Lodgepole Pine Susceptibility Rating of Mountain Pine Beetle Through the Use of a Density Management Diagram

Ninety-four unmanaged lodgepole pine stands were examined to evaluate the relationship between stand density and susceptibility to mountain pine beetle attack. Sample included stands from a broad geographical range in the western United States. Beetle population trends were not significantly related to variation in stand density as measured by stand density index (SDI). The percentage of trees killed per acre by the mountain pine beetle in stands with greater than eighty percent lodgepole pine did vary significantly with changes in SDI. From these data three SDI zones were identified: 1) stands with SDI\u27s of less than 125 showed low potential for attack, 2) stands between 125 and 250 SDI showed much greater levels of tree mortality, gradually decreasing toward the 250 SDI, 3) tree mortality decreased in stands as density increased beyond the 250 SDI value

Estimating Extent of Mortality Associated with the Douglas-Fir Beetle in the Central and Northern Rockies

Data collected from Douglas-fir stands infected by the Douglas-fir beetle in Wyoming, Montana, Idaho, and Utah, were used to develop models to estimate amount of mortality in terms of basal area killed. Models were built using stepwise linear regression and regression tree approaches. Linear regression models using initial Douglas-fir basal area were built for all study sites but produce low precision estimates. Regression tree models using initial Douglas-fir basal area of stand density index or both were also build for all sites. Regression tree models provide a more realistic approach to estimate potential mortality by creating more homogenous mortality classes with reduced variance. The models developed provide land managers with a basis for determining the potential mortality should a Douglas-fir beetle outbreak develop

Within-Stand Spatial Distribution of Tree Mortality Caused by the Douglas-Fir Beetle (Coleoptera : Scolytidae)

The Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, causes considerable mortality in Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, forests. Within-stand distribution of mortality was examined in affected stands using geostatistical techniques. A 10 x 10 m grid was established in two 4-ha study sites. Live and beetle-killed host basal area was measured at each node. In a 16-ha stand, a variable-resolution grid was established and the same information collected. The relationship between Douglas-fir basal area and Douglas-fir basal area killed was examined using non-spatially explicit and spatially explicit linear regression models. A positive linear relationship was observed between the variables. Significant spatially explicit models suggest that the relationship is also true at fine scales. Relative variograms were constructed for Douglas-fir basal area before and after the Douglas-fir beetle outbreaks. For the 4-ha sites, increased spatial dependency in the distribution of Douglas-fir basal area was observed as a result of the Douglas-fir beetle outbreak. For the 16-ha site, kriging was used to estimate live Douglas-fir basal area before and after the outbreak to a 10-m resolution and the stand rated for potential mortality illustrating the potential applicability of geostatistical techniques to rating a stand for potential mortality. Cross-validation analysis indicated that although the potential exists for large estimation errors, the majority of the estimates were within acceptable ranges. The study suggests that geostatistical approaches may be suitable to extend our understanding bark beetle ecology and improving the application of extent of mortality models

Spruce Beetle (Dendroctonus rufipennis) Outbreak in Engelmann Spruce (Picea engelmannil) in Central Utah, 1986-1998

Extensive Engelmann spruce (Picea engelmannii Parry ex Engelm.) mortality caused by the spruce beetle (Dendroctonus rufipennis Kirby) has been occurring at the southern end of the Wasatch Plateau in central Utah. This spruce beetle outbreak is the largest recorded in Utah history. An extensive ground survey was conducted in 1996 on the Manti-LaSal National Forest, Sanpete and Ferron Ranger Districts, to document mortality and impact of a major spruce beetle outbreak on post-outbreak forest composition. In 1998 the same sites were resurveyed. Survey results indicate Engelmann spruce basal area (BA) loss averaged 78% in trees ≥5 inches diameter breast height (DBH) in 1996. Ninety percent of BA ≥5 inches DBH was lost within the same sites by 1998. Tree mortality of spruce ≥5 inches DBH expressed in trees per acre (TPA) averaged 53% in 1996. In 1998 TPA ≥5 inches DBH mortality averaged 73%. Before the outbreak live Engelmann spruce BA ≥5 inches DBH averaged 99 square feet, and TPA ≥5 inches DBH averaged 97. In the sites surveyed in 1996 and resurveyed in 1998, Engelmann spruce BA ≥5 inches DBH averaged 21 and 9 square feet, and TPA ≥5 inches DBH averaged 43 and 25, respectively. Overstory tree species composition changed from stands dominated by spruce to subalpine fir. Stand ratings for potential spruce beetle outbreaks were high to mostly medium hazard pre-outbreak and medium to primarily low hazard by 1998, as a result of reduction in average spruce diameter, total basal area, and overstory spruce

