There will be quite a bit of Liberty being sprayed over the next couple weeks. This is just a quick reminder that the time of day that Liberty is applied has large determination on the success or failure of that application.
If you will recall back in 2012 we conducted a study here in Jackson, TN in conjunction with Stanley Culpepper, my colleague in Tifton, GA, to see if time of day may affect Liberty efficacy on Palmer pigweed control. The study was conducted based off of sunrise (5:56 AM) and sunset (7:48 PM) timings, where applications of 32 oz/A of Liberty were applied on 5 inch Palmer pigweed in cotton 1 hour before sunrise, ½ hour before sunrise, at sunrise, ½ hour after sunrise, 1 hour after sunrise, 2 hours after sunrise, 4 hours after sunrise, and 6 hours after sunrise. Shortly after the sunrise applications, treatment timings based off of sunset commenced. These started at 6 hours before sunset and followed the same trend mentioned earlier, ending at 1 hour after sunset.
The resulting Palmer control 14 days after application showed that adequate control of Palmer pigweed was not achieved until ½ after sunrise and continued to be good throughout the day running onto sunset. Prior to sunrise, Palmer control ranged from 50% to 73%. An hour after sunrise, control of Palmer pigweed was greater than 90% and continued to be that way to 30 minutes before sunset. The results were consistent in both states.
We repeated this study in 2013 in soybean and received similar result where best Palmer amaranth control was achieve with Liberty application that commenced 60 minutes after sunrise to about 60 minutes before sunset.
A twist we did this year was to tankmix a quart of Prefix in with the Liberty to see if that could improve the control when applications where made near sunset in soybean. We got dramatic results where 5” Palmer amaranth control was improved from 30% to 90% by adding in a quart of Prefix with the Liberty during a 7:30 p.m. application timing.
This research would suggest that better Palmer amaranth control can be achieved for Liberty applications made at the beginning of the morning or end of the day by adding in a qt of Prefix. Unfortunately, we have yet to find a tankmix partner that can give us similar good results when spraying cotton. Therefore in cotton the recommendation is to apply Liberty in the window of an hour after sunrise to within an hour of sunset.