ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



69 



pests. Among these may be mentioned 

 Ascogaster carpocapsae Vier., which has been 

 introduced into the Northwest, and which 

 at times parasitizes 25 or 30 percent of the 

 codling moth larvae; Trichogramma minutum 

 Riley, one of the smallest insects, which 

 parasitizes the eggs of the codling moth and 

 other pests; and Aphelinus mali Halcl., a 

 parasite of the woolly apple aphid (fig. 81) 

 which has been successfully introduced into 

 the Pacific Northwest. 



It is difficult to estimate the amount of 

 benefit done by predacious and parasitic 

 insects. The beneficial species prevent many 

 potentially harmful insects from becoming 

 numerous, and therefore should be encour- 

 aged in every way. Frequently, also, out- 

 breaks of serious pests are stopped more 

 completely by beneficial insects than they can 

 be stopped with artificial control measures. 

 Unfortunately the beneficial forms often do 

 not begin to be effective until after the harm- 

 ful species have done much damage, and the 

 fruit grower cannot afford to wait but most control the pests himself. 

 The sprays applied to trees, particularly the contact sprays, may 



Figure 79. — Young of a 

 lacewing fly. X 6. 



Figure 81. — Woolly apple aphids parasitized by Aphelinus mali. 



