Palmer amaranth emergence is very rapid now.  This is about a month early for Palmer emergence to be at this pace in Tennessee. With the spread of dicamba resistance in our Palmer amaranth population Liberty is our last best hope to control dicamba-resistant pigweed escapes in cotton and soybean.  This is just a quick reminder that the time of day that Liberty is applied has a large determination on the success or failure of that application.

From 2012 to 2017 we conducted a good many studies examining Liberty performance on Palmer amaranth as affected by the time of day the application was conducted. All the studies pointed to the same conclusion, that Liberty applied in the middle of the day provided better and more consistent control of Palmer amaranth than either early morning or evening applications (studies conducted in warm weather). As an example, one study (Figure 1.) from 2015 showed good control of 4” tall Palmer amaranth if the Liberty application was applied at noon compared to applications made at dawn or sunset.

In general, the best Liberty performance can be achieved when applications are made from 8:00AM to 6:00PM.

Other environmental factors also greatly effect Liberty’s weed control performance. It controls weeds best if applied on days where the high temperatures for the day are in the 80s or 90s. Also, it works best at higher humidity’s as well. In other words, a typical June or July day.