File:Hazard-rating systems in forest insect pest management - symposium proceedings, Athens, Georgia, July 31-August 1, 1980 (1981) (20573352995).jpg

Title: Hazard-rating systems in forest insect pest management : symposium proceedings, Athens, Georgia, July 31-August 1, 1980
Identifier: CAT91960247 (find matches)
Year: 1981 (1980s)
Authors: United States. Forest Service; Society of American Foresters. Entomology Working Group
Subjects: Forest insects Biological control United States Congresses; Forest insects United States Analysis; Forest insects United States Management
Publisher: (Washington, D. C. ?) : U. S. Dept of Agriculture, Forest Service, (1981)
Contributing Library: U.S. Department of Agriculture, National Agricultural Library
Digitizing Sponsor: U.S. Department of Agriculture, National Agricultural Library

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DEVELOPMENT OF A STAND SUSCEPTIBILITY CLASSIFICATION FOR DOUGLAS-FIR BEETLE Malcolm M. Furniss, R. Ladd Livingston, and Mark D. McGregor1 INTRODUCTION The Douglas-fir beetle (DFB), Dendroc- tonus pseudotsugae Hopk., occurs through- out most of the distribution of its prin- cipal host, Douglas-fir (DF), Pseudotsuga menziesii (Mirb.) Franco (fig. 1). West- ern larch, Larix occidentalis Hook, is also infested, but progeny survive only in felled larch.
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Figure 1.--Geographic distribution of Douglas-fir. 1 The authors are, respectively, Prin- cipal Entomologist, Intermountain Forest and Range Experiment Station, Moscow, Ida- ho; Forest Entomologist, Idaho Dept. of Lands, Coeur d'Alene, Idaho; and Bark Bee- tle Specialist, Northern Region, USDA For- est Service, Missoula, Montana. The DFB is univoltine, overwintering mainly as callow adults (Furniss and Orr 1978). It is a robust flier, taking flight early in spring as air temperature warms above 65° F. We have observed flights of 6 hours' or more duration at an average velocity of 2.5 mph (4 km/hr) on flight mills. Thus, DFB are capable of dispers- ing several kilometers in a single flight, permitting them to reach susceptible stands at some distance from population sources. Much literature about the beetle has been compiled (Furniss 1979), including information related to host susceptibility. However, no susceptibility classification has been published relating probability of mortality to descriptors of trees, stands, or sites. This paper deals, in order of empha- sis, with the natural basis for a suscep- tibility classification, field methodology, and analyses. This information was devel- oped during long-term research from exam- inations of many hundreds of trees, par- ticularly in Idaho, and from the cited works of others. Nonetheless, we have only recently begun a concerted effort to develop a more holistic approach to defin- ing mathematically the probabilities of mortality, given various stand data. Thus, at the time of this symposium, we have not concluded fieldwork and our probabil- ity example is based on a limited data set. We believe, however, that the natur- al basis for the classification and the field methodology will be of interest and will foster communication with others. When our present work is completed, we will compare in a future publication the probabilities of mortality derived from a more adeguate sample base from stands representing a broader range of edaphic, climatic, and floristic condi- tions. We are confident that the outcome will provide protection specialists and resource managers with better means of classifying stands in need of silvicul- tural treatments and other practices to prevent DFB from killing trees. Concur- rently, we hope to provide an avenue for understanding the processes responsible for or related to presence or absence of DFB infestation. NATURALISTIC BASIS FOR CLASSIFICATION In this section, we present informa- tion on beetle behavior, characteristics 115

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