7.1 Application Equipment: Compressed Air Sprayers, Dusters, and Bait Guns

In professional structural pest control, understanding application equipment is vital for safety, regulatory compliance, and treatment efficacy. Under the California Structural Pest Control Board (SPCB) guidelines for Branch 2 (General Pest), technicians must master the tools used to apply pesticides. Proper equipment ensures active ingredients target pest harborages, minimizing chemical exposure to non-target areas. This section covers three primary application tools: compressed air sprayers, dusters, and gel bait tools.

The Compressed Air Sprayer

The compressed air sprayer (commonly called a B&G sprayer) is the industry standard for liquid pesticide applications. It operates by forcing air with a hand pump into the headspace of a sealed tank. This pressurized air pushes liquid pesticide up a supply tube, through a hose and valve, and out the nozzle.

Technicians must know the key parts of the compressed air sprayer and their functions:

1. The Tank: Constructed of stainless steel or brass to resist chemical corrosion and withstand pressures of 50 to 60 pounds per square inch (PSI). Tanks are usually 1 or 2 gallons. Never fill the tank completely. Leave 1/4 to 1/3 of the tank empty as air headspace. Without this air gap, the sprayer cannot maintain pressure.
2. The Pump Assembly: Consists of a handle, pump rod, plunger cup, and a check valve at the bottom of the cylinder. The plunger cup forces air through the check valve. The check valve is a one-way rubber diaphragm that allows air into the tank but prevents liquid from backing up into the pump cylinder.
3. The Hose: A chemical-resistant, reinforced tube carrying pressurized liquid to the valve. It must be inspected daily for cracking, swelling, or leaks.
4. The Valve Assembly: Located at the handle, it controls liquid flow. Pressing the trigger pulls a valve stem away from the seat, releasing the liquid.
5. The Wand: A rigid brass or stainless steel tube that directs the spray precisely into cracks, crevices, or voids.
6. The Nozzle and Tip: Controls the spray pattern and flow rate. Most sprayers use a four-way selector nozzle (Multi-Tip) with these patterns:
   • Coarse Fan: Used for flat surfaces, producing larger droplets that resist drift.
   • Fine Fan: Used for lighter, broader surface applications.
   • Pin Stream: Delivers a concentrated stream into deep cracks and voids.
   • Crack and Crevice Extension: A thin extension straw that injects pesticide directly into narrow gaps.

Dusters: Application of Dry Formulations

Dry pesticide formulations (dusts) are highly effective in dry, protected areas like wall voids and electrical outlets because crawling insects easily pick them up. However, their fine particles carry a high risk of inhalation exposure and drift.

Types of Dusters

• Hand Dusters (Bulb and Bellows): Bulb dusters consist of a rubber bulb and delivery tube. Bellows dusters use a rigid accordion-like chamber. Both are designed for precise crack-and-crevice treatments.
• Power Dusters: Motorized or compressed-air driven dusters used to treat large, unoccupied voids such as crawlspaces and attics.

Proper Filling and Technique

An essential rule for hand dusters is never fill the duster more than half full. A duster filled beyond fifty percent capacity will clump and discharge heavy piles of dust rather than a fine, uniform cloud. The duster needs air space so dust particles can suspend in the air chamber when shaken.

To prevent clumping, place a small ball bearing or marble inside the duster to break up compacted dust cakes.

During application, hold the duster with the nozzle pointing slightly upward or horizontally. Apply light, rapid taps or gentle squeezes to produce a barely visible fog of dust. A visible pile of dust indicates over-application, which repels pests and increases drift hazards.

Bait Guns and Gel Bait Placement

Gel baits are the primary tool for controlling ants and cockroaches under Integrated Pest Management (IPM) programs. Gel baits are applied using syringe plungers or mechanical bait guns.

Operation of Bait Guns

A bait gun holds a disposable plastic gel bait syringe. The gun uses a ratcheting trigger mechanism to push a plunger, delivering consistent, calibrated droplets with each squeeze.

Placement Guidelines

For efficacy and safety, apply gel baits according to these guidelines:

• Small, Frequent Placements: Apply numerous small, pea-sized droplets (0.1 to 0.5 grams per spot) rather than long, thick lines. Multiple small spots increase the feeding surface area and success rate.
• Strategic Location: Place baits in hidden cracks, crevices, corners, and junctions where pests forage (behind cabinets, under sinks, behind appliances).
• Avoid Chemical Contamination: Never apply gel baits on surfaces treated with liquid residual sprays or aerosols. Liquid pesticides repel pests; contaminating a gel bait renders it useless. Do not apply dusts over baits, as they dry out the gel.
• Target Surface Protection: Do not apply bait to surfaces exceeding 120\u00b0F (such as hot water pipes or oven backplates), which causes the gel to liquefy, run, and drip.

Exam Traps and Best Practices

• Headspace Trap: If a sprayer ceases spraying after a few seconds despite being pumped, the tank was likely filled to the top, leaving no air space.
• Over-Dusting Trap: Heavy, visible layers of dust repel pests and pose drift hazards. Apply only a barely visible film.
• Bait Contamination Trap: Keep residual sprays and baits separate. Sprays repel pests; baits attract them. Contaminated bait will be ignored by target pests.