Greg Dahl has a passion for controlling weeds and a curiosity about how
Dahl grew up on his family’s small Minnesota grain and potato farm. His great-great-grandparents and great-grandparents were homesteaders. He spent a lot of time in the fields when he was young and eventually studied at North Dakota State University, earning his master’s degree in agronomy and weed science.
Dahl has worked for Land O’Lakes for more than 20 years. As a senior research manager at WinField United, Dahl has helped develop more than 50 new or improved products for weed management. In his career, he has conducted hundreds of studies and looked at tens of thousands of research plots.
SF: What does it mean to you to be known as the Wizard of Weeds?
GD: It’s a cool thing. It means I have contributed to agriculture. My motto is “people helping people,” and I’m one of those people helping others. It’s fun to be the Wizard of Weeds. People ask me questions and either I know the answer, know someone who does, or no one knows, and we find out together. It makes me feel good that I’ve been able to help, and I’m glad to be part of a community that works together.
SF: What do you enjoy about research and product development?
GD: I hate weeds and love to eliminate them. I’m always impressed with their health and creativity in finding ways to overcome whatever we’re doing to control them. If we do tillage, they figure out ways to survive. If we apply herbicides, they develop resistance. I find it interesting how they can adapt and do it so quickly. Some farmers are doing a really good job managing weed pressure, but in a lot of other cases, the weeds are winning. I’m trying to do what I can to help.
SF: How has weed management changed over time?
GD: I’ve been spraying weeds since 1973, so I’ve been in this game a long time. In the ’70s and ’80s, we had a lot of tillage-resistant weeds that survived our attempts to cultivate and plow and turn everything black. In the late ’80s and ’90s, we were able to get rid of a lot of those weeds by spraying them. Now we face herbicide resistance, so we need to move to the next technology, use all of the tools in our toolbox, and develop a few more.
SF: Which practices help manage weeds?
GD: Weeds are complex. We need to outthink them. I’m excited about the potential cover crops have to suppress weeds. There are many advantages to cover crops, but it takes some management and time, and sometimes things don’t go quite right. In the near future robotics will help, but equipment can break or need maintenance. We need great stewardship, which many farmers are already doing. I applaud them for it. It’s hard work. There will always be weed problems, but we need to produce food in the best manner possible, limiting the harm that could be caused to the environment and to us.
SF: Why isn’t spraying the magic bullet?
GD: Generally, what we want to do is control weeds early in their growth when they’re small, sensitive, and easier to manage. Especially for herbicide-resistant weeds, if you don’t get to the fields quickly and control every growth point on the weed plant, it will grow back. The growing points at the top of the plant develop apical dominance – they get the food from the plant to grow and develop. The growing points on the lower part of the weed are inactive, but when you spray, the chemical often controls the leaves and growing points on the top of the plant because they are active. When the top of the plant dies, those lower growing points now can become activated, grow, and put seed out. So, you need to control every growing point on that plant, and you can do so by spraying earlier.
SF: How should farmers manage weed pressure in the future?
GD: You can’t just do one thing and be done. You have to stay on it all the time because weeds will find a flaw in your system and persevere. You need a strategy that never quits. A crop rotation that has crops with different planting and harvesting dates can interfere with the life cycles of weeds. Find out if you can incorporate winter wheat in your rotation: A lot of weeds, such as waterhemp or Palmer amaranth, that are giving us resistance issues really don’t compete well with wheat. It won’t work for everybody, but it’s something to try.
Put a residual herbicide on at planting time and follow up with postemergence sprays to knock those weeds back. If you have the ability, you should spray after harvest to manage fall annuals and help prepare for the next spring. I realize these strategies cost a lot more money. But these weeds are already costing you a lot of money, and it’s often much more than
Greg Dahl would like to thank:
- My parents, Raymond and Beverly Dahl
- Eddie Bernhardson, Clay County Agricultural Agent
- My teachers and mentors in Weed Science at North Dakota State University
- Dr. John Nalewaja, Dr. Alan Dexter, Dr. Calvin Messersmith, Dr. Steve Miller, Dr. Charlotte Eberlein, Dr. Rodney Lym, Dr. Donald Penner, Dr. Phil Westra and many others
I have been blessed to be a member of many professional weed and agricultural societies. I have been mentored well by members of these societies, which include:
- North Central Weed Science Society, where I served as NCWSS President in 2017; received a Distinguished Achievement Award in 2011; received the NDSU Fellow Award in 2019; and have been a member since 1981
- Weed Science Society of America
- Western Society of Weed Science
- Southern Weed Science Society
- Canadian Weed Science Society
- Council for Agricultural Science and Technology
- American Society of Agronomy
- Certified Crop Advisor, where I have been in good standing since 1998
- I would also like to thank Joe Gednalske, who was the best. It was a real pleasure to work with him developing the great products we did. I learned so much from him and thank him dearly.
- I also want to thank the many other leaders and fine people at WinField United and its predecessor companies who made it such a pleasure to work with them.
- I am also proud of my accomplishments when I worked at the NDSU Extension Service with that amazing group of people. They have served us very well, and I thank them for their service!