California heavily restricts the use of poison for squirrel control, and the rules have gotten stricter in recent years. Whether you can legally use a toxic bait depends on the type of squirrel, where you live, and which chemical you plan to use. Most effective rodenticides now require a permit from your county agricultural commissioner, and several that were once available to homeowners are now banned outright for residential use.
Ground Squirrels vs. Tree Squirrels: Different Rules
California law draws a sharp line between ground squirrels and tree squirrels. If you’re a property owner or tenant dealing with California ground squirrels that are causing damage, you can take lethal action without any special license. Ground squirrels are classified as non-game animals, so the rules are more relaxed.
Tree squirrels are a different story. California’s native gray squirrels are classified as a game species, and killing them typically requires a depredation permit from the Department of Fish and Wildlife. The one exception is the non-native red fox squirrel: if it’s causing property damage, you can remove it at any time without a permit. If you’re not sure which species you’re dealing with, the distinction matters legally before you take any action.
Which Poisons Are Still Legal
California has been steadily tightening restrictions on rodenticides. Here’s where things currently stand:
Second-generation anticoagulant rodenticides (SGARs) like brodifacoum, bromadiolone, difenacoum, and difethialone have been largely banned since January 2021. You cannot use these around homes, restaurants, schools, offices, golf courses, parks, or most commercial properties. Limited exemptions exist for agricultural production sites, food manufacturing plants, warehouses storing food, vector control agencies, and facilities protecting water infrastructure. For most homeowners and property managers, these products are off the table.
First-generation anticoagulants chlorophacinone and warfarin joined the restricted list as of January 1, 2025, under AB 2552. Most uses of these chemicals are now prohibited statewide. They can only be purchased from a licensed pest control dealer, and violating the law carries a civil penalty of up to $25,000 per day.
Zinc phosphide remains available but is a restricted-use material. Only licensed pest management professionals can apply it. It works as a single-dose toxicant, meaning squirrels don’t need to eat it multiple times for it to be lethal. It can be applied as spot treatments near burrows or broadcast over larger infested areas, but it cannot be used in bait stations.
Diphacinone is still permitted for ground squirrel control in agricultural settings through bait stations, spot treatments, or broadcast application, but its use in urban areas is now limited. Bait stations should be placed near runways or burrows, spaced roughly 100 feet apart, and secured so they can’t tip over. These stations are designed to let ground squirrels in while keeping larger animals out.
Fumigants Require Licenses and Distance
Fumigation is one of the more effective methods for ground squirrel control, but California requires specific credentials. As of July 2023, the state created a new fumigation license category (Category M) for anyone using fumigants in burrows on properties like fields, rights-of-way, ditches, and landscaping areas.
Aluminum phosphide is highly effective, achieving 97 to 100 percent control in moist soil conditions. However, it’s a restricted-use product that can only be applied by a qualified applicator. It also cannot be used within 100 feet of buildings or people, which rules it out for many residential situations.
Carbon monoxide devices pump gas directly into burrow systems and work well, but they’re expensive and cannot be used within 50 feet of inhabited structures. If an employee operates one of these devices for hire or for a local government, records of each application must be kept for two years.
Why California Keeps Restricting Rodenticides
The legislative push behind AB 1322 (2023) and AB 2552 (2024) is driven by well-documented harm to non-target wildlife. Anticoagulant rodenticides work their way up the food chain: a poisoned squirrel gets eaten by a hawk, owl, or coyote, and the predator absorbs the toxin. In California’s most recent statewide survey, anticoagulant rodenticides were detected in 95% of mountain lions tested and 83% of bald eagles. Overall, 69% of non-target wildlife tested positive.
State regulators have documented unintended poisonings in at least 38 different species, including San Joaquin kit foxes, northern spotted owls, bobcats, bears, and even river otters, indicating that these chemicals are reaching waterways and aquatic ecosystems. The famous Hollywood mountain lion P-22, who died after being struck by a vehicle, suffered from mange linked to rat poison exposure. These findings are a major reason California’s restrictions are among the strictest in the country and likely to tighten further.
Non-Chemical Options for Ground Squirrels
Given how restricted chemical options have become, many California property owners are turning to other methods. The UC Integrated Pest Management program recommends starting management as soon as you notice new squirrels, since controlling a small population is far easier and cheaper than dealing with an established colony.
Kill traps, such as box traps or Conibear-style traps, work when squirrel numbers are low to moderate. Use these only where there’s no chance of catching a pet or other wildlife. Live-catch traps are less practical because California law prohibits relocating wildlife without a permit. Any ground squirrel caught in a live trap must be released immediately on the same property or euthanized humanely, with carbon dioxide or shooting being the methods recognized by the American Veterinary Medical Association.
Habitat modification also helps. Remove brush piles and debris that provide cover, and periodically check for new burrows. If you have the equipment, deep-ripping old burrow systems to at least 20 inches with a tractor can slow reinvasion. Simply filling burrows with soil doesn’t work because squirrels easily dig them back out.
Hiring a Professional
Because most effective chemical controls now require restricted-use permits and professional licenses, hiring a licensed pest control operator is often the most practical route. A professional can legally purchase and apply zinc phosphide baits, operate fumigation equipment, and navigate the permit process through your county agricultural commissioner. Anyone trapping squirrels for hire also needs a trapping license from the California Department of Fish and Wildlife. When getting quotes, ask specifically which methods they plan to use and confirm they hold the appropriate Category M fumigation license if fumigation is part of the plan.