Zidua in Peanuts (Prostko)

It appears as though the following statement on the supplemental Zidua peanut label has many people confused:

"Apply Zidua as a broadcast spray to peanut from "at-cracking" stage to first true leaf stage through beginning of pod development."

A few points to consider:

a) For whatever reason, most people do not talk about peanut stages of growth as frequently as they do with other crops such as soybean and corn.  However, there are some "official" stages of growth for peanuts (Figure 1).

Figure 1.  Peanut stages of growth (K.J. Boote.  1982.  Peanut Science 9:35-40).

a) Zidua is not labeled for PRE use in peanut for good reason.  Peanuts do not have a 2X tolerance to PRE applications.  In my research since 1997, PRE applications of 2X rates have caused peanut yield losses ranging from 7% to 25%.  The 1X rate of Zidua is 1.5-2.0 oz/A (85WG) or 2.50-3.25 oz/A (4.17SC).

b) I have applied Zidua as early as V2-V3 (10 DAP) and as late as R6 (90 DAP) with no yield loss.  However, applications made at V2-V3 did cause more peanut injury than later applications but this injury did not result in yield loss.

c) I have applied the equivalent of 8 oz/A of 85DG or 13 oz/A of 4.17SC (4X rate) at 44-51 DAP (R1 to R2 stage) with no yield loss.  Not suggesting that growers do this but this is a good indicator of the tolerance of peanuts to POST applications of Zidua.

d) **Bottom line, growers should never apply Zidua PRE and POST applications can be made from the V2 through R3 stages of growth.

Tank-Mixing (Prostko)

Tank-mixing pesticides can be rather complicated especially when numerous products will be mixed.  Here are a few questions and answers based upon some recent inquiries that I have received:

1) Can I tank-mix Prowl EC and Prowl H20?

I have never have done this in my research plots but I recently conducted a small tank-mix test (Figure 1).  With good agitation, I did not observe any problems.  Do not mix these two herbicides together before putting in water.  They should be put in spray tank (already filled with water) separately.

Figure 1.  Prowl H20 3.8ASC + Prowl 3.33EC Tank-Mix (32 oz/A of each in 15 GPA, Prowl H20 was put in 1st)

2) Can I tank-mix dry and liquid Valor formulations together in a spray tank?

I have never done this either in my research plots but I conducted another small tank-mix test (Figure 2).  With good agitation, I did not observe any problems.  Remember, it is always a good idea to pre-slurry dry formulations in water before dumping into a large spray tank.

Figure 2.  Valor SX 51WG + Valor EZ 4L Tank-Mix (3 oz/A of each in 15 GPA)

3)  When tank-mixing various pesticides, what is the correct mixing order?  

The general formulation science mixing order is as follows:

a) water soluble bags (WSB)
b) water soluble granules (WSG)
c) water dispersible granules (WG, XP, DF)
d) wettable powders (WP)
e) water based suspension concentrates/aqueous flowables (SC, F)
f) water soluble concentrates (SL)
g) suspoemulsions (SE)
h) oil-based suspension concentrates (OD)
i) emulsifiable concentrates (EC)
j) surfactants, oils, adjuvants
k) soluble fertilizers
l) drift retardants

For those Millennials out there that sleep with their cell phones taped to their head or hands, there is an app called Mix-Tank (Precision Laboratories) that you might find useful (http://www.mixtankapp.com/). There might be some other apps out there that I am not yet aware of?

4) How do I mix Reflex and Gramoxone?

a) add 1/2 of the required amount of clean water into the spray tank
b) start up and maintain tank agitation
c) add NIS
d) add Reflex
e) add Gramoxone
f) add remaining amount of clean water

5) How do I mix Atrazine and Halex GT?

a) add 1/2 of the required amount of clean water into the spray tank and start/maintain agitation
b) add AMS (**only if water quality sample indicates need)
c) add NIS
d) add atrazine (make sure atrazine is fully dispersed before adding other products)
e) add Halex GT
f) add remaining amount of clean water

Using Pesticides Wisely (UPW) – Last Opportunity for 2018 Classroom Training! (Culpepper)

Over the next few days, please communicate with your growers/applicators that the very last opportunity to attend a UPW Classroom Training will occur on April 4th in Tifton. No additional UPW classroom trainings will be added for the 2018 production season. Please have your growers/applicators RVSP to the number provided in information listed below:

Region: South Central GA
Date: April 4, 2018
Time:  9 AM
Location:  UGA Tifton Campus Conference Center
RSVP #:  229-386-3328
Address: 15 RDC Road, Tifton, GA 31793

Questions of the Week? (Prostko)

Here a few questions that I received over the last few days or so.  Thought all might benefit?

1) How do I control ryegrass prior to planting peanuts if I suspect that I might have glyphosate resistance?

Select 2EC @ 8 oz/A or Select Max 0.97EC @ 16 oz/A (or generic equivalents) + 1% v/v COC  would be a good choice for this problem.  Remember that ryegrass stage of growth is important (Figure 1) and that temperatures below 50 F can significantly reduce control.  Higher rates of paraquat (3.5-4.0 pts of 2 lb ai/gal) can also be effective but 2 applications (10-14 days apart) may be needed.    

Figure 1.  Influence of clethodim timing on ryegrass control.  

