4 BULLETIN 45, HAWAII EXPERIMENT STATION. 
crop failures. It is estimated that from one cause or another at 
least 50 per cent of the crop has been lost during the period under 
observation. The experience of the past two years justifies the con- 
clusion that potato-crop failures in the islands result from the fol- 
lowing causes: (1) Use of poor seed, (2) continuous cropping, (3) 
diseases and insect pests, and (4) unsatisfactory soil conditions. 
Fundamentally diseases and insect pests are the most important 
factors, the others mentioned being merely contributing causes. 
The diseases which have come under observation have been identi- 
fied, and the experience gained furnishes ground for the assumption 
that control measures found useful for combating these same dis- 
eases in other sections are applicable here with but little modifica- 
tion. It is realized that attention has not been devoted to this 
problem for a sufficiently long period to furnish a basis for more 
than tentative conclusions upon many of the problems of potato 
production, but this bulletin has been written in order to put the 
results of the study into the nature of potato failures and control 
measures into shape suitable for meeting the increasing demand for 
information. 
Attention is directed to certain cultural practices in their relation 
to disease, and the preventive and control measures which have been 
found applicable are described. Where no data are available for 
Hawaiian conditions, information as to methods in use in other 
localities is freely drawn upon. The diseases, insect pests, and other 
causes of lessened yields thus far observed are discussed. Several 
serious diseases affecting the Irish potato in other localities but not 
yet found in the islands are described in order that Hawaiian potato 
growers may guard against their introduction. 
PREVENTION AND CONTROL OF POTATO PESTS. 
GOOD SEED. 
The question of w T hat constitutes good seed is fundamental in the 
growing of a healthy potato crop. Good seed potatoes should be 
true to variety, from productive plants, firm, free from disease, 
uniform in size and shape, not overripe, and not weakened by sprout- 
ing. Such seed is difficult to obtain in Hawaii. It is probable that 
satisfactory local seed can best be obtained by each grower's main- 
taining a seed plat, or possibly a few growers in each section might 
well specialize in seed production. 
Certified seed. — The best seed is that from the mainland, certified 
by the authorities of the States. The label " Certified Seed " shows 
that the seed has been grown under a system of State inspection. 
According to the varying requirements of the different States such 
seed is free from certain diseases and shows only a definite allowable 
minimum of other specified diseases. 
