Jan. io, 1914 
Some Diseases of Pecans 
3i3 
affecting the mature trees and consequently has been considered worthy 
of investigation as well from a practical as from a mycological standpoint. 
For several years specimens of leaves showing this disease have been 
received from widely different parts of the pecan-growing territory, 
while within the last two years the writer has made personal observa¬ 
tions in the field over much of this region. From these observations 
and studies in field and laboratory it may definitely be said that the 
brown leaf-spot occurs in South Carolina, Georgia, Florida, Alabama, 
Louisiana, and Texas and that an exceedingly similar if not identical 
disease has in numerous instances been seen on other species of hickory. 
Furthermore, there is little doubt that its range is much greater than 
that above indicated, since it has been found in nearly every pecan sec¬ 
tion visited by the writer during the last three years. 
Observations in several States during the past two years have shown 
very little difference in resistance to the disease among the different 
varieties. For example, in one orchard examined, containing 45 varie¬ 
ties of the pecan, the brown leaf-spot was so uniformly distributed that 
no appreciable difference in the amount of injury could be detected 
among the different varieties. From a number of such observations 
over a wide territory it may be safely assumed that little difference in 
resistance exists among the varieties now commonly planted. 
SYMPTOMS OF THE) DISEASE) 
The leaf blade is the only part of the tree known to be affected. (PI. 
XXXVII, fig. A.) In ordinary seasons or when only a few spots occur, 
there is little or no appreciable injury, but occasionally under conditions 
very favorable to the progress of the disease partial defoliation may 
result. Infections occur from the early part of summer on until fall, 
and under proper conditions of moisture and temperature even well- 
matured leaves may develop the disease. Several days after infection 
(ordinarily 3 to 10) the condition becomes evident through the formation 
of a tiny dark reddish brown spot, which is usually somewhat angular 
in outline and bounded by the veins of the leaf. The spots from the 
earliest visible stages extend through the leaf tissue and appear about 
the same in form and color on both surfaces. The size increases grad¬ 
ually until the diseased areas often attain a diameter of 10 or even in 
some cases 15 mm. With increase in area the spot often loses its angular 
outline and the margin becomes more indefinite, while at the same time 
the center of the spot may in some cases assume a somewhat lighter 
reddish brown color with the darker brown as a border. Very often, 
however, the spots remain angular and with definite margin, though 
in such cases they seldom attain a diameter of more than 2 or 3 mm. 
Microscopical examination showed the cells within the affected areas to 
be de£Jid, more or less opaque, and brownish in color. (Fig. 3.) 
