"Lewis mite is one of those pests that seems to go in cycles – some years we don't see it at all, and some years I get reports as early as August.
This year there seem to be scattered reports. Given that Lewis mite populations can ramp up in a warm fall and rear their ugly heads in October, it seemed like a good time for an update on what's working, and what's not.
Lewis mite is closely related to spider mites (Tetranychus urticae) but is an entirely different species (Eotetranychus lewisi). For side-to-side comparisons of the two species, see this article by UCANR.
Lewis mites are exclusively a pest of poinsettia crops in the greenhouse (unless you're also growing strawberries.) Early detection is difficult since the symptoms are rather subtle at first: faint speckling and chlorosis (see picture below), which can resemble nitrogen deficiency. Additionally, the mite is almost impossible to see without a microscope."
Read more on ONFloriculture.