January 2006 Forest Health Protection and State Forestry Organizations 4.8 WEB April 2012 Management Guide for Fir Engraver By Carol Bell Randall US Forest Service Scolytus ventralis (LeConte) Primary hosts: Reported infesting: Grand fir (Abies grandis) Douglas-fir (P. menziesii) Topics (A. lasiocarpa) White fir (A. concolor- Oregon, Subalpine fir California, Idaho, Utah, Nevada, Western hemlock (Tsuga Damage 1 Wyoming, New Mexico, Arizona, and heterophylla) Life History 1 Colorado) Red fir (A. magnifica- Oregon and Rare occasions: Identification 2 California) Spruce (Piceae engelmanii) Noble fir (A. procera- Washington, Management 4 Oregon, N. California) Silvicultural 5 Treatments Natural Controls 5 Damage Other Reading 6 Unlike other bark beetles, the fir ring-shake, and decay are associated engraver needs only to kill a strip of with old attack scars. These defects Field Guide cambium near its gallery to will reduce the value of true fir for Management successfully reproduce. Because it solid wood markets. Guide Index does not necessarily kill the tree, fir engraver attacks result in a variety of tree symptoms: (1) dead branches, (2) top kill, and (3) complete tree Key Points mortality. Trees that appear healthy are rarely killed except when they Fir engraver needs are affected by root disease or by a only to kill a strip of cambium near severe, temporary stress such as its gallery to drought or defoliation. Fir engraver successfully attacks that do not kill the tree cause reproduce. scars clearly visible on the outer Figure 1. Aerial view of the fir engraver bark. beetle damage. Photo by William M. Fir engraver will Ciesla attack trees of any Various defects such as stain, size. Various defects Life History such as stain, ring- shake, and decay Throughout most of its range fir have an incurved posterior with a are associated with engraver has a one- year life cycle; small central bump that is more old attack scars. two years may be required at high pronounced in the males (fig. 10). A healthy tree can elevations, and during warmer years, There is no evidence of recover if sufficient a partial second generation may aggregation pheromones in fir areas of inner bark form. engraver. The attack dynamics of remain. Adult fir engraver are shiny this species can be explained solely black beetles about 1/5th inch long by its sensitive primary attraction (4 mm). Viewed from the side, they response to host volatiles. Page 2 Back to menu Fir Engraver 4.8 Life History Typically fir engraver leaves after the female begins boring the infested trees from June through The fir egg gallery, a yellowish brown September. Temperature probably engraver (FE) discoloration appears in the is a major pest controls when adults emerge, leading surrounding area. The stain is of true firs to earlier emergence during warmer caused by the fung us throughout the springs and at lower elevations. Trichosporium symbioticum West. Female beetles initiate attacks on Wright, which is carried by the random standing green trees, freshly beetles. cut logs, and recent wind throws. She bores into the tree’s bark and is followed by a male which she mates with. The female bores a horizontal gallery which radiates out on either side of a central nuptial chamber. Yearly mortality The gallery is excavated between the attributable to outer wood and the inner bark, the beetle is scoring the wood (hence the name quite high in “engraver beetle”). The egg gallery parts of its may be anywhere from 4 to 12 range, especially where inches (10-30 cm) long. During the 5 to 7 weeks after mating the female root disease is Figure 2. Gallery pattern of the fir prevalent. will lay between 100 and 300 eggs engraver is perpendicular to the grain of along the gallery. Four to six days the wood. Photo: FE Forest Insect and Disease Leaflet Identification Fir engraver will attack trees of portion of the crown or the entire any size. Often fir engraver will tree in a single summer. The attack the tree crown, killing foliage turns yellow, and then individual branches in larger bright red over the 3 to 6 months diameter trees. The appearance of after attack (fig. 4). yellowed or red branches within a green tree, called flagging, is a sign of attack (fig. 3). The branch collar is a favored attack site of these beetles. Clear streams of pitch Figure 4. Figure 3. Red branches flowing from the entrance holes Red foliage within the a green tree, down the trunk may be present- firs stage on called flagging, is sign of grand fir. attack. Photo by Ken do not produce pitch tubes. Pitch Photo by Gibson. streaming is not frequently observed Dave Powell. in the intermountain West. Reddish brown boring dust in bark crevices of larger diameter trees or cob webs along the trunk is usually present. Numerous attacks over part or the entire bole may kill the upper Page 3 Back to menu Fir Engraver 4.8 Identification Sometimes only strips or patches of side they have an incurved abdomen, the bole are attacked. A healthy tree a characteristic typical of all can recover if sufficient areas of members of the genus Scoltus (fig 9 inner bark remain. Top-killed trees and 11). can produce new leaders. When the Fir engraver galleries may be inner bark heals over, a brown pitch confused with the gallery pattern of pocket marks the injury. The usual evidence of such attacks is roughened patches of bark (fig. 5) or scattered dead branches girdled at the base by the egg galleries. The gallery pattern of the fir engraver is unique. Unlike most other bark beetles, the female fir Figure. 