White covers may be placed on navel oranges during July after the period of physiological fruit drop as the first phase of fruit covering. Then in September, these covers are to be switched out for double-layered black (or yellow) covers until harvest time. The objective of the first phase is to decrease damage from citrus canker and rust mites, whereas that of the second phase is to protect against fruit flies and enhance exterior appearance through promoting color change (covers that block out all light allow fruit to change color in about 35-40 days).