2) What is the best nozzle to use for soil applied residual herbicides?

Generally, nozzle type is not as critical with soil applied residual herbicides when compared to postemergence herbicides.  For many years, I used a flat fan nozzle (11002DG) for all my weed control trials.  Recently, I started using an AIXR11002 nozzle as my standard.  I have also applied soil residuals with a TTI-02 nozzle.  I have not observed any reductions in the performance of residual herbicides when using these larger droplet nozzles.  Check out Figure 2 for a quick look at the coverage provided by these different nozzle types.  However, I would suggest that growers refer to the nozzle manufacturer for more specific information about the potential performance of nozzles with soil residual herbicides.

Figure 2.  Spray Coverage with Various Nozzle Tips

3)  What is ACURON herbicide?

Acuron, from Syngenta, is a mixture of s-metolachlor + atrazine + mesotrione + bycyclopyrone registered for use in field corn, seed corn, silage corn, sweet corn, and yellow popcorn.  Acuron can be applied preemergence or postemergence depending upon the type of corn.  I have tested Acuron for a number of years and it is a very good product.  It would be especially useful to growers who are dealing with glyphosate, atrazine, and/or ALS resistant weeds.  But in the absence of resistance, it's very difficult to for most higher priced new herbicides to beat the cost-effectiveness of a timely postemergence application of glyphosate + atrazine + Prowl tank-mixture in Georgia.   I do not have an exact figure but I have heard that Acuron is a bit pricey?

4) What is SHIELDEX herbicide?  

Shieldex, from Summit Agro USA, contains the active ingredient topyralate.  Shieldex is labeled for postemergence use in field corn, sweet corn, and popcorn.  Shieldex has the same mode of action as several other corn herbicides such as Callisto (mesotrione), Impact (topramezone), and Laudis (tembotrione).  All of these herbicides are HPPD inhibitors (WSSA MOA #27).  There are 2 good reasons why Georgia corn farmers need not worry about this herbicide:  1) it is not yet labeled in GA; and 2) I only have 1 field trial with this product (i.e. not enough data to make a solid recommendation).   

     

Weed Science Update - February 26 (Prostko)

     Over the last several days, a few interesting things have crossed my desk.  Thought you might want to see them as well.  Figure 1 is a picture of a weed from a plantation in SW Georgia (https://plants.usda.gov/core/profile?symbol=pagl17).  Numerous yellow flowered plants are blooming at this time of year so be careful when identifying.  Figure 2 is a picture of Palmer amaranth that has already emerged somewhere in SE Georgia.  Seems too early to me but also serves as a reminder that growers should consider a residual herbicide if planting will be delayed after ground preparation.  Figure 3 is a picture of volunteer Xtend (dicamba) soybeans in winter wheat.  Not an easy weed to control since they are resistant to dicamba.  Depending upon wheat stage of growth, best bet for control might be Harmony Extra + MCPA?  Importantly, these soybeans were not STS/SR.  Figure 4 illustrates how glyphosate rate and timing are important for the control of annual ryegrass.  Assuming resistance is not an issue, I would suggest at least 48 ozs/A of glyphosate are needed.

Figure 1.  Butterweed (Packera glabella).

Figure 2.  Palmer amaranth emergence in February??

Figure 3.  Volunteer Xtend (dicamba) soybeans in wheat? 

Figure 4.  Rate and timing of glyphosate for annual ryegrass control.

Bermudagrass Burndowns (Prostko)

     During the last few weeks, I have received a few inquiries about controlling bermudagrass prior to planting various row crops.  An established stand of bermudagrass can be very difficult to manage.  When dealing with bermudagrass burndowns, glyphosate rate and time of application are crucial.  Here are a few points to consider:

1) When applying glyphosate in the spring, when is the best time of application?  Generally, later applications are more effective after the bermudagrass has greened up and is actively growing (Figure 1).

  
2) Can bermudagrass be effectively controlled with 1 application of glyphosate?  What rate of glyphosate should be used?  In previous UGA research, the most effective control of bermudagrass occurred when 3 applications of glyphosate @ 2 lb ai/A were applied (Figure 2).  Obviously, this program would have to be implemented the year before planting a spring row crop.  I hope you notice that a single application of 4 lb ai/A of glyphosate applied in May was not very effective (38% control).

3) Growers who are relying on spring applications of glyphosate only will almost certainly have to follow up in-crop with 1 or 2 applications of a postemergence grass herbicide, such as Select or Poast (only in labeled broadleaf crops), or glyphosate (only in labeled GR-crops).  Consequently, those extra herbicide costs should be included in their budget plans.  Additionally, it might take a few years of fighting before optimum bermudagrass control will be obtained.

Future Paraquat Changes (Prostko)

Paraquat is the active ingredient in several popular herbicide formulations used in Georgia (Firestorm, Gramoxone, Helmquat, and Parazone).  It has multiple uses including preplant burndown applications, early-postemergence weed control in peanut, and as a soybean harvest-aid.  Paraquat registration has been under review by the EPA and many changes will be occurring in the very near future.  The main reason for these changes is that many people have died over the years from ingesting paraquat that was improperly stored in various types of containers (cans, plastic bottles, cups, etc.)   The following table of future changes was provided to me by Syngenta (the purveyors of Gramoxone) and these dates are subject to change: