About the data

Where it comes from

Anyone applying pesticides commercially in California must report it to the county agricultural commissioner. Applications of restricted materials also require a permit, and a notice of intent before each application. This tracker is built from those three record types, obtained from county agricultural commissioners under the California Public Records Act.

What it covers

• Records from 2020 onward.
• Forestry and timberland applications. Agricultural applications are outside this tracker’s scope. Roadside, invasive-plant and waterway treatments are recognised and stored but not yet published.
• Counties whose records have been obtained and checked. An absence of applications for a county means nothing has been published for it, not that no applications occurred.

How an application is assembled

A single forestry project is usually reported as many separate use reports — one per square-mile section, sometimes one per day. This tracker groups reports that share an operator, a permit, a time and a location into one application, so the public sees the project rather than the paperwork. Every underlying report is kept and listed on the application’s page.

What the maps do and do not show

A pesticide use report gives a location as a public-land-survey section — one square mile — together with the acreage treated. Where the operator’s parcels within that section can be identified from county assessor records, the map outlines those parcels.

An outline shows property associated with an application. It is not a measurement of the area actually sprayed. An operator who reported treating 63 acres inside a 640-acre property did not treat the whole property. The reported acreage is always shown alongside.

Chemical warnings

Two different things are both shown in red, and the tracker always says which it means:

• Regulatory restrictions — a California restricted material or a federally restricted-use pesticide. These are matters of law, cited to the document that establishes them, usually the county’s own permit.
• Editorial watchlist — chemicals the organisation publishing this tracker has chosen to highlight. This is an editorial judgement, not a legal status, and is labelled as such wherever it appears.

Accuracy and corrections

Every published figure comes from a source document, and each page lists the records behind it. Where a record is ambiguous — a site code that disagrees with its printed legal description, an owner name that matches no parcel, a product that cannot be identified — it is held back for a person to check rather than published with a guess.

• Applications are grouped from the underlying pesticide use reports; every source record is preserved.
• A notice of intent states an intention to apply and is not evidence that an application took place.
• Parcel maps show the property associated with an application, not a measured treatment footprint.