432 OHIO EXPERIMENT STATION: BULLETIN 214 
Dry-Rot. The dry-rot fungus (Fusarium oxysporum (Schl.) has become gen- 
erally prevalent in Ohio. This attacks the plant as the result of seed tuber or 
soil infection, causing wilt troubles of the plants (see Fusarium Blight) as wellas 
dry-rotting of the tubers in storage. This tuber dry-rot is shown by the mold- 
like development of the fungus on the tubers. All such tubers should be rejected 
and rotation in potato growing should be practiced. Partly infected lots of 
potatoes held in storage should be promptly used. The infection of seed tubersis . 
‘shown by cross sections near the stem end of the tuber at digging time or later. 
Where infection occurs there will be browning of the vessels near the exterior of 
the potato. In limited infection only small spots will show, but as the infection 
advances these brown tissues show as characteristic rings approaching that in 
bacterial blight. These spotted tissues yield the fusarium of infection in cultures 
as has recently been shown by the assistant botanist. Since we know that this 
parasite develops as a blight of the plant proper, we need to reject all diseased 
tubers for seed. (See Fusarium Blight). 
Early Blight of potatois a premature spotting 
and dying of the potato leaves, due to the work 
of a parasitic fungus (Alternaria solani (E. & 
M.) Jones & Grant). The occurrence of the 
early blight, however, is liable to be influenced 
by the general vigor and other conditions of the 
plant; yet there is no just basis for denying, in 
the light of our present knowledge, the parasitic 
nature of this disease. Jones has madecultures 
of the fungus and produced the disease by inoc- 
ulation (Vt. Exp. Sta. Buls. 24 and. 28; Rept. 
1892) and has secured most admirable results 
by the use offungicides. This successful spray- 
ing initself is in the nature of proof of parasitic 
character. In the potato work at this Station 
it has been the uniform practice to spray 
thoroughly with Bordeaux mixture, adding ar- 
senites for the insects, as required, and it has been 
many years since we have suffered any serious 
loss from early blight. However, the spraying 
for early blight will not prevent the bacterial 
disease above described, and it is doubtless the 
Fig. 82. Farly Blight on potato confusionof these two diseases that has led tosuch 
leaf. (After Jones). differences of opinion among potato growers as 
to the efticiency of spraying with Bordeaux 
mixture for early blight. There is real danger of the confusion of early blight 
with the Fusarium blight described in the following paragrph. Our recom- 
mendation is still that contained in the spray calender, namely: to spray with 
Bordeaux mixture or some modified form of it. 
Fusarium Blight. Early in the season of 1909 it was discovered that a small 
area of one of the unfertilized potato plots at the Station was dying out. . Sub- 
sequently the area became larger and investigation showed the fungus to be that 
of dry-rot, which see. Later it developed that the yield of the entire tier of plots 
grown in three crop rotation, died prematurely although spraying had been 
practiced as usual. The dying plants showed infection and the dead areas had 
