DISINFECTANTS AND DISINFECTION 355 



About one ounce of potassium cyanide to 150 cubic feet of space is required. 



The gas is extremely poisonous and is often destructive to foliage. It is 

 preferably applied at night as it is then less injurious to the foliage. 



C. Sprays and Washes. — Plant pests are most generally destroyed by 

 spraying agents or washes. A wash is really a more liberal application of 

 the spray, the two being alike as to the results to be attained from their use. 



For low plants the remedy can be applied by means of a sprinkling can 

 but the better method is to use some form of force pump with spray nozzle. 

 A good spray pump should maintain a uniformly constant as well as ade- 

 quate pressure, should be simple of construction, with all parts readily 

 replaceable. The nozzle should break up the stream into a fine mist. 



It is, of course, desirable to get as much as possible of the spray to 

 remain on leaf or stem and to have it evenly distributed. If put on too 

 abundantly the fine droplets or gobules on the leaf will run together and 

 roll off to the ground. The nozzle must not be held near the plant to be 

 sprayed in order to get the desirable dew-like deposit on the leaf. 



For scale insects a thorough moistening is necessary, wetting the bark, 

 the scale and eggs. In order to accomplish this the nozzle must be held 

 close 



The following table by Woodworth will indicate the method of pre- 

 paring and using the more important spraying solutions: 



The well known Bordeaux mixture, so extensively used as a spray and 

 wash is prepared as follows: 



Water, 5° gal- 



Copper sulphate, 6 lb. 



Unslaked lime, 4 lb- 



The adhesive properties can be increased by adding soft soap in quantity 

 equal to that of the copper sulphate. It is also advisable to dilute the 

 mixture for spring spra5ang. It is the most effective and perhaps the 

 cheapest fungicide that can be used. 



Aphides (plant lice) and similar plant parasites may also be destroyed 

 with weak solutions of alum (i .5 to 2 per cent.) . Beetles may be killed by 

 sprinkling a mixture of equal parts of red lead, sugar and flour, near their 

 hiding places, or a mixture of borax 20 parts and precipitated carbonate 

 of baryta (native witherite wiU not answer the purpose) . A great variety 

 of substances are recommended for the extermination of ants, as borax, 

 camphor, balsam of Peru, spraying with benzine, etc. In lawns and in the 

 open generally (in ant hills) they are most quickly destroyed by means of 

 carbon bisulphide. This kills the ants as well as the larvae. 



The exterminators for pests of all sorts is legion and those especially 

 interested must consult some standard work on formulas such, as the Scien- 

 tific American Cylcopedia of Formulas (Hopkins). 



