884 ANNUAL REPORT OP THE Off. Doc. 



the nozzle of the spray pump without clogging and more intimately 

 coat the infested surface of the trees. While the services of a trained 

 chemist are not required to mix and boil say 100 pounds of sulphur 

 with 50 pounds of lime in 50 gallons of water, it seems the majority 

 of growers prefer to purchase the concentrated lime-sulphur solu- 

 tion from the commercial manufacturers who are prepared to secure 

 a uniform strength which may be diluted with a given proportion of 

 water at the time of spraying. 



The chemical re-action taking place in the manufacture of lime- 

 sulphur is really an intricate matter, and the object of the manufac- 

 turer is to obtain polysulphides-tetra sulphide and pent-asulphide of 

 calcium — and thiosulphate of calcium, in the highest possible per 

 cent, as these are the only ingredients in lime-sulphur having any 

 insecticidal value. These can be determined only by means of a 

 chemical analysis and are not always indicated by the hydrometer 

 test. There are on the market many brands of concentrated lime- 

 sulphur solution, analyzing anywhere from 27 per cent, to 33 per 

 cent, calcium poly-sulphides and 1 per cent, to 3 per cent, calcium 

 thiosulphate. 



SOAP 



Soap solutions are useful insecticides for killing plant lice and 

 other small, soft bodied insects. The so-called whale oil or fish oil 

 soaps are usually recommended for this use. Many of the commer- 

 cial brands on the market contain impurities as they are usually by- 

 products from the manufacture of other materials, and so are very 

 likely to injure young tender foliage. An excellent fish oil soap can 

 be made after the following formula : 



Caustic soda, 6 pounds. 



Water | gallon. 



Fish oil, 22 pounds. 



Dissolve the caustic in the water, add the fish oil and stir briskly 

 for 15 or 20 minutes. Soaps are useful not only for their direct ef- 

 fects upon insects but also by increasing the efficiency of other 

 sprays. Three to five pounds added to 100 gallons of arsenate of 

 lead spray liquid, will tend to prevent settling and the same amount 

 added to nicotine solution will increase its sticking and spreading 

 qualities. 



EMULSIFIED OILS 



Emulsions are oily sprays in which the minute globules of the oil 

 used are suspended in water, a condition brought about by the addi- 

 tion of soap. Kerosene emulsion is one of the oldest of our contract 

 insecticides. The action of these oils when applied on the insect is 

 to cover them with a hermetically sealed film which produces suf- 

 focation. To this action the soap in the emulsion also contributes. 

 The usual formula for making kerosene emulsion is soap ^ pound, 

 dissolved in one gallon of hot water into which is stirred two gal- 

 lons of kerosene. This stock solution contains about 66f per cent, 

 kerosene. Using this as a basis any per cent, strength of oil desired 

 in the spray, may be applied. Commercial miscible oils are made 



