Mar. 19,1917 
Peanut-Wilt Caused by Sclerotium Rolfsii 
443 
mustard seed near the base of the wilted shoots (PI. 96, B). On 
sectioning the basal portion of diseased shoots it is found that the tissues 
are discolored and decaying, indicating that the wilting of these shoots is 
caused by cutting off the water supply near the base. 
Abundant white mycelium and brownish sclerotia also developed on 
peanut leaves which dropped to the soil about the base of wilted plants. 
Plate 97, A, shows peanut leaflets taken from the surface of Ijhe soil 
under a wilted plant. Thirty-seven sclerotia have been counted on a 
single leaflet; and in many cases sclerotia developed in greater numbers 
about the base of wilted shoots, thus providing ample means for repro¬ 
ducing and spreading the organism in subsequent seasons. 
Although not as commonly observed, the coarse white mycelium and 
sclerotia may also be found on both the outside and inside of pods on 
wilted plants. 
During the seasons of 1915 and 1016 wilted plants were observed 
scattered over the entire area of each plot, indicating that the organism 
was well distributed throughout the soil. In some cases, however, the 
plants in adjoining hills wilted in a progressive manner, as though the 
fungus spread from centers of infection. Plate 97, B , shows three such 
hills, the one in the foreground being infected first. The fungus then 
apparently spreads to the second hill 12 inches distant, and then to the 
third hill, where a portion of one plant had been attacked and had wilted 
at the time the photograph was taken. 
SERIOUSNESS OF THE DISEASE 
As a result of counts made in 1915 it was found that 15 per cent of 
the plants had one or more wilted shoots. Similar counts in 1916 showed 
that the percentage of plants having one or more wilted shoots had 
increased. 
Shoots attacked early in the season produce no peanuts, and those 
infected after peanuts have formed generally become so badly diseased 
that the fruits fail to mature. .The diseased shoots are so withered and 
shrunken that they are of little or no value for hay; therefore, wilted 
plants are practically a total loss. 
PATHOGENICITY AND IDENTITY OF THE ASSOCIATED ORGANISM 
As coarse white mycelium and small brownish sclerotia were constantly 
associated with the wilted plants, it seemed advisable to obtain pure 
cultures of this fungus for identification. Basal sections from numerous 
diseased shoots were externally disinfected in alcohol and in mercuric 
chlorid (1:1,000) and plated in nutrient agar. In five days coarse white 
mycelium had grown out from most of the sections. Transfers of this 
mycelium to tubes of corn meal and bean pods grew rapidly and even¬ 
tually produced brownish sclerotia similar to but somewhat larger than 
those found on the wilted peanut plants. Other fungi grew out from 
