Forest insect surveys of various types have been made in the United States since 
the early days of this century (/37) but, before the passage of the Forest Pest 
Control Act in 1947, they were usually conducted on a more or less unorganized 
basis. Passage of the act made it possible for the first time to conduct surveys on an 
organized, systematic basis on forest lands of all ownerships. In part, the act 
authorized the Secretary of Agriculture, either directly or in cooperation with other 
Departments of the Federal Government, with State and other public agencies, and 
with private organizations and individuals, to conduct surveys to detect and ap- 
praise insect infestations before they develop to outbreak proportions, to appraise 
their potential destructiveness, and to determine the needs for their control. Section 
5 of the 1978 Cooperative Forestry Assistance Act (PL 95-313) retains these same 
provisions. Forest insect surveys are also conducted in Canada. There, the aim 1s 
not only to detect and appraise infestations but also to obtain information on the 
distribution, biology, and cycles of abundance of insect species for taxonomic and 
other purposes (756). 
Basically, forest insect surveys are of two kinds—detection and evaluation—and 
they may be conducted separately or together. Detection surveys are primarily for 
the purpose of discovering threatening infestations. Evaluation surveys are usually 
far more intensive and complex, being concerned with such factors as the intensity 
and the trends of pest populations, the identification and evaluation of natural 
control factors, the size and boundaries of infestations, the value of the resources at 
stake, and the possibilities of economic loss and an estimate of its magnitude if 
suppressive measures are not taken. 
Many methods and techniques are employed in conducting surveys, the choice 
depending on many factors such as the insect species, its life history and habits, the 
nature of the damage it causes, the forest type and terrain, the size and accessibility 
of the area, a working knowledge of natural control factors affecting it, and the 
availability of trained personnel and funds. Aircraft are widely used in detection 
surveys and to a lesser extent in evaluation surveys. Conditions may be recorded by 
trained observers riding with the pilot (6, 557, 559) or by aerial photography (4, 5, 
108, 212, 296, 556, 558, 1256, 1257). Computers process the data, and radio- 
navigational aids keep the craft on the proper course (346, 5/3). Panoramic aerial 
photography (2//) and satellite imagery (324) are under study for delimiting 
outbreaks. The former is effective and cost competitive with earlier techniques, but 
the latter system is expensive and shows only heavy defoliation accurately. Unfortu- 
nately, evidence of infestation by many insect species is difficult or impossible to 
detect from the air. Where these insects are concerned, the only recourse is to use 
ground survey methods (/09, 1339). To the extent that it is possible to use them, 
aerial surveys are far less time consuming and costly than comparable ground 
surveys. 
Ground surveys are not only required to detect infestations of many species but 
are essential for evaluation purposes. In most cases, they are complex and require 
the services of highly trained personnel. Ground surveys for evaluation purposes 
present many different sampling problems, such as when, where, and how to 
sample in order to obtain needed information within desired confidence limits. The 
choice of procedure is governed largely by the insect species and the intensity and 
size of the infestation. Pheromone traps are very useful to detect low populations of 
insects (/0/, 1/99). In addition to data on insect population density and size, data 
also may be collected to identify and record the abundance of natural control 
factors. In all cases information is sought and analyzed to determine two things: 
3 
