Bitter rot appears in the field as tan, sunken, circular lesions that sometimes have pink or orange spores at their centers. Bitter rot usually appears on the sun-exposed surfaces of fruit, and heat injury or sub-lethal sunburn may increase susceptibility of fruit to this disease. In stored fruit, bitter rot sometimes appears as a stem-end decay that causes complete collapse of tissues around the stem.
For an in-depth review of recent literature on bitter rot compiled in January of 2017, click here.
For those interested in the history of bitter rot, Schrenk and Spaulding compiled an interesting USDA Bulletin on this disease in 1903 that you can view here. On pages 36 and 38 of the bulletin (which are pages 34 and 36 of the linked PDF file), I have highlighted three observations that, so far as I can tell, are still valid today:
1. Bitter rot was more likely to appear on trees that previously had the disease than on trees that were free of the disease the previous year.
2. Mummified fruits on the orchard floor can carry the disease through winter and spores from those fruit remain viable into August of the following summer.
3. Insects, including Drosophila fruit flies, can carry the disease from infected fruit to healthy fruit.
Page last updated 27 Dec 2018