Aquatic Drone Spraying: Lake & Pond Weed Control by Drone

By Ag Drone Sprayers Editorial Team · Updated July 9, 2026

Aquatic weed control has an access problem that looks a lot like forestry’s: the water that most needs treating is often the water you can’t launch a boat into or safely wade. A choked shoreline, a scattered patch of milfoil, a stormwater pond ringed by soft bank — a drone reaches all of it from dry ground, and never touches the bottom. Lake-management firms, mosquito districts, and state wildlife agencies are already flying it. Here’s the work, the honest limits, and the three permits that trip operators up.

The work: liquid, granular, and the depth line

Aquatic drone work splits on how the product is delivered, and that split decides what a drone can and can’t do:

• Liquid, for the surface. Floating and emergent targets — water hyacinth, giant salvinia, cattails, common reed (Phragmites), purple loosestrife — and algae, sprayed foliar or broadcast onto the surface.
• Granular, for the water column. This is where a spreader-equipped ag drone shines: fluridone pellets (Sonar), Hydrothol, and Navigate granules broadcast onto the water, then sink to act in the root zone. Bti larvicide granules for mosquitoes fly the same way.
• Flooded rice. A water-seeded rice field is an aquatic system — flooded ground blocks ground rigs, so aerial is often the only tool, and drones are an active extension frontier for late-season weed escapes.

Who hires: lake and pond management firms, HOAs and stormwater-pond owners, golf courses, municipalities, mosquito-control districts, irrigation districts, and state fish-and-wildlife and forestry agencies.

Why drones win here — and where a boat still does

The advantages are real and specific. A drone reaches shallow, choked, and shoreline water that’s off-limits to a boat or unsafe to wade. It never disturbs the sediment — no resuspending nutrients or muck the way an airboat or a wading crew does. And for the scattered patches that most milfoil and weedy-rice infestations actually form, programmed flight lines treat them more efficiently than working a boat across the whole surface.

The honest limit is depth and volume. A drone treats the surface; it can’t place herbicide at the base of a deep weed bed the way a boat trailing weighted hoses can, and extension specialists note that subsurface injection gives much better, longer-lasting control on dense submerged growth. Granular systemic pellets that sink are the drone’s partial answer, but deep, high-volume submerged work stays a boat job. And light drones drift more above about 7 mph of wind — call it low-drift and precise, never drift-free.

The three permits (operators miss this)

Aquatic work carries a regulatory layer farm spraying doesn’t, and it’s three separate approvals — all required:

• The FAA stack. Part 107, a Part 137 agricultural aircraft certificate, and a Section 44807 exemption for the heavy drone. Flying over water changes nothing here — but the product label must permit aerial application.
• NPDES pesticide discharge permit. Because the product lands in, over, or near waters of the U.S., a federal Pesticide General Permit — or, in 47 states, the state’s own program — applies on top of the applicator license. Large programs have to file a Notice of Intent.
• State aquatic applicator category. California Category F, Florida 5A, Texas Category 6, Wisconsin 5.0 — and only aquatic-labeled products may touch water. California adds a separate state drone-pilot certificate, and states like Minnesota and Wisconsin require a waterbody-specific permit for each lake on top of everything else.

For operators: adding aquatic to a farm business

A row-crop operator already holds the FAA authorizations and the core exam. What you add:

• A granular spreader kit — the biggest equipment add, and the one that unlocks fluridone and larvicide work.
• The state aquatic category plus fluency in your state’s NPDES/discharge program and any per-waterbody permits.
• An insurance check. Confirm your policy carries chemical (herbicide) liability and explicitly covers aquatic and environmental work — not every ag policy does.
• Product knowledge. Aquatic-labeled products only, matched to target: systemic fluridone or florpyrauxifen for milfoil and hydrilla, contact products for fast knockdown.

The economics can be compelling: professional aquatic treatment runs roughly $500–$2,000 an acre, and where chemical treatment replaces diver hand-harvesting of invasive milfoil (which can run $15,000–$20,000 an acre), the savings are the whole sales pitch.