Herbicide Risk Comparisons

This website is an accompaniment to the Cal-IPC/Pesticide Research Institute manual, Best Management Practices (BMPs) for Wildland Stewardship Protecting Wildlife When Using Herbicides for Invasive Plant Management, and provides access to comparative risk charts for herbicides commonly used in wildland weed management. Pesticide Research Institute utilized the US Forest Service (USFS) risk assessment worksheets developed by Syracuse Environmental Research Associates to develop a comparison of risks to non-target wildlife for selected herbicides, displayed in graphical form. Herbicides currently included are shown in the table below.

Herbicides used for invasive plant management in California wildlands

Active Ingredient Example Trade Names Uses
Aminopyralid Milestone® Broadleaf species
Clopyralid Transline®, Lontrel® Broadleaf species, particularly Asteraceae (sunflower family) and Fabaceae (pea family)
Chlorsulfuron Telar® Many broadleaf, both annual and perennial, some non-grass monocots (e.g., onionweed)
Glyphosate RoundUp®, Aquamaster® Non-selective, affects both grass and broadleaf species
Fluazifop-P-butyl Fusilade® Annual and perennial grasses
Imazapyr Chopper®, Arsenal®, Habitat®, Stalker® Non-selective, affects both grass and broadleaf species
Triclopyr Garlon 3A® (triethylamine salt), Garlon 4® (butoxyethyl ester) Woody and herbaceous broadleaf species
2,4-D Amine 4®, Weedar® Annual and perennial broadleaf species, some woody species

Risks to wildlife and herbicide applicators were assessed for the receptors listed in the table below. Click on the link to view the risk chart for that receptor. Below are links to find more information on:

Receptor Notes
Workers Workers applying herbicides
Insects Butterflies, bees, wasps, mosquitoes, flies, beetles, aphids
Fish and Amphibians US EPA uses fish as a surrogate for amphibians
Aquatic Invertebrates Includes aquatic phases of terrestrial insects such as dragonfly larvae, as well as crustaceans such as Daphnia, crayfish, etc.
Small Insectivorous Mammals Moles, bats
Small Herbivorous Mammals Rats, mice, squirrels
Large Herbivorous Mammals Deer
Large Herbivorous Birds Geese, ducks
Small Insectivorous Birds Warblers, robins, thrushes