Programs for Controlling Ryegrass and Radish Circular for 2021-2022! (Culpepper and Vance)

Agents, our wheat weed control circular is finalized. For the most part, it remains similar to last year with a few minor adjustments including:

1. Added liquid Zidua formulation (both liquid and dry formulation are labeled)

2. Added comment regarding Fierce and the expectation of the liquid formulation obtaining a label during 2022 (dry formulation labeled now).  

3. Removed Axial from circular; Axial Bold has replaced Axial.

4. Hopefully made tables even more simple to understand. 

If you would like a copy, email Jenna Vance at jcsmith3@uga.edu and ask for one of the following options:

Option 1: Request laminated circulars to be mailed to you. Provide the number of circulars that you would like and provide and address to send them.

Option 2: Request laminated circulars to be brought to you at our Dec. 1 weed training.

Option 3: Request a pdf version. An email response will provide the PDF as an attachment. 

Plans are to bring laminated vegetable circulars to you at our Dec. 1 weed training. In regards to the cotton circular, we are waiting on decisions from the U.S. EPA regarding auxin herbicide labeling requirements/restrictions for 2022 before making edits.

 

 

 

 

Soybean Green Stem (Prostko)

Last week, I received a few phone calls about soybean green stem (SGS) (Figure 1).  The causes of SGS are not well understood but are likely attributed to various stresses that can effect soybean pod development.  Stresses include problems such as stinkbugs, aphids, thrips, disease, viruses, and environmental.   The use of foliar fungicides, especially the strobilurins, have also been associated with SGS.  Cultivar may also be important as well.  

Herbicides such as paraquat, although very useful for soybean leaf defoliation, have been inconsistent in their effect on SGS.  At this time of year (i.e. harvest), the only management tactics for SGS are making sure combine teeth are sharp, reducing combine speeds, and possibly delaying harvest until when/if/maybe a hard freeze occurs.

For more information, check out this recent (September 2021) publication about Green Stem Syndrome in Soybean from Oklahoma State University. https://extension.okstate.edu/fact-sheets/print-publications/pss/green-stem-syndrome-in-soybean-pss-3003.pdf

Figure 1.  Soybean green stem.

Post-Harvest Weed Control (Prostko)

As you have heard many times before, Culpepper and I have been encouraging growers to consider the use of post-harvest (field corn) tactics (tillage, mowing, herbicides) to help manage the soil seedbank for weeds such as Palmer amaranth and tropical spiderwort.  The pictures below are from one of my corn fields that I recently treated with a combo of Gramoxone (paraquat) + Tricor (metribuzin) + NIS.  The green, untreated strips are there by design (checks).  This is one of my preferred post-harvest herbicide treatments especially for Palmer amaranth.  In many fields though, it might be too late if weeds have already produced seeds and/or if younger plants are likely to get terminated (before producing seed) with the first frost (about a month away in many locations). 

FYI, current Tricor label would allow field corn or soybean planting next spring but cotton and peanut rotations are 18 months.  We are trying to get the label changed to allow for a shorter rotation interval for these important Georgia row crops.  

Custer's Last Stand or Using Wipers or Mowers For Late-Season Weed Control in Peanut Fields (Prostko)

At some point, peanut growers must realize that it is futile to continue spraying herbicides over the top of their crop.  Either the weeds are too big and/or pre-harvest intervals cannot be followed.  In that case, there are 2 last resort weed control options for troublesome fields.  These include the use of either a non-selective applicator (i.e. wiper/wick bar) or a flail mower.  Flail mowers (vertical blades) are preferred over rotary mowers (horizontal blades) because they uniformly distribute debris rather than dump it on one side of the mower (which can cause major digging problems).  The main goal with these weed control methods is to increase fungicide deposition and/or improve harvestability.  At this time of year, it is really way too late to recover any weed competition related yield losses.  Here are a few things to consider for both options.

1) A 33% or 50% solution of paraquat (depending upon formulation) is legal to apply in a non-selective applicator for the control of Palmer amaranth.  Check out page 223 in the 2021 UGA Pest Control Handbook for more specifics (tractor speed and weed heights are very important).  This treatment will also work well on Florida beggarweed and sicklepod.  No other herbicides are labeled for this type of application so don't bother asking me about Liberty or dicamba (FYI, they don't work well in these applicators either!!!).  I have tested several types of applicators over the years and prefer any of the ones pictured below. You can also check out the following slide set for more information about the research I have conducted on non-selective applicators (http://www.gaweed.com/slides/prostko-swss-2011/index.html).

2) I have used a flail mower to clean up my weedy test plots for many years.  I usually set the mower to remove about 2"-3" of the peanut crop in addition to topping any weeds that are there.  Generally, 1 pass with the flail mower is OK but 2 passes are better (opposite directions). Check out these pictures from earlier today.

