POTATO PLANT LICE AND THEIR CONTROL. 141 



results, the hard soap being cut into small pieces and dissolved in boiling 

 water before adding to the solution. If liquid soap is used, 1 quart should 

 be added to every 50 gallons of the diluted "Black Leaf 40." In addition 

 to increasing the effectiveness of this nicotine preparation the soap aids 

 materially as a spreader, thus insuring a more uniform coating of the 

 foUage and a more perfect "hit" of the plant lice. 



All of the four dilutions tried showed no foliage injury, but only the 

 1-800 strength met the test of reasonable economy and efficiency. This 

 strength showed nearly a perfect kill. 



The dilution 1-800 reduced to practical terms is as follows: — 



"Black Leaf 40," § pint. 



Hard soap, dissolved in boiling water, . . 2 pounds (liquid soap, 1 quart). 



Water, ........ 50 gallons. 



Reduction to a small amount would be as follows: — 



"Black Leaf 40," IJ teaspoonfuls. 



Hard soap, dissolved in boiling water, . . . . . f ounce. 



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



The cost of this spray material will depend mainly upon the quantity 

 of the "Black Leaf 40," or similar nicotine preparation, purchased. In 

 an amount of 10 pounds, which diluted as recommended (1-800) would 

 give 1,000 gallons of spray mixture, the cost amounts to but little over 1 

 cent per gallon. If purchased in an amount as small as an ounce the cost 

 is increased to something over 4 cents a gallon. 



2. "Black Leaf 40" and Pyrox, etc. — The question has frequently been 

 asked as to whether or not "Black Leaf 40" can be safely combined with 

 Pyrox, Bordo-lead and other materials, such as arsenate of lead and 

 Bordeaux mixture, thus reducing the labor involved in making separate 

 applications. Pyrox and Bordo-lead are a combination of an arsenical 

 and a fungicide, and are used for the control of leaf-eating insects, such as 

 the potato beetle, and fungous diseases. "Black Leaf 40" and Pyrox 

 or Bordo-lead can be safely combined with equally as good results as when 

 these materials are used separately. However, soap should not be used 

 with such a combination, and should never be used in any combination 

 containing Pyrox, Bordo-lead or Bordeaux mixture, as an "incompatible 

 mixture" results. "Black Leaf 40," or any similar nicotine preparation, 

 may also be safely combined with arsenate of lead or Bordeaux mixture . 

 — but without the addition of soap. 



3. "Nico-Fume" Liquid.- — This material is somewhat similar to 

 "Black Leaf 40," being a nicotine preparation containing 40 per cent, 

 free nicotine. There appears to be little or no difference in the effective- 

 ness of these two materials, and since the "Nico-Fume" liquid is the more 

 expensive, it is suggested merely as a possible substitute in case the 

 "Black Leaf 40" is not obtainable. ■ It was used at approximately the 

 same strength as the "Black Leaf 40," and with the addition of a like 



