Buffelgrass (Pennisetum ciliare), originally from Africa, has become an invasive species in the Southwestern United States. Its rapid spread poses a significant threat to ecosystems, as it outcompetes native vegetation, alters natural fire regimes, and negatively impacts wildlife habitat. Effective management of buffelgrass involves a multifaceted approach, including prevention through public education and responsible recreation, early detection, manual removal, targeted herbicide application, and restoration efforts focused on reintroducing native vegetation and employing adaptive management strategies. Visit the USDA Weed Field Guide for the Southwest Website for comprehensive information on understanding, preventing, and managing buffelgrass to protect the health of Southwestern forests and grasslands.

Credit: USDA Weed Field Guides for the Southwest Region

• USDA Field Guide for Managing Buffelgrass in the Southwest PDF

Other Resources:

 

 

Common Sow Thistle (Sonchus oleraceus) is believed to be native to Europe and has become an invasive species in various parts of the world, including North America.

Common Sow Thistle is considered a problem due to its rapid growth, prolific seed production, and the ability to colonize disturbed areas. It can outcompete native vegetation, impacting biodiversity and disrupting ecosystems. The plant is known for its adaptability to different soil types and climates.

Effective management strategies for Common Sow Thistle involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, mowing, targeted herbicide application, and promoting the growth of desirable native vegetation. Integrated pest management practices are often recommended to address the invasive nature of Common Sow Thistle.

Giant Reed (Arundo donax), believed to be native to the Mediterranean region, has become an invasive species in various parts of the world, including the Southwestern United States. This aggressive plant species poses a significant ecological threat due to its rapid growth, which can lead to the displacement of native vegetation, alteration of stream channels, and increased fire risk. Managing Giant Reed involves a comprehensive approach, including prevention, early detection, and control strategies. Control methods may encompass mechanical removal, targeted herbicide application, and follow-up monitoring to prevent its re-establishment. For detailed guidance on understanding and managing Giant Reed, please refer to the provided link on the USDA Weed Field Guide for this species.

Credit: USDA Weed Field Guide for the Southwest Region

London Rocket (Sisymbrium irio) is believed to be native to the Mediterranean region and has become an invasive species in various parts of the world, including North America.

London Rocket is considered a problem due to its rapid growth and ability to colonize disturbed areas. It can outcompete native vegetation, negatively impacting biodiversity and disrupting ecosystems. The plant is known for its adaptability to different soil types and its prolific seed production.

Effective management strategies for London Rocket involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, mowing, targeted herbicide application, and promoting the growth of desirable native vegetation. Integrated pest management practices are often recommended to address the invasive nature of London Rocket.

Malta Star Thistle (Centaurea melitensis) is believed to be native to the Mediterranean region and has become an invasive species in North America.

Malta Star Thistle is considered a problem due to its aggressive growth, rapid spread, and the ability to form dense stands, displacing native vegetation and impacting ecosystems. It is known for its spiny leaves and rapid colonization of disturbed areas, reducing biodiversity and affecting forage availability for livestock.

Effective management strategies for Malta Star Thistle involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, mowing, targeted herbicide application, and the introduction of biological controls, such as insects that feed on the plant. Integrated pest management practices are often recommended to address the invasive nature of Malta Star Thistle. For specific guidance, please refer to the information on the USDA Forest Service website.

Tumbleweed, often referring to Russian Thistle in the context of invasive plants, is believed to have originated in Eurasia and has become an invasive species in North America.

Tumbleweed is considered a problem due to its ability to spread rapidly, especially in arid and semi-arid regions. It can outcompete native vegetation, disrupt ecosystems, and contribute to soil erosion. The plant is known for its tumbling habit, dispersing seeds over large distances, leading to its widespread distribution.

Effective management strategies for Tumbleweed involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, mowing, targeted herbicide application, and promoting the growth of desirable native vegetation. Integrated pest management practices are often recommended to address the invasive nature of Tumbleweed.

Salt Cedar (Tamarix spp.) is native to Eurasia and has become an invasive species in various parts of North America.

Salt Cedar is a problem due to its aggressive growth, rapid spread, and ability to dominate riparian areas. It can outcompete native vegetation, alter hydrological patterns, and negatively impact water ecosystems. The plant is known for its high salt tolerance, enabling it to thrive in saline environments.

Effective management strategies for Salt Cedar involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, cutting, targeted herbicide application, and the use of biological controls, such as insects that feed on the plant. Restoration efforts, including the planting of native vegetation, are crucial for rehabilitating impacted riparian ecosystems. For the best management practices and specific guidance, please refer to the Field Guide for Managing Salt Cedar on the USDA Forest Service website.

Sahara Mustard (Brassica tournefortii) is believed to have originated in North Africa and has become an invasive species in parts of North America.

Sahara Mustard is considered a problem due to its aggressive growth, rapid spread, and the ability to outcompete native vegetation. It can form dense stands, negatively impacting biodiversity and disrupting ecosystems. The plant is known for its adaptability to various habitats, including arid regions.

Effective management strategies for Sahara Mustard involve a combination of preventive measures, early detection, and control methods. Control may include manual removal, mowing, targeted herbicide application, and promoting the growth of desirable native vegetation. Integrated pest management practices are often recommended to address the invasive nature of Sahara Mustard. For specific guidance, please refer to the information on the USDA Forest Service website.

Additional information  Sahara Mustard / UC Statewide IPM Program (UC IPM) (ucanr.edu)

Stinknet (Oncosiphon pilulifer)

Stinknet, an invasive African annual weed that crowds out native plants and becomes a fire hazard in summer, currently spreading in Maricopa, Pinal, and Pima counties. Stinknet, sometimes also known as globe chamomile, is a member of the sunflower family. It can grow more than 2 feet tall and is spreading in Arizona as well as California, Nevada, Australia, and Mexico. The plant grows during winter.

Stinknet has finely dissected carrot-like leaves. Bright yellow spherical yellow flower heads, each consisting of many tiny flowers. Crushed foliage has a pungent, turpentine-like odor. The weed expansion threatens Pima County (Tucson) and surrounding counties in southern Arizona, where it has not yet invaded. It can occupy most habitat types. It is invading natural areas, neighborhoods, and everywhere in between. This species and other invasive weeds fuel wildfires, allowing wildfires to occur more frequently and with greater magnitude.

Noxious Weed Status: Stinknet is listed as an Arizona State Noxious Weed, Class B.

Identification

• Size: 2 inches up to 2+ feet
• Growth Form: Forb
• Leaves: Finely dissected (carrot-like)
• Odor:  Crushed foliage produces a pungent turpentine-like stink.  Flowering plants may emit this odor without disturbance.
• Flower heads: globe/spherical shaped, bright yellow, with many tiny flowers.
• Seed heads are globe/spherical shaped and brownish-tan colored. They consist of tiny individual flowers that have dried out, with a little mature seed at the base of each dried flower.

Residential and Homeowners Guides:

Additional Residential Resources:

• Stinknet: a Weed Advancing in Southern Arizona

• The Arizona Native Plant Society Trifold Brochure

Professional Applicator and Ecologist Guides:

The Regional Stinknet Planning Team has developed a comprehensive Land Managers Guide to effectively treating and managing Stinknet Professionals Applicators and Ecologists Guide to Manage Stinknet:

Additional Proffesional Applicator and Ecologist Guides:

• Stinknet / UC Statewide IPM Program (UC IPM) (ucanr.edu)

• Natural Area Pests: Stinknet (ucanr.edu)

• Stinknet Invasion | Cooperative Extension | The University of Arizona

Photos by Juanita Armstrong