 

Rain Delays and Weed Control (Prostko)

Recent rains over the last few days at the UGA Ponder Farm (1.75"+) have kept me out of the field for today so I thought it would be a good time to squeeze in a quick blog. The frequent rain showers we have had over the last month or so have caused many problems with growers who have not been able to get in the field to make pesticide applications.  Since its now July 20 and getting late for just about everything, here are a few things to think about in regards to weed control in various crops:

1) The application cut-off date for all dicamba applications in tolerant soybean was June 30 and is July 30 for tolerant cotton. 

2) If at all possible, growers need to avoid making applications of Cobra or Ultra Blazer to peanuts during the 60-80 DAP time frame.  There have been yield losses (5-10%) associated with the application of these herbicides during this period (usually R5-R6 or beginning to full seed stage).  Cobra can legally be applied up until ~100-105 DAP since it has a 45 day PHI.  The PHI for Ultra Blazer is 75 days.

3) Yes, it is my opinion that it always a better idea to apply a POST grass herbicide at least 3 days before a peanut fungicide application rather than tank-mixing them together.  However, growers in a tight bind who just have no other choice but to co-apply (fungicide + POST grass herbicide) should consider increasing the rate of the grass herbicide (5-10%) to help overcome potential antagonism.  They must also realize that they still might not get optimum control especially since grasses are likely larger than desired.  Growers will be wasting money on the grass herbicide if applied to large plants.  Generally, flowering grasses are way too big to control with these herbicides.  The POST grass herbicides (Select, Fusilade, Poast) have a 40 day PHI.  Check out page 234 of the 2021 UGA Pest Control Handbook for more information about grass control in peanut:

4) 2,4-DB has a 60 day PHI so legally it can be applied up until ~80-90 DAP (for most peanut cultivars). There are at least 8 different formulations of 2,4-DB out there and these labels can vary slightly.  Late applications of 2,4-DB can be tank-mixed with most fungicides.  Don't expect any home-runs here since 2,4-DB is not very effective on most weeds that are growing above the peanut canopy (except common cocklebur).  

5) Since field corn harvest is rapidly approaching, I have gotten a few questions about the pre-harvest control of annual morningglories.  My usual recommendation is to apply a combination of Roundup + Aim within 3 days of harvest.  This treatment will not miraculously remove the running morningglory plants, but it will desiccate them enough to facilitate harvesting (i.e. makes the vines more brittle and less likely to wrap).  See below for more specifics (from 2021 UGA Pest Control Handbook, page 73).

Tank-Mixing Cobra or Ultra Blazer with Cadre in Peanuts (Prostko)

Over the last few days, I have had a few questions about tank-mixing Cobra or Ultra Blazer with Cadre + Dual Magnum + 2,4-DB.  Most are concerned about potential crop injury but this tank-mix has not been overly caustic in my research (Figures 1 and 2).  But, keep in mind that crop injury with tank-mixes can vary greatly depending upon many factors including time of application, GPA, air temperature, leaf wetness, and humidity.  Thus, I can provide no guarantees when 4-6 products are dumped in 1 spray tank.  

Peanut growers who suspect (or are not sure) that they have ALS-resistant Palmer amaranth and/or other weeds that Cadre is less effective on (i.e. tropic croton) would greatly benefit from this tank-mix.  In this scenario, Dual Magnum could be replaced by Outlook, Warrant, or Zidua (grower preference not mine).  Also, I would probably avoid Anthem Flex in this particular situation because of the Aim (carfentrazone) in the Anthem Flex.  When using Warrant or Zidua, a NIS should be included (0.25% v/v or 1 qt/100 gals).

Figure 1.  Cadre + Dual Magnum + 2,4-DB + Cobra.

Figure 2.  Cadre + Dual Magnum + 2,4-DB + Ultra Blazer.

Weed Control Update - June 16, 2021

Just a few things I thought you might be interested in seeing from my research plots over the last few days (a la Dr. Bob K., the E-Mail King of Georgia): 

1) The most effective weed control program (in any crop) happens by starting clean, using a strong residual program that gets activated by rainfall/moisture, and making timely POST applications.

2) Lots of folks interested in using Anthem Flex (pyroxasulfone + carfentrazone) on their peanut crop.  Anthem Flex is a very good herbicide but it will cause more peanut injury than the other WSSA Group 15's. Growers need not forget the other WSSA Group 15's that work equally as well in the UGA recommended peanut weed control programs including Dual Magnum (s-metolachlor), Outlook (dimethenamid-P), Warrant (acetochlor), and Zidua (pyroxasulfone). 

3) Preliminary herbicide/fungicide/peanut response tank-mix research with Provysol looks promising.  I have observed similar results positive results with Cobra and Ultra Blazer.

4) Check out this soybean injury from 2,4-DB (2 oz/A) applied in combo with Reflex (24 oz/A) + Classic (0.5 oz/A).  The use of 2 oz/A of 2,4-DB in just about every POST herbicide application in soybean was very common in the late 1980's/early 1990's before all of the technology explosions.  Looks worse than I remember.  Good weed control though!