LANDISVILLE, Pa. — Some call it horseweed, some call it marestail, but no-till corn and soybean growers call it a scourge.

Marestail wasn’t the only weed to be scrutinized during Penn State’s annual weed control trials at the Southeastern Agricultural Research and Extension Center in Landisville. But marestail was definitely the featured villain.

The trials were organized by Bill Curran, professor of weed science at Penn State, and Dwight Lingenfelter, Extension associate for weed science.

The trials were organized into seven categories, five for no-till soybeans and one each for no-till corn and wheat.

About 40 people attended a twilight tour of the trials on June 28. A few farmers were at the tour, but most of the attendees were industry reps who sell products and management services to growers, according to Lingenfelter.

The field results are the focus of the tour, he said, but it also brings industry reps together to socialize, share knowledge and see how their products compare to their competitors’ offerings.

For details about marestail during the tour, Curran and Lingenfelter turned the microphone over to Annie Klodd, an Extension associate who started her main campus job in the summer of last year.

Klodd grew up on a farm in Iowa, where her family operates. a vineyard. She earned her master’s degree in plant biology at Penn State, with a research concentration on the use of cover crops to control weeds in vineyards.

Her work now encompasses both vineyards and field crops.

Marestail has been a problem in Pennsylvania for the past seven years, Klodd said, and Penn State Extension has been getting an increasing number of requests for recommendations for control measures.

“One of the challenges of marestail is that it emerges both in the spring and the fall,” she said. “The ones in the fall don’t go to seed, but they overwinter, re-emerge in the spring, and they will go to seed if they’re not controlled.”

Marestail seeds are a lot like dandelion, Klodd said. Even mild breezes can carry the seeds for miles. The Landisville research center has a bountiful seedbank of marestail, she said, and the local population has developed glyphosate resistance.

Resistance generally isn’t good news, but it gives the researchers opportunities to study a variety of control measures.

No matter which controls are used, it’s important to rein in marestail before it’s taller than a soda can, about 5 inches, Klodd said. Once it’s past that height, it’s hard to stop.

Cover crops like cereal rye — planted in the fall, overwintered, then allowed to continue growing in the spring — can shade marestail enough to suppress growth.

Klodd said that approach is being studied at Penn State’s Rock Springs research farm. The study also includes a number of cooperating farmers.

One of Klodd’s job responsibilities is to produce educational materials like the “Marestail Management in Pennsylvania” fact sheet that she wrote with co-authors Curran, Lingenfelter and postdoctoral scholar John Wallace.

The fact sheet was published this spring and is available at any Extension office. Klodd also oversees a website — — which is a wide-ranging source of information on weeds and their control.


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