. 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. 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.) Fra
. 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. 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 Figure 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 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 tr
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