PRELIMINARY AND MINOR PAPERS 
EXPERIMENTS WITH APPEE LEAF-SPOT FUNGI 
By John W. Roberts, 
Pathologist , Fruit-Disease Investigations , Bureau of Plant Industry 
INTRODUCTION 
That Sphaeropsis malorum is the organism which causes the common 
leaf-spot of the apple (Mains spp.) so prevalent in the East and South 
was first shown by Scott and Rorer (1907). 1 The work of these inves¬ 
tigators was later confirmed by the experiments of Brooks and De 
Meritt (1912), Lewis (1909, 1912), and others. 
In various parts of the South—in Virginia, West Virginia, North Caro¬ 
lina, Kentucky, and Tennessee, and probably in other States—this leaf- 
spot, usually so prevalent in the spring, later enlarges and becomes a 
harboring place for various species of fungi. Such enlargements, which 
give to the disease the common name of “frog-eye/' are usually in alter¬ 
nating rings or zones of brown and gray. Sometimes they form com¬ 
plete circles concentric with the original spot, but more often they are 
only half circles whose centers lie near its margin (PL VII, fig. 1). Around 
these enlargements others may be formed until perhaps one-third of the 
leaf is involved. 
Hartley (1908) found that enlargement of spotted or injured areas 
could be induced to a slight extent by Coniothyrium pirinum. Sheldon 
(1908) considers the frog-eye disease in West Virginia to be due to 
Illosporium malifoliorum because of its association with the disease. 
Crabill (1913) gives an excellent description of the disease and expresses 
the belief that Phyllosticta pirina is very probably the factor to which 
the rings are due, the original spots being caused by Sphaeropsis malorum . 
The organism, however, which Crabill calls Phyllosticta pirina , or at least 
his strain No. 2 with pink spore masses, the writer believes to be Phyl¬ 
losticta limit at a. At any rate, since Phyllosticta pirina is a synonym of 
Coniothyrium pirinum , to recognize the two names as applying to two 
different fungi, as Crabill does, would be an obvious error. The fungus 
Phyllosticta pirina was transferred by Sheldon (1907) to the genus Conio¬ 
thyrium on account of the color of its spores, thus making Phyllosticta 
pirina Sacc. a synonym of Coniothyrium pirinum (Sacc.) Sheldon, The 
fungus hereafter mentioned as Phyllosticta limitata has pink spore masses 
on certain culture media and on apple leaf-spots. In cultural characters 
it corresponds to Crabill’s Phyllosticta pirina , strain No. 2. Its spore 
measurements average 7 by 4 microns. 
THE FUNGI 
The writer undertook to determine whether certain leaf-spot fungi 
were capable of enlarging spots already formed. In the beginning the 
following fungi isolated from zoned spots were employed: Coniothyrium 
1 Bibliographic citations in parentheses refer to literature cited," p. 65 . 
Journal of Agricultural Research, 
Dept, of Agriculture* Washington, D. C. 
(57) 
VoL II, No. 1 
Apr. 1$, 1914 
Q-17 
