HOSTS

The only host Keifer identifies [click arrows at right for more info] is "Spiraea densiflora," currently known as Spiraea splendens. However, Table 9 (pg. 34) in Russo's Plant Galls of the Western United States (2021) lists the host for the flower gall "Phytoptus paraspiraeae" as "Meadowsweet (Spiraeae spp.)." Therefore, "Spiraea spp" and S. douglasii are tentatively added as hosts, although further research is needed to verify whether the extremely similar flower galls on S. douglasii are caused by the same species of mites as the S. splendens/densiflora galls.

A further complication is that, although Keifer mentioned that the "closely related" Phytoptus [now Eriophyes] spiraeae causes "similar galls in Spiraea flowers" in Europe, Ellis's well-researched "Plant Parasites of Europe" website describes "Eriophyes spiraeae" as causing "red spots on the leaves and shallow pleats at the upper side between the veins" of "Spiraea" in Europe, specifically "Spiraea x bumalda, crenata, densiflora."