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Timing Herbicide Applications

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Our abundance of rainfall this year has been truly remarkable. I know some local orchard owners that haven’t had to turn on their irrigation yet for all of 2025. Cattlemen are bragging about the abundance of grass in their pastures. 

On the other hand, some stockmen wanting to bale hay or spray for weeds have found it difficult to find enough dry days in a row (that aligns with their own personal schedule). Wet ground means they have had some difficulty finding time to get into their fields.  

As a result of these wetter weather patterns, I have received calls from ranchers wondering if it’s too late to spray weeds. Honestly, that answer depends on the type of weed and what stage it’s in. As we’ll discuss below, timing is crucial for different weeds. 

First, knowing whether your target weed is an annual or a perennial will help you make the best management decision. Let’s break it down by weed type and calendar season to see what can still be done.

Annual weeds are those that germinate, grow, set seed, and die all in one year. These are best controlled when they’re young and actively growing. We’re talking about things like bitterweed, goat weed (Wooly croton), and buttercup. They can be either cool- or warm-season annuals, and right now in July, most warm-season annuals are nearing full size or even flowering.

That means spraying summer annuals now would require a higher rate of herbicide as the early season rate and it won’t be nearly as effective as it would have been back in late April or May. In fact, with mature annual plants, you might see them turn brown, but they’ve likely already produced seed and will be back next year.

If you’ve got a handful of small seedlings popping up in bare patches, spot-treating at a higher rate may still be worthwhile. But in most cases, it’s better to hold off and plan for an earlier application next spring. 

Perennials are a different animal altogether. These weeds—like broomweed, ironweed, dogfennel, and dewberry—come back every year from the same root system. Because of this, the goal is to get the herbicide all the way into the root zone where it can do the most damage.

The two best windows for perennial weed control are (1) right as they begin to bloom and (2) in late summer to early fall as they start storing up food for winter. In East Texas, we are approaching that second window.

When perennials are transitioning toward dormancy, they naturally move nutrients—and herbicides—down into the roots. That’s the perfect time to spray. If you’ve got trouble spots with established perennials, you’re in a great position to knock them back in the coming weeks.

There’s a temptation to “spray and pray” when pastures look rough in midsummer, but it’s important to make sure the plant is still actively growing. Plants that are stressed from heat or drought don’t absorb herbicide well. And with dryer weather coupled with increasingly higher temps, you run the risk of herbicide volatility or reduced uptake.

Likewise, be cautious not to overuse herbicides this time of year. Always follow the label—and I mean always. Often, more than one product can be effective, but rates matter and so does timing.

Keep in mind that if you use a soil residual herbicide like picloram, you may need to be careful with what follows in that pasture or hayfield. There are plant-back restrictions to watch for if you plan to rotate winter clovers or other sensitive crops.

Here’s my simple takeaway for you: Summer annuals? You’ve likely missed the best time of the year unless you see new seedlings. Used increased rates according to the label but plan to treat earlier next spring.

Perennials? You could be entering the best time. Start identifying and treating those patches while the plants are still green and moving nutrients.

When we get into the pattern of dry weather, hold off until you see signs of new growth. A wilted/ drought stressed weed won’t take up herbicide.

If you want a one-time, silver-bullet solution, I hate to disappoint you. But with a little planning, a sprayer calendar, and close observation of your pastures, you can stay ahead of weed problems.

For more details and specific herbicide suggestions, be sure to check out some of the Texas A&M AgriLife websites. One of my favorites is https://foragefax.tamu.edu/.  They’ve got pasture herbicide guides that are tailored for our region and can help you make the best call for your operation.

If you want to learn more about the weather, forecasting and how to plan your outside work, the Angelina County Extension Office is having its Noon Gardening Seminar this Tuesday, July 15, from 12 to 1 pm. Entitled “The sky above and the soil below: Weather’s Impact on Gardening”, the featured speaker is Matthew Addison, a retired USAF Meteorologist and now an Angelina County Master Gardener. Matthew has worked with weather patterns across the globe in service of this country and has a passion for chasing storms! 

Cary Sims
Cary Sims is the County Extension Agent for agriculture and natural resources for Angelina County. His email address is cw-sims@tamu.edu Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion, age, or national origin.

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