Another thing you'd think would exist...

Waterproof, sticky-back labels for putting on pesticide sprayers to identify what sort of pesticide they've been used for.

Maybe sold as an assortment, including a couple stickers each of a few broad categories: INSECTICIDE, HERBICIDE, BRUSH KILLER, GLYPHOSATE, DORMANT SPRAY, that sort of thing.

Because using the brush-killer sprayer for dormant spray would be unfortunate.

Oh, well.  Guess I'll have to use paint markers.

(Yeah, just came back in from spraying the trees.  The new-last-year apple trees seemed to have a touch of fungus last summer.)