Chapter 10. 
A DISEASE OF LEAVES, SHOOTS, AND TUBERS. 
The Late-Blight disease of potatoes. Symptoms and means of 
spreading. Diseased tubers and the wintering of the fungus. 
Treatment of the disease, spraying and the use of resistant 
varieties, 
The Late-Blight of potatoes caused by Phytophthora 
infestans is so common and wide-spread that it is generally 
spoken of as the Potato Disease. Historically, it is cer- 
tainly the oldest of the potato diseases, and it is probably 
responsible for more loss to potato growers than all the 
other diseases of the potato put together. The malady 
first made its appearance in Barone about 1840, and the 
Trish Potato Famine of 1845 was the result of a very severe 
attack of Phytophthora, Whilst its ravages are seldom 
so severe nowadays as they were’ in that year, the disease 
is never altogether absent. In most seasons it makes a 
first appearance about the middle of July, and from that 
date to the end of the potato season it is often difficult 
to find a field of potatoes wholly free from attack. 
Farmers and growers generally, however, do not seem to 
be seriously concerned so long as the tubers are not badly 
diseased. It is an important fact, however, that wherever 
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