EXPERIMENT STATION BULLETINS. 425 



The jug, pot, etc., must never be used for any other purpose after 

 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 than 

 arsenate of lead or arsenate of calcium. The formula given above was 

 designed for spraying fruit trees but we are not at this time recom- 

 mending its use for that purpose. When this poison Is used for pota- 

 toes, 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. 



ARSENATE OF CALCIUM. 



ft 



This spraying material is sold in the form of a fine white powder. 

 It normally costs a little less than arsenate of lead and goes about twice 

 as far. We are not at present recommending its pse on fruit trees be- 

 cause of a delayed burning effect that is apt to follow the application, 

 but we do find it very satisfactory when used on potatoes which seem 

 to stand it very well. It works more quickly than arsenate of lead and 

 is more evenly distributed tlian Pavis-green. Furtliermore it is produced 

 in a much finer powder than the last named poison and is less prone to 

 drip off wiien applied in a coarse spray. 



. From % of a pound to one pound may be used with bordeaux or fresh- 

 ly slacked lime to 50 gallons of water for potatoes and some growers 

 use even a little more. 



Contact Insecticides. 

 For Insects That Suck 



nicotine. 



The insecticide most generally used for the summer spraying of 

 sucking insects, at the present time, is nicotine. ^Nicotine is a clear, 

 colorless, odorless material when pure, although the commercial pre- 

 parations contain impurities which impart both odors and color to the 

 spray. It is marketed in two forms: the volatile, plain nicotine and 

 the non-volatile nicotine-sulphate. For use in greenhouses and forcing 

 houses, the volatile, plain nicotine is preferable because it disappears 

 rather rapidly from the plants treated without leaving any deposit 

 which would be dangerous or offensive. For out-door work, however, 

 the sulphate is much to be preferred, since it is stable and does not 

 evaporate and pass off into the air for a considerable, length of time, 

 at least. A favorite strength for marketing nicotine is 40 per cent, 

 although some of the plain nicotines are put out at 10 per cent and 

 some even stronger than 40 per cent. All references to nicotine made 

 in this bulletin refer to the use of 40 per cent 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. Nico- 

 tine-sulphate may be stirred into the dilute lime-sulphur or arsenate of 



