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plantations rather than natural stands. They may also develop 
in stands weakened or decimated by hailstorms, flood, wind, 
drought, tree diseases, fire, or defoliation or during logging opera- 
tions. Any time a breakdown occurs in the effectiveness of natural 
control factors, or when changes occur in the genetic composition 
of populations, or in the age, composition, and density of stands, 
outbreaks are likely to occur. 
Forest insect outbreaks vary greatly in frequency, size, and 
duration. Fortunately, the majority are small and short-lived, and 
usually consist of only one or a few “spots” in a stand or region. 
Unfortunately, some may expand until they encompass hundreds of 
thousands of acres and last for many years before subsiding. From 
1957 to 1966, a total of 154 different species were recorded in out- 
break status in eastern forests.4 
The following general discussions on forest insects are avail- 
able for reference: Anderson (9); Doane, et al (196); Graham, 
K. (302); Graham and Knight (309) ; Thatcher (710) ; Beal and 
Massey (41); Beal, et al (40); Becker (50); Houser (381); 
Kotinsky (437); MacAloney and Ewan (472); MacAloney and 
Schmiege (473); and Shenefelt and Benjamin (644). 
Forest Insect Caused Losses 
Insects are among the most destructive agents affecting forest 
and shade trees. During 1952 (considered an average year), they 
killed an estimated 1 billion cubic feet of young, growing trees 
and 5 billion board feet of older, more mature trees of sawtimber 
size. In addition, they were responsible for a loss in growth of 1.8 
billion cubic feet in the young, growing stock and 8.6 billion board 
feet in surviving sawtimber trees (729). The.losses in sawtimber 
alone were enough to build 114 million homes. Losses incurred 
during epidemics are sometimes much heavier. Additional losses 
of a considerable but unknown amount are caused by insects that 
bore into the wood of living trees or dead and fallen timber. 
Insects are not only responsible for the killing of valuable trees 
and the loss of growth or recoverable volumes from surviving 
damaged trees, for the weakening or destruction of wood products 
of all kinds, but also for serious losses of other kinds, both 
tangible and intangible. Management plans are often upset and 
fire hazards increased; watersheds and wildlife habitats are im- 
paired or destroyed; water in streams and lakes is polluted; the 
incidence and severity of floods are increased; and the attractive- 
ness of parks and other recreational areas is reduced or destroyed. 
Heavy investments in tree improvement programs are also jeopar- 
dized or upset by the destruction of seeds and cones or valuable 
seed trees in seed orchards; stand composition is often changed, 
leading to the displacement of valuable tree species by others of 
lesser value; and innumerable shade and ornamental trees around 
homes, along roadsides, or along the streets of towns and cities 
are killed or their attractiveness greatly reduced or destroyed. 
*Forest Insect Conditions Annual Reports, 1957-1966 inclusive, USDA 
Forest Service. 
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