Sulfur dioxide, chlorine, and a few other materials used to control microbial pests are effective in their pure, unmodified form. However, manufacturers formulate some microbial pest control chemicals with other substances to improve application effectiveness, safety, handling, and storage. The final product is a pesticide formulation. In addition to the pesticide active ingredient, a formulation may contain some of the following inert ingredients:
a carrier, such as an organic solvent, water, oil, or mineral clay
surface-active ingredients, often including stickers and spreaders
chemicals that improve or enhance pesticidal activity
With dry formulations, the label lists the amount of actual pesticide as the percentage of active ingredient (a.i.). For instance, a 50-W wettable powder contains 50% by weight of actual pesticide. With liquid formulations, the label lists the pounds of active ingredient in one gallon of formulated pesticide. The “4L” on the pesticide label shown at the right indicates that there are 4 pounds of active ingredient per gallon of formulated product.
Selecting a Formulation
Sometimes you have a choice between two or more formulations of the same pesticide to control a microbial pest. When possible, make your selection based on safety, including the safety of pesticide applicators, helpers, and others in or near the application area. Pick a formulation that causes the least impact on the environment. Always choose a formulation that is compatible with available application equipment.