4 FARMERS’ BULLETIN 557. 
ample, in a county where many potatoes are grown, it might be 
possible by legislation to enforce the discontinuance of potato planting 
for a year, requiring at the same time the destruction of the weeds 
which serve as food plants. There are several alternate food crops 
which do not suffer materially from this insect. About the best of 
these are leguminous crops, like beans, peas, cowpeas, alfalfa, and 
clover. These possess a dual value, as they all act as soil restorers. 
Sugar beets, celery, and crucifers are also good as alternate food crops. 
Grains may serve in the same way, as they are not attacked by the 
tuber moth. 
Care in digging is advisable in order not to cut into the tuber or 
leave the dug potatoes in the field over night where reinfestation 
could occur. 
FUMIGATION. 
While all of these remedies are of value, the best remedy is the 
fumigation of infested tubers with bisulphid of carbon or hydrocyanic- 
acid gas. If bisulphid of carbon is used, it should be at the rate of 
3 pounds to 1,000 cubic feet of air space, including the potatoes; 
1 ounce to a barrel of 96 pounds’ capacity would not be excessive. 
With an exposure of not more than 24 hours no harm should be done 
to the potatoes for planting. The bisulphid should be evaporated in 
tins, like pie plates or pie pans, and a cover should be placed on the 
top of the fumigating barrel or box so as to make it as nearly air-tight 
as possible. At the end of 24 hours the potatoes should be removed, 
placed in a fresh barrel, and closed up. 
Where it can be conveniently done, hydrocyanic-acid gas should 
be used in a specially constructed fumigator (see fig. 4), also gas-tight. 
In the case of bisulphid of carbon there is great danger in bringing the 
chemical into proximity to fire, such as a lighted lantern or cigar, for the 
gas is highly inflammable and even explosive. Then, too, the bisulphid- 
of-carbon method costs slightly more than the hydrocyanic-acid-gas 
method. 
Fumigation with hydrocyanic-acid gas, properly performed, is not 
dangerous, but if improperly performed it is decidedly dangerous to 
human and other animal life, as the fumes are very poisonous and 
are deadly when inhaled in any amount. This gas is more penetrating 
than bisulphid of carbon and can be used by an intelligent person 
without trouble, if he first familiarizes himself thoroughly with the 
procedure by carefully studying the printed directions or assisting 
some one who has had experience in this work. The cubic contents 
of the receptacle to be fumigated, on which is based the amount of 
chemicals to be used, can be readily computed. 
The fumigating box shown in the illustration, which will pres- 
ently be described, may merely be taken as an example of what can 
