December, 1911.] 



509 



Plant Sanitation. 



be thoroughly stirred, as the oils are 

 liable to separate upon standing. 



For stirring the emulsion a piece of 

 board about 4| feet long and 4 inches 

 wide, to the base of which has been 

 nailed a strip of board 10 inches long by 

 4 inches wide, has been found con- 

 venient. By using such a paddle the 

 emulsion at the bottom of the barrel, 

 which is thicker than that at the top, is 

 raised and the whole mass becomes 

 uniform. Is is always advisable to test 

 the stock emulsion before taking any out 

 for spraying. If any free oil is found 

 add a little water, and after thoroughly 

 stirring test it again. Continue this 

 until a perfect emulsion is obtained. If 

 this testing is not done, an emulsion 

 with free oil is liable to be sprayed 

 upon the trees, which will kill some 

 of them. These emulsions are rather 

 stable, and after one has determined the 

 amount of water necessary to make a 

 complete emulsion it very seldom varies. 

 Where spraying is being done on an 

 extensive scale the stock emulsion may 

 be placed on the bottom of the spray 

 tank and the water slowly added, 

 stirring the whole until about half of 

 the amount of water has been added, 

 then the rest of the water may be 

 added and the spraying begun. 



The dilutions of all formulas have 

 had to be changed, as all spraying 

 in Porto Rico is done on tree9 with 

 foliage. The dilution of crude oil for- 

 mula set forth in Bulletin 40 of the 

 Connecticut State Agricultural Experi- 

 ment Station was changed from 1 to 

 15 to 1 to 25, the latter strength having 

 exceptional killing powers. It not only 

 kills the young purple scale, but also 

 the females with eggs. 



The same can be said of emulsions in 

 which paraffin and kerosene oil are sub- 

 stituted for the crude oil. The Miscible 

 emulsions made with heavier oils do 

 not evaporate as quickly as those made 

 with lighter oils, and for this reason 

 their killing power is extended over a 

 longer period. It has often been observ- 

 ed that the old scales seem to retain 

 a certain amount of oil which is later 

 on set free by the rains. This seems to 

 be sufficiently strong to kill any crawl- 

 iug young whose mother has escaped 

 being killed. The oil particles of these 

 emulsions made with kerosene were so 

 finely divided that they could not be 

 seen with low powers of a compound 

 microscope. 



All the work done with these emul- 

 sions has been on young trees which 

 were not fruiting. They will be tested 

 on trees with fruit to determine 



whether they cause the young fruit to 

 drop or whether they produce any dis- 

 coloratioo. 



Direction for making Miscible Oils. — 

 There are three steps to be taken in 

 making miscible oil emulsions before the 

 emulsion for spraying is obtained. First, 

 1;he cooking of the soap and the adding 

 of the kerosene and water. Second, 

 making the stock emulsion out of the 

 soap solutions and various oils. Third, 

 diluting the stock emulsion for spraying. 



The 9oap solution should be made in 

 the open air or under an open shed, as 

 the mixture is inflammable when it 

 reaches 300° F. It is also advisable to 

 make the soap solution in a receptacle 

 that is large enough to allow plenty of 

 room for boiling. When the soap 

 reaches 240° F. it begins to boil and con- 

 tinues to boil very violently until it 

 reaches about 280° F. During this time 

 the mixture foams and increases to at 

 least double its volume. It is, therefore, 

 very necessary that the receptacle be 

 sufficiently large. When the soap 

 reaches 300° F. it should be removed from 

 the fire and the kerosene water added. 

 First, pour the kerosene in slowly, 

 thoroughly stirring the mixture ; allow 

 this to cool a little, then add the water. 

 It is better to let it cool until the soap 

 plus the kerosene is below 212° F. The 

 following formula is used in making 

 the soap solution : — 



Menhaden oil ... gallons 10 

 Carbolic acid ... ,, 8 



Caustic potash ... pounds 15 

 Heat to 300° F., and then : add 

 Kerosene ' ... gallons 14 

 Wafce" ... „ 22 



In making the soap it is well to have 

 the kettle covered with boards with a 

 hole in the centre through which a 

 thermometer can be placed to take the 

 readings. It does not harm if the soap 

 reaches 310 or 315° F., but it is not safe 

 to continue the boiling after the soap 

 has reached 300° F., as it is more liable 

 to take fire. After the soap solution is 

 completed, the fire can be drawn and 

 the mixture placed in a barrel, after 

 which the kerosene and water are added. 

 The soap should be slightly ropy, but 

 should run readily and not separate upon 

 standing. A half-barrel of this soap has 

 been left standing for six months with- 

 out undergoing any change. 



Stock emulsions are made by the 

 following formula : — 



Soap solution ... gallons 8 



Crude oil ... „ 18 



Rosin oil ... „ 4 



Water ... „ 3 



