Benefits of Pre-Emergent Herbicides

While herbicides aren’t a magic solution to our problems with herbicide resistance, using them correctly will help slow down the rate at which we see herbicide resistance spreading. For farmers in the United States battling against herbicide resistant water hemp and palmer amaranth, pre-emergents have become an important tool in protecting their crops.

Adding a pre emerge into your IWM plan allows for increased modes of action used on the farm, while managing weeds before they become too large. It can also significantly delay your in-crop herbicide application, reducing in-crop herbicide passes, and making those in crop passes more effective by reducing weed size and application at the time of application (Iowa State University, 2020). Using products with a soil residual also helps to control later weed flushes.

In 2022, Pitura Farms applied a group 14 pre-emergent on a pea field. This saved us from having to apply any in-crop herbicides on that field, that year.

Pre products can also be applied in the fall for crops where the spring application window is tight. This hurts perennial weeds before they can go into dormancy, reducing their winter survivability, and can also provide some residual control in the spring.

Things to consider when picking a pre-emerge:

1.     Activation criteria
Most pre emerge options need rainfall to activate. Consider the weather forecast before applying.

2.     Residual Activity
Using a residual has many benefits, but it’s also important to consider any cropping restrictions that may occur as a result. In the case of a drought year, using a residual product may severely restrict cropping options for the following year.
For example, spring wheat needs 12 months before it can be planted into a field previously applied with Authority Supreme. However, if drought conditions were to follow that application, 2 years would be the recommended wait time.

3.     Weeds controlled
You should also take into consideration which weeds are controlled by your chosen product. If using a contact product, which weeds are already emerged, and will they be controlled? If using a soil residual product, which weeds are you looking to control and will they emerge within your controlled window?

There are many benefits to using a pre emerge. How might they fit on your farm?

~Beth Ens