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Weed Problems After Drought

An AgriLife Extension expert advises- Expect weed growth after drought, wildfires.

“A weed is simply a plant growing out of place or growing in a site where it is not desired.”

Those are the thoughts of Dr. Barron Rector, Texas AgriLife Extension Service range specialist. And he said following this year’s drought, wildfires and tons of imported hay, there may be a lot more weeds for landowners to deal with, and some could be invasive species or even toxic.

Rector recently presented a webinar, “Invasive Plants of Texas Rangelands,” as a part of the AgriLife Extension ecosystem science and management department’s Texas Range Webinar Series. This webinar, as well as others in the series, can be accessed at

“The soundest way to control weeds is to prevent the invasion, which means we must understand the biology, limit the movement, understand the human behavior and actions that can cause the spread, and understand the pathways for its introduction,” he said.

Some “weeds” may be a desirable plant in one location and a weed in another, Rector said. For instance, native weeds serve a role of protecting the soil surface after a disturbance, reducing raindrop impact and solar radiation, and providing some organic matter on the soil surface and below ground.

These native weedy plants depend on natural disturbances, such as grazing, fires, flooding, drought, mudslides, earthquakes, volcanoes and land development to spread and reproduce, he said. However, foreign or exotic invasive plant species can survive, reproduce and advance on the same kinds of soil disturbance and human management that produces native weed and brush problems.

“Our major problem with land management today is our inability to recognize an invasive plant species and deal with it accordingly,” Rector said.

And following the recent influx of hay from other regions of the U.S. and even abroad, landowners should expect more invasive plants, he said.

Invasive species of weeds can cause economic or environmental harm due to habitat degradation, displacement of native plants threatening the reduction of wildlife food resources, alterations to the ecosystem of a region or alterations and changes to natural waterways.

“Invasive plants are those that have a tendency to spread and invade healthy landscapes ultimately causing some kind of negative impact,” Rector said. “Invasive plants are often best defined as plants that do not stay where they are planted.”

Since 2008, portions of Texas have been in moderate to extreme drought, he said. This has had an important impact on forage production for livestock. In response to the drought, many livestock owners have opted not to sell their herds, but to buy hay that is available.

“That hay is coming from Louisiana, Tennessee, Nevada, Florida, Nebraska, Kansas and other surrounding states,” Rector said. “Some individuals have even purchased hay from foreign countries, such as Brazil, Chile, Argentina and Canada.

“This sets up a potential problem because interstate commerce of hay is not regulated for the most part. There’s no one at the state line to inspect the hay for foreign and invasive plants. Many landowners and livestock producers could be setting themselves up for weeds they’ve never seen and introduce potentially invasive plants.”

Experience with this type situation goes back to the drought of the ‘50s when hay and other feedstuffs transported from California to Texas are suspected of setting up the invasion of woolly distaff thistle, a native of Italy and the Mediterranean region, he said.

Research has shown the seed of this plant may be viable in the soil for up to 19 years. Today, because of the aggressiveness of this plant, it now grows in 47 Texas counties.

A second example would be in the drought of 1994-2002, where hay delivered from Louisiana to Jasper County carried the first tropical soda apple to Texas.

The tropical soda apple is listed 94th on the federal noxious weed list, and woolly distaff thistle is on the Texas list of noxious and invasive plants.

“We want to alert landowners who feed hay from another state that it could carry with it viable seed that could come up on their land,” Rector said. “It’s a Catch 22. We bought the emergency hay to feed and hold on to our herds, but there is the potential that we can introduce an unwanted plant that will cost more management dollars in the future trying to get rid of it.”

He said there are 1,400 invasive species documented in the U.S. infecting an estimated 1 million acres, and that number will continue to increase 8-20 percent annually, requiring a destruction cost in U.S. estimated at $100 billion annually.

Producers need to start now learning what plants they should be on the lookout for, Rector said. If the hay was purchased from Nebraska, Kansas, Montana, Wyoming, Utah and Idaho, producers should watch for an invasive plant called leafy spurge. If they purchased hay from Florida to Louisiana, that zone is known for the invasive tropical soda apples weed.

Other plants of concern include Canada thistle, spotted knapweed, blessed milk thistle, Russian knapweed and yellow star thistle, he said. Because of their aggressiveness, these will often be the plants that come up on the disturbed areas.

Not only will these invasive weeds keep landowners from producing valuable grass resources in the future, but they can take the place of native weeds that would have come up, such as broomweed, which provides seed that feeds birds such as quail.

Rector said there are several things a landowner needs to do now to prevent problems later.“The first thing to do is be aware of what invasive plants occur in the area you bought the hay,” he said. “Know what they look like.”

Each state has an invasive plant website or every state can be found on the U.S. Department of Agriculture’s invasive and noxious weeds list at

“Make sure you know what they look like and then be on the lookout for them, starting in March,” Rector said. “If they are a warm-season annual, they will be germinating then.”

In general, annual weeds are treated with chemicals when the plant is 3-6 inches tall, he said. It is important to know what the plant looks like in the seedling, rosette and the early vegetative stages because that is when the chemicals and management practices are the cheapest.

“By the time most weeds are flowering and setting seed, it is too late to use a chemical to control most annual plants,” Rector said.

Once a landowner can identify the plant, they need to know the recommendations for management to reduce the impact or eliminate it from the land, he said.

Rector said landowners can go to and there is a choice of plant identification links that will help a landowner not only identify a plant, but also learn about its habitat, toxicity to livestock and management strategies.

“Try to limit the areas where you feed the hay and not spread it all over your ranch. And then make sure you continually go back and look at pastures where you fed hay in future years,” he said. “With the weather prognosis of continued drought, those seeds may sit in the soil for several years before they emerge.”

By:  Kay Ledbetter

Source:  Texas and Southwestern Cattle Raisers Association and AgriLife Today