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Zap weeds and sweep streets in one pass

  • The City of Lakeport, Calif., has mounted two WeedSeeker units on the rear of its only street sweeper to control plants in gutters, curbs, and sidewalks with targeted herbicide applications.

    Credit: Trimble Navigation

    The City of Lakeport, Calif., has mounted two WeedSeeker units on the rear of its only street sweeper to control plants in gutters, curbs, and sidewalks with targeted herbicide applications.
Meeting two needs with one deed makes Douglas Grider, public works superintendent of Lakeport, Calif., a shrewd manager. He’s combined two tasks — cleaning streets and controlling curbside weeds — into one smooth drive-by activity.

He installed the WeedSeeker spray system on the back of his sole street sweeper, which scrubs all 32 miles of the city’s streets each week. Here’s how it works: Seconds after the sweeper cleans the gutter, the WeedSeeker follows up with a metered spray of herbicide if it senses plants growing in cracks and joints around curbs, gutters, and sidewalks.

Before, the application method depended on location. Workers in a small pickup truck equipped with a tank used a stationary boom with nozzles to apply herbicides to bare ground, pavement, and weedy areas. Whenever vehicles were parked along roads, one person drove the truck while the other got out to manually spray.

“Some people think if a little bit is good, then a whole lot more is better,” Grider says. “With that mentality, 250 gallons can be gone after only five or 10 blocks. This system takes away that variable completely. It does away with someone walking along or driving along and having to think when to turn the spray on or off and guessing how much is enough.”

Automated application also ensures herbicides are used at rates that follow label directions.

Manufactured by Trimble Navigation, each WeedSeeker unit has a circuit board with a built-in LED light source, reflected light detector, electromagnetic valve, and spray nozzle, all housed in a nylon casing with an integrated stainless-steel bracket. Each unit has a 12-inch field of view.

The sensor surveys the ground for the presence of chlorophyll. If a plant is detected, a valve activates the nozzle to spray a controlled amount of herbicide.

“You replace two guys in a pickup truck and an application system with a vehicle you already own and one employee already doing another task,” says Grider. “Now he’s also taking care of weed control on the curb, gutter, and front edge of the sidewalk.”

  • One control panel mounted near the driver can operate up to 40 WeedSeeker units.

    Credit: Trimble Navigation

    One control panel mounted near the driver can operate up to 40 WeedSeeker units.
A sensor can detect weeds as small as a dime, and spot and spray at speeds of up to 10 miles per hour. Coverage may be widened by adding more units. Each unit runs independently of others. The control panel manages up to 40 units, a volume often used for large-scale agricultural spraying. The devices may be angled to spray weeds under open guard rails and along ditches, or to reach over sidewalks.

Grider estimates the city will recoup its investment in three years, with savings in crew hours, chemicals, and equipment use.

“My staff has dropped 50 percent from eight years ago,” he says. “So if you have two guys just spraying weeds, then you don’t have two guys out patching potholes or repairing sidewalks.”

- Leslie Drahos is a freelance writer in Sagamore Hills, Ohio.