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Pest SolutionsPESTS + WEEDSUSING PESTICIDES OR HERBICIDES?
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Tansy Ragwort
Senecio jacobaea
Updated Oct 26, 2024
Make a Positive Identification
- Tansy ragwort is an herbaceous plant (soft stems and leaves) with yellow flowers. The stems grow upright 0.5–4 feet tall. It is a widespread weed in the Pacific Northwest.
- Its life cycle is biennial. Following germination, tansy ragwort forms a rosette with shallow roots. The rosettes have light-green leaves that grow close to the ground. During its second growth year, one or more flowering stems form.
- Mature plants produce 100,000 seeds or more. Tansy ragwort spreads easily by seed.
- It forms dense stands and crowds out other herbaceous plants.
Species: Tansy Ragwort
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Tansy ragwort stems grow 1.5–4 feet tall. It forms dense stands. Tansy ragwort thrives in areas with disturbed soil.
Species: Tansy Ragwort
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Its leaves are dark green on top and lighter underneath. They have deeply lobed leaves with a ruffled look.
Species: Tansy Ragwort
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
Tansy ragwort has yellow, sunflower-family flowers. They have 15-ray flowers that look like petals.
Species: Tansy Ragwort
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
After a tansy ragwort seed germinates, plants form a rosette. The rosettes have light-green leaves that grow close to the ground. The leaves are lobed.
Species: Cinnabar Moth
Whiteway, iStock
The cinnabar moth (Tyria jacobaeae) was introduced to the Pacific Northwest as a biological control for tansy ragwort. The larvae have distinct orange and black stripes, which can help you to identify tansy ragwort. The larvae of the moth defoliate tansy ragwort. See below for information about biocontrol.
LOOK-ALIKES: COMMON TANSY AND ST. JOHNSWORT
Species: Common Tansy
Photo credits
Left:
"20120803_SunsetBeach_TanacetumVulgare-Tansy_Cutler_P1290088a" by wlcutler is licensed under CC BY 2.0.
Common tansy (Tanecetum vulgare) also has lobed green leaves and yellow flowers. But its flowers are button-shaped. They don’t have the ray flowers. Common tansy is also weedy, but not as aggressive as tansy ragwort. It is less poisonous to livestock. Control methods for common tansy are similar to the solutions for tansy ragwort.
Species: Common St. Johnswort
Steve Dewey, Utah State University, Bugwood.org
Common St. Johnswort (Hypericum perforatum) is another weedy plant species with yellow flowers. It has star-shaped flowers with five petals as shown in the photo. Its stems are reddish compared to tansy ragwort. It grows upright to 1–2.5 feet tall.
Tansy Ragwort Benefits
- Tansy ragwort is an invasive weed. It doesn’t have any benefits for people or the environment.
Tansy Ragwort Risks
- If left unmanaged, tansy ragwort forms dense stands. It crowds out other herbaceous plants.
- It has little food value to native animals and insects.
- Tansy ragwort reduces the habitat value of an area by excluding native plants.
- Tansy ragwort is toxic to all livestock, especially cattle and horses.
Risk Card
Does it cause harm?
Adults & Children
Some
Toxic to people and source of pollen that affects people with allergies
Property
High
Takes over areas
Pets
Very High
Toxic to livestock
Annoyance
High
Difficult to control
Environment
High
Crowds out other herbaceous plants
Action Highly Recommended
Take action to control this invasive weed
Take Action
If you have tansy ragwort on property you manage, control it to limit the spread.
Do I need to take action?
Yes. Remove individual plants and small patches. Established patches require several years to control.
What if I do nothing?
Tansy ragwort will spread by seed and take over areas.
If you believe your horses or cattle have eaten tansy ragwort, contact your veterinarian right away. Both fresh and dried tansy ragwort plants are toxic to horses and cattle. Sheep and goats are less susceptible to tansy ragwort poisoning.
