Organic Control of Perennial Weeds with Vinegar and Biologicals

Final Report for FW11-024

Project Type: Farmer/Rancher
Funds awarded in 2011: $20,790.00
Projected End Date: 12/31/2012
Region: Western
State: Montana
Principal Investigator:
Jess Alger
Organic control of Perennial Weeds
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Project Information


The purpose of this project was to determine effective, sustainable ways to control perennial, noxious weeds with biologicals and vinegar on organic farms and ranches. We found that vinegar was a very effective organic control for bindweed, Canada thistle, spotted knapweed and whitetop. We learned that 15% vinegar solution was strong enough to be effective, and that timing and treating especially first year growth increases treatment success. Re-treatment is also necessary for these persistent weeds; for best results, re-treating as often as four times in a growing season. Also, it is important to flush vinegar out of spray equipment to lengthen its life. Biological controls were effective treatments for leafy spurge and Canada thistle, though patience is required to see full benefit.


Noxious weeds are persistent and hard to kill, even with the best technology. On organic farms and ranches, there has not been any good techniques demonstrated for effective long-term control of these types of plants. This project was developed to help determine what techniques might prove effective enough to be reasonable and sustainable so that a working organic farm or ranch might find them to be beneficial and economically justifiable.

Project Objectives:

The objective of the project was for each of the producers to try new ways of treating their respective weeds of concern and find acceptable methods that would meet organic producer and economic targets.


Click linked name(s) to expand/collapse or show everyone's info
  • Casey Bailey
  • Jan Boyle
  • Rick Caquelin
  • Bob Herdegen


Materials and methods:

The project was conducted on four separate private ranches in Montana. Each ranch treated the noxious weeds present on that ranch with a variety of methods of organic controls, including vinegar applications, biological insect releases, mowing, hand pulling and black plastic.

We used a 30% strength vinegar from Fleishmann Vinegar from Sumner WA. We added equal parts of water to make a 15% solution to spray on the weeds. The vinegar only burns down what it contacts, so the weeds need to be thoroughly wet.


Casey Bailey, on his farm near Ft. Benton, investigated controlling Canada Thistle using biological pests and alfalfa. He released stem gall wasps and stem weevils. He purchased a variety of alfalfa designated for irrigation fields with a tested winter hardiness for our area. The purpose of this was to enable an easier termination of the alfalfa at the end of its rotation and an easier transition back to annual grains. Termination is a problem with old varieties of alfalfa bred for dryland strength and winter hardiness.

He underseeded 40 acres of safflower with alfalfa on June 1st. This was a tremendous success. Both the safflower and the alfalfa did well despite the dry summer. The safflower set 700 lbs/acre of seed, yet remained quite short, most likely due to water limitation. The alfalfa underneath had plenty of light since safflower is a non-competitive crop.

He also seeded a 50-foot swath of alfalfa on the edge of a 270 acre field, hand-spinning alfalfa seed were thistle extended beyond 50 feet. This was seeded into a standing crop of peas, kamut and lentils. The alfalfa was very small through the season and did not receive much rain after harvest until late in the fall. Next year will show the results. This is the first year alfalfa was seeded into established crop and established Canada thistle patches. It will be interesting to see if the small alfalfa plants can germinate and outgrow crop and thistle that has a head start.

Two more fields were seeded to alfalfa that have a history of both Canada thistle and bindweed. This begins the first year of transition to be organic.

Within the alfalfa fields that are hayed twice a year, the Canada thistle is disappearing. Year Two after the bugs were released, there was one gall and minimal apparent activity.

The hand-spun field edges and draws contain both alfalfa and thistle. In these locations the fight begins. The alfalfa is certainly holding the thistle back, the question is, will it outcompete it enough so the thistle recedes even in the unfarmed ground?


The efforts to combat Field Bindweed on the Alger Ranch by Stanford have simply consisted of spraying the plant wherever it occurs, usually only once a year, with 15% Vinegar. Sometimes Field Bindweed has gone to seed unnoticed in a wheat field; then we combine around the bindweed, spray it with vinegar and mow it with a bagging mower to remove the seeds.

We did find Tortoise beetles munching up Bindweed. These beetles look very much like orange ladybugs. At the slightest disturbance, they drop to the ground and hide. The beetles remove circles from the leaves and some Bindweed vines were nearly defoliated. Despite the damage the beetles had done, the vines they were on had already set seeds.


We buy 55 gallon barrels of 30% strength vinegar from Fleischman’s in Auburn, WA and use it diluted with half water to make a 15% solution. The vinegar burns down only the foliage it contacts. The effect is quite rapid; before one hour has passed the foliage will be wilted, and within five hours on a warm sunny day, the sprayed area will be brown. All of the patches that I have knowledge of that have totally disappeared, the plants were pulled by hand or dug up by hand.

Research results and discussion:

The potential impacts of this project are far-reaching. The use of herbicides is negatively affecting water quality world-wide. The cost of these chemicals is often prohibitive and based on continued increasing use, largely ineffective. This project demonstrates that vinegar application and use of biological controls can make weed management economically viable and many times safer for the environment.

The Black plastic used at Jess Alger Ranch was about 90% effective. Just a few plants survived on outside of the plastic. Basically a dead spot in the field. Need to replant alfalfa.

Participation Summary

Research Outcomes

No research outcomes

Education and Outreach

Participation Summary:

Education and outreach methods and analyses:

There was a Bug/Weed Field Day held at the Birdtail Ranch, 45 south of Chinook, on August 24, 2012 with 13 participants attending. This was followed up by an article entitled “Bug Tour at the Birdtail Ranch” by Liz Carlisle in the Trader’s Dispatch and The Montana Organic Association Newsletter. We are not sure how to get our report out to producers.

Education and Outreach Outcomes

Recommendations for education and outreach:

Potential Contributions

We made several advances in our understanding of the most beneficial use of vinegar in treating weeds. First, we determined that a 15% solution of vinegar was adequate to treat even these persistent weeds. We recognized that to be effective treating new growth, treating the whole plant, treating around the edges of a weed patch and re-treating as many as four times in a year was instrumental in having the best treatment results. We also believe the use of an organic surfactant will increase the effectiveness of the treatments. Jan Boyle used the surfactant with her vinegar. Jan reported the white top was burned down by the vinegar, the plants did not go to seed and the stand was substantially weaker the next year. Finally, we learned the need for rigorous clean-up of spray equipment to maximize its service life.

Future Recommendations

This funding was easy to work with and helped us accomplish our objective in a short two years; really increasing our learning curve. Without the grant we would have been years behind in advancing our ability to sustainably control our noxious weeds.

Producers need to know which of the three types of Knapweed they have so they can order the correct Biological insects.

We would like to see more information about the Biological Control insects. (Possibly in a brochure.) Many producers are not informed on Biological Insects or the Vinegar Spraying.

Planting alfalfa on farm ground and haying a few years gets rid of the Canada Thistle.

There are White Top Biologicals, but they will not be released until they are deemed safe to only eat White Top. These need to be studied.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.