12 MASS. EXPERIMENT STATION BULLETIN 201, 



(3)" Rosin Fish-oil Soap, Soap "Stickers." 

 On plants having a smooth and waxy foliage, such as cabbage and 

 similar types, lead arsenate and Bordeaux mixture will not adhere at all 

 well unless used with some kind of soap as a "sticker." Types of resinous 

 soaps have come into use under the general name "Resin (Rosin) Fish 

 Oil Soaps," and are especially adapted for such purposes. These are 

 recommended to be used at the rate of 3-4 pounds to 50 gallons of spray 

 (or about 1 ounce to 1 gallon), and to be added to the diluted spray ma- 

 terial immediately before it is to be applied. In the preparation of this 

 type of soap for a spray it is necessary to add the water a httle at a time, 

 stirring vigorously all the while, until the soap has entirely dissolved; 

 otherwise the resinous nature of the material repels the water, making a 

 solution almost impossible. 



Except on the particular types of plants just mentioned (cabbage and 

 similar plants), soap should not be used with arsenicals or Bordeaux 

 mixture. Arsenicals are unstable in the presence of the alkali of the soap, 

 with the consequent danger of the formation of soluble arsenic (20). In 

 this particular case, however, the application is made so soon after the 

 soap is added that there is little opportunity for breakdo-^m; and, further, 

 the waxy leaves seem to offer more resistance to arsenical injury than 

 would foliage of ordinary texture. The alkahes entering into the com- 

 position of our common soaps are mainly compounds of sodium and po- 

 tassium. Such soaps are the only ones soluble in water. When, however, 

 soap is combined with Bordeaux mixture or lime-sulfur sprays, calcium 

 soaps are formed which are insoluble in water, making a gummy, sticky 

 mass which is apt to clog the spray apparatus. Moreover, other products 

 of this breakdown are formed which are either actively dangerous to the 

 plant or are of no use whatever as an insecticide. 



(4) Fish-oil Soajjs and Nicotine. 

 Commercial brands of fish-oil soaps combined with a small amount of 

 nicotine are on the market and appear to have a considerable sale. These 

 are rather expensive, and usually their nicotine content is quite low, so 

 that in general, better satisfaction can be obtained by combining soap and 

 nicotine solutions as needed. (See Nicotine Sprays, page 20.) 



2. Sulfur Sprays. 



These are efficient contact poisons for certain scale insects, and possess 

 substantial fungicidal value as well. They are supplanting the miscible 

 oils, probably due in large measure to the deleterious after-effects of the 

 latter. Concentrated lime-sulfur solution, dry lime-sulfur, barium tetra- 

 sulfide (B. T. S.), and sodium polysulfide, or so-called soluble sulfur, will 

 be considered. All of these materials seem to have the following properties 

 in common : — 



