Glomerella cingulata (Ston.) Spauld. & Schrenk.
Bitter rot of pears is primarily an orchard disease. In the past it was fairly widespread in pear-growing regions east of the Rocky Mountains. The disease is of little economic importance now because of effective spray programs. Its occurrence is restricted mainly to those producing regions where hot humid weather prevails for days at a time during the growing season, and where the spray program is inadequate.
Immature pears may be infected on the tree, but more commonly the disease attacks fruits that are starting to ripen. Rot spots are typically brown, dark brown, or nearly black. They are usually circular and firm. When the lesion exceeds 1/2 inch in diameter, the rot surface may be dotted with sticky pink or cream-colored spore masses, often arranged in concentric circles (see photo).
The disease rarely appears on pears on the market, and then only in ungraded or poorly graded fruits. Bitter rot must be controlled in the orchard. Recommendations of the State agricultural extension service or experiment station should be followed (see also Apples, Bitter Rot).
Bitter rot on pear