ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



45 



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 alfal- 

 fa or mustard, or into 

 the stems of their food 

 plants. But if apples 

 are near by, and par- 

 ticularly 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 

 negligible. If it should 

 occasionally become 

 serious, it can be re- 

 duced by keeping the 

 orchard free of dock 

 and related plants or 

 by propping up low- 

 hanging branches, and 

 by banding the props a nd the tree trunks with cotton or some sticky 

 substance in August and leaving the bands on until after the fruit has 

 been harvested. 



Ants 



Orchards of the Pacific Northwest are sometimes troubled by ants, 

 particularly the large pugnacious red ants (Formica spp.) that build 

 nests in the ground, often covered with rather conspicuous heaps of 

 dried stems and twigs of plants. These ants are attracted to the trees 

 primarily to feed on the honey dew excreted by aphids. At times the 

 ants may chew the blossoms and cause direct injury in that manner. 

 If the nests are not adjacent to the trees or other valuable plants, the 

 ants may be eradicated or greatly reduced in numbers by placing about 

 an ounce of granular calcium cyanide in the center of the hill or nest, 

 several inches below the surface, and covering it with dirt. This 

 material is dangerous to use near growing plants, and in such cases 

 some control may be obtained by drenching the nests with water 

 containing a pyrethrum extract. This should be used at the strongest 



Figure 53. — Larva of dock sawfly in apple. 



