Metribuzin on Soybeans (Prostko)

As many of you know, I have been trying my very best to prevent the overuse of Valor and Reflex in soybeans, especially for growers who also plant cotton and peanuts.  Growers who want to protect Valor and Reflex (PPO's) have many other PRE options including Dual, Warrant, and metribuzin.  For you Roundup babies out there, let me remind you of a few things about metribuzin.

1) Metribuzin used to be sold under the trade names of Sencor (Bayer) or Lexone (DuPont).  Many moons ago, about 20% of the US soybean crop was treated with metribuzin.  

2) Current trade names for metribuzin include the following: Tricor, Metribuzin, Dimetric.

3) Metribuzin is also a component of many soybean pre-mixes including the following: Authority MTZ (metribuzin + Spartan), Boundary (metribuzin + Dual Magnum), Canopy or Canopy Blend (metribuzin + Classic) ), Intimidator (metribuzin + Reflex + Dual Magnum), and Trivence (metribuzin + Valor + Classic). 

4) When using metribuzin in soybeans, soil type, OM and pH are very important.  Metribuzin should not be used on coarse soils (i.e. sandy loam or loamy sand) with less than 1% OM and/or in soils with a pH greater than 7.5.  Refer to the individual product labels for more specific information about use rates, soil types, and organic matter restrictions.

5) Metribuzin should not be used on sensitive soybean varieties.  Check out page 268 of the 2016 UGA Pest Control Handbook for a partial list of soybean varieties that have been screened for tolerance.  Also, check out the following publication from the University of Arkansas ( http://mssoy.org/wp-content/uploads/2014/12/2014-SOYBEAN-VARIETY-METRIBUZIN-SCREENING-UA1.pdf).  

6) Metribuzin is in the same herbicide family as atrazine (triazine). Metribuzin is a PS II inhibitor (WSSA Group 5).

7) Metribuzin injury symptoms on soybeans are presented in Figures 3 and 4.  

Figure 3.  Metribuzin injury on soybeans.

Figure 4.  Metribuzin injury on soybeans.

Prowl vs. Sonalan in Peanuts (Prostko)

Recent price increases in Sonalan 3EC (ethalfluralin) have many growers taking a closer look at the cheaper priced pendimethalin formulations (Generic Prowl 3.3EC and Prowl H2O 3.8ASC) for use in peanuts.  With the exception of use in reduced tillage systems (i.e. Prowl is preferred there), there have been no consistent differences in peanut tolerance and weed efficacy between Sonalan and Prowl in peanut (Table 1).  It has always been my position that I have no preference between these two herbicides and that every peanut acre in Georgia should be treated with one of them.  If a grower is trying to save a few bucks on input costs, there is no reason not to use a cheaper formulation.

A couple of other comments about this issue:

1) The Weed Science Group at UGA has not been able to detect any major differences in the performance between Prowl 3.3EC and Prowl H20 3.8ASC.
2) 2016 estimated costs for 1 qt/A are as follows:  Sonalan 3EC = $10.50; Generic Prowl 3.3EC = $6.75; and Prowl H2O 3.8ASC = $8.75.
3) The lb ai/A for each formulation are slightly different at the 1 qt/A typical use rate as follows:  Sonalan 3EC = 0.75 lb ai/A; Generic Prowl 3.3EC = 0.83 lb ai/A; and Prowl H2O 3.8ASC = 0.95 lb ai/A.  This might need to be considered when figuring the true cost differences per acre.