The Complete Handbook of Pesticides

Chapter 1: Understanding Pesticides

A pesticide is a chemical tool designed to kill, repel, or inhibit the growth of a specific organism or group of organisms—usually insects, mites, fungi, weeds, or rodents. But that definition alone is useless to someone who needs to actually solve a pest problem. What matters is understanding what a pesticide does in your specific environment, under your specific conditions, with your specific application method. That knowledge is built on two separate but equally important concepts: the active ingredient and the formulation.

Start with the active ingredient. This is the chemical compound that actually does the pest-control work. If you buy a product labeled "bifenthrin 2.0%," bifenthrin is the active ingredient. It works by disrupting the nervous system of insects. If you buy a product with "mancozeb 80%," mancozeb is the fungicide that prevents fungal spores from germinating on plant surfaces. The active ingredient is what the EPA registers, what resistance develops against, and what determines the core mechanism of action. Two products with the same active ingredient at the same percentage will have the same fundamental pest-control capability—all else being equal.

But "all else equal" is rarely where you are in the field. That's where formulation enters the picture. The formulation is everything else in the container: the inert carriers, solvents, surfactants, stickers, spreaders, thickeners, and other compounds that determine how the active ingredient actually reaches the pest, sticks to the target surface, moves through the environment, or breaks down over time. Two products with