CARBON DISULPHID AS AN IISrSECTICIDE. lY 



EFFECT OF CHARACTER OF THE SOIL. 



Sandy soils permit an even but too rapid diffusion and loss of 

 vapor. Rocky soils are not of even texture, and naturally the vapor 

 follows the line of least resistance. Heavy clay soils, when very dr}^, 

 are usually much broken by cracks and fissures which may run from 

 the surface to a considerable depth and permit the gas to escape 

 without permeating the soil to any considerable extent. When such 

 soil is moderately moistened it is even in texture and favorable to 

 treatment. 



DEPTH OF SOIL. 



The depth of the soil is an important factor in determining how 

 much clisulphid should be used for a given area. If surface soil is 

 very shallow and the subsoil very dense and impervious, it is evident 

 that much less liquid will be required to produce a killing atmosphere 

 than will be needed in soil of much greater depth. The amount of 

 liquid used should be proportional to the permeable depth of the soil. 

 In heavy, compact soils increase the number of injections and di- 

 minish the dose in each ; in light, deep, permeable soils decrease the 

 number of holes and increase the dose in each. 



AMOUNTS TO USE. 



Grapevines growing in medium fine, moderately moist soils were 

 uninjured by doses of from 1 to 1-| ounces in each of three holes made 

 at about 16 inches from the base of the vine and at a depth of about 

 20 inches, while 2-^ ounces to a hole proved fatal to them. 



REPEATED TREATMENTS. 



Best results are obtained b}' dividing the amount of liquid to be 

 applied and giving two applications of the half dose, separating the 

 applications by from 6 to 10 daj^s. The holes made for the second 

 treatment are then placed intermediately between those used for the 

 first. The depth of holes may range from 12 to 16 inches. Spring 

 is the most favorable season for treatments. 



TREATMENT FOR ROOT-MAGGOTS. 



Carbon disulphid has been used with varying degrees of success 

 for the cabbage root-maggot since 1880. Its efficacy varies consider- 

 ably with the nature of the soil, and many of the failures reported 

 haA-e been due Aery largely to improper or too tardy application. If 

 the liquid comes into direct contact with the roots of the young 

 plants, it is sure to prove fatal, but a considerable proportion of the 

 vapor will do no harm. If treatment is delayed until after the 

 plants have wilted, it is very likely that they will not i-ecover, even 

 though the enemy may be killed, but the death of such plants in such 

 cases can not be attributed fairly to the disulphid treatment. Many 



