METHODS NOW USED IN FIGHTING THE GIPSY MOTH. 65 



500 tons of this poison were used in New England for spraying the 

 trees. Considerable spraying was done to destroy the elm leaf- 

 beetle (GaleruceUa luteola Miill.), and this poison was used exclu- 

 sively in the work. The best results are secured in spraymg for the 

 gipsy moth when the caterpillars are very small, but in covering so 

 large an area it is impossible to provide machines enough to do all 

 the work early in the season. Ten pounds of arsenate of lead to 

 100 gallons of water is a satisfactory strength to use, but after the 

 caterpillars are haK grown it is often desirable to increase this amount 

 to 12 or 15 pounds to the same amount of water. Spraying late in 

 the season after the larvae are nearly fullgrown is of doubtful advan- 

 tage, as the caterpillars are very resistant to poison, and as a rule 

 will pupate and transform to moths. 



The power spraying machines used in 1909 were superior in every 

 way to any that had been designed previously, and plans for im- 

 provements on these machines have been considered for the work 

 next season. Barrel sprayers fitted with hand pumps are used to 

 some extent for treating shrubbery and orchards, and in some cases 

 high trees are treated by using these outfits, especially when it is neces- 

 sary to prevent buildings from becoming discolored by the poison. 

 The use of these small outfits is impracticable when it is necessary 

 to cover in a period of six weelcs the large areas which must be 

 sprayed, and as a result of varied tests of power outfits a system has 

 been devised for using what is known as "solid-stream spray." 



About 1895 Mr. J. A. Pettegrew, who was then superintendent of 

 Prospect Park, Brooklyn, N. Y., constructed a steam spraying outfit 

 for use in treating the trees which were being severely injured by the 

 elm leaf -bee tie. Sufiicient pressure was developed to spray high 

 trees from the ground, the shape of the nozzle being such that a solid 

 stream was carried high in the air, where it was broken into a mist. 

 This sprayer was described and illustrated by Dr. L. O. Howard in 

 an article on spraying." Soon after Mr. Pettegrew became superin- 

 tendent of the Boston city parks he used a similar outfit for spraying. 



In 1905, this method of treatment was tested by Gen. S. C. Law- 

 rence, of Medford, Mass., who was carrying on extensive spraying 

 operations to protect the trees from the gipsy moth. This outfit 

 was built by a Boston firm, and was equipped with a high-power 

 gasoline engine instead of with steam to generate power. The 

 experiment was successful and since that time the use of outfits built 

 on the same general lines has been gradually increasing. Mr. George 

 H. Kermeen, one of the representatives of the firm alluded to, was 

 an early advocate of this system of spraying, and in addition to 



""The use of steam apparatus for spraymg," Yearbook, U. S. Department of 

 Agriculture, 1896. 



40705°— Bull. 87—10 5 



