Ch.4: Pesticide Formulations

2. Reading the label suffix

• A suffix on the brand/trade name signals the formulation (Table 4.1).
• Solid formulations: suffix number = % a.i. by weight → BugGone 20WP = wettable powder, 20% a.i. by weight.
• Liquid formulations: suffix number = pounds a.i. per gallon → WeedXterminator 3.3EC = emulsifiable concentrate, 3.3 lb a.i./gal.
• No suffix? Find it in the Product Information section of the label.

3. Table 4.1 suffixes

4. Solubility and mixtures

• Solubility = ability of a substance to dissolve in a solvent (usually water). Salt = soluble; oil = insoluble.
• True solution — can't be separated by filtration; doesn't settle out or need shaking (e.g., SP in water).
• Suspension — solid particles that don't dissolve, dispersed in liquid; needs agitation or particles settle/float; looks cloudy.
• Emulsion — a special suspension: droplets of one liquid in another; looks cloudy/milky. An emulsifier keeps it from separating (oil rising to the top).

5. Formulation types — defining traits & key pros/cons

• Emulsifiable Concentrate (EC) — a.i. insoluble in water, dissolved in a petroleum solvent (solvent odor). ✅ easy to handle/pour, little agitation, not abrasive. ❌ easily skin-absorbed, corrosive, flammable, can deteriorate rubber/plastic. Keep off skin — high a.i. concentration.
• Ultra Low Volume (ULV) — almost 100% a.i., very fine droplets at high pressure. ❌ high drift, high dermal and inhalation risk. Best outdoors (mosquito, forestry).
• Wettable Powder (WP) — dry solid that doesn't dissolve; diluted with water → suspension. ✅ less skin/eye absorption and less plant harm than ECs. ❌ inhalation hazard while mixing, must be weighed, abrasive, clogs nozzles, needs constant agitation.
• Soluble Powder (SP) — looks like WP but dissolves into a true solution (no extra agitation). Has all WP advantages with only one disadvantage: inhalation hazard during mixing.
• Water-Dispersible Granule (WDG / DF) — WP made into granules: pours easier, suspends better, less inhalation risk; still a suspension needing agitation; granules break into fine powder in water.
• Liquid Flowable (L / F) — thick liquid suspension. ✅ low inhalation risk, seldom clogs nozzles. ❌ shake before mixing, moderate agitation, abrasive, visible residue.
• Microencapsulated (M / ME) — a.i. in tiny plastic-coated capsules → slow release, effective longer. ❌ needs constant agitation; hazard to bees (carry capsules with pollen to the hive).
• Dust (D) — always used dry; a.i. + fine carrier (talc, chalk, clay). Good where spray moisture would damage. ❌ drifts easily, poor adherence, high inhalation risk.
• Granule (G) — a.i. on clay/porous material; nearly always treats soil; slow release (may need soil moisture).
• Pellet (P) — like granules but uniform in size/shape (granules vary); spot applications; ❌ bird hazard (mistaken for food).
• Bait — a.i. + food/attractant; a.i. usually < 5%. ✅ whole area needn't be covered. Rodent baits often require tamper-proof bait stations; remove old bait so it doesn't feed pests.
• Water-soluble bag (WSB) — premeasured, lowers exposure to concentrated a.i. Never puncture or break it open — add whole to water.

6. Adjuvants

• Adjuvant (additive) = material added to the tank mix to aid/modify the formulation's action or the mixture. Most common for foliar applications.
• Surfactants (wetting agents, spreader-stickers) — reduce surface tension, increase spreading on leaves (like soap in water); the ones applicators add most.
• Drift reduction (thickening) agents — help reduce but not eliminate drift.
• Compatibility agents — allow effective mixing of two or more pesticides.
• Add carefully: some need a specific mixing order; too little/much can ruin the mix or injure plants.

7. Choosing a formulation

1. #1 concern: the product is labeled for your site/plant/crop.
2. Signal word — between two that work, choose the less toxic.
3. Applicator safety (inhalation vs. skin) — have the right PPE.
4. Environmental safety — caution with drift-prone/volatile products; some are more toxic to aquatic life.
5. Pest biology, surface (staining, plastic, foliage damage), equipment (abrasive/corrosive).
6. Cost matters, but safety and pest management come first.

Key Vocabulary