THE PEACH SAWFLY. 293 



than it does in the air, and spreads through the soil. It is used 

 in this country in various ways for underground insects, espe- 

 cially iii killing ants. Professor Slingerland of Cornell Uni- 

 versity has used it successfully in experiments against the cab- 

 bage maggot.* 



In our tests two cages were used like those described for the 

 cultivation experiments. These cages were placed in the rows 

 with the others, and the same check cages served for both 

 experiments. 



In one cage the carbon disulphide was used at the rate of one 

 fluid ounce to a square yard, and in the o'ther twice that amount, 

 two ounces to a square yard. Holes five or six inches deep were 

 made about eighteen inches apart, or four to the square yard, 

 and an. ounce of the liquid was divided between the four holes, ' 

 or about two teaspoonfuls put in each hole, after which the 

 opening was quickly closed witk the foot. 



The ground in the second cage was treated in the same manner 

 excepting that double the quantity was used. This treatment 

 proved effective, as no adults emerged in either cage. The 

 insects might have been killed with a smaller amount of carbon 

 disulphide, although the actual amount required would depend 

 upon the mechanical condition of the soil. A light, dry, porous 

 soil will require more than a heavy, compact, moist soil, as in 

 the former the carbon disulphide is evaporated much more 

 rapidly and the fumes would not be retained long enough to kill 

 the insects unless a large quantity was used. The greatest 

 drawback, however, is that there is no tool on the market with 

 which the carbon disulphide can be injected into the soil. An 

 instrument was devised by Mr. McGowen, inventor of the 

 McGowen spray nozzle, called the McGowen Injector, and was 

 suited for just such work as is mentioned above. The injector 

 was put on the market, but owing to the small demand for such 

 an instrument, its manufacture was discontinued. 



Treating an orchard with carbon disulphide, even with a 

 suitable injector, would of course be very expensive, but the 

 experiment was made before we were sure that spraying could be 

 practiced, and had the latter proved impracticable, this would 

 have been the only treatment we could recommend. 



♦Cornell Expt. Station Bull. 78, p. 531, 1894. 