Prevent Tansy Ragwort
Utah State University , Bugwood.org
Look for Tansy Ragwort Seedlings and Rosettes
- Return to the site after control activities and look for regrowth. Tansy ragwort regrows from seeds in the soil that remain viable for many years.
- Look for tansy ragwort seedlings like those shown in the photo. Take action as needed.
Weston Miller, Oregon State University
Remove Dirt from Shoes and Equipment
- After working or traveling in a patch of tansy ragwort, clean your boots and tools. Use a wire brush to remove soil and plant material.
- If you drive into the tansy ragwort stand, clean your vehicle.
Weston Miller, Oregon State University
Install New Plants
- Take care of the plants to get them established and suppress tansy ragwort regrowth.
- Replanting stabilizes the soil surface, shades tansy ragwort seedlings, and creates habitat.
- A tansy infestation and removal activities may significantly damage a site. There may be few or no remaining desirable plants.
- Plan for at least 2-3 years of monitoring and maintenance.
- Your local Extension specialist, soil and water conservation district, or a professional revegetation specialist can suggest strategies for your area.
Utah State University, Bugwood.org
Pasture Management
- If you have pasture areas and graze livestock, it is critically important to manage tansy ragwort. All plant parts are poisonous to cattle and horses. Sheep are not susceptible to tansy ragwort poisoning.
- The best option to control tansy ragwort in pasture areas is to promote a healthy stand of grasses and broadleaf plants. Avoid overgrazing.
- The photo shows the impact of pasture management on tansy ragwort growth. On the left side of the fence, the pasture is free of tansy ragwort flowering stems. On the right side of the fence, different management over time has led to a tansy ragwort infestation.
Solutions for Tansy Ragwort
Early Detection & Rapid Response
Watch for tansy ragwort on property you manage. Remove it before it becomes a bigger problem.
Physically Remove Plants & Non-Chemical Options
- Dig out plants by the roots when the soil is moist. Place tansy ragwort stems, roots, and flowers into thick plastic bags. Dispose of these materials in the trash. Or take the bags to the sanitary landfill.
- Seedlings germinate in the late summer, fall, and spring. Seedlings are easier to kill than larger plants.
Herbicides (Weed Killers)
Herbicides effectively control tansy ragwort when used according to the label instructions.
Monitoring & Follow-Up
Following removal, return to the area every 2–3 months. Look for regrowth and seedlings. Take action as needed.
NEED HELP?
Consider a licensed pest control company. Learn How to Hire a Pest Control Company.
Your local Extension Specialist in Oregon and other states can suggest other methods.
Jump to
| Method | Does it work? | Is it safe? | Recommendation |
|---|---|---|---|
A Physically Remove Plants |
Effective |
Low risk |
Recommended |
B Biocontrol for Tansy Ragwort |
Somewhat effective |
Low risk |
Recommended |
C Control with Herbicides |
Effective |
Moderate risk |
Use if Necessary |
|
D If Using Herbicides, Protect Yourself & Minimize Risks
|
A
Physically Remove Plants
Non-Chemical Method
Weston Miller, Oregon State University
Physically Remove Plants
Recommended
- Hand-pull tansy ragwort by grasping the center of the plant close to the ground. Or dig out plants with tools.
- Remove as much of the root system as possible.
| Does it work? | Effective Use preventive measures for best results. |
| How much effort? | High effort Plants have deep roots and are challenging to remove. |
| What's the risk? | Low risk |
| Possible risk of exposure or harm from chemicals | NONE |
Tansy ragwort is easiest to remove when the soil is moist. Pull or dig out plants by the roots to keep them from regrowing.
Chris Evans, University of Illinois, Bugwood.org
B
Biocontrol for Tansy Ragwort
Non-Chemical Method
Whiteway, iStock
Biocontrol for Tansy Ragwort
Recommended
- Noxious weed management agencies in the Pacific Northwest recommend 3 insects that feed on tansy ragwort.
