The Diseases of the Irish Potato. 
By Professor F. M* Rolfs* 
.(The following paper was lavishly il¬ 
lustrated with stereopticon views of the 
different forms of fungus growth and we 
very much regret our inability to re¬ 
produce these views in this report.—Sec¬ 
retary. ) 
Mr. Presidentj Ladies and Gentlemen: 
Our potato industry frequently suffers 
severely from the invasions of various 
plant organisms which are more or less 
common to the potato fields of this State. 
The object of this paper is to describe the 
most destructive diseases, and suggest 
such methods of treatment as have been 
successfully employed in holding these 
diseases in check. It is often difficult to 
distinguish some of these diseases without 
the aid of a miscroscope, still it is well to 
know the symptoms of the principal 
ones so as to be able to use rational 
methods of treatment. Doubtful cases 
may be referred to the Experiment 
Station. 
Altenaria solani (E. and M.) Sorour. 
Early Blight —^^This is a wide-spread 
disease. It attacks both leaves and stems. 
Plants usually show no signs of the dis¬ 
ease until they are six inches high. The 
first indication of its presence is the ap¬ 
pearance of small circular, brown spots on 
the older leaves. The spots gradually ex¬ 
tend and form large areas of dead tissue. 
The younger leaves soon show signs of 
invasion, and unless the plants are spray¬ 
ed at once the entire foliage soon becomes 
involved. In the advance stage the tips 
and margin of the leaves roll up. The 
large -spots frequently show concentric 
markings. Because of its slow progress it 
is usually mistaken for the natural ripen¬ 
ing of the plants. The development of the 
tubers stop as soon as the leaves become 
thoroughly involved, and the yield is often 
cut short as much as 20 barrels per acre. 
Plants which are weakened from any 
cause are liable to be invaded by this fun¬ 
gus. Bordeaux mixture will hold this 
disease in check. Applications of this mix¬ 
ture should be made when the plants are 
four inches high, and repeated at inter¬ 
vals of about ten days until six applica¬ 
tions have been made. 
Phytoplitliora infestens (De By.) 
Late Blight —This disease invades all 
parts of the plants and tubers"! The first 
sign of its presence is the appearance of 
small brownish or black areas on the leav¬ 
es. These areas which rapidly increase in 
size followed by the curling of the leaves. 
If a spell of warm, moist weather follows, 
the leaves and stems turn black and decay 
within a few days, giving off a disagree¬ 
able odor. Badly infected plants have only 
small tufts of green leaves at tips of stalks. 
Many of the leaves hang shriveled as if 
scorched by fire. The under surface of the 
diseased leaves are covered with mildew. 
This mildew is composed of minute, tree¬ 
like, branching structures which support a 
