| J. | 2 es is nen Sn 
the North, the second winter is spent as a mature larva in a cell 
at the end of its tunnel. 
Small trees are occasionally killed by larvae girdling be- 
neath the bark. Larger trees are seldom killed outright, but the 
large larval tunnels make them susceptible to windbreakage. They 
may be literally riddled with tunnels. Larval openings and tun- 
nels serve aS openings for various rots, decays, and other in- 
jurious insects which may kill the tree or degrade the lumber. 
Poplar plantations may be ruined and valuable shade trees severely 
damaged. Damage in forest stands also may be severe. In the 
Lake States, successful attacks appear to be concentrated in 
individual trees or small groups of trees unevenly distributed 
throughout the stand. These trees, commonly known as brood 
trees, are usually the larger, faster-growing trees in stands aver- 
aging between 8 and 7 inches d.b.h. Lakes States infestations also 
tend to increase with a decrease in stand density. 
The best practice in the management of poplar in the Lake 
States apparently is to maintain well-shaded stands and then 
clear cut them at maturity. The removal of “‘brood trees” should 
also be helpful (234). 
The roundheaded apple tree borer, Saperda candida F., occurs 
in Canada and throughout eastern United States. It is most seri- 
ous as a pest of apple orchards, but it also breeds in mountain- 
ash, Crataegus, and shadbush. The adult is brilliantly white ex- 
cept for three broad, brown, longitudinal stripes extending the 
full length of the back, and is from 15 to 20 mm. long. Full-grown 
larvae are creamy-white and about 30 mm long (344). 
Adults are present from June to September and deposit their 
eggs in slits cut in the bark at the base of living trees. They feed 
on the foliage and sometimes on tender bark. The larvae feed 
beneath the bark for one year and then bore into the wood, 
making large excavations and riddling it. The presence of ten- . 
drils of frass on the bark or at the base of the tree is evidence 
of attack. Heavily infested trees may be killed in a single season. 
Two or more years are required to complete the life cycle. Keep- 
ing trees healthy is an effective preventive measure. Borers in high 
value trees can be killed by injecting a fumigant into borer 
burrows. 
The linden borer, Saperda vestita Say, occurs in the Northeast- 
ern States and Canada. Its preferred host is basswood but it also 
attacks poplars. The adult is reddish-brown, densely covered with 
prostrate fine olive-yellow hair, and from 12 to 21 mm. long. 
The tips of the antennae are brown, and there are three small 
black spots on each wing cover. Adults feed on leaf petioles, the 
larger veins of leaves, and the bark of growing shoots, often kill- 
ing the tips of infested branches. The larvae feed beneath the 
bark and often bore deep into the wood. Unhealthy and weakened 
trees are most susceptible to attack. 
Saperda discoidea F. breeds in dead and dying hickories and 
butternut from New York to Louisiana and Nebraska. Hickory 
trees infested with the hickory bark beetle are particularly sub- 
ject to attack. Adults are 10 to 17 mm. long. The male is blackish 
with reddish legs and lines of grayish fine hair on the thorax. The 
female is reddish-brown or nearly black, clothed with yellowish 
187 
