Results from our greenhouse screens of Palmer amaranth to Liberty has been very encouraging. We feared that the Liberty resistance documented in Arkansas had crossed the river. The good news is that we have seen good control with a 32 oz/A rate of Liberty on all the Palmer populations tested (Picture 1).
At rates less than 32 oz, it is evident that some populations have better tolerance than others. These populations likely would escape in the field if the weather was not an ideal Liberty day (>80 and humid). My understanding is that the Arkansas Liberty-resistant Palmer populations were surviving a gallon/A of Liberty in the greenhouse. Thankfully our most tolerant populations were controlled with 32 oz/A.
Unfortunately, the dicamba resistance was still present in these Palmer amaranth populations (Picture 2). Liberty will need to be used to clean up these escapes in the field. Remember Liberty works best on hot and humid days and when applied in the middle of the day. (9:00 a.m. to 5:00 p.m.).