- Check that you have the biological agents present at your site.
| Does it work? | Somewhat effective
|
| How much effort? | Low effort
|
| What's the risk? | Low risk |
| Possible risk of exposure or harm from chemicals | NONE |
"cinnabar moth caterpillars on tansy ragwort" by Andrew Reding is licensed under CC BY-NC-ND 2.0.
Mark Schwarzlander, University of Idaho, Bugwood.org
Eric Coombs, Oregon Department of Agriculture, Bugwood.org
Biocontrol Tips
- Both the tansy flea beetle and the cinnabar moth are well established in western Oregon. Numbers go up and down with the ebb and flow of tansy ragwort populations.
- Consider including biocontrol agents in your long-term tansy ragwort control plan by leaving plants that have the cinnabar moth caterpillars on them or watching for the tell-tale holes in the leaves of tansy rosettes in October.
- A strong pasture with little bare ground will resist weeds like tansy ragwort.
- Call your local Extension office or Soil and Water Conservation District for help in grazing management to reduce the risk of tansy ragwort and other weeds.
How to Collect Biocontrol Insects
- Collect insects from established stands of tansy ragwort. Use a stick to strike plant stems and collect the insects on a fabric or paper surface.
- Transport the collected insects to your tansy ragwort infested area in a container. Provide cool, dry, and uncrowded conditions in ventilated containers. Include fresh tansy ragwort stems, leaves, and flowers in the container. Release the insects as soon as possible.
- Distribute the insects onto tansy ragwort plants.
Biocontrol Reference
For more information about biocontrol for tansy ragwort, see Weed Biological Control (Oregon Department of Agriculture).
C
Control with Herbicides
Chemical Method: Use with caution
Chameleonseye, iStock
Control with Herbicides
Use if Necessary
| Does it work? | Effective
|
| How much effort? | Moderate effort
|
| What's the risk? | Moderate risk
|
| Possible risk of exposure or harm from chemicals | El uso de herbicidas conlleva cierto grado de riesgo. El riesgo más bajo se presenta con el uso de métodos alternativos. You may be exposed to an herbicide if you:
Follow directions closely to reduce risk. |
Some herbicides are available for home use. A few are listed below. These active ingredients, used individually or in a mixture, are suggested chemical treatments to control tansy ragwort. Look for these chemical names in the “Active Ingredients” section of product labels.
- 2,4-D + Dicamba
- MCPP-P
- Quinclorac
- Sulfentrazone
- Glyphosate
Suggested active ingredients are from the Pesticide Information Center Online (PICOL) Database. They are permitted for HOME use in Oregon. Read the label for application directions and effectiveness information.
ONLY professional pesticide applicators can use Restricted-Use Pesticides (RUP) that may be more effective. If you need further support, contact a licensed pesticide applicator.
Herbicide Application Tips
- These ingredients will damage most plants and grasses. Don”t let the spray contact plants you want to keep.
- Apply herbicide to actively growing tansy ragwort seedlings and rosettes. Follow the label directions.
- Seedlings germinate in fall and spring. Less herbicide is required to spray seedlings than established plants.
- Don’t treat tansy ragwort plants that have already flowered. Herbicide applications are not effective after flower stalks start forming. Dig out and bag plants that have already flowered.
- Expect that some tansy ragwort will regrow after treatment with herbicides. New seeds will germinate. Look for regrowth and seedlings. Control as needed.
- Using herbicides comes with real risks. ALWAYS read the entire label front to back. Review instructions even for brands you know.
Minimize the potential impact of herbicides to bees and other pollinators. Treat tansy ragwort plants before they flower. If plants are flowering when you need to treat them, apply in the morning or evening when bees are less active. Avoid spraying pollinators directly. For more information, see OSU’s How to Reduce Bee Poisoning from Pesticides
If Using Herbicides, Protect Yourself & Minimize Risks
Chemical Method: Use with Caution
Why is it important to read herbicide labels?
- They have detailed information on how to use the product correctly and legally.
- They contain information on potential hazards of the product.
- They provide instructions you should follow for poisonings and spills.
- Following label instructions helps you to minimize the risks and maximize the benefits.
