Invasive Plants in the Preserve

As development expands into the Sonoran Desert, invasive plants have spread into natural open spaces. In the McDowell Sonoran Preserve, they increase wildfire severity and spread, displace native plant species, and reduce biodiversity. Invasive plants also provide less desirable forage for wildlife and can cause direct harm in some cases.

The Sonoran Desert experiences very low natural fire incidence, with most fires resulting from human ignitions. The ecosystem is not fire-adapted and can take decades to recover after a burn. It is also not fire-reliant, meaning it does not depend on fire for regeneration. When wildfires occur, invasive plants quickly colonize the disturbed landscape, outcompeting native species and raising the risk of repeated fires.

For details on local invasives, visit the South and Central AZ Invasive Species page from SWVMA.

Non-native species with high impact in the Preserve include:

• Fountain Grass
• Buffelgrass
• Stinknet
• Sahara Mustard
• Red Brome
• Russian Thistle (Tumbleweed)

Invasive plant management in the McDowell Sonoran Preserve is a collaborative effort involving Scottsdale Fire, utility providers, Tonto National Forest, Maricopa County, and other regional partners. The goal is to protect infrastructure, improve wildfire control, and minimize ecological impact.

The Preserve follows an integrated pest management (IPM) system that combines multiple strategies:

• Prevention: Trail users are encouraged to brush off shoes, clothing, and bicycles before and after entering the Preserve to prevent seed spread and to stay on designated trails. Boot brushes are available.
• Proper Plant Identification
• Pre-treatment Mapping, Assessment, and Planning: Treatment plans consider population size, location, and density.
• Treatment:
  • Mechanical: Hand-pulling plants or removing seed heads.
  • Chemical:
    • Post-emergent herbicides target and kill individual plants while sparing nearby native vegetation.
    • Pre-emergent herbicides prevent seed germination to maintain fire breaks and reduce fine fuel loads, while leaving established vegetation unharmed.
• Post-treatment Monitoring and Assessment
• Restoration: Native plant revegetation and seed dispersal.
• Repeat treatments as needed.

• Brush off your shoes, clothing, and bicycles before and after visiting the Preserve—especially if you have been in other natural areas. Boot brushes are provided at the Preserve. For more information read: I Didn't Know That!: Boot Brushing
• Stay on designated trails.
• Be aware of and stay clear of City staff, volunteers, or contractors performing treatments.
• Join as a McDowell Sonoran Conservancy Steward to help eradicate invasive plants.

Herbicide applications in Arizona are regulated under Arizona Revised Statutes Title 3 (Agriculture), Chapter 20 – Pest Management Division, and related Arizona Administrative Code rules. Requirements include:

• Use of certified applicators licensed by the Arizona Department of Agriculture
• Detailed recordkeeping for each application (site, date/time, product name, and EPA number)
• Adherence to label restrictions and federal standards under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA)

The city maintains full compliance through annual applicator certification, accurate reporting, and adherence to best management practices.

Product labels and MSDSs

Product labels and MSDSs are available upon request. Contact the City for information on herbicide chemicals used in the Preserve.