Warrant Receives Peanut Label (Prostko)

Warrant recently received both federal (January) and state (February) approvals for use on peanuts in Georgia. Here are a few of my thoughts regarding its potential use in 2014:

1) The current supplemental label only permits PRE and/or EPOST applications (before flowering).  

2) Of these 2 timings, I would prefer to see EPOST applications of Warrant tank-mixed with Gramoxone + Storm + NIS.  

3) At this point in time, I have NOT observed any real differences in weed control between Dual Magnum and Warrant based peanut weed control programs (Figure 1).  However, there is some data that suggests that Warrant might be a better choice for non-irrigated fields.

Figure 1.  Dual Magnum vs. Warrant Based Weed Control Programs

4)  A copy of the current supplemental Warrant peanut label can be viewed at the following location:

http://www.cdms.net/LDat/ld9KA011.pdf

5)  I have made some suggestions to Monsanto that hopefully will result in a better and more usable label in the near future.

Peanut Yields and Cobra + 2,4-DB (Prostko)

Frequently, peanut growers get concerned when they make herbicide applications that "burn" their crop.  One of the herbicides that can cause this type of injury is Cobra (Figure 1).   Recent results from tests conducted in Florida reconfirm that the injury caused by Cobra or Cobra + 2,4-DB is cosmetic in nature and does not negatively impact peanut yields (Figure 2).  In these tests, Cobra or Cobra + 2,4-DB treated plots yielded 97-105% of the non-treated check plots. Cobra or Ultra Blazer + 2,4-DB is recommended for the control of Palmer amaranth in peanut fields when Cadre is not a viable option due to ALS-resistance or crop rotation concerns (page 460 of 2014 UGA Pest Control Handbook). 

Figure 1.  Peanut leaf burn caused by Cobra.  

Berrien County Atrazine Resistance - Part 2 (Prostko)

In my last blog, I informed you of the recent discovery of atrazine-resistant (AR) Palmer amaranth in Berrien County.  After a more thorough investigation by Berrien County Agent Fast Eddie Beasley, it was discovered that the corn rotation in this field was shorter than expected (Figure 1).  Because this rotation is different from the fields where AR-Palmer was first confirmed in Georgia, there is some concern about how the resistance occurred.  Here are a few things that you might want to consider before thinking that the sky has fallen:

1) AR is not a brand new phenomenon.  The first (ever) reported case of herbicide resistance was AR-groundsel (Senecio vulgaris) way back in 1970 in the Pacific Northwest.

2) AR-Palmer was confirmed in Georgia in 2008 (Macon County).  Thus, the UGA Weed Group has had 6 years to work on this problem.  As indicated in the previous blog, numerous other herbicides are available for use in field corn that will provide outstanding pigweed control (page 155 of 2014 UGA Pest Control Handbook). However, atrazine is still very much needed in our corn weed control programs for troublesome weeds such as sicklepod and morningglory.

3) It is possible that AR-Palmer evolved in this field via pollen movement or physical seed movement (birds, equipment, animals, gnomes, etc.).

4) It might also be possible that AR-Palmer evolved in this field due to the fact that the resistance is metabolism-based rather than target-site based.  It has been documented in other weeds species with metabolism-based resistance that cross-resistance can occur in the absence of selection pressure.  This has been confirmed in some ACC-ase resistant Rigid ryegrass (Lolium rigidum) populations that were also cross-resistant to ALS herbicides that were never used in the field.  Mother Nature at its finest (i.e. genetics and evolution)!!!!

5) Herbicide resistance is a complicated issue for sure.  Consequently,  it is very important for our growers to be proactive and make every effort to delay the evolution of herbicide resistance in all of our crop production systems (tillage, cover crops, crop rotations, mode of action rotations, hand-weeding, soil seed-bank management, etc.).