ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



43 



COXTROL 



The pear leaf worm is very easily controlled by the use of 

 lead arsenate in the proportion of 2 pounds to 100 gallons of 

 water, applied just after the 

 petals have fallen. This is 

 the same as the usual calyx 

 application for the codling 

 moth. 



DOCK SAWFLY 



Apples are occasionally 



found in the fall with round 



holes in them resembling 



those made by full-grown 



codling-moth larvae. If the 



fruit is cut open, a bright- 

 green worm may be found 



inside (fig. 53). This is the 



larva of the dock sawfly 



(Ametastegia glabrata Fall.), 



an insect that has come in 



from Europe. The adult 



sawfly lays eggs in the leaves 



of dock, wild buckwheat, 



sheep sorrel, and related 



plants, which often grow 



along ditch banks and in 



moist places in orchards. 



The young feed altogether on these plants (fig. 54), and when full grown 



they search for suitable places in which to transform to adults. 



Usually they burrow 

 into the dry, hollow, 

 or pithy stems of 

 alfalfa or mustard, or 

 into the stems of their 

 food plants. But if 

 apples are near by, 

 and particularly if 

 they are hanging low 

 in the cover crop, the 

 worms may construct 

 cells in the apples 

 instead of in the plant 

 stems. The injury 

 caused by this insect 

 is ordinarily negli- 

 gible. If it should 

 occasionally become 

 serious, it can be 

 reduced by keeping 

 the orchard free of 

 dock and related 



plants or by propping up low-hanging branches, and by banding the 



props and the tree trunks with cotton or some sticky substance 



Figure 52.— Pear leaf worm: A, Injury to leaf; B. egg in 

 tissue and young larva feeding (twice natural size); C, full- 

 grown larva (six times natural size). 



Figure 53.— Larva of dock sawfly in apple. 



