as bacteria, fungi, and viruses, and those that have no infective agent, but 
are brought on by abnormal physiology or by injuries, Injuries may be grouped 
as mechanical, chemical, physical, and insect. Apples are, therefore, subject 
to many diseases. A number of diseases develop only in the orchard, but may 
be included in the packed fruit. Other diseases develop only after harvest, 
The origin of some can be traced to the orchard, whereas others are entirely 
independent. 
Although some diseases, such as water core, that are associated with 
natural environment cannot be readily controlled, most diseases are controll- 
able. In controlling apple diseases after harvest, emphasis is placed on good 
cultural practices, orchard control of diseases and insects, careful handling 
to avoid mechanical damage, chemical treatment where advisable, prompt storage 
and rapid cooling to the desired storage temperature, and proper storage en- 
vironment, which for certain varieties is controlled atmosphere. 
Only important diseases will be listed, and only those which have had 
additional research since 1945 will be discussed in detail. 
Literature on the following diseases, which originate or develop in the 
orchard, are not reviewed: Apple cedar rust (Gymnosporangium juniperi- 
virginianae Schw.), bitter rot (Glomerella cingulata (Ston.) Spald & Schrenk), 
black pox (Helminthosporium papulosum Berg), black rot (Physalospora obtusa 
(Schw.) Cooke), fly speck (Leptothyrium pomi (Mont. & Fr.) Sacc.), fruit spot 
(Mycosphaerella pomi (Pass.) Lindau), quince rust (Gymnosporangium clavipes 
Cke. & Pk), and sooty blotch (Gloeodes pomigena (Schw.) Colby). 
Recent literature was not found on some of the diseases that develop 
after harvest, such as fisheye rot (Corticium centrifugum (Lev.) Bres.), and 
side rot (Phialophora malorum (Kidd & Baum.) McColloch). 
Of the physiological diseases, internal cork was omitted from the litera- 
ture review because its control is part of production management. No recent 
literature was found pertaining to internal cork as a marketing problem. The 
literature on storage (superficial) scald and on bruising are reviewed in sepa- 
rate sections. 
Fungus Diseases 
Alternaria Rot (Alternaria tenuis auct.) 
Alternaria rot is usually of minor importance on apples. The causal 
fungus, a weak pathogen, is always present in the orchard on dead and dying 
plant tissues. Injured or weakened apple tissues appear to be necessary for 
infection either in the orchard or after harvest. York Imperial apples with 
numerous slight cracks of the skin and lenticels often develop alternaria rot 
during storage. 
According to Tweedy and Powell (168) 1/ alternaria rot has caused about 
1 percent loss of Jonathan and Golden Delicious apples in Illinois each year 
since 1958, Fruit infection was always associated with an injury. 
They identified the causal fungus as Alternaria mali Roberts and named 
the rot "cork rot'' to distinguish it from the usual alternaria rot caused by 
Alternaria tenuis. 
1/ Underscored numbers in parentheses refer to Literature Cited, p. 180. 
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