113 



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

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

 bly harm the plants affected. 



The Jiydrocyanlc acid gas vietJwd would, of (course, kill all of the 

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

 living and feeding l)eneath 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 sufiicKiitly 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 larvre, and tobacco is, more- 

 over, a fertilizer of considerable value. 



When practicable, it is always well to sterilize the soil or manure 

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

 and su))jecting it to aliout 1.50 to 200'-' F. of heat. The same ol)ject 

 can be obtained b}" passing hot steam or hot air through the material 

 used. 



Ulsxdpliide of carhon and ZvwAsv^^r'enudsion applied to the soil about 

 the roots of affected plants will kill the larva?, 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 injui-ious insects that may happen to l)e in the greenhouse, all of 

 which are immediately killed when they 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 seal), 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 tAvo insecti- 

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

 in Farmers' Bulletin No. 127 of this Department. 



3253— No. 27—01 8 



