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Pest SolutionsPESTS + WEEDSUSING PESTICIDES OR HERBICIDES?
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Johnsongrass
Sorghum halepense
Updated Nov 04, 2022
Make a Positive Identification
- Johnsongrass is an invasive, Eurasian perennial (lives many years) grass that grows up to 8 feet tall. It spreads by seeds and creeping rhizomes (roots). Populations are scattered throughout the Pacific Northwest.
- It thrives in agricultural and disturbed sites. Such sites include orchards, vineyards, cultivated fields, roadsides, irrigation canals, drainage ditches, and riparian areas.
- Johnsongrass quickly forms dense stands that suppress crop growth. It displaces native species in natural areas.
Species: Johnsongrass
Stefan.lefnaer, CC BY-SA 4.0, via Wikimedia Commons
Johnsongrass grows up to 8 feet tall. It thrives in disturbed areas. It is most often found in croplands, rangeland, drainage ditches, roadsides, and riparian areas.
Species: Johnsongrass
"Sorghum halepense leaf4" by Macleay Grass Man is licensed under CC BY 2.0.
Mature grass blades are flat with a prominent white midrib as shown in the photo on the left. Blades are 12–30 inches long and ½ –1 inch wide.
Species: Johnsongrass
"Sorghum halepense - Johnsongrass" by Matt Lavin is licensed under CC BY-SA 2.0.
Johnsongrass’s round stems stand upright and are hairless and sparsely hairy where the leaf blade meets the stem. A papery flap of material called the ligule grows from where the leaf blade connects to the stem (leaf sheath). Ligule growth is variable. It can be intact and ¼-inch long or hidden, or show as fringe.
Species: Johnsongrass
Harry Rose from Dungog, Australia, CC BY 2.0, via Wikimedia Commons
Flowers grow in a pyramid- or cone-shaped flower head from late spring to early fall. They range from purple-brown to golden to pale green.
Species: Johnsongrass
Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org
Johnsongrass flower heads form abundant fruits and then seeds that spread to new locations.
Species: Johnsongrass
Steve Dewey, Utah State University, Bugwood.org
Seedlings closely resemble corn seedlings. They are similar to rhizome sprouts.
Species: Johnsongrass
Steve Dewey, Utah State University, Bugwood.org
This perennial grass grows creeping rhizomes (roots) to form a dense clump.
LOOK-ALIKES: REED CANARYGRASS AND OTHER SORGHUM SPECIES
Species: Reed canarygrass
Michael Shephard, USDA Forest Service, Bugwood.org
- Reed canarygrass (Phalaris arundinacea) grows up to 8 feet tall. It grows in agricultural fields, drainage ditches, roadsides, and natural areas.
- Reed canarygrass flowers grow in dense spikes. In comparison, johnsongrass flowers grow in pyramid- or cone-shaped flower heads.
Species: Sudangrass
"Nick and sudan grass" by William Moore Farms is licensed under CC BY-ND 2.0.
- Milo (Sorghum bicolor) and sudangrass (Sorghum × drummondii) are crop plants. They are both tall growing and are related to johnsongrass.
- The photo shows a stand of sudangrass cover crop.
- Both crops are annual plants (complete their life cycle in a year) that don’t spread via roots.
Different risks or methods
Milo and Sudangrass usually don’t require control efforts.
Johnsongrass Benefits
- Johnsongrass is a destructive weed. It doesn’t have any benefits for people or the environment.
Johnsongrass Risks
- Johnsongrass quickly forms dense stands. It crowds out desired vegetation, significantly reducing crop yields.
- It also damages irrigation and drainage infrastructure.
Risk Card
Does it cause harm?
Adults & Children
None
Property
High
Pets
Some
Damaged or stressed Johnson grass accumulates hydrocyanic acid in amounts that harm livestock
Annoyance
High
Difficult to control
Environment
Some
Dominates areas where it is allowed to establish
Action Highly Recommended
Take action in gardens, landscapes, orchards, and restoration areas
TAKE ACTION
If you have johnsongrass on your property, take action to control it.
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?
Johnsongrass forms dense stands and is difficult to control. The longer you wait to act, the more difficult it will be to control it.
PREVENT JOHNSONGRASS
Steve Dewey, Utah State University, Bugwood.org
Look for Seedlings and New Growth
- After you dig out johnsongrass or treat it with herbicide, look for new growth.
- Rhizome fragments will continue to grow and produce new plants. New seeds will germinate. It emerges throughout the growing season and early spring.
- The best johnsongrass control is to prevent it from getting established. Monitor your property each year.
Weston Miller, Oregon State University
Remove Dirt from Shoes and Equipment
- After working or traveling in an area with johnsongrass, clean your boots and tools.
- Use a wire brush to remove all soil that likely contains seeds.
- Use a pressure washer to clean vehicles and heavy equipment after working in an infested area. Don’t work at a new site until the equipment is cleaned.
Laura Taylor, West Multnomah Soil & Water Conservation District
Replant With Technical Support
- Johnsongrass is difficult to get rid of in an infested area. Replanting a previously infested area requires planning and effort.
- Create a multi-year revegetation plan. Plans include site preparation and planting details, plant care, and follow-up control for johnsongrass and other weeds. 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.
