the Northeast. There are two generations per year in the Northeast: in the southern 
Appalachians, two and occasionally three generations are produced (/3, 47). 
The balsam woolly adelgid feeds at any point on the tree where it can reach the 
parenchyma of the cortex with its mouth parts. During feeding, it introduces an 
irritating salivary substance into the tissues that causes an abnormal multiplication 
of cells and excessive growth in the vicinity of the point of attack. Infested twigs 
and small branches become swollen and distorted. Swellings are particularly 
noticeable at nodes and around buds. Branchiets may thicken, twist irregularly, and 
bend down at the ends. The main stem tapers rapidly toward the top. The tip 
becomes bent or flattened and is usually killed. This results in a condition com- 
monly known as ““gout.”” The wood of infested trees becomes hard and brittle, and 
its surface is usually marked with dark, reddish-brown blotches. This type of wood, 
which resembles “compression” wood, is produced in greatest amount on moder- 
ately infested fast-growing trees. Trees suffering from heavy stem attack may be 
killed in 2 or 3 years (fig. 28). 
The balsam woolly adelgid is subject to a considerable amount of control by low 
winter temperatures, especially in the northern portions of its range. Tree resistance 
is also an important control factor, some trees being less favorable for multiplication 
of the insect than others. So far, no insect parasites of the adelgid have been found. 
Quite a large number of predators have been recorded and additional ones have been 
imported to supplement native species. However, adelgid populations expand so 
rapidly and some firs are so sensitive to attack that predators effect little control 
before trees are damaged irreversibly. 
In a few situations, the spread of infestations may be checked by the prompt 
salvage of infested stands during the winter. Short rotation and cutting cycles, 
combined with silvicultural methods of reducing the balsam fir content of stands, 
have helped in reducing infestations in New Brunswick (50). 
Adelges laricis Vallot, an introduced species, occurs in southern Canada and 
south and east in the Eastern States to Washington, D.C., and the Lake States. Its 
hosts are recorded as European larch, tamarack, and spruces, principally red and 
black. Infestations on larch appear as white woolly masses on the needles and as 
clusters of adelgids at the bases of needles. Infestations on spruce may be recog- 
nized by the presence of small pineapple-shaped galls at the tips of new growth. A 
related species, A. lariciatus (Patch), occurs on larch and various species of spruce 
(272). It produces galls similar to those produced by the eastern spruce gall adelgid. 
The pine bark adelgid, Pineus strobi (Hartig), a widely distributed species in 
Europe and North America, occurs over most of the United States wherever white 
pines grow. It is small, dark, and covered with flocculent wax. Infestations may be 
recognized by the presence of spots and patches of white cottony material on the 
smooth bark of the trunks and limbs (fig. 29), at the bases of needles on twigs, or on 
buds. Feeding, though, is limited to the bark. The trunks of heavily infested trees 
often appear as if whitewashed. 
Eggs are laid in the spring by overwintering females, and the eggs hatch into both 
winged and wingless females. Winged forms, though, are produced less consis- 
tently than wingless ones. The wingless forms remain on the pine host and 
reproduce repeatedly. Five generations per year have been recorded as far north as 
the Lake States (/0/0). Although winged forms may fly to spruce and lay fertile 
eggs, both adults and offspring eventually die. 
Trees in parks and recreational areas, ornamentals, and small nursery stock 
sometimes become heavily infested by the pine bark adelgid. However, it is 
84 
