CONTROL OF WHITE GRUBS. 7 



in favor of either form of the cyanide as a killing agent. In all eases 

 the injection at three inches gave better results tlian at live inches. 

 However, neither form of potassium cyanide gave results that would 

 warrant its use as a soil fumigant in controlling the Avhite grub. 



The experiments tend to show that the poison has but small 

 powers of penetration when applied in such a manner. The dan- 

 ger incident upon the application of such a powerful poison under 

 existing labor conditions, would in any case render the advisability 

 of using this substance very doubtful. 



Tobacco. 



Tobacco is an old-time remedy for insect pests, and although it 

 is only effective when used against delicate soft-bodied insects, fre- 

 quent attempts were made to control the white grubs with it. Tht- 

 following experiment indicates the average results obtained with thi?? 

 substance. Tobacco water was made by steeping eight ounces of cured 

 tobacco in three gallons of water. It was then applied in pint doses 

 to holes in the soil around the cane stools. 



Experiment VII. — Experiment with Tobacco Water Against the White Grub. 



How aitplieil 



Hole in center of slool 

 Hole each side of stool 



When 

 applied 



March 28 



When 

 examined 



April 2 



No. of grnbs found 



Alive 



45 

 33 

 45 

 42 



Dead 



R 

 5 



It is readily seen that the tobacco in this form had but very lit- 

 tle effect on the white grubs. It is too weak in action and too ex- 

 pensive as well to apply in this mauner. 



Vaporite. 



The last substance to be discussed under the heading of soil fu- 

 migants is vaporite, a commercial preparation put out in the form 

 of a gray powder, which on coming into contact with moist soil grad- 

 ually gives off a vapor. In accordance with directions for the most 

 efficient method of using this material, it should be applied at some 

 depth below the root system of the plant treated so that the vapoi- 

 given off will kill the grubs and other insets infesting the roots as 

 it rises to the surface. 



