Introduction
Birdsfoot trefoil (Lotus corniculatus) is a persistent invasive legume at Nachusa Grasslands.This plant can form dense mats that smother and outcompete native plants. Current management of this weed involves herbicide treatments that aim to kill the plants fully to the roots and remain in the soil to prevent seeds from establishing. This weed is one of our main targets during weed season. Because of its strong establishment at Nachusa Grasslands we have also used pre-emergent treatments to work towards getting rid of this plant. Here is a post that explains that: Weed management | grassland restoration network. For members of the Fabaceae family, such as birdsfoot trefoil, sweetclover, and crown vetch, chemicals such as aminopyralid, clopyralid, and 2,4-D are often recommended for management. At Nachusa, the crew uses a mixture of Milestone (aminopyralid), Garlon 3A (triclopyr), and Methylated Seed Oil (MSO) during the heaviest part of the weed season to treat multiple weeds. This mixture covers a larger range or broadleaf plants. For this experiment we tested the crew’s current mixture against Transline (clopyralid) and a lower percentage of Milestone (aminopyralid) without the addition of Garlon.
| Treatment | Mixture |
|---|---|
| A | Milestone 0.5% (v/v) Garlon 3A 1% (v/v) MSO 0.5% (v/s) |
| B | Transline 1% (v/v) MSO 0.5% (v/s) |
| C | Milestone 0.075% (v/v)* MSO 0.5% (v/s) |
*Using 0.1 ounces per gallon
Observations
In late June the plants were treated using backpack sprayers. Each plant was labeled with a flag marking which treatment was received. Before pictures were taken, and plants were checked every week following. Initially, the plants in treatment groups with Transline (treatment B) and diluted Milestone (treatment C) showed slower symptom development than those in that treatment group with the crew’s mixture (treatment A). In group A the plants started browning a few days after being treated and a noticeable kill zone surrounding the plants was observed. By early July plants in treatment B were noticeably curled and wilted but continued to produce seed at normal rates unlike plants in groups A and C which still had some plants forming seed pods present, but in lower numbers than group B. By the end of July it was clear that all plants were dead, however the plants exposed to milestone did die more rapidly. Of the two treatments using Milestone the one containing Garlon (treatment A) did have a more rapid impact on the plants than the one without (treatment C), but both treatments were effective at killing the plants. Treatment C also showed less impact on surrounding plants than treatment A.
Discussion
These treatments were applied later in the season (end of June), treatment for this plant at Nachusa usually begins at the end of May. The birdsfoot trefoil plants treated were fully in bloom when sprayed and gearing up to produce seeds which impacted the results of this study. At Nachusa we treat birdsfoot trefoil with both Transline or Milestone mixtures. Both herbicides have worked for us historically. However, this experiment suggests that when spraying later in the season it might be beneficial to utilize a faster acting herbicide to reduce seed production.
Aminopyralid (Milestone) and clopyralid (Transline) are both effective in treating Birdsfoot trefoil, but the aminopyralid (Milestone) is often found to have a stronger biological effect (higher activity), than clopyralid (Transline) according to this study: A Comparative Analysis of Aminopyralid and Clopyralid Efficacy in Broadleaf Weed Management. This study conducted by BenchChem found the following;
“Both aminopyralid and clopyralid are effective herbicides for the management of a wide range of broadleaf weeds. However, experimental data consistently demonstrates that aminopyralid offers a significant advantage in its ability to provide high levels of control at lower application”
This concept may also add some context as to why the plants treated with Milestone showed symptoms so much faster than those treated with Transline. It also potentially helps to explain why plants treated with Transline ended up producing more seed then those treated with Milestone. In terms of late season applications, Milestone performed better for our objective by killing the plants before they could fully complete seed production.
The product labels and fact sheets suggest that Milestone has a strongest residual activity (~6-12 months) compared with Transline (~2-6 months) and Garlon 3a (~2 months). This suggests that when battling a large build up of seed in the soil using milestone might be wiser given its long-term residual activity. In this study we analyzed top-kill and seed production only with visual observations. A more in depth expansion of this study might observe these plant populations over more time to better understand how the residual effects of these herbicides are impacting the rhizomes and the seeds in the soil as well as any regrowth from established plants.
