Mildewcide

No roofing maker or association document read for this entry publishes a definition of "mildewcide," and neither do the EPA pages it cites. The Tile Roofing Industry Alliance names mildew as one of three growths on tile, with algae and moss, and never names a product class for treating it.

The shingle and metal documents follow the same pattern. They name ingredients for one roof material at a time, such as ARMA's household bleach and water for asphalt shingle, and none of them calls what it names a mildewcide. That gap is stated here plainly rather than filled with a definition none of these publishers wrote.

The word is built from its two parts, the same way EPA's own class names are: fungicides kill fungi, algicides kill algae, biocides kill microorganisms. Put mildew in front of that ending and the compound names an agent aimed at mildew.

US EPA describes pesticide active ingredients by the pests they control or how they work, and its list includes this line: "Fungicides kill fungi (including blights, mildews, molds and rusts)." That is the closest published match for what "mildewcide" implies, a fungicide aimed at mildew, though the EPA page never uses the word mildewcide itself.

EPA's broader frame sits one level up. Its page on antimicrobial pesticides defines them as substances or mixtures used to destroy or suppress the growth of harmful microorganisms, fungi among them, on inanimate objects and surfaces, the frame the biocide entry covers along with registration. That pairing of destroy or suppress is why this entry defines mildewcide as an agent that kills or suppresses mildew, not only one that kills it outright. Whether a soft wash kills roof growth or clears it is argued at whether soft washing kills algae or removes it. TRI Alliance's own line about mildew, algae and moss settling on the dust on tile is quoted in the roof cleaning page's section on black streaks.