Driving across West Tennessee last week it is very apparent we have taken a step backward on Palmer amaranth control. Many fields that looked clean from the road in late July are now showing large Palmer amaranth escapes. Upon closer inspection the pigweed escapes are at least partially affected by the dicamba applications which resulted in them staying hidden from the road until the last couple of weeks.
The Palmer amaranth infestations in these cotton and soybean fields range from a few scattered pigweed to large patches of escaped Palmer (Picture 2 and 3) to some fields with even more serious infestations (Picture 1). What is more of a concern is these pigweeds have by all accounts often escaped multiple robust rates of dicamba.
In most cases, fields where Liberty was also used have fewer Palmer amaranth escapes (Picture 3). It is safe to say that if not for Liberty many fields would be covered stem to stern with pigweed. It is clear that Liberty will need to be relied on more than ever in 2024 to have any success controlling this weed.
From the combine or picker, it is very easy to note Palmer amaranth escapes. Fields with serious infestations will need to have a very aggressive weed management plan in 2024. The weed management plan should start with the theme to never let pigweed emerge. This will help delay Liberty resistance from developing. We must keep Liberty in play on Palmer amaranth as long as possible. In many fields Liberty is now the last, best pigweed control option.