Agrobase Canada
Brooks spot (Brooks fly spot)
Mycosphaerella pomi

The disease attacks apple and crabapple trees and rarely is found in well-sprayed orchards. When sprays are stopped too soon, or when trees are not well-pruned and sprayed, severe losses can occur. Varieties such as Grimes Golden, Jonathan, Rome Beauty, and Stayman are quite susceptible. Brooks spot appears on immature fruit in late June and July. Spots on fruit are about 1/4 inch in diameter, irregular in shape, slightly sunken, and usually most numerous on the calyx end. On red-skinned varieties, lesions are dark red to purple. On light-skinned varieties, lesions remain dark green. Unless infected fruit is placed in cold storage immediately after harvest, the spots increase in size and become more sunken, thus more visible.