ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



61 



CONTROL 



If the root form is numerous enough to affect the growth of the 

 trees, it should be controlled. This may be done with some effective- 

 ness by using paradichlorobenzene, as recommended for the peach 

 borer (p. 52). The aerial form may be controlled readily with the 

 the usual nicotine sprays. 



PEACH TWIG BORER 



Ripening peaches are sometimes wormy, and this worminess may 

 be associated with a split pit. The brown worms in these peaches 

 are peach twig borers (Anarsia lineatella Zeller), so named because 

 early in the spring the young worms burrow into 

 the tender terminal growth of the trees and 

 cause the rapidly growing twigs to wilt (fig. 72). 

 The injury is twofold: (1) The development of 

 the new growth is interfered with; and (2) there 

 is a direct loss of fruit. The peach twig borer 

 also attacks prune and apricot trees, and the 

 twig injury is especially serious on nursery trees 

 or in young orchards. The species originated 

 in Europe and has been in the United States for 

 many years. 



LIFE HISTORY 



The young peach twig borers pass the winter 

 in very small silk-lined burrows, known as hiber- 

 nacula,in the bark. These are usually construc- 

 ted in the folded bark found in the crotches of 

 the younger branches. Each burrow has a char- 

 acteristic projecting tube or " chimney," com- 

 posed of silk and tiny pieces of bark, which it 

 is difficult to see without a lens. The small 

 worms leave these winter quarters as soon as 

 twig growth has commenced and burrow into the 

 new shoots, where they feed on the pith and inner 

 bark, thus causing the shoot to wilt. Frequently 

 a single worm injures several twigs in this manner. 



By May the worms are mature, nearly one half inch long, and red- 

 dish brown in color. They spin loose cocoons in rough places in the 

 bark or in curled leaves, and the small, inconspicuous, grayish moths 

 emerge in June. These lay minute eggs on the bark, and the tiny 

 worms hatching from them attack the fruit as well as the new growth. 

 They usually burrow into the peaches near the stem end and feed 

 around the pit; or if this is still soft, they enter it and feed on the 

 kernel. This second brood of worms also produces a brood of moths 

 which lay eggs, and the young worms hatching from these build the 

 silken burrows in which the winter is spent. 



Figure 72. — Injury to peach 

 shoot by the peach twig 

 borer. 



CONTROL 



The peach twig borer is very easily controlled by an application of 

 lime-sulphur solution as used for the San Jose scale (p. 10). If 

 there is no scale infestation, a dilution testing 3.5° Baume is adequate 

 (table 1, p. 68) and may be applied at any time in the spring before 



