274 Effective Farming 



when making the test. Stir, take out a test jar nearly full, and place 

 the hydrometer in the liquid. Next determine the ratio of dilution and 

 dilute some of the material to a specific gravity of 1.03. To determine 

 the ratio of dilution, divide the decimal of the specific gravity of the con- 

 centrate by the decimal desired for the dilute material. Suppose the 

 concentrated solution tested 1.30 and it is desired to dilute to 1.03. 

 Dividing .30 by .03 gives 10 as the ratio of dilution. The concentrate, 

 then, contains 10 times the quantity of combined sulfides that is desired 

 in an equal volume of dilute solutions. Thus, 1 volume of the con- 

 centrate must be added to 9 volumes of water to get 10 volumes of the 

 desired strength. Suppose the concentrate tested 1.24. Dividing 

 .24 by .03 the ratio is 1 to 8 and 7 volumes of water should be added to 

 1 volume of concentrate to make the dilute solution. 



3. Kerosene emulsion. An emulsion made of kerosene, soap, and 

 s water is a standard remedy for plant-lice. To make a stock solution, 

 combine two gallons of kerosene, one-half pound of whale-oil soap with 

 one gallon of water as follows : Boil the water and dissolve the soap in 

 it and while still boiling hot pour the soapy solution into the kerosene 

 (have the kerosene away from the fire). Next, churn the mixture vio- 

 lently for about five minutes by means of a spray-pump with a direct- 

 discharge nozzle by throwing a stream of the liquid back into itself, 

 or if no such pump is available, stir the material vigorously. At the end 

 of the time the mixture should be of the consistency of cream. This 

 stock solution is diluted for use as needed. The usual dilutions are 

 from fifteen to twenty parts of water to one of the solution. 



4. San Jose scale. Write to the entomologist of the experiment 

 station of your state and ask whether or not the San Jose scale is found 

 in your vicinity. If so make a special trip to near-by orchards and 

 try to find infested branches. Carry some of them to the school for 

 further study. There is no danger of spreading the pest in this way, 

 because when the branch dies, the scale dies also. 



Draw a section of a twig as it appears under the magnifying glass. 

 Compare the infested twigs with Fig. 110. 



5. The codlin-moth. Secure some apples that have been made 

 wormy by insects of the first brood of codlin-moths. Cut them through 

 the exit hole and the core as shown in Fig. 111. See if you can find 

 apples made wormy by the larvae of the second brood and determine 

 the route taken by the worms. 



During a field trip search for cocoons of the codlin-moth. They 

 may often be found on the under side of the bark of apple trees. 

 Compare the number of windfalls under sprayed and unsprayed apple 

 trees. 



