52 CIRCULAR 270, U.S. DEPARTMENT OF AGRICULTURE 



periodically for borers, especially if they are not making good growth 

 or do not appear to be thrifty. The borers are most commonly found 

 in the region west of the Cascade Mountains, but sometimes become 

 injurious elsewhere. 



LIFE HISTORY 



The peach borer (Synanthedon exitiosa Say) and the western peach 

 borer (S. opalescens Hy. Edw.) are both found in the Pacific North- 

 west. The former is an eastern species that has been introduced in 

 nursery stock. The adult is a steel-blue moth with a wing expanse of 

 more than an inch. The wings of the male moth are clear, except for 

 the margins, but the fore wings of the female are opaque. The female 

 of the eastern species has an orange band about the abdomen, while 

 in that of the western species the whole abdomen is steely blue. The 

 male moth of the eastern species has several narrow yellow bands on 

 the abdomen and yellow markings on the wings ; these do not appear 

 on males of the western species. Otherwise the two species are very 

 similar in appearance, and their habits are the same. 



The moths appear in the orchards in July and August, flying about 

 very actively during the warm part of the day. Each female lays 

 several hundred oval, cinnamon-brown eggs, singly or in groups on the 

 tree trunks. The eggs hatch in about 10 days, and the young borers 

 crawl down the trunks and enter the damp bark just beneath the 

 surface of the soil. They at once begin feeding on the inner bark and 

 continue doing so until late in the fall, remaining quietly in the burrows 

 during the winter. In the spring feeding is resumed, and the borers 

 become full grown in May and June, when they are about 1 inch long, 

 yellowish white or cream colored, with brown heads. They construct 

 cocoons of silk and frass at the surface of the soil, either in the tunnel 

 or close to the trunk, within which they change to pupae and several 

 weeks later to moths. There is only one generation annually. 



CONTROL 



The peach borer was formerly combated by ••'worming" the trees. 

 The soil was removed from about the trunk, the tunnels of the borers 

 were located by means of the exuding gum, and the borers were cut 

 out and destroyed. This had to be done early in the spring or late in 

 the fall to be effective, and was a rather slow, tedious method, accom- 

 panied by some injury to the trees in addition to that occasioned by 

 the borers. A cheaper, easier, and more effective control measure is 

 to place paradichlorobenzene ("PDB") about the tree trunks in the 

 fall. This chemical is in the form of white crystals having a charac- 

 teristic odor a little like that of naphthalene, and forming a gas that 

 is heavier than air. When properly used, paradichlorobenzene kills 

 practically all of the borers without injuring the trees, and is not 

 harmful to man or animals. 



After the ground has been leveled off, the paradichlorobenzene 

 should be placed about the tree trunk in a ring about VA inches from 

 the trunk and 1 or 2 inches wide (fig. 62), using from % to 1 ounce of 

 the crystals to each tree, depending on its size. Care should be taken 

 not to place the crystals in contact with the tree trunk as they may 

 injure the tree, and not to make the ring more than 2 inches from the 

 trunk, as it would not be so effective at a greater distance. The ring 

 of paradichlorobenzene should be covered with several shovelfuls of 



