METHODS AND RESULTS OF FIELD INSECTI- 

 CIDE WORK AGAINST T\\\i SAN JOSE 

 SCALE, 1899-1902.'" 



On April 11, 1899, an emerg-ency bill was approved by Gov- 

 ernor John R. Tanner of Illinois requiring- the State Entomologist 

 to "treat and disinfect once thoroughly," at the expense of the 

 State, all orchard proj^erty which that officer had reason to believe 

 had become infested with the San Jose scale before the year 1899, 

 a fact which marked a new departure in the struggle for the con- 

 trol of the San Jose scale in Illinois. Unfortunately, the appro- 

 priation of $6,000 made for the expenses of this work was 

 insufficient for its purpose, being indeed but half the sum esti- 

 mated by me as necessary to give a single insecticide treatment to 

 all the premises then known to be infested. This fact put an 

 effectual bar upon preliminary experiments with insecticides, since 

 it was evidently my duty to apply the appropriation at once and as 

 far as it would go to the immediate purpose expressed in the law, 

 that of a thorough insecticide treatment of infested premises. 



Being thus limited to action on lines fixed by the existing state 

 of our knowledge of insecticide methods, it was my first duty to 

 make choice of the procedure which seemed most likely to enable 

 me to exterminate the scale locally by a single treatment. This 

 choice necessarily lay between liquid and g-aseous insecticides, 

 applied by spraying and by fumigation respectively. 



The liquid insecticides well enough known at the time to make 

 them practically available for the destruction of the San Jose scale 

 were the whale-oil soap solution and the emulsions or mechanical 

 mixtures of kerosene and water. Crude petroleum was then com- 

 ing- into use, it is true, but the results reported were too variable 

 to entitle it to confidence as both efficient and safe. To extermin- 



*This article was originally published as Bulletin No. 80 of the State Agricul- 

 tural Kxperiment Station, under date of October, 1902. 



