New Section 24(c) Label for Fierce in Wheat (Culpepper, 2015) - For UGA Extension Agents Only

Fierce, active ingredient pyroxasulfone and flumioxazin, just obtained a new approval for postemergence applications in Georgia wheat as a Section 24(c) Special Local Need Label.  We did have a label for Fierce last year but we improved its use pattern for this 2015/2016 season.   

Our goal is to help growers struggling with ryegrass that is resistant to postemergence herbicides; although our research would also suggest that Fierce provides good to excellent wild radish control.  Our intentions for the 2015/2016 crop are to have a controlled use of Fierce allowing growers the chance to determine if the herbicide can be used to effectively manage problem weeds while having acceptable crop injury.  

Application of Fierce:

1.  Follow the label exactly (Figure 1).

2.  Wheat must be planted 1 to 1.5 inches deep and cannot be broadcast spread.

3.  Apply Fierce at 1.5 oz/A in ONLY CLEAN water when wheat is between the spike and 2-leaf stage; ryegrass needs to be ½ inch or hopefully much smaller.

4.  Apply Fierce only in water.  Notice I just mentioned twice that you cannot have anything in the tank other than clean water and the herbicide; no exception!

5.  Must use 10-15 GPA; prefer 15 GPA if weeds are emerged.

6.  Do not apply with airplane.

7.  Only for wheat!!  Again, only wheat.

8.  DO NOT USE ON SANDS!

Crop Injury:

1. Greatest potential for injury occurs when 1) label recommendations are not followed and 2) when open/cracked seed furrow allows herbicides to directly contact the seed, when seed are planted to shallow, or when seed are planted in a deep furrow that allows herbicide concentration after a rain/irrigation event while wheat is growing. 

2.  Even when following the label, injury will occur in some environments.  This is why we are taking such a conservative approach.  With that said, our research suggests the benefits in weed control far outweigh injury concerns when following the label; you guys need to tell us if the research is accurate or not.

3.  Strongly suggest growers try only few field acres; do not treat the whole farm!!!! 

Also, just a reminder about Zidua which is the other new ryegrass herbicide we have available.  See the 2015-2016 UGA Wheat Production Guide for the lastest weed control information.

Figure 1.  24(C) Special Local Need Label for Fierce use on wheat in Georgia.  

What's that Weed? (Prostko)

In the last few weeks, I have received a few samples of  the weed known as old world diamond flower or flat-top mille graines (Hedyotis corymbosa) (Figures 1 and 2).  Its not very common, at least in my world.  In fact, I only touched it for the first time last year in a corn field in Decatur County. This summer annual plant is a member of the Rubiaceae (Madder) family and is closely related to more common plants such as poorjoe and Virginia buttonweed.   

Can't find any control data for row crops but a bunch exists for turf.

Figure 1.  Old world diamond flower (Photo Source: C. Tyson - Tattnall County)

Figure 2.  Old world diamond flower

Screening Palmer Amaranth Samples for Liberty Resistance (Culpepper and Prostko)

Without question, the amount of Liberty (glufosinate) applied during 2015 was much greater than in previous years.  Unfortunately, overuse and abuse of the herbicide was also more prevalent.  If Liberty is lost to resistance, it is questionable if our agronomic growers will remain viable in the long-term.  We must work hard to help growers make better decisions with Liberty and we must also determine where resistance develops rapidly.

Therefore, we are committed to screening some pigweed samples taken by county agents this winter.  Fields treated numerous times with Liberty, fields treated with Liberty multiple years in a row, or fields in which you felt timely Liberty applications were made but control was inadequate are ideal situations. 

The screening process is only as effective as the sampling technique.  Some suggested guidelines for seed collection are as follows:

1.  Harvest at least 25 FEMALE seedheads when MATURE.

2.  Female seedheads are usually the prickly ones and, of course, have the seeds.

3.  At least 75% of the seeds must be completely dark black; if they are burgundy or lighter in color they are likely not viable.  To check seed color/maturity, shake seedhead over hand allowing seed and seed cover to fall in hand; rub aggressively and seed should dislodge from cover. 

4.  Place seedheads in a paper bag (suggest cutting seedheads in sections so the will lay down in bag). Do not use a plastic bag!

5.  Write GPS coordinates, county, and your name and/or grower name on bag.

6.  Carry samples back to office, open bag, and place them in dry area for a few days.

7.  Bring to Tifton when visiting or send with someone going to Tifton.

8.  Drop off at Dena Watson's office in Horticulture Building.

 Note: Palmer amaranth plants are currently mature in fields that were planted during late April or very early May and the pigweed emerged with the crop.  Pigweed emerging later in the season are probably still a few weeks from being mature.

Figure 1.  A large Palmer amaranth plant survives an untimely application of Liberty. Not good for long-term resistance management!!!!!!!  

Soybean Weed Control (Prostko)

On occasion, someone might come up to me and randomly say something like "When are you going to figure out how to control pigweed in soybeans?"  When I hear that, it makes me think about what planet that person has been living on the last few years.  As far as I am concerned, Georgia soybean growers have had all the tools needed to control herbicide-resistant Palmer amaranth since day one.  The problem has been getting folks to do what UGA has recommended. Check out the following picture from some of my soybean plots taken earlier this morning.  

