Jan. io, 1914 
Some Diseases of Pecans 
3 i 7 
of 50 or more mm. is often attained by individual colonies after a growth of several 
weeks. 
Filter Paper.—Growth on filter paper moistened with sterile distilled water 
caused the formation of dark reddish brown circular spots very similar in appearance 
to those formed on the leaf, while for a radius of 10 to 12 mm. around the spot the paper 
took on a pinkish cast. An extremely scant white to pinkish aerial mycelium was 
often developed. 
Oxalic-Acid-Agar Slant Tubes.—Colonies are more or less convex, becoming 
wrinkled with age. The rather scant aerial growth is white to pale pink, while the 
submerged mycelium is seal brown to black and made up of densely anastomosing and 
variously contorted hyphae. The colonies are rarely over 10 mm. in diameter. After 
several weeks' growth the medium loses its pink color and assumes the shade of ordi¬ 
nary beef agar. 
Potato Cylinders.—The colonies are very convex, with white to pinkish aerial 
mycelium and olive-gray surface growth which becomes much wrinkled with age. 
A diameter beyond 8 to 10 mm. is rarely attained. The potato cylinder assumes a 
dark-gray cast for several millimeters beyond the outermost fungous growth, due 
evidently to enzym action. 
Prune-Agar Slant Tubes.—The colonies are little or not at all raised above the 
surface of the agar, with a fine, velvety, Indian red aerial growth. In the older and 
drier parts of the culture a scant white to pinkish aerial mycelium develops. A 
diameter of about 15 mm. is usually attained. 
Synthetic-Agar Slant Tubes (PL XXXVII, Fig. J ).—The colonies are extremely 
convex with a light to dark olive-green velvety surface growth. Numerous guttate 
drops of liquid are scattered over the surface during the earlier stages. A dark-brown 
to black, leathery pseudoparenchyma is developed beneath the surface, and with age 
the whole colony becomes considerably wrinkled. Growth continues until the agar 
has almost completely dried down, so that the whole slant surface of the medium is 
often eventually covered by the fungus. 
Morphology and Taxonomy 
A comparison of the characters of this fungus with the description of a 
Clasterosporium published by Heald and Wolf and an examination of 
their type material deposited in the pathological herbarium of the Bureau 
of Plant Industry have shown that the two are undoubtedly the same 
species. Their description is as follows: 
Clasterosporium diffusum .—Maculis indefinite marginatis, amphigenis; irregularibus, 
aequaliter brunneis, 5-10 mm. diam.; hyphis effusis prostratis, saepe laxe gregariis 
atque erectis; conidiis curvulis, clavatis, pluriseptatis, brunneis, 45-135 X 4-5 /*. 
On Hicoriapecan (Marsh) Britton. Victoria, 2536; Gonzales, 2695 (type); Yoakum 
2770, Halletsville, 2783. 
This fungus produces circular or irregular, indefinite margined, brown spots, which 
are uniformly brown on both surfaces of the leaflets. Dark-brown hyphae run 
throughout the dead tissue or creep over either surface of the affected area, or are 
sometimes aggregated to produce clusters of erect conidiophores. 1 
After a careful study of this fungus from both the humid and semi- 
arid parts of the pecan belt it has seemed to the writer to conform more 
nearly with the Cercospora than with Clasterosporium characters. 
Typically, the latter is saprophytic and possesses a prostrate or creeping 
mycelium with sporophores either short or differing but little from the 
1 Heald, F. D., and Wolf, F. A. New species of Texas fungi. Mycologia, v. 3, no. 1, p. 21, 1911. 
