BOTRYOSPHAERIA AND PHYSALOSPORA ON CURRANT 
AND APPLE 1 
By C. L. Shear and Neil E. Stevens, Pathologists, and Marguerite S. Wilcox, 
Laboratory Aid, Office of Fruit-Disease Investigations, Bureau of Plant 
Industry, United States Department of Agriculture 
The economic importance of black rot of apple (Pyrus malus) and cane blight 
of currant (Ribes rubrum) seems to make advisable a statement of our present 
knowledge regarding their causal organisms even though our investigation of 
this group of fungi has not reached a point which warrants a detailed account 
of the synonomy of these species or of their life histories, genetic relationships, 
and distribution on the 26 hosts from which closely related fungi have already 
been collected and critically studied. The information at present available 
indicates that the ascogenous stages of these fungi are so similar as to suggest 
their very close relationship, and that both forms of Botryosphaeria ribis 2 occur 
on apple, on which host at least one form seems to be parasitic and capable of 
producing a fruit rot under some circumstances. 
REVIEW OF EARLIER WORK 
The life history of the currant cane blight fungus was worked out by Grossen- 
bacher and Duggar (2) 3 who also established its parasitism. To this fungus 
they gave the name Botryosphaeria ribis, distinguishing between the parasite 
and a purely- saprophytic form which occurred commonly on currant, by the fact 
that the parasite developed a “purplish pink color” when grown on starch paste, 
while the saprophyte, which was morphologically identical with the parasite, 
developed no such color. 
The literature on the black rot of apples and its causal organism is voluminous. 
Until 1913, however, it dealt almost exclusively with the pycnidial form of the 
fungus which was usually referred to as Sphaeropsis malorum. In December 
of that year, both Hesler (4) and Shear (10, 14, P • 107) published the results of 
pure culture studies which established the relationship of Sphaeropsis malorum 
to its ascogenous stage. This perfect stage Hesler referred tentatively to Physa - 
lospora cydoniae Arnaud, while Shear repeated his suggestion made three years 
earlier (9) in describing the life history of what is apparently the same species 
on grape, that it was Melanops quercuum (Schw.) Rehm forma vitis Sacc. or a 
variety of this species. 
Three years later Shear and Beckwith (11) announced that pycnospores of 
the Sphaeropsis malorum type had been produced in pure culture from single 
ascospores from a variety of hosts including apple, and that pycnospores of the 
type of the currant cane blight fungus, which they refer to as a Dothiorella, have 
1 Received for publication Feb. 6, 1924. 
2 The name Botryosphaeria is used here for species congeneric with Botryosphaeria ribis , Qrossenbacher 
and Duggar, as represented by specimens in Fungi Columbiani No. 3409 labeled B. ribis achromogena, 
Qrossenbacher and Duggar. As thus defined the genus comprises part of the species included by 
Cesati and de Notaris (1) in their original description of this genus. This name is adopted instead of 
Melanops because of general usage. Fungi Columbiani No. 3408 represents B. ribis chromogena of this 
paper. 
3 Reference is made by number (italic) to “Literature cited," p. 598. 
Journal of Agricultural Research, 
Washington, D. C. 
(589) 
Vol. XXVIII, No. 6 
May 10,1924 
Key No. G-385 
