Vegetable Weed Management Circular Update (Culpepper and Vance)

The 2020 finalized circulars are ready: 1) 2020 Broccoli, Cabbage, Cauliflower; 2) 2020 Watermelon, and 3) 2020 Fumigation/Herbicides for Tomato/Pepper/Eggplant.  Squash and sweet potato will not change from 2019.

These circulars should be on-line (www.gaweed.com) by mid-February but if you want one before then or want laminated copies, do the following:

E-mail 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 for each crop that you would like and provide an address to send them.

Option 2: Request a PDF version.  An e-mail response will provide the PDF as an attachment.

Georgia Peanut Achievement Club Results - 2018 (Prostko/Monfort)

One of the most beneficial slides that I present at my county meetings is the data collected from the Georgia Peanut Achievement Club (GPAC) growers in regards to the various practices that they use to help manage weeds (Figure 1).  At the last few peanut meetings I have attended, I have been asked for similar information regarding other production practices for other pests.  To that end, I have also attached some data (compiled by Team Monfort) which lists all production inputs for the 2018 GPAC growers (Figures 2 + 3). (Click on pictures for higher resolution)

Dual Magnum vs. Outlook for Tropical Spiderwort Control (Prostko)

At the recent Decatur County Weed Meeting (January 7), I was asked by an attendee about the differences in the control of tropical spiderwort between Dual Magnum (S-metolachlor) and Outlook (dimethenamid-P).  Outlook is the activated isomer of the herbicide formerly sold as Frontier (dimethenamid).  If you are not very familiar with Outlook, it is in the same herbicide family as Dual Magnum (chloroacetamide), has the same mode of action (very long chain fatty acid synthesis inhibitor - WSSA#15), and this active ingredient has been around since the 1990's.  For whatever reason, Outlook never really received much attention during my career but recently BASF has dusted it off. 

My first response to the question was that I did not think that I had any data.  In my defense, you must remember that I have been in Georgia now for more than 20+ years and have conducted 50-70 field trials every year since then.  So the immediate recall of historical data can be challenging, especially for a 56 year old guy who played 12 years of Pop Warner, high school, and D-3 college football long before concussion protocols were common.  However, after reviewing my old files, I discovered some data from 2002 that compared the performance of Outlook to Dual Magnum in a peanut trial conducted in Grady Co.  The results of this trial are presented below (click on graph to download or view a higher quality graph):

It is obvious from this data that Outlook is not quite as effective for the control of tropical spiderwort as Dual Magnum.  However, it is only 1 year's worth of data.  In 2020, I will be looking for a peanut field to conduct some additional spiderwort control research so please keep your eyes open.

2019 Extension Drift Survey Summary (Culpepper).

 Agents, many of you participated in our drift survey during our weed science training back in December 2019. The figure below shares the results from 2014 through 2019. Your impact through our Using Pesticides Wisely (UPW) program and your county programs have been monumental with the overall goal of protecting pesticide users, by-standers, consumers, and our environment. Obviously, these results would not have been possible without a strong supportive and cooperative commitment among all of our Georgia agricultural family including growers, consultants, retailers/dealers, industry, and the Georgia Department of Agriculture.

In 2019, cotton, pecan, and fruits and vegetables (mostly gardens) received the most drift complaints at 38, 15, and 14%, respectively. Pesticides which led to the most extension drift visits included dicamba, 2,4-D, paraquat, 2,4-DB and cotton defoliation mixtures. For both dicamba and 2,4-D, complaints were significantly less in 2019 when compared to 2018.

No final decisions have been made on UPW 2020 as of Jan 7 but hopefully our plan will be in-place by mid-January with meetings planned for March 2020.

Cadre (imazapic) Carryover and Oats (Prostko)

I had 2 inquiries earlier this week about the potential of Cadre, when normally applied to peanuts during the growing season, to cause injury to fall planted oats.  This was one issue I tackled very early on in my career here at UGA.  Here are a few things for you to consider: 

1) According to a recent (2018) USDA/NASS survey of pesticide use in peanut, Cadre is used on 59% of the peanut acres in Georgia.

