POTATO DISEASES IN HAWAII. 23 
mained almost without a trace of blight spots, and at the end of the 
fourth month 20 hills were dug, yielding 9-J pounds of fair-sized 
tubers. The Hamakua Hybrid grew through weather favorable to 
blight for most of the period of the experiment. 
It appears from the foregoing that the Hamakua Hybrid and one 
of its parents, the Portuguese Purple, possess a real resistance to 
the late blight under Hawaiian conditions. Should the indicated re- 
sistance to late blight of the Hamakua Hybrid be of more than local 
importance, the quality of the tubers can doubtless be improved by 
selection in the direction of market requirements, though there is not 
the discrimination here against colored and long potatoes that is 
characteristic of the eastern markets. 
Early Blight or Dry Blight (Alternaria solani). 
Early or dry blight, a fungus disease (PL VI) attacking only the 
foliage of the potato and producing a characteristic spotting and 
death of the leaves, is prevalent in the Territory in dry, hot seasons 
and occasionally may cause a loss of from 5 to 25 per cent of the crop 
in affected fields. As previously noted, the name " early blight " as ap- 
plied to this disease on the mainland has little significance in Hawaii, 
unless it be that the disease attacks the plants earlier in their period of 
growth than is characteristic of the late or wet-weather blight. As 
previously noted, the name dry blight or dry-weather blight is locally 
more appropriate for this disease. 
The parasitic fungus produces circular to more or less angular, 
dry, brown leaf spots, often with concentric markings with something 
of the appearance of a target (PI. VI). The spots are from one- 
sixteenth to one-fourth inch in diameter and sometimes confluent, and 
frequently the dry tissue falls out, giving a shot- hole effect to the 
leaves. The spread of the spot may be limited in certain directions 
by the leaf veins, in which case it is more or less angular in shape. 
The spots caused by the dry blight are from the first dry and brown 
and the progress of the disease is comparatively slow. The badly 
affected leaves dry and die after a few weeks. The stems and tubers 
are not directly affected, but as a result of defoliation and early 
maturity of the plant the yield is materially reduced. 
Early or dry blight appears to be only occasionally serious in the 
islands. The prolonged drought during the summer and fall of 1917 
in the Hamakua district of the island of Hawaii was particularly 
favorable to its development. A loss of 25 per cent was observed 
in some cases, most of it due apparently to this disease, though the 
mite disease, subsequently to be discussed, and bud and leaf infesta- 
tion with the tuber moth were undoubtedly responsible for a portion 
of the damage. 
