All life stages overwinter within the galls.
Mites are active within the galls from April to October, completing a generation every 2 to 3 weeks, which results in 8 or more generations per year. From May to August, some of the mites migrate to new, unfolding leaves, where they begin feeding by sucking the plant sap. The mites are protected from predators and insecticides while inside the gall. Newly formed galls are soft and green, but later in the summer become hard and brick red. Galls may grow to 3-4 cm in diameter.