-2- 



Additional infection periods occurred here on May 8-9, 13-14, and 

 16-19 from which scab spots have not yet developed. Since the winter spore 

 supply in the old leaves is almost completely exhausted, the principal source 

 of scab spores for further infections will be summer spores produced in the 

 new fruit and leaf spots . 



—0. C. Boyd 



TEIvlPERATURE RELATIONSHIPS FOR APPLE STORAGE ROTS 



A study of apple storage rots in the state of ViTashington revealed 40 

 species of fungi to be associated with loss of apples in cold storage. Only 

 about a dozen rots are of common occurrence in Massachusetts apple storages. 

 Although all organisms able to bring about the decay of apples at cold stor- 

 age temperatures will cause more rapid decay at higher temperatures, certain 

 fungi are able to cause definite decays in ordinary storages but are totally 

 inactive in cold storage. An examination of some of the literature dealing 

 with apple storage decays reveals the following classification of storage rot 

 organisms according to their relationship to temperature. 



1. Fungi unable to cause decay in cold storage but capable of causing 

 rapid decay in conmon storage and on the markets RhiZopus nigricans (the 

 Bread Mold Fimgus); Phoma sp., cause of Phoma Rot. 



2. Fungi unable to cause decay at cold storage temperatures but able to 

 cause spot rots at higher temperatures: Glomerella cingulata, the cause of 

 Bitter Rot, is a typical example. It does not make progress at temperatures 

 below 50° F. The disease is common in a few orchards in the southeastern part 

 of this state. Helminthosporium papulosum, cause of Black Pox Rot, and Myco- 

 sphaerella pomi (Brooks' Spot or New Hampshire Fruitf are other examples. 



3. Fungi causing spot rots in cold storage but more rapid decay at higher 

 temperatures: Volutella fructi (Spongy Dry Rot) ; Alternaria spp. (Alternaria 

 Rot); phoma sp. (Phoma Rot); Gloeosporium sp, (Anthracnose Rot, which is sim- 

 ilar in appearance to Bitter Rot but behaves entirely differently at cold 

 storage temperatures); Physalospora cydoniae (common Black Rot); and Venturia 

 inequalis (Scab). 



4. Organisms capable of causing complete rotting of apples during their 

 usual storage life in cold storage: Mucor piriformis (Mucor Rot); Penicillium 

 expansum (Blue Mold Rot); Botrytis spp. (Gray Mold Rot); Physalospora cydoniae 

 (ordinary Black Rot), i 



The storage rots most common in Massachusetts and also the ones that 

 develop most rapidly in cold storage are Blue Mold Rot, Gray Mold Rot, and 

 Black Rot. All make definite headway at 32° F. By comparison. Scab and 

 Spongy Dry Rot develop very slowly. 



—0. C. Boyd 