A retrospective assessment of partial cutting to reduce spruce beetle-caused mortality in southern Rocky Mountains

Tree susceptibility to bark beetle-caused mortality has been linked to stand characteristics such as basal area (BA) and average tree size, factors that can be manipulated through partial cutting. There is no experimental evidence, however, demonstrating the efficacy of partial cutting in spruce type. Such experiments are very difficult to complete because of the inability to manipulate bark beetle populations needed to challenge treated stands. To circumvent this difficulty, we identified spruce stands that were partially cut (for nonexperimental reasons) in advance of beetle activity and compared beetle-caused mortality to that in nearby spruce stands that were not treated. Treated stands had fewer infested stems and less infested BA than untreated stands, as well as smaller proportions of infested stems and BA. Untreated stands, however, had more residual spruce stems and BA than treated stands. Most of this difference was among stems 3-11 in. dbh with little difference in survivorship among larger stems. Spruce regeneration was not significantly different among treated and untreated stands. Spruce stand density index, spruce BA, and the number of spruce stems Ͼ11 in. dbh were the stand variables most strongly correlated with host mortality measurements. Insect population pressure appears to influence the degree of protection to residual spruce following partial cutting. Keywords: Engelmann spruce, bark beetle management, Dendroctonus rufipennis, vegetation management, thinning B ark beetles are natural disturbance agents of western conifer forests. Bark beetle outbreaks modify stand development and production Stand conditions have been consistently linked with bark beetle infestations in western coniferous forests It is challenging to implement robust experiments that test the efficacy of partial cutting for reducing losses to bark beetles. For example, it may take years or decades for treated stands to be exposed to bark beetle populations, and without some degree of beetle pressure, such an experiment may have inadequate results. Thus, a rigorous experimental approach is difficult to complete. Alternatively, it is possible to evaluate partial cutting as a preventive strategy by retroactively examining stands that were treated as part of forest management activities. This approach circumvents the difficulties of installing an experiment and the wait for beetles to challenge treated areas. Tradeoffs include a lack of experimental control over factors such as treatment type and their random assignment to Manuscript received April 27, 2009; accepted August 13, 2009. E. Matthew Hansen ([email protected]), US Forest Service, Rocky Mountain Research Station, 860 N 1200 E, Logan, UT 84321. Jose F. Negron ([email protected]), US Forest Service, Rocky Mountain Research Station, 240 W. Prospect Rd., Ft. Collins, CO 80526. A. Steven Munson ([email protected]), US Forest Service, Forest Health Protection, 4746 South 1900 East, Ogden, UT 84403. John A. Anhold ([email protected]), US Forest Service, Arizona Zone Office, 2500 S. Pine Knoll Dr., Flagstaff, AZ 86001. Thanks are due to our National Forest System cooperators (Bill Ripley, Colby Peterson, David Keefe, Laurie Parry, Allan Henningson, Monty Cartwright, Jenneka Knight, Shawn Martin, Robbyn Bergher, and Andy Cadenhead

Managing Slash to Minimize Colonization of Residual Leave Trees by Ips and Other Bark Beetle Species Following Thinning in Southwestern Ponderosa Pine

12 pp.Pine Bark Beetles, THE PIÑON IPS BARK BEETLE, FIREWOOD AND BARK BEETLES IN THE SOUTHWEST, USING INSECTICIDES TO PREVENT BARK BEETLE ATTACKS ON CONIFERS, GUIDELINES FOR THINNING PONDEROSA PINE FOR IMPROVED FOREST HEALTH AND FIRE PREVENTIONVarious techniques to reduce brood production of Ips and Dendroctonus spp. in ponderosa pine slash are discussed