The data from this study suggest that the choice of herbicide for treating birdsfoot trefoil should be based on timing. Treatment C (milestone) acts more slowly compared to treatment A (Milestone and Garlon), it is still effective in killing birdsfoot trefoil plants. It may be best suited for early-season applications when plants are still in the growing stage (May-June). When preventing seed production becomes more important adding in the Garlon 3A might be the solution. Here the crew often does two sweeps of areas with particularly bad infestations of birdsfoot trefoil. I can see a reasonable way to apply these findings being having them complete their first sweep with the concentration of milestone from treatment C and following up later with the Garlon 3A and higher Milestone concentration mixture.
Conclusion
This study found that
- Transline = most selective of three treatments, slowest activity, late season spraying didn’t prevent seed production.
- Milestone + Garlon = fastest control, greatest non-target effects.
- Lower-rate Milestone = less selective than the Transline, slower activity than the Milestone with Garlon, prevented seed production better than the transline treatment.
Management of this weed will continue as is for the remainder of this current season, however next year it may be worth evaluating the herbicides and concentrations we are using. As I stated above I will make a recommendation for the crew to decrease the milestone percentage, at least at the beginning of weed season. There are many reasons why the crew might opt to keep the Garlon addition in this mixture. It increases the spectrum for broadleaf weeds they can treat with the same mixture preventing them from frequent remixing of chemical or having to keep more equipment so they could switch chemicals in the field. For this reason, I understand they will probably continue to use this broader coverage mixture. Dropping the Milestone from 0.5% to 0.1 oz per gallon should still result in effective top-kill of birdsfoot trefoil plants. One of the benefits of using Milestone over Transline is its strong effectiveness in low concentrations. Every birdsfoot trefoil seed prevented today is one less plant to battle tomorrow, knowing that our treatments are working is crucial in the continued management of our wonderful prairies.
Sources for this post
“Milestone Fact Sheet.” n.d. Accessed August 5, 2026. https://forages.tamu.edu/wp-content/uploads/sites/26/legacy-files/PDF/milestone.pdf.
A Comparative Analysis of Aminopyralid and Clopyralid Efficacy in Broadleaf Weed Management. n.d. https://pdf.benchchem.com/1667/A_Comparative_Analysis_of_Aminopyralid_and_Clopyralid_Efficacy_in_Broadleaf_Weed_Management.pdf.
“Kill Birdsfoot Trefoil in My Yard without Killing the Grass. Product Recommendation Please – Ask Extension.” n.d. Accessed July 31, 2026. https://ask.extension.org/kb/faq.php?id=838569.
Maroso, Rita Poles, Cerci Maria Carneiro, Simone Meredith Scheffer-Basso, and Daniela Favero. 2009. “Morphological and Anatomical Aspects of Birdsfoot Trefoil and Big Trefoil.” Revista Brasileira de Zootecnia 38: 1663–67. https://doi.org/https://doi.org/10.1590/S1516-35982009000900004.
Taylor, T. H., W. C. Templeton Jr., and J. W. Wyles. 1973. “Management Effects on Persistence and Productivity of Birdsfoot Trefoil (Lotus Corniculatus L.).” Agronomy Journal 65 (4): 646–48. https://doi.org/10.2134/agronj1973.00021962006500040035x.
“Transline® Herbicide.” n.d. Accessed August 5, 2026. https://www.corteva.com/us/products-and-solutions/land-management/transline.html.
“What You Should Know about Garlon® 3A Herbicide.” n.d. Accessed August 5, 2026. https://www.arborchem.com/images/label-sds/qa_Dow_Garlon3A.pdf.























































