Citrus rust mite (Silver mite)

Phyllocoptruta oleivora

This pest is known as the rust mite on oranges and the silver mite on lemons. It is an occasional pest in coastal areas of southern California and is a problem in some years in inland southern California growing areas. Citrus rust mite is about the same size as a bud mite and requires a hand lens to view; it is deeper yellow in color than the bud mite and wedge shaped. A generation may be completed in 1 to 2 weeks in summer, but development slows or stops in winter, depending on temperature.
The rust mite feeds on the outside exposed surface of fruit that is 0.5 inch (1.3 cm) or larger. Feeding destroys rind cells and the surface becomes silvery on lemons, rust brown on mature oranges, or black on green oranges. Rust mite damage is similar to broad mite damage, except that somewhat larger fruit are affected. Most rust mite damage occurs from late spring to late summer.