EXPERIMENT STATION BULLETINS. 530 



Stock arsenic solution. Mix by stirring thoroughly, and the spraying 

 mixture is ready for use. The arsenic in this mixture is equivalent to 

 four ounces of Paris-green." 



''The pot, jug, etc., must never be used for any other purpose :ifft'i- 

 using it for making this mixture." 



If an additional pound or two of lime be added to the mixture it will 

 help to make the application permanent and conspicuous without in any 

 way interfering with its effect. 



The final product obtained in the spraying tank is arsenite of calcium 

 (not arsenate of calcium) which kills more quickly tluui arsenate of lead 

 or arsenate of calcium. The formula given above was designed for 

 spraying fruit trees. When this poison is used for potatoes, use twice 

 as much of the stock solution, or 1 quart to 40 gallons of water. Some 

 potato growers prefer to use it even stronger than this. 



CONTACT INSECTICIDES. 

 For Insects That f^uck. 



NICOTINE. 



The insecticide most generally used for sucking insects, at the present 

 time, is nicotine. Nicotine is a clear, colorless, odorless material ichcn 

 pure, althougli the commercial preparations contain impurities whicli 

 impart both odors and color to the spray. It is marketed in two forms: 

 the volatile, plain nicotine and the non-volatile nicotine-siilpliate. For 

 use in greenhouses and forcing houses, the volatile, plain nicotine is 

 preferable because it disappears from the plants treated rather rapidly, 

 without leaving any deposit which would be dangerous or offensive. For 

 outdoor work, however, the sulpliate is much to be preferred, since it 

 is stable and does not evaporate and pass otf into the air for a consider- 

 able lengtli of time, at least. A favorite strength for marketing nicotine 

 is 40%, altlumgh some of tlie plain nicotines are put out at 10% and 

 some even stronger than 40%. All references to nicotine made in this 

 bulletin refer to the use of 40% nicotine-sulphate, since the bulletin deals 

 with outside spraying and is not intended to include remedies for crops 

 grown under glass or for vegetables such as lettuce, where the sprayed 

 part is to be eaten soon after the application. Xicotine-snlphate may 

 be stirred into the dilute lime-sulphur or ar.senate of lead or a comliina- 

 tion of the two immediately before the spray is applied. It slionld not 

 be stirred and allowed to stand before the application is made. In case 

 nicotine is added to any otlier spraying compound, soap should never be 

 added. In case, however, nicotine is used by itself alone and diluted 

 with water, soap adds greatly to its efficient^- by causing it to spread 

 better and i3erhaps in other ways. The favorite strength used in orchards 

 and small fruit spraying is 1 part to 800, in other words, 1 pint to 100 

 gallons of wat(M- with '• or 4 pounds of soaj), or 1 pint to 100 gallons of 

 dilute limesulphur without soap. Some growers dilute the nicotine 

 still further, using 1 part to 1,000 of water or other spraying material. 

 Of course, if one uses 10% nicotine, one should use four times as much 



