Biological pest control is the use of natural enemies to help suppress pest populations to acceptable levels. Once the agent becomes established, control is self perpetuating, potentially reducing the need to use pesticides.

Pest Biological Agent/Mechanism
Gorse Gorse Mite, Seed Weevil
Bull Thistle Bull Thistle Gall Fly
Yellow Star Thistle Seed Head Weevil, Gall Fly, Hairy Weevil, Peacock Fly
Scotch Broom Seed Weevil, Stem Boring Moth
Ash White Fly Parasitic Wasp
Italian Thistle Seed Weevil
Puncture Vine Seed Weevil
Purple Star Thistle Seed Weevil
Klamath Weed Beetle
Canada Thistle Mechanical and chemical removal
Plumeless Thistle Mechanical and chemical removal