HANDBOOK OX INSECT ENEMIES OF FLOWERS AND .SHRUBS 39 



more maggots may be found feeding in 

 one mine. When they are full-grown 

 they come to the leaf surface, pupate, 

 and transform to small two-winged flies. 

 Several generations occur during the 

 season. The seedlike pupae of the last 

 generation are thought to overwinter in 

 the soil. 



Treatment. — Remove and destroy 

 all infested leaves, thus killing the in- 

 sects therein. Spray thoroughly with 

 nicotine sulfate or pyrethrum if the 

 infestation is severe. 



Prevention. — Remove and burn all 

 plant remains in the fall, and cultivate 

 thoroughly the soil around the base of 

 the plants to destroy any overwintering 

 pupae that might be present. 



Other Pests of Delphinium 



Pape 



R ed spiders 11 



Stalk borer ■—. 34 



Japanese beetle 48 



Asiatic garden beetle .__ 21 



Rose bud worm 83 



DOGWOOD 

 Dogwood Borer 



The caterpillar of the dogwood borer 

 (Thamnosphecia scitula (Harris)) makes 

 an irregular burrow under the bark on the 

 trunk, around the base of limbs, or fre- 

 quently at the edges of wounds or scars 

 on dogwood trees. Small trees or the 

 base of branches may be girdled, or old 

 wounds enlarged. Healthy trees may 

 be attacked by this borer. The whitish 

 caterpillars pass the winter in the bur- 

 rows under the bark, where they com- 

 plete their feeding and transform to 

 pupae in the spring or early summer. 

 When full-grown they are about % inch 

 long. The adult clear-winged moths 

 emerge from late in the spring until after 

 midsummer and lay their eggs on the 

 bark, usually in places where it is 

 roughened. This insect also infests 

 pecan trees and is sometimes called the 

 pecan borer. 



Treatment. — Examine the trees late 

 in the summer and in spring for evi- 

 dence of injured bark or of fine boring 

 dust being pushed from the burrows, and 

 cut out the borers with a sharp knife. 

 Small wet areas on the bark earlier in 

 the summer may indicate the presence 

 of the young borers just starting to 

 work. It is advisable to clean the dead 

 material from the larger wounds, trim 

 the edges smoothly back to green bark, 

 and then paint the wound with shellac 

 or a tree-wound dressing. 



Flathead Borers 



Transplanted dogwood trees, or those 

 seriously weakened from other causes 

 such as drought, defoliation, or scale 

 insects, are often attacked by one or 

 more species of small wood borers, 

 known as flatheaded borers. The flat- 

 headed apple tree borer (Chrysobothris 

 femorata (Oliv.)) is one of the more 

 common species and attacks many 

 kinds of deciduous shade trees, fruit 

 trees, and shrubs. The adult beetles 

 emerge in late spring and early summer 

 and are attracted to weakened trees and 

 shrubs, where they lay their eggs in 

 bark crevices. The grubs make broad, 

 irregular tunnels filled with boring dust 

 under the bark. When nearly full- 

 grown, in late fall or spring, they bore 

 into the wood, where pupation occurs 

 prior to the time of adult emergence. 

 The yellowish-white legless grub (fig. 

 64) is about an inch long when mature. 

 The body is somewhat flattened, and the 

 first segment just back of the head is 

 much broader than the remainder of the 

 body. The adult is a brownish, metal- 

 lic, flattened beetle about % inch long, 

 blunt at the head end, and more pointed 

 at the posterior end. 



Another flatheaded borer, Agrilus 

 cephalicus Lee, attacks weakened or 

 dying dogwood trees in a similar manner. 

 The whitish grubs are elongate and 

 flattened, but the segment back of the 

 head is not enlarged so much as that of 

 the species discussed above. 



Treatment. — Since these beetles 

 attack seriously weakened trees, the best 

 preventive is to keep the trees growing 



Figure 64. — Larva, or grub, of the flat- 

 headed apple tree borer in a tunnel 

 under bark. Slightly enlarged. 



