What to check before buying a used spot sprayer

A practical checklist for sensor and camera spot sprayers, based on GRDC guidance.

Optical spot sprayers only open a nozzle when a weed is detected ahead of the boom. Bought well, a used unit can be a cost-effective entry point. Bought badly, you inherit dirty sensors, worn solenoids and software you can't update.

1. Know which type you're buying

Sensor-based (green-on-brown): measures reflected light from chlorophyll to detect green weeds on bare ground, which suits fallow spraying (GRDC).
Camera-based: takes many images per second and uses algorithms to find weeds; can work in fallow and potentially in-crop (green-on-green), where one camera directs several nozzles (GRDC).
In-crop (green-on-green) use depends on label registrations and regulation still being developed for these use patterns (WeedSmart). Check the products and uses you intend are permitted.

2. Sensors and cameras

Count the sensors/cameras and check each one powers up and reports with no errors. Look for cracked or scratched lenses: the sensor must be able to see the weed, so lenses need to be clean (GRDC).
Ask for calibration records and any recent dealer service report.
For camera systems, ask which software version is installed, whether updates are still provided, and whether any detection subscription or licence transfers.

3. Nozzles, solenoids and plumbing

Spot sprayers typically use narrow-angle flat fan nozzles (such as 30°, 40° or 65°); standard 110° nozzles are generally not suited where a single nozzle treats a weed, and changing nozzle type is likely to require recalibration (GRDC).
Run the boom with water and check every solenoid opens and closes cleanly, with no dribbling or stuck valves.
Check filters, lines and pumps for chemical build-up.

4. Boom and height control

Detection and placement depend on correct sensor height and a stable boom, so check boom height control, suspension, wings and breakaways for wear.

5. Records and history

Hours on the sprayer and, if possible, on the spot-spray system.
What it was used for (fallow vs in-crop), chemicals used, and cleaning practice.
Maps or reports showing area sprayed and percentage of nozzles triggered, if the system records them.

6. Before you pay

See it running in a paddock or with a test target.
Search the PPSR for money owing.
Get a receipt listing the sensor/camera system and serial numbers, software version and any licences included.

Sources

General information only, not financial, legal or agronomic advice. Check details with the manufacturer, your dealer and product labels. Last reviewed 16 October 2026. Spot an error? Tell us.