THE PEAR RUST MITE, Epitrimerus pyri Nalepa, has been a persistent but sporadic pest of pears in California. When present in the orchard, it is of major concern to growers because the russeting type of feeding damage can affect the market value of the fruit. Russeting can be caused by a relatively small number of mites beginning early in the season, while very high mite populations can cause defoliation. It is therefore sometimes necessary to use chemical controls against this mite, particularly when chemical controls for other pests destroy the mite's predators.