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What is The Value of Weed Biology Research to Applied Management?

Posted by John Spring, Oregon State University | July 28, 2022

I finished graduate school at WSU in the spring of 2017. Just last week, a weed science team from WSU (Ian Burke, Drew Lyon, Frank Young, Samuel Revolinski, and myself) finally got official acceptance of a scientific paper outlining the results of my main dissertation topic, the population genetics of Russian-thistle in Pacific Northwest wheat fallow fields. For those unfamiliar with the academic system, that’s a long pause for something that most students finish at the end of their graduate program, or shortly thereafter, and I’m sure my advisor and committee members had given up hope of publication at least a time or two during the interim. We had to repeat the entire project twice due to faulty DNA sequencing the first time around, write a considerable amount of custom computer code for analysis (all done by Samuel, while he also finished his own PhD), work through two academic journal rejection/resubmission cycles, and overcome maybe just a little bit of procrastination on my end. I share all this not to brag or complain, but to hopefully convey a sense of how much effort and behind the scenes work can go into these sorts of weed biology research projects.

For all of that time and work, we must have come out with some really useful results, right? Something that growers can take and immediately apply to improve field management? As far as I can see now, not so much. Don’t take me wrong, I think that weed biology and ecology research is absolutely critical as we look towards the looming roadblocks and dead ends that herbicide resistance poses for our current weed management systems. I also think there is a great deal of value in better understanding the basic biology of weeds outside of the immediate management implications we hope for as applied researchers. In this particular case, however, the applied implications were fairly minimal. To play devil’s advocate, I could argue that we really just confirmed things that were really already known.

To summarize, a single species of Russian-thistle is present in Washington wheat fallow, which taxonomists have largely agreed on since the 1950s. (They did get it wrong in California, however, where there are no less than 4 genetically separate Russian-thistle species which were confused by taxonomists prior to modern genetics techniques. So, certainly worth checking for in the PNW, but not the case here.) We also found that Russian-thistle has high genetic diversity, no surprise to anyone who had looked closely at the multitude of growth forms we have in the PNW. Most of this diversity is not distributed in any particular pattern. Individuals growing closer together tend to be slightly more similar genetically than those growing far apart, but only 15% of the total genetic variability in the area has any tie to geographic distance. So, managers can think of this variability as ‘random noise’ that won’t really help us better understand the species for management. The lack of geographic structure does indicate that herbicide resistance or other adaptive traits can be expected to spread very rapidly across the entire region. Again, this should be no surprise to those who remember how quickly resistance to Glean (chlorsulfuron) spread.

Two Russian-thistle plants with different growth forms evident, presumably reflecting genetic differences between the two plants. The majority of genetic diversity in our collection was distributed on an individual basis, and not explained or structured by geographic distance or other factors. Thus, we can think of this diversity as ‘random’, and not organized in any particular way we might be able to use. On average, these two individuals growing side-by-side share only 15% more genetic similarity than would, for example, one plant from Asotin and one from Almira.

The vast majority of the time, science returns incremental progress, where small and not-very-exciting-by-themselves results of many single studies eventually string together into a coherent picture that expands our understanding of the world, and can be used to advance management. There are notable exceptions, of course, but few and far between. This study certainly fits into the first case, and that’s okay. Basic biological knowledge accumulated over time does help us frame and deepen our thinking about problematic weeds in a useful way, and to explain, confirm, and quantify the patterns and responses we see in the real world. We generated robust data that provides strong support for what was only suspected before, and ruled out several alternative hypotheses that could have had very different implications. Still, as I struggled to make some management-oriented conclusions from the results, I couldn’t help but try to think of cases where weed biology had a direct and obvious link to improved management actions or strategies, and hope that the results of some other biology-oriented projects I’ve started are more like that. The sort of case where a grower or weed manager could point to a specific new detail of weed biology as reason to adopt or change a specific management action, and realize better control of the weed in question as a result. I’m excluding herbicide efficacy results from ‘basic biology’ research here. Facts like ‘95% of cheatgrass seeds survive only 1 to 2 years in the soil’, or ‘Russian-thistle seed doesn’t mature and become viable before mid-August at the earliest in eastern Washington’ are the sort of things I’m thinking of, and form the basis of two of the best examples of management actions suggested (or, at least whose effectiveness is explained by), knowledge of weed biology.

As a scientist, I certainly have a particular perspective on this, however, and I am curious what growers, agronomists, and other non-academics directly managing weeds think. Are there examples of weed biology research that you found particularly useful to inform improvements in your weed management programs? If so, please share them in the comments. Weed scientists, feel free to join in as well.

4 thoughts on "What is The Value of Weed Biology Research to Applied Management?"

  1. Thank you for this post. While I was familiar with most of the information provided, it’s good to be reminded on occasion about the meticulous procedure that goes into getting research published, and that peer reviews are necessary for credibility.

    1. John Spring says:

      Thanks Tracy, appreciate your reply! The publication and review process almost always makes for better research and better papers, even if we don’t usually get the chance to thank the anonymous reviewers and journal editorial staff properly in the end. Certainly did in this case. – John

  2. Drew Lyon says:

    John, studies on weed seed survival in the soil have been very helpful for weed management. For example, studies that showed that many annual grass weed seeds, such as downy brome, jointed goatgrass, and feral rye, do not survive long in the soil, supported the idea that crop rotation could play an important role in managing these weeds. As herbicide resistance in many of these annual grass weeds increases, I think crop rotation will need to play a much larger role in weed management than it has for the past several decades.

  3. Population genetic studies (a type of weed biology study) of non-crop weeds can tell us a lot about the geographic origins of invasive weeds, their routes of invasion, and genetic diversity within and among populations. This information has direct and immediate consequences in terms of preventing the further spread of the weed and preventing its introduction into areas where it is still not found. In addition, population genetic information is essential to determining whether biological control is likely to be successful in managing the weed and, if yes, where to look for appropriate biocontrol agents.

    For crop weeds, it is essential that ecological research be conducted examining the effectiveness of various non-herbicide practices that farmers can easily adopt on reducing the competitiveness of the weed against the crop instead of simply assessing a new herbicide or combination of herbicides. I view ecological research as “weed biology” research thus again illustrating that weed biology studies can have immediate and effective contributions towards weed management.

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