DOUGLAS FIE PITCH MOTH. 



19 



of the investigations and experiments (Table I) made it evident 

 that to accomplish any permanent good under general forest condi- 

 tions it is best to extend control over large areas. In Project III, 

 for example, where the infestation is in general rather slight, col- 

 lecting was done within a 5-section limit over 460 acres only, in 

 strips containing a stand of trees of a character more susceptible to 

 attack, and while the destruction of the larva? resulted in some 

 reduction of the annual infestation, it could not in any sense be 

 regarded as an important factor in reducing the ultimate deprecia- 

 tion of the timber without the application of constant attention. 



Table I. — Control of the Douglas fir pitch moth: Projects and results. 



Project 

 No. 



Damage. 



Sec- 

 tions. 



Acres. 



Larvee collected. 



Remarks. 



1913 



1914 



I 



II 



Medium... 



5 



3,200 



30 

 460 



40 

 10 



790 



101 

 94 



207 

 41 



74 



5 

 53 



16 



9 

 2 



To June; from August to December, 8 larva found 



in area. Collected thoroughly. 

 Thorough search. 



III 



IV 



Slight 1 .3 



From 1913 oviposition. 



From 191 4 oviposition. Collected during Decem- 

 ber. Collecting done in strips of reproduction 

 within the mature stand. 



From 1913 oviposition. 



V 





From 1912 oviposition. 









Project, 



Age of stand. 



Local conditions. 



I 



Years. 

 10-40 





II 



30 



Northern exposure; practically isolated, except for adjoining stand 



III 

 IV 



120, with strips of reproduc- 

 tion from 1 to 40 years old. 

 40 



of mature timber. 

 Heavy mountain forest in a solid stand which extends for miles. 



Creek bottom: flat surrounded by steep hills stocked with 10-vear- 



V 



15-20 



old and younger reproduction. 

 Practically isolated, beincr surrounded bv vellow-nine stand free of 







any 



sesiid. 





In Project I, which also covers five sections, the larva? were de- 

 stroyed throughout, and during the autumn of 1014 but 8 larva? Avere 

 found near the border of the area. In Project I a daily inspection at 

 the proper period in the year along the border would be amply suffi- 

 cient to protect the entire area from a serious infestation until such 

 time as the trees shall have outgrown the danger stage. 



The principle of "isolating" stands susceptible to infestation 

 should be the potent factor in control of this insect. Let us take a 

 practical example of what is meant by isolation in this regard. Two 

 streams, distant from each other in an air line say a couple of miles, 

 run parallel from their source ;it the base of a mountain to the open 

 farm lands, bu< between them is. as usual, ;i dividing ridge. Along 

 both streams, in favorable locations, the moth is equally numerous, 

 yet elimination of the moth along the entire length of one stream 



