310 GREENHOUSE MANAGEMENT. 



full size, they are hard to destroy. As a preventive, 

 greenhouses should be fumigated once or twice a week if 

 insects are troublesome. Kerosene emulsion, and 

 buhach, either as a powder or in water, are also quite 

 effectual. The black chrysanthemum aphides are even 

 more difficult to destroy than the green fly, and tobacco 

 will have but little effect, if they once get their growth ; 

 the remedies last given will, however, be found effectual. 

 The black aphis of the violet is quite troublesome 

 in some sections, but can be readily destroyed with hy- 



FIG. 106. WINGED MALE APHIS. 



drocyanic acid gas, as can the gall fly which attacks the 

 violet leaves. 



The blue aphis sometimes appears upon the roots of 

 plants that have in some way been stunted, particularly 

 if they have been kept unduly dry. The plants should 

 be shaken out, placed in whale-oil soap solution, and 

 repotted in fresh soil. 



PLANT BUGS. 



When plants are housed in the fall some of the in- 

 sects that have been working upon them out of doors 

 may be housed with them. Among the most common 

 are the Yellow-lined plant bug and the Tarnished plant 

 bug. They feed upon a number of plants and some- 



