News Release 

Study shows importance of tailoring treatments to clearly defined weed control objectives

Cambridge University Press

WESTMINSTER, Colorado - SEPTEMBER 16, 2019 - A new study in the journal Invasive Plant Science and Management shows that working smarter, not harder, can lead to better control of invasive weeds. And the first step is to clearly define your weed control objectives.

Do you want a quick, short-term reduction in a weed population or long-term control? Is your weed problem limited to a specific area, or are you also concerned about adjacent fields?

"Answering such questions can help you select the most appropriate management options and eliminate wasted effort," says Katriona Shea, a researcher at Pennsylvania State University.

To illustrate the importance of upfront decisions, researchers conducted a two-year study involving invasive thistle, a weed often found in pasturelands and rangelands. Mathematical models were used to determine which of 14 mowing strategies would best support each of three different management objectives: reducing the density of an existing thistle infestation, decreasing long-term population growth and limiting the weed's spread.

Contrary to conventional wisdom, researchers found that fewer, well-timed mowing events were more effective than mowing as often as possible - making it possible to produce a better outcome with less effort.

Intense mowing both before flowering and during the peak flowering period, for example, produced the best long-term control of invasive thistle and reduced both its abundance and its spatial spread. A single, intense mowing during the peak flowering period was the most effective approach for short-term management, which is good news for land managers with limited time and resources.


To learn more, read the article "Working smarter, not harder: objective-dependent management of an invasive thistle, Carduus nutans" - now available online.

About Invasive Plant Science and Management

Invasive Plant Science and Management is a journal of the Weed Science Society of America, a nonprofit scientific society focused on weeds and their impact on the environment. The publication focuses on invasive plant species. To learn more, visit

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