68 BULLETIN 351, U. S. DEPARTMENT OF AGRICULTURE. 



The soap was dissolved in the water and to this the oil was added. 

 The whole was churned through a spray pump until no free oil 

 remained. The emulsion was then diluted to the required strength 

 and applied. 



Figure 20 shows that portion of the Wertz orchard in which most 

 of the experimental work was done. The orchard is in apples, inter- 

 planted mostly with Smock and Chair's Choice peaches. The trees 

 were 11 years old in 1912 and very vigorous. At the beginning of 

 the investigation these trees were grouped into 14 major plats, as 

 shown in the figure. The check plats were used as such until a better 

 method of checking was devised, when they were subplatted and 

 sprayed. Most of the checking was done by scale counts from 

 tagged branches upon special check trees left within the plats. 



The rosin-oil emulsion was very efficient so far as killing scales was 

 concerned. This oil dried rapidly, the trees soon appeared as if 

 covered by a varnish, and the scales died almost at once. Unfor- 

 tunately this oil gave very severe spray injury and some of the 

 trees were so severely damaged that they required drastic pruning 

 and stimulation to save them. While the spray injury could have 

 been lowered by reducing the amount of oil, it was not thought 

 advisable to continue the experiments. 



The corn oil, which was also used as a 20 per cent emulsion, was 

 equally good as a scale killer but formed a waxy scum over the 

 branches and penetrated deeply into the tree, causing the death of 

 many large limbs. These trees required drastic pruning and stimu- 

 lation, but the injury was not so severe as in the case of the rosin oil. 

 It was, however, too severe to justify its further use. 



The gasoline, which was used as a 10 per cent emulsion, had a very 

 low efficiency as a scale treatment but gave promise in other ways, 

 as it readily dissolved the wax film which protects the scale from 

 water, and it caused the scales to loosen temporarily from the bark. 

 After the emulsion evaporated, however, the scales soon resumed 

 their normal condition. This emulsion produced no spray injury. 



MISCIBLE OILS (PROPRIETARY EMULSIFIABLE OILS). 



In order to secure data for the better understanding of the factors 

 that enter into the successful use of miscible oils the sprayings 

 enumerated in Table XXXIX were made. 



