Expect more weeds, even invasive or toxic, to appear in areas hit by drought, wildfires and where hay has been imported. So said Barron Rector, Texas AgriLife Extension Service range specialist, in a recent webinar called Invasive Plants of Texas Rangelands.

Producers who’ve bought hay from Nebraska, Kansas, Montana, Wyoming, Utah and Idaho should watch for the invasive leafy spurge. Hay from Florida to Louisiana may contain the invasive tropical soda apples weed, Rector said.

Other weeds to be on the lookout for include Canada thistle, spotted knapweed, blessed milk thistle, Russian knapweed and yellow star thistle. Because of their aggressiveness, these will often come up on the disturbed areas and keep landowners from producing valuable grass resources. They can also take the place of native weeds that would have come up, such as broomweed, which provides seed that feeds birds such as quail.

Interstate commerce of hay is not regulated for the most part, Rector said. “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.

“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. 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.”

A total of 1,400 invasive species have been documented in the U.S. infecting an estimated 1 million acres. That number will continue to increase 8-20% annually, causing destruction costs in the U.S. at an estimated $100 billion annually.

To prevent problems later, he said, “be aware of what invasive plants occur in the area you bought the hay. Know what they look like.”

Each state has an invasive plant Web site or every state can be found on USDA’s invasive and noxious weeds list at http://plants.usda.gov/java/noxiousDriver.

“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 plants are 3-6” tall, he said. Know what the plant looks like in the seedling, rosette and the early vegetative stages, when chemicals and management practices are more cost-effective. “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.

For management strategies, landowners can go to http://essmextension.tamu.edu/plants. The site also offers plant identification links that also inform about plant habitat and toxicity to livestock.

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

Find more stories, photos, videos and audio at agrilife.org/today. The webinar is part of the AgriLife Extension ecosystem science and management department’s Texas Range Webinar Series.