113 



ever is used should be tested first in a small way before trying it on a 

 larger scale. This is particularly true of remedies which might possi- 

 bly harm the plants affected. 



The hydrocyanic acid gas method would, of course, kill all of the 

 adult insects, but would hardly have any effect whatever on the larvae 

 living and feeding beneath the surface of the ground. 



Tobacco in various forms is the standard remedy against similar 

 insects, and, if used in liberal quantities in proper manner, should 

 always produce good results. Some of our correspondents report sat- 

 isfaction with this remedy against other insects, while others report 

 that it is not entirely efficacious. Refuse tobacco stems kept moist 

 about the plants are sufficiently deadly in their effects on the adults as 

 to keep them in subjection. Some of the juice which soaks into the 

 ground would have the same effect on the larvae, and tobacco is, more- 

 over, a fertilizer of considerable value. 



When practicable, it is alwaj^s well to sterilize the soil or manure 

 used in the greenhouse by placing it in large closed metal receptacles 

 and subjecting it to about 150 to 200° F. of heat. The same object 

 can be obtained by passing hot steam or hot air through the material 

 used. 



Bisidphide of carbon and kerosene emulsion applied to the soil about 

 the roots of affected plants will kill the larvae, but the former method 

 is rather expensive. 



A method of killing the parent flies said to be employed in mush- 

 room cellars in Europe for similar species consists in placing small, 

 lighted lamps in shallow pans filled with water with a little kerosene 

 floating on the surface. This attracts vast numbers of flies, as well as 

 other injurious insects that may happen to be in the greenhouse, all of 

 which are immediately killed when the>^ come into contact with the 

 kerosene. This, though not a perfect remedy, may be of assistance in 

 reducing the numbers of the pest. 



Other remedies recently recommended against the related gnats 

 which are the cause of potato scab, namely, solutions of formalin 

 and of corrosive sublimate, should be tested where their use is indi- 

 cated, as in the case of peas about to be planted. Full directions for 

 this method of treatment and for the preparation of these two insecti- 

 cides, which, it should be remarked, are fungicides as well, are given 

 in Farmers' Bulletin No. 127 of this Department. 



19288— No. 27—01 8 



