Treat for Winter Weeds, Fire Ants Now

We are now in a fall weather pattern, according to local weathermen, with milder temperatures and rain in the forecast. I am ready for a change. While this forecast spells relief from another hot, dry summer, it also will trigger some unwelcome pests to our yards. A couple of these are winter weeds and fire ants.

Winter Weeds. Winter weeds, like henbit, chickweed, and annual bluegrass (Poa annua), may seem a long way off, but late summer to early fall is the best time to apply pre-emergent herbicides to lawns before weed seeds begin to germinate. Most homeowners don’t think about winter-weed control in their lawns until the weather starts to cool down, but by then it may be too late.

The optimal time to apply herbicides in our area is early to mid-September. One reason pre-emergent herbicides fail to work is because they are not watered in after being applied. Water lawns immediately or at least within a day of applying the herbicide to allow the chemical to soak in, applying about a half-inch of water.

Before buying a pre-emergent herbicide, read the label carefully to determine if the material is appropriate for your type of grass to be treated. Carefully follow instructions on how much to apply. Calculate the lawn’s square footage to determine how much to apply. Lawn areas can be measured by walking length by width, taking roughly 3-foot strides.

For annual winter broadleaf weeds that have already emerged, apply a post-emergent herbicide for that type of weed. Allow the post-emergent material to dry on the foliage for about two days before mowing. The best time to treat for emerged winter broadleaf weeds is in the fall and early winter while the weeds are young and actively growing. Don’t wait until spring to apply the herbicide because by then, the weeds will be mature and difficult to control.

Continue using best cultural practices to maintain a healthy lawn through the fall and winter including regular mowing, timely irrigation and appropriate fertilization. Turfgrass experts all agree that a dense healthy stand of grass is our best defense against weeds.

Fire Ants. The Texas A&M AgriLife Extension Service is working to help Texas residents manage one of the most prevalent and least popular insects in the state.

The second week of September has been designated statewide as Fire Ant Awareness Week, and AgriLife Extension experts spread the word to help control this perpetual Texas pest.

“Fire Ant Awareness Week was made official statewide more than 10 years ago and fire ant awareness efforts are still ongoing,” said Molly Keck, AgriLife Extension integrated pest management specialist for Bexar County.

Keck said the week was established as a means of helping Texas residents realize the importance of fall treatment for fire ants. “Most people only think about treating for fire ants in the spring, but it’s equally important to treat for them in the fall to keep them from returning the following spring,” she said.

According to the Texas Imported Fire Ant Research and Management Project, the impact of red imported fire ants in the state of Texas is estimated at about $1.2 billion annually. The project’s Web site ( notes that red imported fire ants can pose a serious health threat to plants and animals, and that the project’s goal is “to find effective methods to eliminate this invasive species as a major economic and medical pest.”

One of the most effective large-scale fire ant management methods identified by the project and AgriLife Extension integrated pest management specialists statewide has been coordinated community fire ant management efforts.

Fire ant control is more effective when homeowners in a neighborhood commit to treat their yards at the same time so fire ants can’t relocate and build fresh mounds in a neighbor’s yard, said Elizabeth “Wizzie” Brown, AgriLife Extension integrated pest management specialist for Travis County.

“While people in South and South Central Texas in particular haven’t seen as many fire ant mounds or as much fire ant activity lately due to the drought, just because they’re out of sight doesn’t mean they’ve disappeared,” Brown said.

She said while fire ants have gone underground during the drought to escape the heat and find moisture, they will return to the surface and build mounds as soon as the area receives enough rain.

“Along with helping reduce fire ant population during the next spring, fall treatment more immediately reduces fire ant numbers, which is important because fire ants in Texas are typically active through the month of November,” she said.

Another recommendation of the fire ant project is the “Texas Two-Step” approach to fire ant control, said Dr. Bart Drees, AgriLife Extension statewide fire ant specialist. The first step involves broadcasting fire ant bait over an entire yard, using a hand-held seed spreader or a larger spreader for more spacious yards and landscapes.

The technique is most useful when there are five or more ant mounds per one-quarter acre or the equivalent of more than 20 mounds per acre, Drees said. “Broadcasting will typically take care of 80 to 90 percent of the mounds, then you need to treat the remaining mounds,” he said.

The second step of the two-step process involves applying bait to individual mounds, particularly those next to building foundations and high-traffic areas.

“But remember to read labels carefully before buying bait,” Drees said. “This will help you determine if the product is effective against fire ants and will guide you on where to use it and how much to use.” He added that it is best to apply ant bait during temperatures between 65 degrees to 95 degrees as this is the range when fire ants typically come out to forage.

Drees said the project uses other methods of fire ant control, including the use of phorid flies.

“The phorid fly is a biological control and we have been establishing colonies of them throughout the state,” he said. “They have been growing and spreading, and over time we expect there to be populations all over Texas.”

Drees said further information on statewide fire ant research and control can be found at the project’s web site, Another good resource is on the national Extension web site,

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