No definite cause for the areas of high and low per cent. of infection
was determined. The highest percentages of infection are found on the
summit and on the south slope of the ridge. Also this portion of the
area supports more old infection than any other part of the mountain.
In part, this may be due to the higher percentage of chestnut on the
summit and south slope, and to the fact that most of it is young
coppice. Such stands appear very susceptible to the disease. The theory
that varying chemical elements, derived from the rock strata, affect
the amount of infection is not supported by any evidence gathered in
this work, for on the three general rock formations of this tract, as
well as along the edge of the adjacent limestone, high and low per
cents. of infection seem equally common. No evidence sheds any light
upon the belief that the distribution of disease is along any definite
compass direction. If there is any proof at all toward this end, it
lies in the fact that infections on the south are more uniformly
distributed than on the north. It is probably true that the advance
infections came from the south and crossed the mountain northward,
but areas of thick infection are not confined to any character of
topography, slope, or elevation.
The accompanying maps give in detail the percentages of blight found in
the Mahoning Valley and Topton Mountain areas.