476 
Journal of Agricultural Research 
Vol. XI, No. id 
pod, but more frequently at or near the ventral suture (PI. 42, B). If 
infection occurs near or at the dorsal or ventral suture, the fungus spreads 
in all directions in a circular or semicircular manner, the hyphae growing 
among the cells of the pod below the epidermis. The extent of the hyphal 
growth of the fungus among the cells is indicated by the darkening of the 
pod above the invaded area, evidently the first signs of the exhaustion of 
the food supply and approaching death of that part of the pod. This is 
soon followed by numerous, minute elevations over the surface, the points 
where the pycnidia are forming. These lifted points are at first gray, but 
as soon as the pycnidia break through the epidermis they become nearly 
black and protrude in a domelike manner from the surface. They are 
often, though not always, arranged concentrically and stand apart; or two 
or more may be confluent in a cluster or chainlike manner. Upon the 
death of the pod the fungus grows rapidly through the tissues, the 
pycnidia breaking out more or less over the entire surface (PI. 42, C). 
The fruiting bodies which are formed subsequent to the death of the pod 
are usually not formed concentrically. 
Under field conditions the fruiting bodies of the fungus are often found 
on the dead and more rarely on moribund stems. It is exceedingly 
uncommon to find typical infections of living stems, and the writer has 
never been able to produce infection of living stems artificially. The 
pycnidia, however, appear abundantly after the death of the vine on 
stems that have been sprayed with spores of the fungus. 
The disease is much more common and destructive on the pole Lima 
beans than on the bush Limas. 
ETIOLOGY 
The podblight of Phaseolus lunatus is caused by a fungus pathogen to 
which various names have been given at different times. The use of 
different names is largely due to the lack of a knowledge of the life his¬ 
tory of the fungus and to the practice of many mycologists in separating 
the genera Phyllosticta and Phoma, respectively, according to whether 
the fungus occurs on the leaf, or on the stem, or on other parts of the 
host. 
Halstead (16) first reported this disease in 1891 as causing considerable 
damage to the pods and leaves, and attributed it to a species of Phyllo¬ 
sticta. He was evidently in doubt as to the species, for he does not 
refer it to Phyllosticta phaseolina Sacc. (50, p. 149), which had been 
described some years earlier and which occurs commonly on Lima beans, 
on Phaseolus diversifolius, Kansas (Kellerman), New Jersey (Ellis), 
Canada (Dearness) on Phaseolus perennis , Missouri (Galloway) and on 
cowpea, Kansas (D. B. Swingle). In 1905 Smith (jj) proved the patho¬ 
genicity of this organism on the leaves of Lima beans and other varieties, 
such as kidney and wax, and on cowpeas. He found that the pods 
were not affected. 
