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MISC. PUBLICATION 62 6, U. S. DEPT". OF AGRICULTURE 



the pruned and broken ends of stems. 

 In both cases the injured portions wilt 

 and finally die. To the latter group 

 belong the leaf-cutter bees (p. 79) and 

 the curled rose sawfly (p. 80). Among 

 the borers that attack unpruned shoots 

 the three species discussed below are the 

 more important. 



The rose stem sawfly, or borer 

 {Hartigia trimaculata (Say)), is a 

 wasplike insect occurring in early sum- 

 mer and laying its eggs in punctures 

 made in the rose canes. The larvae 

 hatching from the eggs are whitish and 

 feed within the canes. They bore 

 through the pith (fig. 129), causing the 

 shoots to become stunted and die back. 



Figure 129. — Young rose shoot cut 

 open to show the rose stem borer min- 

 ing in the pith. Note the stunted tip 

 resulting from its injury. About 

 twice natural size. 



The rose stem girdler (Agrilus com- 

 munis rubicola Abeille) is a small 

 bronze-green beetle about % inch long. 

 The adult beetles appear in June and 

 July, feed on the foliage, and lay their 

 eggs on the rose bark. On hatching the 

 flattened, whitish, legless grugs enter 

 the wood and make spiral mines for a 

 short distance, and over these the rose 

 shoot swells (fig. 130). The resting 

 stage is spent in a cell in the pith. 



The raspberry cane borer (Oberea 

 bimaculata (Oliv.)) is a slender beetle 



-\'i 



Figure 130. — Swelling on rose stem 

 caused by the rose stem girdler work- 

 ing under bark. 



i 



Figure 131. — Work of the raspberry 

 cane borer in the pith of a rose stem. 

 Bark cut away to expose tunnel. 



with black wings and yellow waist. 

 Although primarily a pest of raspberry, 

 it often leaves its preferred host and 

 feeds on rose. The beetle girdles the 

 tip of the shoot by making two rows of 

 punctures, about an inch apart, around 

 the stem, and between these the eggs 

 are laid. As soon as the cylindrical, 

 whitish, legless grubs hatch they bore 

 into the pith and work downward 

 through the shoots (fig. 131), thus 

 causing the shoots to wilt and die. 



