Photo: Cheatgrass, southwest Montana. © 2020 Delena Norris-Tull
The Myth of Eradication of Invasive Plants
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, October 2020.
Robert Jenn, retired Supervisor for the Sheridan, Wyoming, County Weed and Pest program, in an interview with Becky McMillen in 2014, summed up the herbicide challenges: In the 1980s, “the main (program) for the District was to conquer leafy spurge. We haven’t found out how to do it yet. Dr. Harold Alley was one of the great mentors for the weed and pest program. We started out using Tordon at a gallon to the acre. The first two years we quickly found out that that did nothing but produce a new carpet of leafy spurge by the next year. So we cut back to a quart of Tordon per acre, mixed with some other chemicals, and that worked a lot better. The industry, along with us, hasn’t found a chemical that will really eradicate leafy spurge. We can control it for a couple of years at a time, but that’s about it.”
In the interviews of Wyoming Weed and Pest Supervisors, conducted by Becky McMillen, I noticed that several of the interviewees seemed to still believe that herbicides can eradicate weed species. Surprisingly, these were individuals that had been working in the weed and pest field for 30 plus years.
Some of my first interviews were with Phil Westra and George Beck, at Colorado State University. These long-time weed researchers alerted me to the mounting problems of herbicide-resistance in various weed species. Phil Westra also told me that “95-98% of weed control is with the use of herbicides. In Colorado, there is not enough moisture to grow cover crops, as an alternate to using herbicides.”
Phil Westra added, “At Colorado State University, they use advanced molecular techniques to study the evolution of weeds under rapid selective pressure. They do genome sequencing of weed species to look at genetic changes to weeds, due to pressure from herbicide use.”
Similar to the problem of resistance to antibiotics, that has emerged in medical fields in recent decades, the petrochemical industry is now faced with the reality that, because herbicides do not, in fact, actually eradicate a species, herbicide-resistant weed species has become a major problem. Unfortunately, many State policies on weed management still refer to “eradication,” as though that were both possible and desirable. Today, more weed managers are recognizing that “eradication” can only be attempted when a newly arriving weed species is found in a very small population. It may be possible to eradicate that population. But the invasive species could return in the future.
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The Myth of Eradication of Invasive Plants
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, October 2020.
Robert Jenn, retired Supervisor for the Sheridan, Wyoming, County Weed and Pest program, in an interview with Becky McMillen in 2014, summed up the herbicide challenges: In the 1980s, “the main (program) for the District was to conquer leafy spurge. We haven’t found out how to do it yet. Dr. Harold Alley was one of the great mentors for the weed and pest program. We started out using Tordon at a gallon to the acre. The first two years we quickly found out that that did nothing but produce a new carpet of leafy spurge by the next year. So we cut back to a quart of Tordon per acre, mixed with some other chemicals, and that worked a lot better. The industry, along with us, hasn’t found a chemical that will really eradicate leafy spurge. We can control it for a couple of years at a time, but that’s about it.”
In the interviews of Wyoming Weed and Pest Supervisors, conducted by Becky McMillen, I noticed that several of the interviewees seemed to still believe that herbicides can eradicate weed species. Surprisingly, these were individuals that had been working in the weed and pest field for 30 plus years.
Some of my first interviews were with Phil Westra and George Beck, at Colorado State University. These long-time weed researchers alerted me to the mounting problems of herbicide-resistance in various weed species. Phil Westra also told me that “95-98% of weed control is with the use of herbicides. In Colorado, there is not enough moisture to grow cover crops, as an alternate to using herbicides.”
Phil Westra added, “At Colorado State University, they use advanced molecular techniques to study the evolution of weeds under rapid selective pressure. They do genome sequencing of weed species to look at genetic changes to weeds, due to pressure from herbicide use.”
Similar to the problem of resistance to antibiotics, that has emerged in medical fields in recent decades, the petrochemical industry is now faced with the reality that, because herbicides do not, in fact, actually eradicate a species, herbicide-resistant weed species has become a major problem. Unfortunately, many State policies on weed management still refer to “eradication,” as though that were both possible and desirable. Today, more weed managers are recognizing that “eradication” can only be attempted when a newly arriving weed species is found in a very small population. It may be possible to eradicate that population. But the invasive species could return in the future.
Next Sections on Hericides & other Pesticides:
Next Sections on Managing Invasive Plants: