3i6 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
Thus a carload of Georgia peaches spoiled by brown-rot in New York means 
loss of transportation and handling as well as of the original value of the 
fruit. An annual sum of $30,000,000 is said to be a conservative estimate 
of the loss in the United States between the field and the consumer, while 
in 1919 the total loss with fifteen principal food products is estimated at 
nearly a billion and a half dollars. Even land values are frequently seriously 
depreciated when the soil is so infested as to preclude the raising of the 
particularly profitable crop, as, for example, when the tobacco wilt pos- 
sesses land in the bright tobacco belt, leaving a farm which is comparatively 
worthless for any other crop, or again, as I have seen, when the wilts of 
cotton, cowpeas, and melons all occur upon the same field. 
As civilization advances, intercourse between regions more or less 
remote increases and the disease range and prevalence expand. Thus, 
much as with human and cattle diseases, though to much greater extent, 
the number of plant diseases known in any community is annually increased 
by additions from near-by regions or from far-away continents. Pre- 
sumably the potato late-blight fungus began its journey of conquest in the 
Andes, and as early as 1845 caused famine in Europe and much loss in 
many continents. The asparagus rust appeared in New Jersey in 1896 
and spread until it reached California in 1901. Many other serious diseases 
have come to us from abroad, including the sorghum smut, grape anthrac- 
nose, cucurbit mildew, carnation and chrysanthemum rust. 
Numerous serious diseases have likewise invaded other countries from 
here, among them the grape black-rot and downy mildew. Of interstate 
migration interesting cases are afforded by pear blight, from the Hudson 
valley in 1792 to California in 1895, and by peach yellows from Philadelphia 
in 1806 to Maine and Illinois in 1886. Among the late continental arrivals 
are the pine blister rust, which is under such headway that it seems to be 
impossible of extermination. The value of the susceptible pines is such 
that the loss may readily reach a hundred million dollars. 
The chestnut-bark disease caused a loss of $25,000,000 from 1904 to 
191 1. Much more serious is the loss to be borne as it invades the great 
chestnut forests of the Appalachians. Citrus canker, imported from Japan 
about 1910-11, bids fair to ruin large industries. Potato wart entered 
Newfoundland in 1909 and was found in Pennsylvania in 1918. It is of 
interest to note in passing that, were agriculture not taught in the public 
schools, its presence might yet be unsuspected. Flag smut of wheat was un- 
discovered in America until May 5, 1919, and is as yet known in but one 
county in Illinois. This disease is said to cause loss ranging from 10 to 50 
percent in Australia. 
As increased long-distance communication gives intercontinental trans- 
port to disease, so congestion of crop population creates a bridge by 
which the causal organism may more readily pass from plant to plant or 
from farm to farm. In these two conditions, facility of transportation and 