5. Signs of fir engraver constructs a horizontal egg engraver attack. Bark is gallery, perpendicular to the grain of bubbled and rippled from Figure 6. Fir engraver galleries. Photo by outside. the wood (fig. 6). Eggs are deposited David Beckman, Idaho Dept. of Lands Photo by Chris Schnepf. on each side of the gallery and the larvae tunnel at right angles to the another bark beetle, Pseudohylesinus egg gallery paralleling the wood sericens. The presence of small, grain. The larvae are white, legless shiny black beetles in the galleries grubs, reaching a length of about one will confirm that the attacking insect -eighth inch at maturity (fig. 7). The is fir engraver, Pseudohylesinus are pupa is also white and approximately dull in appearance. the size of the adult (fig. 8). Adult Fir engraver and another bark beetles are shiny, black and about beetle, Pityokteines elegans, often one-eighth inch in length. From the attack the same grand fir (Abies grandis) trees. Figure 7. Fir Engraver larva. Figure.8. Fir engraver pupa. Figure 9. Fir engraver adult Photo: National Agriculture Library Photo: National Agriculture Library Photo by Donald Owen Figure 10. The characteristic incurved abdomen Photo: FE Forest Insect and Disease Leaflet Figure 11. Photo: University of British Columbia Page 4 Back to menu Fir Engraver 4.8 Identification Recent studies show a moderate Fir engraver is often associated Fir engraver level of competition between these with roundheaded fir borer, caused fir two bark beetles; they did not Tetropium abietis Fall, or the mortality often partition the bole of the host flatheaded fir borer, Melanophila increases in drummondi Kirby; however the response short according to diameter. P. elegans winding galleries of both borers duration would either colonize an area of are largely limited to the lower, stressors, bark before fir engraver, which especially would in turn not initiate attack, or thick barked areas of the trunk. drought or in which both species would co- During outbreaks, fir engraver epidemics of attack a host, but fir engraver would alone is generally responsible for defoliating avoid phloem colonized by P. most of the damage. insects. elegans. Management Considerations Overview- resources, while diseased trees are Silvicultural practices aimed at unable to fully utilize the resources maintaining healthy stand available to them. If a stress is of conditions appear to offer the best sufficient duration and severity, the chance for minimizing engraver- tree may be unable to resist attack caused losses. Overcrowding, by fir engraver. disease, and drought often result in stress. Overcrowded trees compete Hazard rating index-- Overstocked Schenk et al (1977) developed with one another for limited grand fir a stand hazard index to rate grand stands have fir stands for susceptibility to the greatest beetle attack based on stand chance of parameters measuring competitive beetle attack. The Under-story stress and species diversity. This Schenk et al. (1976) have identified groups of under- story system, which utilizes Crown plant species which are highly Competition Factor (CCF) as a correlated with moisture regimes measure of stress, and Diversity necessary for the vigorous Index (DI) as a numerical rating growth of grand fir. The presence of oceanspray for species diversity has shown (Holodiscus discolor), Dewey's that pure, overstocked grand fir sedge (Carex deweyana), stands have the greatest chance of sandwort (Arenaria macrophylla) beetle attack. As overstocking is or yerba buena (Satureja douglasii) on a site was strongly relieved and the grand fir correlated with increased FE component is reduced, the risk of caused tree mortality. Sites with fir engraver infestations is reduced. queencup beadlily (Clintonia Data required to derive both the uniflora) or pipsissewa (Chimaphila umbellata) CCF and DI values (species, d.b.h., experienced less FEB caused number trees/plot) are routinely tree mortality. taken during standard timber inventories. Page 5 Back to menu Fir Engraver 4.8 Silvicultural Treatment Silvicultural treatment.-- with susceptibility to fir The maintenance of vigorous engraver attacks in white stands through the elimination of and red fir.