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Journal of Agricultural Research 
Vol. XXVIII, No. 7 
characteristic serves for the ready identification of this rot. In addition it is 
often possible to see with the aid of a hand lens the little “sporodochia” of the 
Hainesia (Patellina) stage of the fungus on the surface of the spot. Teased 
and microtome sections show, according to Stevens and Peterson, that the host 
cells are filled with hyphae. 
THE LEATHER ROT OF STRAWBERRIES 
The leather rot, as Rose 5 calls the disease, is caused by a Phytophthora very 
similar to P. cactorum and is characterized by a definite though slight softening 
of the affected tissues and by internal discoloration. It is a typical field rot 
attacking berries in all stages of growth, and is most common following rainy 
periods, a characteristic which results in the name “water soak” often used 
by growers. The results of Rose’s inoculation experiments did not lead him 
to conclude that the hyphae of this Phytophthora can penetrate the unbroken 
strawberry epidermis. In the field, however, berries touching the ground were 
first affected on the under side, suggesting that the fungus may be a true soil 
organism, and that it may be able to penetrate the unbroken epidermis under 
favorable circumstances. 
Green fruit becomes brown where attacked, and fruit that has turned red 
before the fungus gains entrance presents a series of color changes as the disease 
progresses. At the center of the spot the color becomes yellow to light brown, 
spreading out from here the color changes to purple and then to the natural 
red as sound tissue is approached (PI. 1, J). The most characteristic feature 
of the rot is shown in sections of the fruit. The vascular tissue becomes markedly 
discolored, being a much deeper brown than the affected pulp (PI. 1, K). In the 
early stages of the disease vascular browning may be the only symptom. There 
is no clear line of demarcation between sound and diseased tissue, such as is 
characteristic of the hard brown rot. Neither can the diseased tissue be scooped 
out as it can be in the case of the Pezizella rot. One striking characteristic 
of leather rot is that even slightly rotten berries are bitter to the taste. 
THE BOTRYTIS BROWN ROT OF STRAWBERRIES 
Strawberries attacked by Botrytis present symptoms which in the early 
stages of the disease are quite different from those shown in the later stages. 
As the hyphae penetrate into the pulp it loses its natural color and turns light 
brown. Later the color becomes somewhat darker (PI. 1, I). The rotting 
pulp is at first rather soft, almost watery, though never leaky. This stage is 
soon superseded by a drying out so that the berry becomes firm. After the 
disease has run its course, the berry is found to be hard and dry, 6 which results 
in the use of the term “dry rot” among growers. The tendency, however, to 
make use of color characters describing rots will always prevail to a certain extent, 
so that shippers and inspectors no doubt will continue to use the term brown 
rot for this and similar diseases. 
As soon as aerial hyphae with their crop of conidia develop, the surface of the 
berry presents a characteristic appearance which is referred to as “gray mold.” 
Sections of immature or green berries recently affected with Botrytis rot do not 
show a distinct line of demarcation between healthy and diseased tissue. The 
diseased pulp is of a darker brown near the surface. The color shades off to a 
lighter brown and ends with the natural color of the healthy fruit in parts not 
invaded by the mycelium. Stevens 7 who investigated the host parasite relation 
6 Rose, D. H. leather rot of strawberrries. Jour. Agr. Research, 28: 1924. 
6 Stevens, Neil E., and Wilcox, R. B. further studies of the rots of strawberry fruits. U. S. 
Dept. Agr. Bui. 686, 14 p. 1918. Literature cited, p. 14. 
7 Stevens, Neil E. pathological histology of strawberries affected by species of botrytis 
and rhizopus. Jour. Agr. Research 6: 361-366, pi. 49-50. 1916. 
