in stands weakened or decimated by hailstorms, flood, wind, drought, disease, fire, 
defoliation, or during logging operations. Outbreaks are likely to occur any time 
there is a breakdown 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. 
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 
a few thousand square kilometers and last for many years before subsiding. From 
1977 to 1981, more than 75 different species were recorded in outbreak status in 
eastern forests. Some 40 of these are considered to be of major importance (587, 
750). Many general discussions on forest insects are available (2/7, 74, 76, 83, 314, 
492, 605, 644, 674, 691, 767, 768, 1078, 1196). 
Losses Caused by Forest Insects 
Insects are among the most destructive agents affecting forest and shade trees. 
They are not only responsible for killing valuable trees and for the loss of growth or 
recoverable volumes from surviving damaged trees, but also they weaken or destroy 
wood structures. They are responsible for serious losses of other kinds, both 
tangible and intangible. Management plans are often upset and fire hazards in- 
creased, watersheds and wildlife habitats are impaired or destroyed, water in 
streams and lakes is polluted, the incidence and severity of floods are increased, 
and the attractiveness of parks and other recreational areas 1s reduced or destroyed. 
Heavy investments in tree improvement programs also are jeopardized 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. Innumerable shade and ornamental trees around homes or 
along roadsides, and street trees of towns and cities, are killed or their attrac- 
tiveness is greatly reduced or destroyed. 
Forest Insect Surveys 
It has long been recognized that successful control of forest insect outbreaks 
depends not only on the control method used but also on knowledge of the insect 
situation in immediate, surrounding areas. When an outbreak is discovered, it is 
necessary to know whether it is increasing or decreasing. It is also important to 
locate the center of greatest concentration and the direction of spread (262). When 
an outbreak occurs, it is also important to Know the value of the resources at stake 
and the status of natural control factors before decisions to apply control are made. 
Of like importance is the possession of a general knowledge of insect conditions 
throughout a timber type or region. This is helpful in developing plans for the 
detection of outbreaks in their early stages, a time when they may be suppressed 
most easily and economically and before heavy losses are incurred. Similarly, it is 
helpful to have a continuing record of the presence and abundance of the less 
spectacular types of insects to determine if, when, and where their number or 
damage is reaching economic levels of concern, even though not an outbreak. 
Where intensive management of the forest for timber or other objectives is being 
practiced, it is also important to have up-to-date information on all destructive pests 
to allow for their early control where needed. Such information is sought or 
acquired through surveys. 
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