Pesticide Formulations, Mixing, and Compatibility
Formulation letters tell you how to handle the product
A formulation is the active ingredient plus carriers and adjuvants that make it usable. Learn the common abbreviations and their handling implications: EC (emulsifiable concentrate - solvent-based, can damage sensitive plants, flammable), WP/WDG (wettable powder/water-dispersible granule - requires good agitation, can be abrasive), SC/FL (suspension concentrate/flowable - shake and agitate), S (solution - usually no agitation needed), G (granular - applied dry, risk to birds), and D (dust). Understand that the active ingredient per gallon or pound differs by formulation, so rate calculations must use the labeled product, not the active ingredient alone.
Mixing concepts: read the label for the correct carrier (water vs. oil), use the labeled order of addition, and always perform a jar test when tank-mixing unfamiliar products. Compatibility falls into physical (clumping, separation, sludge) and chemical (one product deactivating another) categories. Adjuvants - surfactants, stickers, spreaders, and drift-control agents - are used only when the label permits. Know the difference between a tank mix and a pre-mix product.
Trap: questions that ask you to calculate product per tank using active-ingredient percentage. Work the math in labeled product units. Another trap: assuming more surfactant is better - excess surfactant can cause runoff and phytotoxicity.
Worked example: a label calls for 1.5 lb active ingredient per acre and the product is a 75% WDG. Product needed = 1.5 ÷ 0.75 = 2 lb of product per acre. For a 20-acre spray, that is 40 lb of product.