Solutions for Johnsongrass
Early Detection & Rapid Response
Watch for reed johnsongrass on property you manage. Remove it before it becomes a bigger problem.
Physical Removal of Plants & Non-chemical Methods
Dig out single plants and small patches to remove the root mass and all of the rhizomes.
Herbicides (Weed Killers)
Herbicides effectively control johnsongrass when used according to the label instructions.
Monitoring & Follow Up
- Restore the area by planting native trees and shrubs to shade out johnsongrass. Monitor the area and re-treat as needed.
- It takes repeated effort over several years to get rid of a large, established stand of johnsongrass.
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 Removing Plants, Mowing & Disking |
Effective |
Low risk |
Recommended |
B Glyphosate and Grass-Selective Herbicides |
Effective |
Moderate risk |
Use if Necessary |
|
C If Using Herbicides, Protect Yourself & Minimize Risks
|
A
Physically Removing Plants, Mowing & Disking
Non-Chemical Method
Weston Miller, Oregon State University
Physically Removing Plants, Mowing & Disking
Recommended
Dig out small patches with tools. Mowing and tarping are useful methods for johnsongrass, but other methods are necessary to get rid of it.
| Does it work? | Effective
|
| How much effort? | High effort All rhizome fragments must be removed. This is extremely difficult if managing an established stand. |
| What's the risk? | Low risk |
| Possible risk of exposure or harm from chemicals | NONE |
- Dig out young, individual plants and small patches to remove the root mass and all the rhizomes.
- Repeated mowing effectively controls johnsongrass spread. However, other control actions, such as herbicides, are required to reduce or eliminate the patch.
- Similar to mowing, johnsongrass is sensitive to disking or plowing. Further action is required to get rid of it.
Soil Disturbance and Erosion
- Minimize soil disturbance as much as possible.
- Regrade the soil after digging johnsongrass roots. Apply mulch (when appropriate).
- Take steps to prevent erosion as needed.
- Replant the area to shade johnsongrass regrowth and seedlings.
B
Glyphosate and Grass-Selective Herbicides
Chemical Method: Use with caution
Chameleonseye, iStock
Glyphosate and Grass-Selective Herbicides
Use if Necessary
Herbicide products that contain active ingredients glyphosate and herbicides that target grasses (grass-selective) are effective treatments for johnsongrass when label directions are followed.
| Does it work? | Effective Use preventive measures for best results. |
| How much effort? | Moderate effort Requires several years of monitoring and treatment. |
| 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. |
Herbicide products containing active ingredients glyphosate and and grass-selective herbicides such as fluazifop effectively control quackgrass when label instructions are followed. Look for these chemical names in the “Active Ingredients” section of product labels.
Weston Miller, Oregon State University
Weston Miller, Oregon State University
Herbicide Application Tips
- Premixed products are available in stores.
- Killing rhizomes is critical to eliminating johnsongrass.
- Herbicide products applied to the leaves in spring or fall are effective at controlling spread.
- Herbicides applied after flowering are more effective at killing rhizomes.
- However, the specific timing and application method depends on the herbicide product. Follow the label instructions for best results.
- It takes repeated effort over several years to get rid of a well-established stand of Johnsongrass.
Herbicide Application Requirements for Aquatic Areas
- Herbicides applied over or near a water body must be registered for aquatic use.
- Treating Johnsongrass near aquatic areas requires specialized skills. This ensures the herbicide is applied effectively. It also protects waterways.
- Consider hiring a licensed pesticide applicator to manage this weed in aquatic areas. Aquatic-use products are rarely sold at plant nurseries or garden centers. They are available through specialty pesticide dealers.
- Aquatic formulas of herbicide products that contain active ingredient glyphosate effectively control johnsongrass when used according to label directions.
- Other aquatic-use herbicide products may be legal in your area. Consult a licensed pesticide applicator or your local university extension agent before purchasing or using an aquatic herbicide product.
If Using Herbicides, Protect Yourself & Minimize Risks
Chemical Method: Use with Caution
SteveOehlenschlager, iStock
Why is it important to ready 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 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.
Don’t Spray into Water
- It’s illegal to apply herbicides in a stream or slow moving/wetland pool.
- You need a product registered for aquatic areas. This includes waterways, ditches, drains, and other places where water collects.
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.
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 Johnsongrass is costly.
- Please do your part to control it on property you manage. It can spread beyond your property and impact your neighbors.
If you think you’ve found Johnsongrass in the grey areas of this map, please report it to the Oregon Invasive Species Hotline at: 1-866-INVADER (1-888-468-2337) or use their online reporting form
Invasive species data @ 2022, iMapInvasives (NatureServe)
View Larger Map >
If you find Johnsongrass in a new area (orange shows already reported cases), please report it
Content provided by editor Weston Miller and writer J. Jeremiah Mann. Pesticide safety information edited by Kaci Buhl.
Peer reviewed by OSU Department of Horticulture.
Johnsongrass References
Johnsongrass
Washington Noxious Weed Control Board
Johnsongrass
University of California IPM
Johnsongrass (PDF)
Weed Control in Natural Areas of the Western United States, University of California
Weed Control User Tool
University of California ANR