Buy the Stihl gas-powered leaf blower. Dont be a dummy and skimp on the CFM, buy the nice $700 one. Note the size of the opening whence flows the air.

Visit your local grocer or produce stand and acquire some appropriately sized oranges, with a diameter to not quite overmatch the measurement from Step 1.

Cram the orange in said opening and aim at the nearest wayward teen.

Depress the trigger in an aggresssive manner. This is key. You do NOT want to half-ass it. Jam that fucker all the way down.

Shoot some trees now so you can enjoy making marmelade-flavored havoc in peace; the teens having fled in panic.