174 EXPERIMENT STATION. [Jan. 



strengths. More detailed accounts of tLc use of each of those, 

 and the results, follow : — 



Carhon Dlsidfid. — This substance has Leon recommended as 

 very effective. It is applied in shallow grooves near the plants, 

 so that the gas into which it becomes converted may penetrate 

 through the soil to the onions and destroy the maggots. The 

 fluid itself, however, is liable to kill the plants if it reaches 

 them. 



In this experiment a shallow groove was made about 2 inches 

 from each plant, and a little of the liquid was poured into this. 

 The groove was then quickly covered. The application is rather 

 slow and tedious, particularly if more than a small area is thus 

 treated, as the grooves must be short, unless considerable mate- 

 rial is wasted, in order to cover quickly. 



This treatment proved to be very unsatisfactory. For some 

 reason many of the plants were killed, indicating that either 

 too much disulfid was applied; that the grooves were too near 

 the plants ; or that the gas as well as the liquid is dangerous to 

 use. In this experiment about 90 per cent, of the plants died. 

 On the other hand, a large proportion of the plants which 

 escaped destruction by the treatment became infested with mag- 

 gots, from which it may be concluded that where the application 

 is so far from the plant or so little is used as to avoid in- 

 jury no protection from maggots is obtained. It is possible that 

 with an exact amount of material to apply to each plant care- 

 fully worked out, and the distance to apply this also known, 

 protection without injury might be secured ; but it is evident 

 that such care in application as this would require would be 

 impossible in the case of large fields, where the amount of time 

 demanded to do it properly would make the cost prohibitive. 



Even when not applied with the utmopt care the cost is great. 

 Carbon disulfid in small quantities costs about 30 cents per 

 pound. It might, perhaps, be obtained in bulk for half this 

 price, but taking the higher cost and calculating the amount 

 necessary to treat 1 acre we would have an expenditure of from 

 $12 to $14, while the time required to apply it to this area, 

 based on Avages at $1.75 per day, would be rather more than 

 this, and if more care in the application were given the time 

 would probably be more than doubled. The cost of using carbon 



