Ch.13: Mixing and Loading Pesticides

2. Mixer Safety (PPE)

• Wear the PPE listed on the label. If none is specified, at minimum: chemical-resistant gloves and protective eyewear.
• Wear PPE (especially gloves) even for water-soluble packets or closed-handling systems — studies show they still expose you to residues.

3. Protecting Water

• Water at risk: wells, ground and surface water, and municipal drinking water.
• Protect it three ways: spill containment, setback requirements, and avoiding back-siphoning.

Spill containment

• Mix and load over a spill containment surface (mixing and loading pad) — from a 5-gallon backpack to a 500-gallon rig. Sometimes required by federal or state law (depends on amount).
• For a backpack: put it in a plastic bin while filling. Any secondary containment controls spills, protects the environment, and speeds cleanup.

Setbacks from wells/surface water

• Some states set specific setbacks. Take extra care near wells: poorly constructed, improperly capped, or abandoned wells can let pollutants enter groundwater directly.
• Labels may specify their own setbacks — the label is the law. (Example label: no mixing/loading within 50 ft of streams, lakes, or wells.)

Back-siphoning

• Back-siphoning (backflow) = the reverse flow of liquids into a fill hose, which can pull tank contents into the water supply.
• Simplest prevention: maintain an air gap between the water line and the tank solution. The air gap should be at least twice the diameter of the discharge pipe.
• Also use a backflow prevention device or check valve.
• Even with these, never leave equipment unattended while filling.

4. Water Chemistry & pH

• pH measures the acidity or alkalinity of water. The scale runs 0 to 14, with 7 neutral; 1–6 is acidic, above 7 is alkaline.
• Some pesticides lose effectiveness in alkaline (high-pH) water. If pH is wrong, add buffering agents per the label.
• Open-source water (ponds, streams) may carry sediments that clog equipment, alter the mix, or bind the pesticide and reduce effectiveness.

5. Adding Pesticide

• Open bags with a sharp knife — then clean it and don't use it for anything else.
• Pour liquids well below eye level to avoid splashing your face/eye. Use a pump to remove concentrate from a large container.
• Close unemptied containers immediately and return them to storage (or, at an application site, store them securely until you return them).

6. Emptying & Rinsing Containers

• Fully empty a container: rinse plastic/metal or cut open paper containers. This saves money, protects the environment, meets regulations, and makes it a solid waste (even if it held a hazardous pesticide).
• Triple rinse as soon as you empty the container (delay = dried residue is hard to remove). Don't leave rinsed containers at the site (someone might reuse them). Puncture them to render them unusable. Disposal is your responsibility.
• Pressure rinsing (alternative): a nozzle pierces the container and washes residues out at high pressure — rinse directly into your spray tank, and wear eye protection and other PPE.

7. Tank Mixing & Compatibility

• Tank mixes control a range of pests in one application (save time and fuel) but can cause problems.
• Never assume two pesticides can be mixed unless at least one product label specifies the combination.
• Compatible = can be mixed and applied together without reducing effectiveness or changing physical/chemical properties.
• Incompatible = combining gives an un-sprayable mixture or reduced effectiveness (or increased toxicity). Two types: physical and chemical.

Physical vs. chemical incompatibility

• Physical: mixtures don't blend — solids settle out or the mix separates into layers. Usually easy to SEE.
• Chemical: products physically mix but effectiveness is reduced or destroyed — you CAN'T tell by looking, so you may not find out until too late. Can also raise toxicity or phytotoxicity.

8. Proper Mix Order & Jar Test

• Incompatibility can arise even when labels say products can be mixed — from the wrong mixing order or an untested adjuvant. Wrong order can affect water pH and how ingredients dissolve. Read the label/manufacturer info for whether and how to mix.
• Small jar test: same proportions/water as your tank, on a small scale. It identifies incompatible mixes that cause clogging, separation, or system damage. Wear label PPE; use the same water/diluent; if it mixes well, rinse the jar into the larger mixture.

Mixing order (simplified, if not on the label):

1. Shake liquid containers.
2. Fill the tank halfway with clean water/carrier — never pour concentrate into an empty tank.
3. Add dry formulations first (wettable powders, water-dispersible granules, water-soluble packets) — pre-slurry them.
4. Agitate until all products form a solution.
5. Add emulsifiable concentrates and microencapsulated formulations.
6. Add liquids, flowables, and soluble concentrates.
7. Add adjuvants last (surfactants, crop oil concentrates).
8. Top off with the required amount of water.

Jar test procedure

• Mix products in a quart jar (some labels suggest two). Label each jar clearly. Shake and let stand 10 to 30 minutes.
• Curdles/separates → shake again. Won't disperse after the second shake → add a compatibility agent and shake again. Still won't mix → try a different agent or decide not to use the tank mix.
• Mixes easily (no agent needed) → you must still constantly agitate the mixture in your spray tank.

Key Vocabulary