142 MASS. EXPERIMENT STATION BULLETIN 177. 



amount of soap. Combinations of "Nico-Fume" liquid with other in- 

 secticides and fungicides can be made with the same restrictions as for 

 "Black Leaf 40." 



4. Fish-oil or Whale-oil Soaps. — These soaps have long been used for 

 the control of plant lice. Three dilutions were tried, — 1 pound to 5 

 gallons of water, 1 pound to 6 gallons of water, and 1 pound to 8 gallons, 

 the soap being cut up into small pieces, dissolved in boiling water, and 

 diluted with cold water to the required strength. The 1-5 and 1-6 

 strengths showed high efficiency. The 1-8 strength was unsatisfactory, 

 not more than half of the plant lice being killed. There was some sus- 

 picion of foliage injury at the 1-5 strength, but this was not extensive, 

 and, since some of the tops had been killed by the plant lice, this point 

 could not be definitely determined. The 1-6 strength proved efficient and 

 showed no injury. Used at this strength the cost of fish-oil or whale-oil 

 soap spray is approximately that of the "Black Leaf 40" solution, 1-800; 

 that is, less than 2 cents per gallon where a quantity of the soap to the 

 amount of 5 pounds or more is purchased. Since the amount of soap to 

 be dissolved in case the fish-oil or whale-oil soap is used is greater than 

 the quantity used with the "Black Leaf 40" solution, the latter is perhaps 

 somewhat preferable because of the smaller outlay of time and bother 

 thus involved. These soaps, however, furnish an excellent substitute in 

 case of difficulty in obtaining the nicotine preparation. Pyrox, Bordo- 

 lead, Bordeaux mixture or similar materials should never be used with 

 soap of any kind. 



5. Kerosene Emulsion. — This material was made according to the usual 

 stock formula, as follows : — 



Hard soap, . . . . - . . .J pound (liquid soap, J pint). 



Water, ........ 1 gallon. 



Kerosene, ....... 2 gallons. 



The soap is cut into small pieces and dissolved in the water, which 

 should be boiling. The soap solution is then poured into the kerosene 

 while hot, and churned back and forth with a spray pump until a creamy 

 mass is formed and no free oil is present. This can usually be done satis- 

 factorily in from ten to fifteen minutes. The emulsion formed is a stock 

 solution, which should be diluted at the rate of 1 part to 9 parts of water 

 for plant lice. 



It was supposed that kerosene emulsion, a standard remedy for plant 

 lice and other soft-bodied insects, would prove highly effective against 

 potato lice, but the trials with this material proved disappointing, as not 

 more than 90 per cent, of the insects were killed. This indicates an effi- 

 ciency for kerosene emulsion considerably less than that of the "Black 

 Leaf 40," 1-800, and the fish-oil soap, 1-6. Furthermore, the trouble and 

 time involved in making the emulsion, as well as the danger of foliage 

 injury when this material is improperly made, militate against its use 

 where the other materials referred to above arc obtainable. The cost of 