2) The official labeled rotation restriction for oats after an application of Cadre is 18 months!

3) Field research conducted in Georgia indicated that the rotation for oats could potentially be reduced to 4 months (like other small grains) but the label was never changed (and will not be changed) due to the limited amount of oat acres planted.  Oats were planted on 70,000 acres in Georgia in 2019. U.S. total planted oat acres were 2,810,000 in 2019.

4) Oats planted less than 4 months after a Cadre application could very likely be injured (Figure 1).  Note that Cadre injury to oats also looks very much like phosphorus deficiency and/or cold injury so these potential problems would need to be investigated as well.  We had at least 1 freeze event here in Tifton around November 13.   

5) When Cadre was applied to bare-ground (a worse case scenario, i.e. 100% of Cadre reaching the soil surface and no peanut uptake/metabolism) either 5, 4, 3, 2, or 1 month(s) before oat planting, total forage yield was only significantly reduced by the 1 and 2 month timings (61.6% and 22.4% forage yield losses, respectively).  Interestingly, oat grain yields were not reduced by any pre-plant application of Cadre.

6) I do not have any hard data to back this statement up but it makes sense that oat injury could be worse in short-planted fields where Cadre-treated dryland peanuts were grown.  

7) Complete results of this Cadre/oat research can be obtained from the following paper:

Prostko, E.P., T.L. Grey, R.N. Morgan, and J.W. Davis.  2005.  Oat (Avena sativa) response to imazapic residues.  Weed Technology 19:875-878.

8) Culpepper is the small grain weed guy so he would be more than happy to walk any and all small grain fields including oats!!!!!!

Figure 1.  Cadre injury symptoms on oats.

Direx 4L FIFRA 24(c) Special Local Need Label Approved for Georgia Cotton Growers (Culpepper).

At the recent Weed Science Update in Tifton, we discussed that federal diuron labels only allow applications between 15 and 45 days prior to planting cotton and that our state label providing a more flexible and effective use of diuron at burndown had expired. Thanks to the help of ADAMA, the Georgia Department of Agriculture, and the U.S. EPA, our growers once again have a state diuron label with flexible and effective use patterns to combat Palmer amaranth and other problematic weeds just prior to planting. Make sure growers understand that “strip-till” by our definition includes a ripper shank.  ***Direx 4L by ADAMA is the only diuron product available in Georgia with the shortened plant-back interval.  The 24(c)-SLN label is presented below (click on pictures to view better quality picture and/or download):

Syngenta's New Gramoxone 3SL (paraquat) Formulation (Prostko)

Syngenta recently received a label for their new formulation of paraquat sold under the trade name of Gramoxone 3SL (3 lb ai/gal).  As you may recall from a previous blog (March 10, 2019), many rules regarding the purchase, handling, and application of paraquat are changing.  Most notably, all non-bulk paraquat products (with new labels) must adhere to closed-system packaging requirements set forth by the EPA's Paraquat Dichloride Human Health Mitigation Decision by November 2020.  Also, all paraquat applicators are required to complete an EPA-approved training module before applying.

In my recent discussions with both Syngenta and AMVAC field personnel, there will still be some of the older labeled paraquat formulations (2SL and 3SL) in the marketplace for 2020 but these will disappear when supplies are exhausted.  Thus, growers need to be very aware of the label requirements of the container(s) they have in their possession.

A couple of quick links for you to review and share with your growers:

1) New Gramoxone 3SL label:
http://www.syngenta-us.com/current-label/gramoxone_sl_3.0

2) Current bulk handling systems already meet the new closed-system packaging requirements.  Tank adaptors for new closed system 2.5 gallon containers should be available from dealers and/or manufacturers?????  In my opinion, this headache will likely push more growers to bulk handling systems.  

3) EPA-Approved Paraquat Training Information:
https://www.epa.gov/pesticide-worker-safety/paraquat-dichloride-training-certified-applicators

4) Generally, research results from my 2019 field trials with the new Gramoxone 3SL formulation have been very positive (see below).