POTATO FAILURES. 
T I 
And if the fungus continues its attacks, or if other fungi in¬ 
vade the injured parts, repeated efforts are made to repair 
the damage, and the surface of the potato may be brought 
into a rough or cracked condition, giving it an unsightly ap¬ 
pearance. An extreme case of such injuries is shown in 
Platell. Fig i. That Rhizoctonia is the cause of this condition 
is proven by the following simple experiment. 
On September 11, 1901, small amounts hyphae from pure cultures 
of the fungus were placed on the surface of eighteen small growing po¬ 
tatoes and covered with sterilized grafting wax. On September 25th, 
two of these potatoes were examined and a number of brown spots 
were observed on the inoculated surfaces. By a careful microscopic 
examination it was found that the hyphae had entered the lenticells and 
produced a small rupture in the skin. On September 26th, a third in¬ 
oculated tuber was examined and a number of cracks each starting 
from a lenticell were observed. On October 10th, the remaining fifteen 
tubers were examined and it was found that ten of these had developed 
sclerotia abundantly, and the entire covered surface was a 
net-work of cracks. Two of the remaining five had each a deep crack 
extending across the tuber. All inoculations produced brown rough 
surfaces. An abundance of the fungus was found on each tuber, while 
the five checks which had been treated in the same way with the ex¬ 
ception of adding Rhizoctonia culture, remained free from cracks. 
METHODS OF TREATMENT. 
It is difficult to treat this disease, since the external 
characters usually do not appear until the tissues of the 
plant are thoroughly invaded with the fungus. Applica¬ 
tions of fungicides to affected plants would have little or no 
influence on the disease. Under favorable conditions 
the fungus spreads rapidly through the soil in various direc¬ 
tions. There is no practical method of checking its spread 
after it is once introduced into the soil. The only way of 
dealing with it is by preventive means. From the nature 
of this fungus, it is evident that diseased seed potatoes are 
frequently the means of introducing the disease into clean 
fields; hence, too much care cannot be exercised in select¬ 
ing clean seed. But even then, the potatoes are apt to har¬ 
bor the fungus if they have been in contact with infected 
tubers. Danger from this source may be largely overcome 
by the treatment given on page 12. 
The disease may be carried on beet roots, or dead po¬ 
tato stems or on the dead stems of many of the weeds 
which grow in the potato fields. Infected potato and weed 
stems often find their way into the barn-yard and compost 
heap, thus manure may become a source of general infec¬ 
tion to clean fields. Great care should be taken to keep dis¬ 
eased plants and tubers out of the manure. The burning 
of all vines and weeds, as soon as the potatoes are harvest¬ 
ed, is an excellent practice. 
