b FARMERS BULLETIN 862. 



Table I sets forth the general results of experiments made to test 

 the value of fumigation. The work was performed during the years 

 from 1909 to 1917, under the climatic conditions normal to orchard 

 fumigation in southern California. 



Table I. — Results of ftnnif/dtioii iritli Iij/ilritcijdnic-dcid <jns (Kjuinst the Cdiiiiiion 



nicali/bu(j. 



A. S-OUNCE r. S. ARMY DUCK TENT. I 



SINGLE CHARGE. < 



Dosage 

 schedule. 



Exposure. 



No.li 



Two and three 

 times No. 1. 



Small percentage killed. Commercially inelTectivc 

 85 to 95 per cent killed. 



REPEATED CHARGE LTNDER SAME TENT. 



First charge. 



Dosage 

 schedule. 



No.l 



One and one-half 



times No. 1. 

 No,l 



Exposure. 



Second charge. 



Sf,: Exposure. 



No.l. 

 No.l. 



30 minutes . 

 1 hour 



Small percentage living. 

 99 per cent killed. 



B. GAS-TIGHT TENT. 



Sodium cyanid 

 per 100 cubic feet. 



I ounce . . 



II ounces 



1 hour. 

 do. 



Sometimes a few living; usuiiib- all kilUd. 

 All killed. 



C. GAS-TIGHT BOX OF 100 CUBIC FEKT CAl'ACITY 



I This schedule is given on page 34 of Bulletin No. 90 of the Bureau of Entomology, U. S. Department 

 of .Vgriculture. 



These results show the ineffectiveness of single-do.sage fumigations 

 under army duck tents, even where excessive dosages are used. Ke 

 peated charges give better results but can not be recommended except 

 in the case of a limited number of trees where other control measure; 

 are not readily available, or where cost and possible injury are sec-j 

 ondary to immediate control. Since 8-ounce United States Arm^ 

 duck retains hydrocyanic-acid gas better than any other cloth ot 

 which fumigation tents are constructed at present, results equally 



