Tackling Weeds in The Fall

WIN THE FIGHT AGAINST LATE SEASON INVADERS!

Did you know that one of the best times to promote a healthy lawn and treat for weeds is the fall? Yes, it’s true! During the summer, the weed lifecycle is dominated by foliar top growth, but as fall approaches, perennial weeds begin to transport energy in the form of sugar down to their roots systems in order to prepare for the impending winter. This is a great time to apply both pre- and post-emergent herbicides. As plants transition from storing energy in their leaves to their roots, post-emergent herbicides will be absorbed foliarly and transported down into the roots resulting in highly effective control. A fall treatment will not only control pervasive fall weeds, but also defend against early spring invaders as well.

WHY ISN’T A SINGLE HERBICIDE APPLICATION IN THE SPRING ENOUGH?

Weeds can invade your turf grass anytime of the year. There are numerous summer annual and biennial weeds that need to be controlled in order to defend against outbreaks. If you have weeds in spring, it’s a safe assumption that many of them were already entrenched in your lawn the previous fall. This is the primary reason you shouldn’t treat for weeds only in the spring. As previously mentioned, perennials that grow in late summer/early fall will begin to store energy in their roots to overwinter, so by treating in the fall, you’re effectively preventing a spring outbreak.

SHOULD I USE A PRE OR POST-EMERGENT HERBICIDE?

For maximum effectiveness, try to find a lawn care product that contains both. The benefit is “two for one” when you treat your lawn for weeds in the fall because you can target both annual and perennial broadleaf invaders with an herbicide that combines pre- and post-emergent control. A post-emergent attacks weeds that are already established while a pre-emergent tackles newly germinated weeds before they can establish and disperse.

Before applying any fall herbicide treatments, closely examine the product’s active ingredients or AI’s. There are a wide variety of pre-emergent herbicides offered in the market. Some of the more prominent technologies include Prodiamine, Dithiopyr (Dimension®), and Specticle®. There are also a wide variety of technologies that provide post-emergent control, many of which stack multiple technologies in one formulation. Common post-emergent chemistries include 2,4-D; MCPP; and dicamba. Combining multiple technologies allows for a wider spectrum of broadleaf weed control. 

• NOTE: Carefully examine the list of “controlled weeds” (typically labeled on each bag) in order to determine if the control agent is the right one for your situation.
• ProTip: Herbicides can be applied in liquid or granular form. Herbicides are often combined with fertilizers so you can kill the weeds and feed your turf in one single application.

TREATMENT TIMING

The best times to apply herbicides in the fall vary with region and climate. For cool season grasses in southern regions (south of the Ohio River), fall treatments may be applied as early as September and as late as November (often in conjunction with fall fertilization). In northern regions, treatments can be applied as early as Labor Day, typically ending by early November. A good rule of thumb is to apply herbicides when air temperatures average at least 50° F or above. To help determine the best timing for herbicide applications in your area, contact your local extension agent. 

• NOTE: Read and follow all directions of use and application instructions prior to the use any lawn care product.

Get started on the lawn care weed battle for next year by following through with pre and post-emergent treatments this fall. Take down those invaders before they become a nuisance next spring!

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