THE SWEET POTATO IX HAWAII. 11 
Comparison of the cost of producing stbeet potatoes in Hawaii and on the mainland. 1 
Location. 
Expenditures. 
Central Haiku sub- 
station, station. 
Mainland. 
Plowing (3 times) ; $18/00 , 118.0 $15.00 
disking- 6.00 : 9.00 
ing 3.00 
Plank dragging , 1. 00 
Rideins. . . 
Plants 
Planting... 
Cultivation 
Removing vines 
6.00 5.00 
15.00 15.00 
8.00 6.50 
6.00 , 4.50 
-11.00 2 9.00 
15.00 
10.00 ! 
Hauling | 5.00 | 7.50 
4.00 
10.00 
5.00 
5.00 
Harvesting 16.00 j 15.00 | 25.00 
Extra cost, due to experimental data obtained 10. 00 
104.00 ; 90.50 ! 64.00 
1 See Farmers' Bui. 324, Sweet Potatoes, p. 38. 
- The item of cost in removing the vines is recovered by disposing of the vines as a soiling crop. They 
were delivered to the piggery of the Haiku substation for S5 a ton. 
The above table shows that the cost of production at the experi- 
ment station was considerably more than was the case at either the 
Haiku substation or on the mainland. This difference was largely 
due to the great care which was exercised in the planting, cultivation, 
and weighing of the roots and vines, grown as they were under experi- 
mental conditions rather than under ordinary field conditions. 
The figures of the Haiku substation serve as representative items 
in the cost of production when the crop is grown on a commercial 
basis in Hawaii. At this substation the cost per cultivation was 
SI. 50. or three cultivations for 84.50; the cost of removing the vines 
and loading them on to the wagon was at the rate of SI. 50 per ton, 
or 6 tons for S9. An item of 15 cents represents the actual cost of 
preparing, harvesting, cleaning, grading, and sacking a 100-pound 
sack of sweet potatoes for delivery from the field. On the basis of 
100 sacks per acre the cost would be $15, as indicated. The hauling 
charge was 81.50 per ton. 
The mainland cost for producing an acre of sweet potatoes is decid- 
edly low, as shown by the table. The use of labor-saving devices and 
the growing of the crop in extensive areas make the low figures 
possible. The item of S15 for three plowings also includes the cost 
of disking and leveling the surface prior to ridging, and the item of 825 
for harvesting, includes cost of cleaning, grading, sacking, and 
hauling. 
INSECT ENEMIES AND METHODS OF CONTROL. 
The sweet potato in Hawaii is attacked by a number of insects 
which feed upon the leaves, stems, and roots. Leaf-eating insects 
cause little permanent injury to the plant, owing to its vigorous 
frowth. and they can be brought under control with proper measures. 
; Tactically all of the insects attacking the crop have been described 
in Bulletin 22 of this station, and only those which are especially 
injurious are mentioned here. 
