50 BULLETIN 427, V. S, DEPARTMElSrT OF AGRICULTURE. 



kills the parasites. The tuber moth is more apt to pupate imder 

 clods and rubbish in the field than are any of the parasites, hepce 

 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 mf ested 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 pupae and eggs, wiU 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 smnmer, 

 or in two weeks in winter. Careful watch should be kept, and if the 

 tuber moth is still workmg, another fumigation should be given. 



In fumigating with carbon disulphid the Hquid 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 

 aU 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 aU the 

 loss. 



