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caused a multiplicity of studies and research duplication. 
4. Even though it had been noted that early manifestation of disease 
could be either foliage discoloration or foliage thinness, contro 
versy developed because interpreters were looking for the wrong 
symptom of early signs of the disease, and the word "damage" usually 
remained undefined. 
5. One thing universally agreed upon was that color and color-infrared 
aerial photographs were superior to black and white photos for 
vegetation damage analysis. 
Although- other problems of that era can probably be pinpointed in 
other papers, Heller’s paper does form a basis to present the present stage of 
vegetation damage interpretation. However, late in 1972, a "Guide to the Photo 
Interpretation of forest Damage in Canada" was published (Murtha, 1972). In 
that "guide", damage to forest trees was described on the basis of syndrome, 
and four major damage types were described. All of the damage symptoms caused 
by any insect or disease in forest trees can be categorized by means of the 
"key". The only requirement being that either the morphology or physiology 
of the tree is affected. It is clearly evident that a single type of insect 
or disease can cause numerous damage syndromes, and conversely a single 
damage syndrome can be caused by any one of a number of damaging agents. 
SOME APPLICATIONS 
The present "state of the art" of interpretation of vegetation damage, 
extensively managed lands can be shown by citing some selected papers. Others 
may exist and no doubt could be quoted, but the "art-level" can be indicated by 
the following: 
In March, 1973, a panel on "Uses and applications of infrared 
photography" emphasized the need for more practical application of remote 
sensing knowledge and photo interpretation at the field management working 
level (Murtha, 1973a). At the same time the panel indicated that the greatest 
problem to overcome was a communication gap between the research and the work 
ing level. It was acknowledged that research results were published (eventually) 
but that only a restricted circle of scientists read the papers. The "tech 
niques" were not getting into the hands of the working staff. In the examples 
that follow, a spruce budworm damage survey is looked at, as well as a gypsy 
moth damage survey, more on bark beetles is given, the effect of SO 2 damage is 
outlined, and scale effect is examined. 
The extent and severity of spruce budworm damage in Fundy National 
Park, New Brunswick was interpreted from 1:10,000 color-infrared aerial photo 
graphs (Murtha, 1973b). Five mortality classes and five defoliation classes were 
used during the photo interpretation survey. The five mortality classes were 
based on estimates of numbers of dead trees in a given forest type i.e. no mor 
tality, 0-10%, 11-25%, 26-50%, 51% or more conifer mortality, whereas the defol-