Key Herbicide Safety Tips
- Read the entire label front to back.
- Follow the instructions.
- Review the instructions even for brands you know.
- Only apply the product where the label says it may be applied.
- Be precise in your application. More is not better.
The Label is the Law
ALWAYS read the label before using herbicide products. The label is a legal document that provides information on how to safely use the herbicide. This helps avoid harm to human health and the environment. Using an herbicide in off-label ways is illegal. It can result in legal enforcement actions.
READ THE LABEL & Follow Instructions
It has instructions to protect you and the environment.
- Labels are different for every product and they often change over time.
- Use a magnifying glass for small print.
- Pay attention to CAUTION, WARNING, and DANGER statements.
- Pay attention to the PRECAUTIONARY STATEMENTS.
- The law states you must read and follow herbicide instructions.
Protect Yourself
Eye, skin & lung irritants
- Wear the right protective gear. This often includes chemical-resistant gloves, safety glasses, a long-sleeve shirt, pants, socks, and shoes.
- Mix outdoors or in a well-ventilated area.
- Wash hands after mixing or applying, and before eating or smoking.
- Take a shower immediately after handling herbicides.
- Wash clothes worn while mixing or applying separately from other laundry.
Protect Children & Pets
Children and pets are at risk if they eat or touch the plants before it dries.
- Keep them away during and after applying herbicides (read label for how long).
- Remove toys and pet dishes from yard before applying.
- Don’t track herbicide products into your home on shoes or clothes.
Protect Plants You Want to Keep
- Glyphosate and similar herbicide ingredients damage both grass and broadleaf plants.
- Minimize spraying of foliage, stems, exposed roots, or the trunks of desirable shrubs or trees to avoid harm.
- Follow the label to avoid damaging the roots of trees and shrubs.
Avoid Wet, Windy, or Hot Weather
Use during favorable weather for best results.
- Don’t spray when it’s raining or when rain is expected in the next 24 hours.
- Wind causes spray to drift that can get on you and desired plants.
- Herbicides may be less effective in hot weather if the target plants are moisture-stressed.
- Some herbicides can turn into a vapor in hot weather and damage nearby plants.
Protect Pollinators
- Apply in the early morning or evening when bees are less active.
- Kill weeds before they flower. Avoid spraying flowering plants.
- Do not spray on bees or insects.
Storage & Disposal
- Store in a secure area away from children.
- Don’t put unused herbicide products in the trash.
- Never pour down any drain or waterway.
- Take unused herbicides to a hazardous waste facility.
Call 1-800-CLEANUP (1-800-253-2687) to find out where to dispose of herbicides.
For the Portland metro region in Oregon, contact Metro’s Recycling Information. Call 503-234-3000, email or visit Metro’s website
More about:
About Using Pesticides on School Grounds in Oregon
If using pesticides on school grounds, there are special rules in Oregon. See School Integrated Pest Management (Oregon Department of Agriculture).
NEED HELP?
The National Pesticide Information Center (NPIC) can answer questions about pest control chemicals.
1-800-858-7378 or npic@ace.orst.edu
Consider using a licensed pest or weed control company. Learn How to Hire a Pest Control Company.
Your local Extension Specialist in Oregon and other states can suggest other methods.
Invasive Species Alert
- Invasives are non-native species that spread aggressively and alter the environment.
- Controlling unwanted tansy ragwort is costly.
- Please do your part to control tansy ragwort on property you manage. It can spread beyond your property and affect your neighbors.
Invasive species data @ 2022, iMapInvasives (NatureServe)
Tansy ragwort is very widespread in Oregon. There’s no need to report infestations of it.
Content provided by editor Weston Miller and writer J. Jeremiah Mann. Pesticide safety information edited by Kaci Buhl.
Peer review facilitated by OSU Department of Horticulture.
Tansy Ragwort References
Tansy Ragwort
OSU Extension Service
Tansy Ragwort
Washington State Noxious Weed Control Board
Tansy Ragwort Identification and Control
King County, Washington