f f 
F-519918, 519919 
Figure 127.—The cottonwood borer, Plectrodera 
scalator: A, adults; B, larva. 
root collar and tunnel downward into the roots. Coarse, fibrous frass may be ejected 
from galleries at the root collar during early larval development. Part of a brood 
develops in | year and the remainder in 2 years (878, 1/30). Young plants may be 
hollowed, partially severed, or girdled at or slightly below the root collar, causing 
breakage (875). Damage has been greatest in nurseries, young plantations, and 
young natural stands growing on sandy soils. Infestation counts have run as high as 
27 percent in I- and 2-year-old nurseries (//30). Borer populations and losses can 
be reduced by using borer-free planting stock and by plowing out and destroying 
nursery rootstock at 3-year intervals. Insecticides can be used to control the adults 
before oviposition. 
The sugar maple borer, Glycobius speciosus (Say), breeds in living sugar 
maples in southern Canada and throughout the Northeastern States, westward to the 
Lake States and southward through the Appalachians. The adult is robust, velvety 
black, and from 19 to 28 mm long. The head is clothed with fine yellow hairs; the 
pronotum is much wider than long, constricted at the base, and marked with two 
parallel yellow bands on each side. Each elytron bears five yellow bands, with 
those at the front forming a W-shaped design. Full-grown larvae reach a length of 
50 mm (583). 
Eggs are deposited in bark crevices, under bark scales, or around wounds, 
usually during July and August. The larvae feed beneath the bark. Their tunnels run 
more or less across the grain and cut deep channels in the wood. The winter is spent 
as a larva in a chamber formed in the sapwood. The following spring, feeding is 
resumed, with the larva cutting a larger gallery in the sapwood. The mature larva 
bores deep into the wood and constructs a pupal cell at the end of its tunnel. Before 
entering the cell, it cuts an exit hole through which the adult emerges. During this 
activity, the larva pushes considerable quantities of sawdust to the outside. Pupation 
occurs in the spring, and the life cycle requires 2 years (766, 1/56). 
The presence of transverse ridges or elevations on the large limbs or trunks of 
sugar maple, or of sawdustlike frass and moisture on the bark, are evidence of 
attack by the sugar maple borer. The bark over ridges is pushed outward at an angle 
or is broken up in the form of cracks, some of which may completely girdle the tree. 
290 
