Service Castro/ Hale/Lamb County 325-665-8790 Kristie.keys@ag.tamu.edu Commercials are running. Social media is full of striped, golf-course lawns. Garden centers have pallets stacked high with bags that promise “ weed prevention.”
Yes, it’s pre-emergence season on the Texas High Plains!
But before you grab a spreader and head outside, let’s talk about what preemergence herbicides actually do and how to use them correctly.
What is a pre- emergence herbicide?
These are chemicals designed to control weeds by interfering with germination and emergence. Think of these like weed preventers that form a barrier when your lawn is actively growing. When weed seeds begin to germinate, they encounter that barrier and never successfully emerge. Pre-emergence does not kill weeds but stops new weeds before they become problems. It’s a prevention tool, not a rescue treatment!
When timed correctly, pre-emergent products can reduce competition from annual weeds like crabgrass, improve turf density by giving grass the advantage, reduce the need for multiple post-emergence herbicide applications, provide safer weed control for established lawns.
On the High Plains, where wind, heat, and limited rainfall already stress turfgrass, reducing weed competition is a big win!
When should I apply?
There are two times a year when you should be making pre-emergence applications. Spring and Fall. In the spring, this application targets summer annual weeds like crabgrass. Make these applications between February and April when soil temperatures are 55*F consistently for 4-5 days. For the fall application, we are targeting winter annual weeds. This application should be made between August and October when soil temperatures are 70* consistently for 4-5 days.
Taking soil temperatures is easy and no fancy equipment required. You’ll need a meat thermometer and ruler! Measure 1 inch from the tip of your thermometer and mark it. Insert the thermometer into your turf in an open area and give it a few seconds to measure your soil temperature.
A few things to keep in mind: check the label! Preemergent can harm newly established lawns. Effectiveness can be affected by timing, precipitation, environmental conditions, and targeted weeds. Always wear proper Personal Protective Equipment when making applications. Lastly, don’t forget to water in your pre-emergent to active the chemical and push it into the soil where the weeds growing. Apply an ½ inch of irrigation or apply pre-emergent when there is a forecasted rainfall in the few days following application.
Do not use weed and feeds when lawns are not actively growing. This is a waste of nitrogen products. Finally, more herbicide is not always better and can cause stress to your lawn and bad for the environment.