It seems like weed control is a year round sport anymore. In fact, planning your herbicide program prior to any weed emerging is the key to the success of your control. There was a time when it was vogue to wait until weeds emerged to apply herbicides. The logic was that you knew exactly what weeds needed control, and the population that had to be dealt with. It was also assumed that the herbicides in the tank would give you acceptable and consistent control. That thought has changed significantly, especially with the onset of resistant weeds, a larger variety of weed species in fields, and less tillage.
Another major problem that comes from less tillage is the increase in the amount and variety of winter annual weeds, and early emerging broadleaf weeds like kochia, russian thistle, marestail, and prickly lettuce. These species can be very tough to control with the herbicides we have available, and also due to resistance – especially kochia. If you are dealing with these types of weeds, it is imperative that you pull the sprayer out very early in the spring. The key to success is treat early. In fact, treating just prior to any spring germination has proven to be very effective. In many cases, we have seen kochia emerging on a warm day in late January or February. Russian thistle follows a similar pattern. Once kochia and thistle get a little size on them, they become very tough to kill. These small weeds can be ‘wounded’ quite easily, but trying to kill a wounded weed is very tough. Subsequent treatments can be very frustrating.
There are options available that will control these early emerging weeds, by utilizing residual herbicides that can keep your fields clean up to, and through planting. Good weed control programs should be built around the idea of not seeing a significant crop of weeds emerge. Good weed control programs utilize different modes of action, a combination of contact and residual herbicides, and reduce the probability of creating resistant weed populations. Your Crop Quest Agronomist can put together a herbicide plan that will deal with your entire weed spectrum, all the way from those early spring weeds through those late germinating weeds after crop canopy. Visit with your Agronomist soon to build the program that best fits your needs for the fast approaching season.
Written by: Dwight Koops, Ulysses, KS
Photo by: Phil Westra, Colorado State University, Bugwood.org