burndown, field corn can be planted immediately.  However, I would still prefer planting into dead stuff. 

2) How long do I have to wait to plant peanuts if I use 1 pt/A of 2,4-D amine in my pre-plant burndown.

UGA research has shown that peanut planting can occur 7 days after an application of 2,4-D amine.

3) When tank-mixing glyphosate with atrazine or other herbicides for POST applications in field corn, is an adjuvant still needed?

If the formulation of glyphosate is "loaded" (i.e. already contains surfactants) then additional adjuvants (NIS or COC) are not really needed and may increase potential crop injury. Rather than re-invent the wheel, my weed science colleagues at Penn State University have put together an up-to-date list of the different formulations of glyphosate.  Check out the following link:

http://extension.psu.edu/agronomy-guide/pm/tables/table-2-4-1a

Ammonium sulfate (AMS) should always be used with any glyphosate treatment in situations where hard water (higher amounts of Ca, K, Mg, Na, etc.) is a problem.  The AMS must be added to the spray tank before the glyphosate.

4) What are some potential causes of "white" or off-color field corn seedlings?

a) stress inhibiting chlorophyll accumulation (i.e. compaction, cold temperatures)
b) low temperature sunscald & cold banding (cool, clear dewy nights followed by sunny mornings)
c) genetics
d) herbicide injury (Halex GT, Capreno, Laudis, glyphosate, others?)

5) What is the potential for Strongarm carryover in field corn in Georgia?

a) The labeled rotation restriction for field corn is 18 months.
b) Research and experience over the past 17 years would suggest that the risk of Strongarm carryover (irrigated fields only) would be low.  However, I will never say never! It would not be a good idea to plant field corn in a dryland field where Strongarm was used in peanuts the previous year!
c) If you suspect herbicide carryover in early-season field corn, I would strongly suggest that you collect both a soil pH and nematode sample because both of these problems are much more common than herbicide carryover.  Soil pH and nematode problems cause corn injury symptoms that look very similar to herbicide injury.

A Hose is a Hose? (Prostko)

Despite 15 years of on-farm use, I continue to receive frequent questions at winter grower meetings about cleaning sprayers of Valor residues.  The Valor label has very specific instructions about the correct method for sprayer clean-out.  These instructions are very labor/time intensive thus I am not sure if growers are willing to follow all the required steps, especially when in a hurry? Check out the June 3, 2013 UGA Weed Science Blog for the labeled instructions.  Valent also sells their own tank cleaner, creatively named Valent Tank Cleaner, to help with this problem.  Since the degree of tank-cleaning success seems to vary by grower, it might just be more of an art than science?

If you have a grower that continues to struggle with Valor clean-out issues, you might want to find out what kind of hoses are on the sprayer.  Although naked to the human eye, rubber hoses, especially older ones, often have cracks and crevices that can trap Valor residues which can then be released at a later date (Figures 1 and 2).  Valor-challenged growers might want to consider replacing older rubber hoses with new polyethylene hoses. Although they can be more expensive (~$3/ft), there is some evidence to suggest that this type of hose is less likely to hold on to herbicide residues.    

Figure 1.  Scanning electron micrograph of a brand new Goodyear rubber spray hose (black, Versigard, synthetic).  Photo courtesy of Drs. Gary Cundiff and Dan Reynolds, Mississippi State University, 2016. 

Figure 2.  Scanning electron micrograph of Goodyear rubber spray hose (black, Versigard, synthetic) used 8 times.  Photo courtesy of Drs. Gary Cundiff and Dan Reynolds, Mississippi State University, 2016.

Inzen Z Grain Sorghum and Zest Herbicide (Prostko)

The EPA recently approved the use of Zest herbicide for use in the Inzen Z ALS-tolerant grain sorghum system.  The following are some questions and answers that might be helpful to you:

1) What is Inzen Z herbicide-tolerant grain sorghum?

 Inzen Z herbicide-tolerant grain sorghum is sorghum that has been traditionally bred (i.e. NON-GMO) for resistance to certain ALS-inhibiting herbicides.  This technology was originally developed by Kansas State University and licensed to both DuPont and Advanta Seeds.  The resistance to these herbicides came from ALS-resistant shattercane, a close relative of sorghum.

2) What is Zest herbicide?

Zest is a new liquid formulation of the active ingredient, nicosulfuron.  You may recall that nicosulfuron is the active ingredient of the old corn herbicide sold under the trade name of Accent. Nicosulfuron is also an ingredient of several other corn herbicide pre-mixes such as Steadfast Q (nicosulfuron + rimsulfuron) and Revulin Q (nicosulfuron + mesotrione).  The use of Zest herbicide on conventional grain sorghum varieties will result in severe crop injury/death (Figure 1).  At the time this blog was penned, a Zest label was not yet available.  The official Zest label is anticipated in April??????

Figure 1.  Weed control in Inzen Z grain sorghum with nicosulfuron in 2013.  Conventional sorghum variety in right picture was completely killed by nicosulfuron.

3) Has the Inzen Z herbicide-tolerant sorghum been tested system in Georgia?

Yes! UGA weed scientists have worked with this technology for several years.  When available, it will be very beneficial for grain sorghum growers who struggle with Texas millet/buffalograss control.  However, resistance management will be crucial to the long-term viability of this technology. Georgia growers will be encouraged to start clean, use a residual herbicide at planting (Dual or Warrant), tank-mix atrazine with the POST application of Zest (Figure 2), and rotate crops.

Figure 2.  Weed control in Inzen Z grain sorghum - 2014.

4) Will Inzen Z grain sorghum hybrids be available to Georgia growers?

Since Georgia is not a leading producer of grain sorghum (only 50,000 acres planted in 2015), I expect that our growers will be on the end of the list in terms of getting hybrids that are well-adapted to our region.  In 2016, Advanta (Alta Seeds) is scheduled to release one Inzen Z hybrid to a small group of growers in Kansas and Texas.  In 2017, Advanta hopes to launch an additional two Inzen Z hybrids. Pioneer will potentially launch in 2018.  

UGA Weed Science Web-Page Updates (Culpepper and Prostko)

Numerous circulars and slide presentations have been added over the past few weeks for agent use on the UGA Weed Science Web-Page (www.gaweed.com).

Circulars (found on home page):

1.  Methyl bromide alternatives

2.  Weed control in broccoli, cabbage and cauliflower

3.  Weed control in watermelon

4.  Controlling Palmer amaranth in cotton

Slide Presentations (click weed management toolbar on homepage; then click slide presentations):

1. 2016 Cotton Weed Control
2. 2016 Fumigant Systems
3. 2016 Vegetable Pesticide Update: Weeds
4. 2016 Vegetable Weed Control
5. 2016 Watermelon Weed Update
6. 2016 Wheat Weed Control

7. Influence of Nozzle Type of Peanut Weed Control Systems

8. 2,4-D and Dicamba Resistant Soybeans in the Southeast

9. Influence of Tractor Speed and Boom Height on Spray Coverage