50 BULLETIN 427, U. S. DEPARTMENT OF AGRICULTURE. 
kills the parasites. The tuber moth is more apt to pupate under 
clods and rubbish in the field than are any of the parasites, hence 
the destruction of potato tops would be a more serious check to 
the parasites than to the tuber moth. It seems that if growers 
destroy waste tubers and keep the rest protected so that the tuber 
moth must breed on potato tops, the parasites will keep the tuber 
moth from becoming dangerously abundant. 
DIRECT CONTROL METHODS. 
Experiments were made to determine a cheap practical method of 
treating tubers infested with the tuber moth. As the tuber takes up 
odors and flavors readily, and retains them for indefinite periods, 
only a few methods were tried. 
The only promising unobjectionable applications tested were for- 
malin dilutions and water used as dips, and carbon disulphid and 
hydrocyanic-acid gas as fumigants. Of these four, the only one which 
was at all successful was carbon disulphid. 
Carbon disulphid naturally has many advantages as a fumigant 
for potatoes. It does not injure the tubers, it can be applied for 
long periods and thus penetrate thoroughly, and finally, it is heavier 
than air and if liberated at the top will go entirely through a pile to 
the floor. Various dosages and periods were used for fumigation, 
but it was early apparent that for all-around results the material 
should be used at the rate of 2 pounds to 1,000 cubic feet, and fumi- 
gation should last 48 hours. At this strength the larvae and adults, 
and practically all the pupa? and eggs, will be killed, and the long 
exposure to the vapor insures thorough penetration. 
If potatoes are to be stored they should be fumigated promptly. 
Cheap gas-tight bins may be made by lining temporary structures 
with tarred paper and painting the seams. If the tubers are notice- 
ably infested the fumigation should be repeated in a week in summer, 
or in two weeks in winter. Careful watch should be kept, and if the 
tuber moth is still working, another fumigation should be given. 
In fumigating with carbon disulphid the liquid should be placed 
on top of the sacks in shallow tin pans, and care should be taken not 
to expose the gas to fire, as it is explosive when mixed with air and 
ignited. 
OTHER REMEDIES. 
TRAPPING THE ADULTS. 
As the adult is attracted to light, some authors recommend trap- 
ping with lanterns. This remedy is of questionable value, as not 
all the adults could be trapped, and there is much doubt as to whether 
the numbers could be sufficiently reduced to make a difference at 
harvest time. In this connection it must be remembered that it is the 
multiplication of the insect in storage that causes practically all the 
loss. 
