Cold Temperatures and POST Field Corn Herbicide Applications (Prostko)

Over the next few days (April 1-4), low daily air temperatures are expected to drop below 50 and even 40 degrees in many areas.  Consequently, I would encourage any field corn grower who wants to make a POST herbicide application during this time period to consider waiting until next week when temperatures get warmer.  It has been my experience that when herbicides are applied in colder temperatures, weed control will likely be reduced/slowed and crop injury increased (i.e. reduced plant metabolism).  As of today, weather conditions for herbicide applications next week (April 5-9) look very favorable and weed growth from now until then would not be significant enough to negatively impact control.  In general, summer annual weeds do not grow as fast in April as they do in May/June.

A few years ago, I applied Halex GT + Atrazine + Induce early (V2 stage) during a cold period (8/15 days with low temps below 50 F) and observed significantly more crop injury than usual (Figure 1).  The good news is that the field corn recovered from this injury and final yields were NOT reduced by the 1X rate.  FYI, I am not picking on Halex GT (one of many awesome field corn herbicides) here since increased crop response could happen with almost any POST herbicide when applied in unfavorable environments.  

 

Figure 1.  Field corn injury from Halex GT + Atrazine + Induce applied at the V2 stage of growth during colder weather in 2018 (low air temperatures <50 F for 8/15 days).

   

Acuron GT For Weed Control in Field Corn (Prostko)

Syngenta recently received registration for a new postemergence field corn herbicide sold under the trade name of Acuron® GT.  Acuron® GT is very similar to Halex® GT but it contains an additional active ingredient (bicyclopyrone).  Syngenta has several similar field corn herbicides in the market and I have summarized them in Table 1.  I have only had the opportunity to evaluate Acuron® GT for 1 year (Figure 1) so I would encourage any interested GA growers to use it on a limited basis until I can get more data in 2021.  A complete copy of the Acuron® GT label can be downloaded here: https://www.syngenta-us.com/current-label/acuron_gt.   

Table 1. A comparison of Acuron, Acuron Flexi, Acuron GT, and Halex GT.

Trade Name	Active Ingredients (lbs/gal) (WSSA MOA)
	glyphosate (9)	mesotrione (27)	bicyclopyrone (27)	S-metolachlor (15)	atrazine (5)
Acuron	-	0.240	0.060	2.14	1.0
Acuron Flexi	-	0.320	0.080	2.86	-
Acuron GT	2.00	0.200	0.095	2.00	-
Halex GT	2.09	0.209	-	2.09	-