POTATO DISEASES IN HAWAII. 
29 
fection through the use of good seed, crop rotation, control of dis- 
eases and insect pests as far as possible, careful handling of the 
crop, and storage at the lowest available temperature. 
Tuber Moth (Phthorimoea operculella) . 
The tuber moth is the most serious insect pest of the Irish potato 
in Hawaii because of the damage it does and the difficulty with which 
it can be controlled. It ranks second only to late blight as a poten- 
tial pest of this crop, though the conditions favorable to the one are 
unfavorable to the other. This insect also attacks tomato, eggplant, 
and tobacco (as splitworm), though less actively than it does the 
potato. 
The moth, which is small and grayish in color (fig. 4), lays its 
eggs upon the leaves or other parts of the plant. The larva? or 
worms quickly enter the 
leaves, mining between 
the surfaces, or bore 
into the stem or tubers 
(PI. XI). Affected 
tubers soon rot, due to 
invasion by one or more 
of the numerous wound 
bacteria or fungi. In 
Hawaii there are prob- 
ably several generations of the pest during the year. The moth is 
most prevalent during the dry season, that is, from May to October. 
The damage it does in drought years is almost unbelievable. 
Control. — The tuber moth is very difficult to control, even under 
the best systems of potato culture, and the regrettable lack of system 
in Hawaii greatly increases the difficulties. With potatoes growing 
in every month of the year, with practically no rotation in general, 
and with volunteer potatoes allowed to mature with corn or beans, 
etc., where an indifferent rotation obtains, the outlook is not encour- 
aging. The procedure outlined on the mainland for the control of 
this pest is cited below, and as far as practicable these methods should 
be followed. 
Clean cultivation : All volunteer potato plants as well as all solanaceous weeds 
should be pulled out and destroyed. When a potato crop is harvested the vines 
and all small tubers should be gathered up and burned. 
Crop rotation : Crop rotation is essential, and the cooperation of all growers 
of a section is necessary. Crops which can be used in rotation with potatoes 
are beans, peas, corn, cowpeas, alfalfa, and clover. 
Hilling : Hilling up the potato plants much more than is generally practiced 
here, thus increasing the depth of the tubers, will probably help to prevent tuber 
infestation during the maturing of the crop. 
Digging and sorting: The crop should be dug as soon as mature and brought 
in from the field before late afternoon. If the tubers are infested, as is indi- 
Fig. 4. — The potato tuber moth : Natural position at rest. 
Much enlarged. (From U. S. Dept. Agr. Bui. 427.) 
