POTATO DISEASES IN HAWAII. 33 
confusion of these forms, and it is hoped that the descriptions of dis- 
eases herein will help the grower to distinguish them in order that 
the proper treatment may be applied. Bordeaux mixture, which is so 
serviceable as a preventive spray for the two blights above men- 
tioned, will keep the mites off the plants for from one to two weeks, 
but eventually sprayed plants are as badly affected as if they had 
received no treatment. Sulphur, on the other hand, is effective 
against mites, but it is not to be recommended for the late blight if 
it is possible to use Bordeaux mixture. 
Nematodes (Gall worms or Eelworms). 
The potato gallworm or eelworm, one of a large number of species 
of nematodes, is a factor of considerable importance in potato pro- 
duction in Hawaii. These minute pests are not insects but micro- 
scopic round worms. The same sort of parasite is responsible for the 
rootknot disease of various crops. The gallworm attacks the tubers 
and causes the skin to become roughened or cracked and covered with 
irregular galls or pimples (PI. XIV, fig. 1). Badly infested tubers 
shrivel up, remain partly developed, and become soft and otherwise 
unfit for table use. When broken across, such tubers show a line of 
glistening specks just beneath the skin (PI. XIV, fig. 2). These are 
the encysted nematodes. 
There are few cultivated crops not subject to attack by species of 
gallworms, and when once established in a field their elimination is 
practically impossible. In greenhouses they can be killed by steam 
sterilization, but in the open field this is seldom practicable. They 
are carried into new soils by infested seed tubers, nursery stock, etc. 
Infested seed potatoes, which are of course unfit for planting, con- 
stitute a serious menace to the potato industry. 
Gallworm injury to garden crops has been observed on Hawaii, 
Maui, and Oahu. A general infestation of fields with these pests 
would be disastrous, and it is essential that their spread be limited 
so far as possible. The cultivated fields of the Territory which are 
infested will be determined as opportunity permits and crops sug- 
gested for rotation where possible. 
Control. — Seed potatoes should be carefully examined for the pres- 
ence of nematode galls before planting. As far as possible, seed stock 
should be secured from fields known to be free from this pest. Break 
open any suspicous looking tubers and examine the outer third of tjie 
flesh for minute brownish spots with pearly white centers. In case of 
doubt, such tubers should not be planted, and specimens should be 
submitted to the station for examination. 
There are over 500 plants susceptible to the attacks of gallworms, 
including many garden crops. It profits little to plant potatoes upon 
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