. Hazard-rating systems in forest insect pest management : symposium proceedings, Athens, Georgia, July 31-August 1, 1980. Forest insects Biological control United States Congresses; Forest insects United States Analysis; Forest insects United States Management. Figure 7A.—Tree shows no from 1942 (left) to (From Furniss 1954.) change in risk 1953 (right). Contingent Research After the California System was estab- lished, several studies analyzed, explained, qualified, or elaborated the principles behind risk; six of these are worthy of brief review. Changes in Risk The question was logically a
. Hazard-rating systems in forest insect pest management : symposium proceedings, Athens, Georgia, July 31-August 1, 1980. Forest insects Biological control United States Congresses; Forest insects United States Analysis; Forest insects United States Management. Figure 7A.—Tree shows no from 1942 (left) to (From Furniss 1954.) change in risk 1953 (right). Contingent Research After the California System was estab- lished, several studies analyzed, explained, qualified, or elaborated the principles behind risk; six of these are worthy of brief review. Changes in Risk The question was logically asked about the permanence in the risk class of a tree, does the risk of a tree tend to in- crease gradually (or quickly), does it remain fairly constant, or does it even decrease? Eaton (1941) initiated a photographic study to answer these questions. Forty- eight trees representing the four risk classes were selected for periodic photog- raphy. Furniss (1954) reports the follow- ing results after 13 years: Accidentally cut 5 Killed and showed increase in risk 11 Still alive 32 The 32 trees still alive showed as follows: An increase in risk 2 No change in risk (fig. 7A) 3 A decrease in risk (fig. 7B) 27. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. Forest Service; Society of American Foresters. Entomology Working Group. [Washington, D. C. ?] : U. S. Dept of Agriculture, Forest Service, [1981]
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