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).