14 
Bulletin 91. 
parts of the plants were severely injured, and many of the tops 
showed marked sun scald injuries, which were followed by an in¬ 
vasion of Altenaria and many of the plants died before the close 
of the season. 
The Seed Potato. —The sclerotia on the seed tubers is one of 
the principal means of disseminating this malady. It is almost 
impossible to find a lot of tubers entirely free from them, and 
some of our leading seed men send out seed tubers which are 
thoroughly infected. We have observed as high as 75 per cent, of 
infected tubers in lots offered for seed. 
In storing seed careful attention ought to be given to temper¬ 
ature and moisture of the cellar. A comparatively dry cellar at a 
temperature of about 40 ° F. prevents the growth of this fungus, 
but infected tubers stored in a cellar which is warm and sufficient¬ 
ly damp give rise to a profuse development of both hyphae and 
sclerotia. A few diseased tubers in a lot of clean ones may great¬ 
ly injure the seed value of the entire lot. (See Bulletin 70 , p. 10 ). 
Insect Injuries. —Frequently the larvae of insects make tun¬ 
nels of considerable depths into both the stems and young tubers. 
The hyphae of this fungus frequently enter such wounds and may 
extend the injury. 
Infected Plants. —-This disease may be carried on the roots and 
stems of the various cultivated plants and weeds which grow on 
infected soil. (See Bulletin 70 , p. 4 ). Infected stems and roots 
often find their way into barn yard manure and compost heaps; 
thus the manure may become the source of general infection to 
clean fields. Infected potato stems are frequently left scattered in 
the field after harvest; these are blown about by the wind and 
many of them finally find their way to other fields and thus become 
the means of general infection to new fields. 
REMEDIAL MEASURES. 
The Soil. —When a field has once become thoroughly infected 
with this fungus, it is cheaper to put it in other crops for at least 
three years. Evidence indicates that root crops should be avoided; 
cereals which are probably not attacked by the fungus should be 
sown on infected ground and all weeds should be kept down. 
Comparatively dry and loose soils, especially if they have a gravelly 
sub-soil, are less favorable for the development of the fungus than 
heavy soils. Losses from this disease are often lessened by giving 
carefnl attention to the physical condition of the soil. 
Cultivation. —Too much care cannot be given to the prepara¬ 
tion of the soil. Plowing under a green crop on infected ground 
from seven to eight inches deep just before planting gives good 
