Most food-plotters know how to spray weeds after they’ve germinated. But herbicides that control weeds before they germinate may be more effective in the long run.
For the diehard food-plotter, it doesn’t get much worse than pouring time and resources into the perfect deer food plot only to see your hopes and dreams overtaken by undesirable weeds. Unfortunately this has been going on for quite some time. In fact, Genesis 3:17-18 states after Adam had eaten the forbidden fruit that “cursed is the ground because of you; through painful toil you will eat of it all the days of your life. It will produce thorns and thistles for you.” While this curse remains in full effect, fortunately we have access to more modern tools than Adam did back in the day – but you have to use them.
While mechanical methods such as disking and mowing have their place in an integrated weed management program, chemical weed control is most effective. There are many types of herbicides that have specific applications, and they are becoming increasingly popular as food plotters become more familiar with them. However, the vast majority of managers use post-emergence applications – applying herbicides after a crop has germinated and emerged – and miss out on other types that may be easier to implement or assist in accomplishing specific objectives that otherwise might not be an option. Thus, the purpose of this article is to define the three primary types of herbicide applications that pertain to food plots and discuss options for managing various forages using them. Here’s a look at each.
Please note: This article is not a substitute for reading and following the recommendations on the label of any herbicide you use. Be sure to read the label before buying or using any herbicide.
Pre-Emergence
As the name implies, these herbicides can be applied before weed seedlings emerge to help control them before they have a chance to become established.
Prowl will control many grass and broadleaf weeds before they ever emerge and is often the only herbicide application needed for a weed-free food plot.
Typically, they are applied to the soil at the same time the plots are planted – literally they are sprayed on top of the dirt. Since you have to visit the food plot to plant the seed, you might as well add some protection while you are already there! Pre-emergence herbicides are soil active, so they will remain effective in the soil to provide control for weeks or even months at a time, depending on the specific herbicide. They can also be used in existing perennial clover/chicory plots in early spring and/or fall to control weeds before they start to emerge. It is also important to remember that many pre-emergence herbicides need moisture for best results, so it will be important to apply when rain is in the forecast within a couple days of the application. This is typically when you would be planting a food plot anyway, so the timing works well.
A good example of a pre-emergence application that is commonly used for food plots is to use the herbicide Prowl (active ingredient: pendimethalin) when planting species such as corn, soybeans, cowpeas, alfalfa, sunflowers, or Austrian winter peas. This will control many grass and broadleaf weeds before they ever emerge and is often the only herbicide application that will be needed for a weed-free plot. It does not control weeds that are already established and growing
Another pre-emergence option for a cool-season planting is OutRider (sulfosulfuron). If you have significant problems with both grass and broadleaf weeds in your plots, such as wild mustard, chickweed, brome, cheat, or buttercup, you can plant an awnless variety of wheat and use OutRider for weed control. Once the weed seed levels in the seedbank have been depleted over a couple years, you can begin incorporating other forages in the mixture.
Pre-Plant Incorporated
This application is very similar to pre-emergence in the way that the herbicides used are soil active and that they control weeds before they emerge. However, as the name implies, this application requires the herbicide to be incorporated into the soil by disking or cultivation after it is sprayed on the soil. Obviously this takes an extra step unless it is done in conjunction with covering the seed that is being planted. Although similar, it is important to note that pre-emergence and pre-plant incorporated herbicide applications are not the same. There are specific situations where one method needs to be used instead of the other. Also, some herbicides can safely be applied pre-emergence but not pre-plant incorporated, and vice versa.
A good example of a pre-plant incorporated application is to use the herbicide Dual Magnum (S-metolachlor) to control many grass and broadleaf weeds, as well as yellow nutsedge, in plots you want to plant in corn, soybeans, cowpeas, peanuts, or sunflowers. Dual Magnum does not control weeds that are already established and actively growing.
Post-Emergence
One of the dangers of post-emergence applications is that weeds can take over the plot before you have a chance to spray them. Post-emergence applications need to occur when weeds are less than 6 inches tall for best results.
This is by far the most commonly used method for wildlife food plots, primarily because many food plotters are unfamiliar with pre-emergence or pre-plant incorporated options that are often more effective and less time consuming. The objective of a post-emergence herbicide application is to kill weeds that are already established and actively growing, thus, the herbicide is applied to the leaves of the plants. Most post-emergence herbicides used for managing food plots are not soil active.
One of the dangers of post-emergence applications is that weeds can take over the plot before you have a chance to spray them. Post-emergence applications need to occur when weeds are less than 6 inches tall for best results. Otherwise the effectiveness of the application decreases, particularly with certain weed species.
Some of the most common post-emergence applications include using Roundup (glyphosate) to prepare a field for planting or when using Roundup-Ready crops. Another application is to use Clethodim 2EC (clethodim) or Poast (sethoxydim) to kill grass weeds after they emerge in plots planted in broadleaf species, such as soybeans, cowpeas, alfalfa, clovers, brassicas, or Austrian winter peas. Lastly, herbicides such as 2,4-D, Butyrac (2,4-DB), Banvel (dicamba), or Clarity (dicamba) are commonly used to kill established broadleaf weeds in plots that have been planted in grass species, such as corn, wheat, oats, or triticale.
Crop-Rotation Restrictions
It is important to note that herbicides that are soil active (used pre-emergence and/or pre-plant incorporated) have crop-rotation restrictions, which means there is a minimum time period between when the herbicide is used and when the next crop can be safely planted in the same field. This time period varies according the species that is to be planted as well as the herbicide that was used.
For example, if you use the pre-plant incorporated method mentioned above using Dual Magnum in your cowpea plots because yellow nutsedge always takes over every time you disk the field in the summer, then you need to allow 4½ months before planting cereal grains (wheat, oats, cereal rye) in the same field the following fall. With this application, the crop rotation for planting clovers after spraying the field with Dual Magnum is 9 months. Thus, if you plant both summer and fall crops within the same field each year, you must consider crop-rotation restrictions if using pre-emergence or pre-plant incorporated applications.
Crop rotation and other important information can be found by reading the herbicide label. Alternatively, Dr. Craig Harper with the University of Tennessee has rolled all of this information up into a fantastic book/field guide that every food plotter should keep in their vehicle as a resource for making management-related decisions on the property they manage. The book Wildlife Food Plots and Early Successional Plants can be purchased here at NDA’s online store. It is important to always read the herbicide label and familiarize yourself with the limitations and restrictions of the specific herbicide you are using.
While herbicide technology gives us plenty of options to help accomplish our food plot objectives, perhaps the most important component of a successful weed management program is knowledge of the weeds, both cool-season and warm-season, that are present on the property you manage. This may take a couple years to sort out, but once you can identify the weeds that give you the most trouble, you can develop a specific herbicide strategy that addresses the problem effectively and efficiently. This often takes an integrated approach, using a combination of different methods. Initially it can be overwhelming, but cracking the code and developing an effective solution is very satisfying.