East Texas Ag News: Plan now to stop weeds in the early spring

Published: Sep. 15, 2022 at 3:45 PM CDT
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ANGELINA COUNTY, Texas (KTRE) - Cooler temperatures have been teasing us as we near fall. You’ve battled drought and probably some other issues in your lawn this year. One way to get a jump on those early weeds that will appear next spring in your lawn is with the application of a pre-emergent herbicide. And now is the time to take action.

A “preemergence herbicide” is an herbicide that is designed to control weeds by interfering with an undesirable weed seed’s germination and emergence. You may find them often referred to as “weed preventers” in the garden centers. After application, these products form a protective barrier in the soil of your lawn during critical times when weeds are most actively germinating and beginning their growth.

Contrast these products with “postemergence herbicides” which will instead work to control established weeds that are already up, growing, and looking unsightly. Even still, there are a few herbicides have both pre- and postemergence activity. These work both to stop seeds from germinating and work on already established weeds.

Different preemergence herbicides will have different modes of action or a different manner in which they work. Several of the preemergence herbicides available for homeowners are classified as “inhibitors of microtubule assembly.” In plainer terms, these products stop cell division, resulting in seedlings that are stunted, deformed, and unable to emerge as healthy plants.

So, what are the benefits of using a preemergent herbicide? First, preemergence herbicides are generally the most effective option for controlling challenging annual weeds like crabgrass and annual bluegrass. Secondly, they provide protection during critical seasons of early spring and late fall when turfgrass may be less able to compete with weeds.

Lastly, in many cases preemergence herbicides can reduce the number of postemergence herbicide applications required to maintain a healthy lawn. And when used as directed by the label, many preemergence products can be safer to use around established plants in the landscape compared with select postemergence products.

Now you ask, “What are some commonly found products that I can use?” Look for brand names that have the following active ingredients. Benefin works well on grasses and some small-seeded broadleaf weeds. Corn gluten meal is good against annual grasses. Isozaben won’t help with grassy weeds but is effective against broadleaved weeds. The last three, Oryzalin, Dithiopyr, Pendimethalin, and Prodiamine, all target grasses and some broadleaf weeds.

When using these products, ALWAYS FOLLOW THE LABEL. Consider all parts of the label including recommended personal protective equipment (PPE), as well as proper application rates and timing of application. The performance of preemergence herbicides can be significantly affected by timing, precipitation, environmental conditions, and the specific weeds you are targeting.

Preemergence herbicides can injure newly established or overseeded turfgrass lawns. Remember, their job is to stop seeds from germinating! Applying too much of select preemergence herbicides can injure established turfgrass. Never exceed the maximum annual rate specified by the product label.

Two preemergent herbicide applications per year are generally recommended for best results: one in the spring and one in the fall. Recommendations for preemergence herbicide timing are generally based on the soil temperatures at which common turfgrass weeds such as crabgrass and annual bluegrass germinate. As such, application timing can fluctuate by several weeks based on region and annual weather conditions. You will find the recommended soil temperatures on the product label.

You can monitor soil temperature yourself using a soil thermometer or even a household meat thermometer. Measure the soil temperature for the uppermost 1″ of soil, where most weed seeds will be concentrated. Be mindful that some seeds may be on the soil surface, which will warm more quickly leading to earlier germination.

If the saying “an ounce of prevention is worth a pound of cure” has any validity, then these next few weeks is the time to control early spring weeds.


Cary Sims is the County Extension Agent for agriculture and natural resources for Angelina County. His email address is cw-sims@tamu.edu