FUMIGATING WITH TOBACCO. 89 



are freely used in all the houses. The quantity must 

 also be varied in accordance with the plants growing in 

 the house. Some plants are much more easily injured 

 by the smoke than others, and the amount used must 

 be insufficient to hurt the most tender plants. Less in- 

 jury is apt to result if the houses and plants are dry ; wet 

 foliage is quite easily scorched by the smoke. Our method 

 of starting a "smudge" is to place a single sheet of 

 newspaper, previously lighted, in the bottom of the burner, 

 and upon this the stems are immediately placed. If prop- 

 erlv dampened, they will take fire readily and smoulder 

 without blazing. 



The frequency with which a house should be smoked 

 cannot be definitely stated. Some conservatories will re- 

 quire the operation scarely more than two or three times 

 during the winter, while others may need that many treat- 

 ments each week. In the latter case, it is well to have 

 the smudges upon consecutive days, as in this manner 

 insects receive a second treatment before they have re- 

 covered from the first. The evening is perhaps the best 

 time for fumigating, as most of the disagreeable odor is 

 thus escaped. But it may be advisable, in badly infested 

 houses, to follow the evening treatment by another the 

 next morning. In such cases, care should be exercised 

 that the houses do not become overheated by the morn- 

 ing sun. 



Tobacco smoke may be used successfully in the de- 

 struction of the various aphides which are found upon 

 greenhouse plants, and of a small white fly, a species of 

 aleyrodes. Other insects cannot be practically treated by 

 its use. 



The rose-leaf extract of tobacco we find to be one of 

 the best of all insecticides for glass houses. It is a 

 liquid, which we reduce one-half with water, then drop 

 a large piece of hot iron into it. The fumes are fatal 

 to aphis, but have proved to be harmless to plants 

 with us. 



