20 



BULLETIN 838, U. S. DEPARTMENT OE AGRICULTURE. 



appears to be very resistant, for no burning occurred at any time 

 from the application of the spray. 



It "was discovered that the small larvae were much more easily 

 killed than the adult females. All larva? could not be killed with 

 one spraying, however, on account of the long period of hatching. 

 The last of the brood were not hatched by the time the first were 

 becoming adults; consequently two sprayings were necessary, one to 

 exterminate the early hatched larvae, the other to exterminate those 

 hatched later. 



Table II. — Record of spraying experiments performed upon the cypress bark 



scale. 



No. 



Date. 



Formula. 



Number 

 of trees. 



Per cent 



of 

 efficiency. 



Remarks. 



1918. 

 Feb. 25 



Mar. 



...do 



Mar. 28 

 Apr. 10 

 ...do 



Crude-oil emulsion, 7 J per cen.t. 

 Distillate emulsion, 3 per cent. . 



Apr. 24 



June 4 

 July IS 



Mar. 28 

 Mar. 29 



Apr. 24 

 ...do. — 



Oct. 7 



...do 



July IS 



Oct. 7 



...do 



Distillate emulsion, 5 per cent 



Distillate emulsion, 6 per cent 



Distillate emulsion, 7J per cent 



Distillate emulsion, 7% per cent, and 



washing powder, 1 pound to 20 gals. 



Distillate emulsion, 12 per cent 



Carbolic sheep dip, 3 per cent. 

 Carbolic sheep dip, 6 per cent. 



Oct. 26 

 Oct. 28 

 ..do 



Miscible oil No. 1, 6 per cent 



Miscible oil No. 1, 6 per cent, and wash- 

 ing powder, 1 to 20. 



Miscible oil Xo. 1, 12i per cent 



Miscible oil No. 1, 12J- per cent, and 

 washing powder, 1 to 20. 



Miscible oil No. 1, 124 per cent 



Miscible oil No. 1, 8 per cent... 

 Miscible oil No. 2, 12J per cent. 



.do. 



.do. 



.do. 

 .do. 

 .do. 



In shade. 



Rained that night and fol- 

 lowing 3 days. 



Do. 

 In shade. 

 Warm, dry. 



Do. 



Do. 



Hot, dry. 

 Do." 



Warm, in shade. 

 Warm, dry. 



Do. 



Do. 

 Warm, dry: repeat on 



No. 12. 

 Warm, dry; repeat on 



No. 11. 

 Warm, dry; killed 50 per 



cent adults and 99 per 



cent laryge. 

 Warm, dry; rained 2 days 



ago. 

 Rained 2 days ago; repeat 



on 1 tree No. 16. 

 Hedge of young trees. 



Do. 

 Repeat on tree Xo. 38 of 



Experiment Xo. 19. 



In experiments Nos. 1 to 7, percentages are of actual oil content, not emulsion content. 



RECOMMENDATIONS FOR CONTROL. 



The following measures are recommended for the control of the 

 scale insect. 



Cut out all dying trees or limbs of trees beyond saving and destroy 

 them in order to reduce all possible sources of infestation. 



Purchase clean nursery stock for planting. If the stock is infested, 

 return it to the nursery and demand clean stock to replace it, 



Most fruit growers now realize that spraying is necessary for the 

 maintenance of healthy trees and the production of clean fruit. Most 

 people, however, still believe that a shade tree should always be able 



