INSECT CONTROL 337 



reported when stick sulphur has been burned at the rate of 

 two pounds per 1000 cubic feet of space. The chief objection 

 is the strong bleaching effect of the fumes in presence of 

 moisture and their destructive action on vegetation. The 

 germinating power of seeds is quickly destroyed, but they 

 are not injured for food. One to five per cent of the gas, 

 with an exposure of twenty-four hours, is effective for most 

 seed and grain pests. It cannot be used on vegetation or 

 for moist fruits, and tarnishes brass, nickel or gilt and may 

 bleach fabrics. 



Tobacco Fumes. Tobacco is extensively used as a fumi- 

 gant for aphides in greenhouses and for certain plants, such 

 as melons, by using it under covers. Several forms are now 

 commonly used. Tobacco or nicotine extracts are sold 

 under various trade names and are volatilized by heating 

 either with a small lamp or by dropping hot irons into the 

 dishes containing the fluid. The same material may be pur- 

 chased in the more convenient form of paper which has been 

 saturated with the extract and which is burned according 

 to directions, a certain amount being sufficient for so many 

 cubic feet of space. These tobacco preparations are excel- 

 lent for the fumigation of household plants, which may be 

 placed in a closet and then fumigated according to the direc- 

 tions of the particular brand employed. Melon vines, 

 young apple trees, bush fruits, and similar outdoor crops 

 may be effectively rid of plant-lice by fumigating with 

 tobacco-paper under a frame covered with canvas or muslin 

 sized with glue or linseed oil. 



4. Repellents include any substances which may be ap- 

 plied to a plant or animal to prevent insect attack. A pop- 

 ular notion that any vile-smelling substance will repel insect 

 attack seems to have very little evidence for its support. 

 Tobacco dust, air-slaked lime, or even fine road dust, thor- 



