TOBACCO 271 



always stock this mixture in large quantities, in order to 

 be able on the first appearance of the pest to syringe by 

 means of a pump spray all affected plants. As an illus- 

 tration of its effect, we may mention that on a certain 

 estate the number of bales of tobacco has been reduced 

 from 300 to 30 through the attack of green-fly. 



Petroleum-soap emulsion against ants, which remove 

 the seed from the seed drills, and a churner for its pre- 

 paration, are generally in use at the instigation of the 

 Deli Testing Station. 



Of recent date also is the application on a large scale 

 of carbon disulphide as an insecticide for Lasio derma. 

 This small beetle settles in the piles of fermenting 

 tobacco, in which it occasions extraordinary damage. In 

 order to put an end to this destruction and to safeguard 

 the unloaded bales -of suspected tobacco against further 

 attacks, they are, when quite ready for shipment, placed 

 by hundreds at a time in hermetically sealed small sheds, 

 and exposed for a certain time to the fumes of carbon 

 disulphide. This will destroy all life without in any way 

 affecting the quality of the tobacco. The crops of entire 

 estates have been put on the market after having been 

 disinfected in this way. 



As parasites of the injurious insects appeared to be 

 very scarce in Deli and very insignificant, it was con- 

 sidered advisable to try to import some 'from elsewhere, 

 to increase them artificially, and to liberate them in the 

 open, in order to combat the tobacco-damaging insects. 



With this object Dr. de Bussy made a trip to 

 the United States in 1910, not only to try to import from 

 there already known parasites, but also to study the 

 methods adopted in that country. With the assistance 

 of the Bureau of Entomology at Washington, he finally 

 succeeded in transferring a number of different kinds 

 alive from North America to Sumatra. 



An assistant collected and cultivated the desired speci- 

 mens in the south of the United States, and forwarded 

 them in cold storage to Amsterdam, where another 

 assistant formed an intermediate depot, and bred where 

 necessary new generations ; refrigerators were then again 

 resorted to to retard development as much as possible 