Variables Associated With the Occurrence of Ips Beetles, Red Turpentine Beetle and Wood Borers in Live and Dead Ponderosa Pines with Post-fire Injury

Recently, wildfires and prescribed burning have become more frequent in conifer forests of western North America. Most studies examining the impacts of insects on trees with post‐fire injury have focused on contributions to tree mortality. Few studies have examined fire‐caused injuries to estimate the probability of attack by insects. Scant data quantifying insect associations with one another, or with live and dead fire‐injured trees, are available. We examined live and dead trees with varying levels of fire injury in wildfires in Colorado, Montana, Arizona and the Black Hills aiming to determine fire injury associated with insect infestation, co‐occurrence between insects and insect association with live and dead fire‐injured trees. Bole scorch height estimated the likelihood of attack by Ips spp. Diameter at breast height, bole scorch height and crown scorch height estimated the likelihood of attack by Dendroctonus valens LeConte. Diameter at breast height and bole scorch height estimated the likelihood of attack by wood borers. Ips spp., Dendroctonus valens and wood borers were associated with one another. Ips spp. beetles and wood borers were associated with dead fire‐injured trees, whereas D. valens was often associated with live fire‐injured trees. Focusing on certain fire‐caused injuries may identify trees targeted by Ips spp. beetles, Dendroctonus valens and wood borers

The Effects of Mechanical Fuel Reduction Treatments on the Activity of Bark Beetles (Coleoptera: Scolytidae) Infesting Ponderosa Pine

Selective logging, fire suppression, forest succession and climatic changes have resulted in high fire hazards over large areas of the western USA. Federal and state hazardous fuel reduction programs have increased accordingly to reduce the risk, extent and severity of these events, particularly in the wildland–urban interface. In this study, we examined the effects of mechanical fuel reduction treatments on the activity of bark beetles in ponderosa pine, Pinus ponderosa Dougl ex. Laws., forests located in Arizona and California, USA. Treatments were applied in both late spring (April–May) and late summer (August–September) and included: (1) thinned biomass chipped and randomly dispersed within each 0.4 ha plot; (2) thinned biomass chipped, randomly dispersed within each plot and raked 2 m from the base of residual trees; (3) thinned biomass lopped- and-scattered (thinned trees cut into 1–2 m lengths) within each plot; (4) an untreated control. The mean percentage of residual trees attacked by bark beetles ranged from 2.0% (untreated control) to 30.2% (plots thinned in spring with all biomass chipped). A three-fold increase in the percentage of trees attacked by bark beetles was observed in chipped versus lopped-and-scattered plots. Bark beetle colonization of residual trees was higher during spring treatments, which corresponded with peak adult beetle flight periods as measured by funnel trap captures. Raking chips away from the base of residual trees did not significantly affect attack rates. Several bark beetle species were present including the roundheaded pine beetle, Dendroctonus adjunctus Blandford (AZ), western pine beetle, D. brevicomis LeConte (AZ and CA), mountain pine beetle, D. ponderosae Hopkins (CA), red turpentine beetle, D. valens LeConte (AZ and CA), Arizona fivespined ips, Ips lecontei Swaine (AZ), California fivespined ips, I. paraconfusus Lanier (CA) and pine engraver, I. pini (Say) (AZ). Dendroctonus valens was the most common bark beetle infesting residual trees. A significant correlation was found between the number of trees chipped per plot and the percentage of residual trees with D. valens attacks. A significantly higher percentage of residual trees was attacked by D. brevicomis in plots that were chipped in spring compared to the untreated control. In lopped-and-scattered treatments, engraver beetles produced substantial broods in logging debris, but few attacks were observed on standing trees. At present, no significant difference in tree mortality exists among treatments. A few trees appeared to have died solely from D. valens attacks, as no other scolytids were observed in the upper bole. In a laboratory study conducted to provide an explanation for the bark beetle responses observed in this study, monoterpene elution rates from chip piles declined sharply over time, but were relatively constant in lopped-and-piled treatments. The quantities of b-pinene, 3-carene, a-pinene and myrcene eluting from chips exceeded those from lopped-and- piled slash during each of 15 sample periods. These laboratory results may, in part, explain the bark beetle response observed in chipping treatments. The implications of these results to sustainable forest management are discussed