Figure 1.  Soybean Weed Control Tests, Attapulgus, GA, August 31, 2015.  Asgrow 7934 planted on May 12.

The soybeans in the picture without any pigweed were managed the following way:

1) Started clean.
2) 2 residual herbicides (1 PRE + 1 POST).  For RR soybeans, I prefer Boundary or Dual Magnum or Warrant - PRE followed by Roundup + Reflex or Prefix (Reflex + Dual Magnum) - POST.  In 2016 , a new formulation of Warrant + Reflex (Warrant Ultra) will be available for those growers who prefer Warrant over Dual (FYI, I do not have  preference!!!!).  
3) POST applications were timely (24 DAP).
4) This particular soybean field was under grown under a center-pivot.  It is very unlikely that dryland soybean growers will be able to achieve optimum weed control on a consistent basis when relying on rainfall for the activation of residual herbicides.  That is one of the biggest perils of dryland farming. 
   

Pre-Harvest Applications of Aim or ET in Peanuts (Prostko)

Been getting many questions lately about late-season annual morningglory control in peanut.  I partially addressed this issue in a previous blog (August 29, 2013).  In most cases, it is too late in the year to legally apply herbicides.  Pre-harvest intervals (PHI) of peanut herbicides with POST activity on annual morningglory are as follows: Cadre = 90 days; Cobra = 45 days; Ultra Blazer = 75 days; 2,4-DB = 45-60 days.  In my opinion, the best thing a grower can do for annual morningglory this late in the season is to apply a pre-harvest application of either Aim or ET (i.e. 7 days before digging).  Both herbicides will provide sufficient dessication of annual morningglory plants (except smallflower) to improve peanut vine flow through a digger with minimal effect on the peanuts (Figures 1 and 2). It is very important that the peanuts be dug in 7 days after treatment (or as soon as possible after that time).  If digging is delayed, the morningglory vines could start to recover/regrow especially after a rainfall event.  Specific recommendations for these herbicides can be found on page 502 of the 2015 UGA Pest Control Handbook.   

Figure 1.  Annual morningglory response to Aim (5 DAT).

Figure 2.  Peanut injury caused by a pre-harvest application of Aim (5 DAT).

Clethodim Formulations (Prostko)

In order to minimize any confusion about the use of clethodim for postemergence grass control in peanuts, the following is a list of all the different formulations that are labeled (at least the ones that I could find).  Pay close attention to the lb ai/gal since this will influence specific use rates.

Trade Name	Clethodim (lb ai/gal)	Manufacturer (s)	Labeled Use Rate for Most Annual Grasses (oz/A)	Labeled  Adjuvant for Peanuts
Arrow	2	ADAMA/MANA	6-8	COC (1% v/v)
Clethodim 2EC	2	Albaugh, Amtide, Tide International, Willowood	6-8	COC (1% v/v)
Intensity	2	Loveland	6-8	COC (1% v/v)
Intensity One	0.97	Loveland	9-16	NIS (0.25% v/v) or COC/MSO (1% v/v)
Section	2	Winfield	6-8	COC (1% v/v)
Section Three	3	Winfield	4-5.33	COC (1% v/v)
Select	2	Valent	6-8	COC (1% v/v)
Select Max	0.97	Valent	9-16	NIS (0.25% v/v) or COC/MSO (1% v/v)
Shadow 2EC	2	Arysta	6-8	COC (1% v/v)
Shadow 3EC	3	Arysta	4-5.33	COC (1% v/v)
TapOut	0.97	Helena	9-16	NIS (0.25% v/v) or COC/MSO (1% v/v)
Volunteer	2	Tenkoz	6-8	COC (1% v/v)

Morningglory Identification - Prostko

Just got out of a peanut field with Tift County Agent, Scott Carlson.  We were talking about weed ID and general peanut stuff.  Many of the weeds that were present in this peanut field were various species of morningglory. Consequently, I thought you might benefit from some of the following information:

1) An old publication that helps with the identification of adult morningglory plants.  Great to keep in your truck!  

Figure 1.  Identifying Morningglory Species.  Source: Dr. Dick Oliver, University of Arkansas,  Weeds Today

2)  Some very good close-up pictures of seedling morningglory plants.  Pictures are from LSU and Virgina Tech.  Also, something good to keep in your truck (besides a sandwich and a Dr. Pepper).

3) Why is this important?  Not all morningglories are controlled equally by certain herbicides. Here are a few examples:

a) Gramoxone (paraquat) is generally good on most morningglory species but not smallflower. 

b) Basagran (bentazon) is generally not effective on most morningglory species but will control smallflower.

c) Staple (pyrithiobac) is generally considered to be an excellent morningglory herbicide but not on tall.

d) 2,4-DB is less effective on pitted morninglory than other species.

e) Aim (carfentrazone) is considered a good morningglory herbicide but not on smallflower.