TEEATMENT FOR SAN JOSE SCALE IN 



OllCHAIiDS.^^- 

 I. ORCHARD FUMIGATION. 



p. A. SIRRINE. 



SUMMARY. 



It is unsafe to leave trees in orchards exposed to action of 

 hydrocyanic acid gas for periods of twelve hours. 



With perfect covers, debarring accidents, it is possible to kill 

 every living specimen of pernicious scale on medium sized fruit 

 trees without injury to the trees and thus to exterminate the 

 pest in isolated sections. 



With large pieces of potassium cyanide and an excess of acid 

 and water, rapid and uniform action results. 



Double the amount of potassium cyanide usually recom- 

 mended for nursery fumigation should be used in orchard fumi- 

 gation. 



Tents have less waste space and require less chemicals than 

 other forms of coverings, but neither accurate nor thorough 

 work can be done with them. 



Under favorable conditions thorough work can be done with 

 box fumigators, but they require more chemicals than tents. 

 They have the advantage of fixed dimensions. 



Cost of fumigation depends upon so many variable factors 

 that it cannot be fixed. 



INTRODUCTION. 



Undoubtedly no one insect has attracted more attention dur- 

 ing the past few years than the Pernicious scale-insect 

 {Aspidiotiis pemiciosiis), generally called " San Jos6 scale." As 

 this pest has been widely distributed to most sections of the 



*A reprint of Bulletin No. 200. 



