354 PHARMACEUTICAL BACTERIOLOGY 



active, that is, in the early morning or in the evening. Lime is used where 

 paris green is not permissible, as with fruit plants and edible herbs. 



b. Sulphur. — The flower of sulphur or ground sulphur is a very widely 

 used remedy for fungous pests, as mildew; also for the red spider and 

 thrips. Sulphur is active only in the sunlight, particularly on a hot day. 



The flower of sulphur gives better results than the ground sulphur be- 

 cause it " sticks " better. It should be applied evenly and not too thickly. 

 Remember that sulphur dioxide is very injurious to plants, therefore 

 fumigation by burning sulphur is out of the question. 



c. Paris Green and Other 'Arsenicals. — These are generally not used in 

 the dry powdered form. When so used they are diluted with flour, dust 

 or other inert powdered material. Must be sparingly applied and evenly 

 distributed, otherwise serious damage may be done to the foliage. 



B. Gases. — Gases diffuse with great rapidity and when applied within 

 an enclosed space will, in a short time, be uniformly distributed throughout 

 the enclosed space. The rapid diffusion of gases is a great hindrance to 

 their practical utiUzation in the open as in orchards, fields and gardens. 

 Their use is quite limited. 



a. Carbon Bisulphide. — ^This is not used with growing plants though it 

 is applied to stored seeds, and dry plants and grains, for the purpose of 

 kilUng insects and other destructive animals. It is also used to kill pests 

 which live in the soil, as the grape Phylloxera. For this purpose a machine 

 is used which injects the bisulphide into the soil. To destroy pests in drug 

 plants, seeds and grain, enclose them in a space, place a dish containing 

 the bisulphide on top of the material. The vapor being heavier than the 

 air, gravitates downward and soon fills the entire enclosed area. The 

 amount necessary to do the work will depend upon the nature of the ma- 

 terial to be treated and the tightness of the enclosure. Roughly estimated 

 a dram of the carbon bisulphide to five pounds of the material is sufficient. 

 Grainmen usually apply one pound to the ton of grain, if the bin is tight. 



Carbon bisulphide is one of the most effective remedies against the 

 gopher and the ground squirrel. Use the remedy after a rain as the soil 

 is then less porous. Pour an ounce over a rag or other porous substance 

 (horse droppings are much used), stuff this into the hole and plug with a 

 ball of dirt. The bisulphide is also used to kill the yellow-jacket, which is 

 very injurious to fruit, also the root crown borer of the peach, and to disin- 

 fect grapevine cuttings, etc., etc. 



b. Hydrocyanic Acid Gas. — This is about the only gas which is powerful 

 enough to kill insects and yet not injure the foliage. It is used by covering 

 the tree, shrub or bush with a tent doth or canvas which should be oiled to 

 keep in the vapor. The vessel containing the chemicals is placed under- 

 neath. Exposure of from thirty to fifty minutes is usually sufficient. 



