In writing on how to make the various Palmer pigweed control programs work consistently, I started with the LibertyLink system. I believe that system is all that is holding the door on herbicide resistance until we get to the next step — whenever and whatever that may turn out to be.
I have already covered two keys to making the LibertyLink system and Ignite herbicide consistent. The first is starting clean. Weeds must be small enough at planting that a burn-down program will work or tillage must be used.
The second key is using a residual herbicide. Almost any residual will look good with properly timed applications of Ignite.
I like the goal of shooting for 80 percent control with the residual program. You may be thinking, “You must not have much confidence in the Ignite!” Just the opposite is true. The thing that sets the LibertyLink system apart is the postemergence activity of Ignite. You have the capability to get nearly 100 percent control with two timely applications of Ignite even if the pre-emergence herbicide fails.
However, the objective is to achieve consistency over a lot of acres under a range of environmental conditions. The goal is 100 percent control resulting in zero pigweed seed production. Therefore, shoot for 80 percent control with the residual component and go from there.
The third key component in having a consistent LibertyLink program is timely Ignite applications. The ideal timing for the first Ignite application is 10 to 14 days after emergence (DAE). Timing is extremely important and I using DAE is the best way.
Since a most growers record planting dates, some prefer to add about five days to the days after emergence and use planting dates. If that works better for you the result will be the same as long as conditions favor rapid crop emergence.
I have found most people underestimate weed size. Also, pigweeds grow extremely fast. If you measure them today and it is a few days before the sprayer gets there, they could be double or triple the size when you measured.
If you use days after emergence, you can schedule the spraying well in advance and have the sprayer in the field the day you may have been measuring otherwise.
Ignite will kill big weeds sometimes. This can keep you in trouble most of the time. If you are using weed size and you know the herbicide can sometimes kill them bigger than the ideal timing, sometimes the sense of urgency gets lost. If you just schedule the treatment and go do it, then this potential error is removed.
Measuring weed size also does not take into account soil moisture. Spraying 3-inch weeds growing in good moisture can have a much different result than spraying 3-inch weeds that are drought-stressed. Normally if you have adequate soil moisture for crop and weed emergence, you will not have drought-stressed weeds by 10 to 14 DAE.
However, as you delay the application, you may be dealing not only with bigger weeds but drought-stressed weeds as well. This is often a double whammy.
I am often asked, “Won’t my residual herbicides buy me some time?” They may or may not. Everything I have written still needs a scouting component. The residual herbicide may or may not get activated. Even if it is activated, it must hold all of the weeds back in order to buy time. If it gives you 80 percent early control, you may still need the same timing on the escapes that you would have needed if it did not get activated. I never see anyone in trouble because they sprayed their first postemergence herbicide treatment too early.