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:  

Cold Temperatures and Herbicides (Prostko)

     Growers who have sprayed certain POST systemic herbicides (i.e. Roundup, Poast, Select) over the last 15 days are likely to observe slower and/or reduced performance due to the cold weather.  When temperatures drop below 50 F, weird things start to happen because plant growth is stalled and physiological processes such as absorption and translocation are reduced.  In the past 15 days, most areas in Georgia had 10-11 days of temperatures below freezing (Figure 1).  Those temperatures are not very herbicide friendly.  Daily low temperatures are expected to be below freezing through Saturday night (Jan 20).  Growers with ants in their pants might want to wait until Sunday or later to resume any herbicide spraying that is needed. If a grower has already made an herbicide application during this cold snap, I would suggest that he/she evaluate the situation 10-14 days after treatment and re-treat if needed and if the label permits.

Chart Source:  UGA Environmental Network, accessed 01/16/18

Weed Control in Field Pea (Prostko)

      In some areas of our state, the poultry industry is encouraging growers to plant winter field peas for use as chicken feed.  Unfortunately, the UGA Weed Science Group has limited (i.e. no data) on herbicide use in this crop.  I have put together the following table of herbicides that are labeled for use in field pea.  However, there is no UGA research data supporting crop tolerance and/or weed efficacy.   My research counterparts are in the process of setting up field trials right now in Plains and Athens.  Will let you know how they turn out. (click on chart to make it larger).  

     Other herbicides such as Valor (flumioxazin) or Tricor (metribuzin) are registered for field pea use in other states but not in Georgia.  Since these are not labeled and we have no supporting data, it would not be a good idea use these!!!!