Using residual herbicides is something we must learn to do again. Everyone likes the “spray twice with two postemergence treatments and be through.” That was a nice program when you could kill them anytime you wanted to.
It was easy to get through planting and then start spraying. The problem is that program quit working.
Some look at the level of control with two properly timed applications of Ignite in a LibertyLink program and think that is the way to go. You may ask, “If the program is that good, why all the talk about residuals?”
The use of residuals in the LibertyLink program will make it much more consistent and it is also a much better resistance management program. Also keep in mind our goal is 0 percent seed production and that is tough to achieve.
I am often asked, “What is the best residual program to use in a LibertyLink system?” The combinations of herbicides you can choose are nearly infinite. For that reason I am not going to attempt to cover them all.
If you look at the University of Arkansas research to date, Prefix applied pre-emergence has been the standard to compare everything back to. Prefix actually fits the LibertyLink system better than the Roundup Ready or conventional system. If you use Prefix in those systems you can not use enough Flexstar postemergence without getting into label restrictions and rotation issues.
In the Liberty Link system, you do not need the Flexstar, so Prefix is a natural. Prefix is a premix of metolachlor (Dual and others) and Reflex (fomesafen). There are generics for both herbicides so you can also make your own Prefix equivalent if that is a better choice. I have also heard generic combinations are coming as well.
Valent also has a new pre-emergence combination treatment called Fierce that has looked very good in research. It is Valor with a new grass herbicide in it and is supposed to be available in limited quantities in 2011. It will certainly be worth a look.
I mention this in most every article I write about herbicides containing Valor, but you can get injury with this herbicide if rainfall occurs at cracking or emergence. The soybeans usually outgrow it, but it can look pretty tough in some cases.
I still like the Valor-containing herbicides better when applied a couple of weeks prior to planting.
Authority MTZ is another pre-emergence herbicide that has looked pretty good. As a standalone, it is not as good as the two mentioned above. However it can still be a good choice, especially in situations where perhaps a Valor-containing product has been used earlier.
If you look at the University of Arkansas research trials, almost any soil residual herbicide program looked good when followed by timely applications of Ignite. Single applications of metolachlor (Dual and others), pendimethalin (Prowl and others), and trifluralin (Treflan and others) were among these.
As mentioned earlier, two properly timed applications of Ignite alone can look very good, so this isn’t surprising. Keep in mind though the better soil residual treatments will come to the top in situations where timely postemergence applications can not be or are not made.
I am often asked, “What about just going back and incorporating something like Treflan?” You can try it. Before Roundup Ready there were a lot of situations where Treflan would provide at least 80 percent control. On the other hand there were fields where it was totally ineffective due to resistance issues.
Choosing a residual program is a good place to ask a lot of questions at meetings this winter. I have thrown out the concept and a few examples. I like the concept of shooting for 80 percent control with the residual program. I believe it has to be done. However, you also have to be prepared for when they do not work.
Surface-applied herbicides are moisture dependent and can be finicky. Therefore you must be prepared to still make timely postemergence applications.