ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



53 



earth, which should be packed down with the back of the shovel. 

 The paradichlorobenzene should be applied between August 15 and 

 September 15. At this time the borers are small and easily killed. 

 Later, cold weather may hinder the formation of gas from the crystals, 

 as this process requires a soil temperature of at least 60° F. In order 

 to prevent any possible injury to the trees from the gas, the remaining 

 crystals of paradichlorobenzene should be scattered away from the 

 tree with a shovel a month or 6 weeks after they are applied. If 

 paradichlorobenzene 

 is to be kept for a time, 

 it should be stored in 

 airtight containers to 

 prevent loss by evap- 

 oration. 



OTHER BORERS 



Flat-headed borers 

 are often found in the 

 trunks of prune trees, 

 particularly in trees 

 not in the best condi- 

 tion. A darkened 

 area of bark is an in- 

 dication that the bor- 

 ers may be present. 

 The shot-hole borer is 

 another insect that 

 attacks unhealthy 

 trees, making round, 

 shot-like holes in the 

 trunks. Both of these 

 pests are discussed on 

 page 32. 



PEAR THRIPS 



The pear thrips 

 (Taeniothrips incon- 

 sequens Uzel) causes 

 more injury to prune 

 trees in the Pacific 

 Northwest than to 

 pears or other fruits. 

 The insect occurs in western and northeastern Oregon, in southeastern 

 Washington, and in western British Columbia. It has apparently 

 been introduced from Europe. There are three types of injury. The 

 most serious injury is caused by the adult thrips, which emerge from 

 the ground in the spring, feed in the developing buds, and produce 

 deformed leaves and blossoms (fig. 63), thus causing a reduction of 

 the crop. Later the adults lay eggs in the stems of the fruit and 

 foliage. Both the young and the adults feed by rasping the surface 

 and then sucking out the plant juices. 



LIFE HISTORY 



There is only one generation of the pear thrips annually. The 

 adults, which are small, less than one twentieth inch long, slim and 



Figure 62.— < 



trolling the peach borer. 



