Douglas-fir Beetle Research Articles

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

Abstract Data collected from Douglas-fir (Pseudotsuga menziesii) stands infested by the Douglas-fir beetle (Dendroctonus pseudotsugae) 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 or stand density index or both were also built 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. West. J. Appl. For. 14(3):121-127.

Growth and virulence of Ceratocystis rufipenni and three blue-stain fungi isolated from the Douglas-fir beetle

Blue-stain fungi were isolated from the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, and from Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, colonized by the beetle. Growth of the three most commonly isolated blue-stain fungi (Leptographium abietinum (Peck) Wingfield, Ophiostoma europhioides (Wright & Cain) Solheim, Ophiostoma pseudotsugae (Rumbold) von Arx), and Ceratocystis rufipenni Wingfield, Harrington, & Solheim, an important associate of the spruce beetle, Dendroctonus rufipennis (Kirby), was studied in sapwood and phloem of live Douglas-fir trees, on malt agar, and on malt agar under oxygen-deficient conditions. The two Ophiostoma species grew better in the phloem and induced longer phloem necroses than the other fungi. Ceratocystis rufipenni and O. europhioides grew better in the sapwood and induced deeper sapwood occlusion. All fungi were relatively fast growing on malt agar, with O. pseudotsugae growing fastest and L. abietinum, slowest. Growth of C. rufipenni and O. europhioides was inhibited less by low oxygen levels than the other fungi, and this may explain why these two fungi were better able to colonize live sapwood.Key words: Ceratocystis rufipenni, Dendroctonus pseudotsugae, Douglas-fir, Leptographium abietinum, Ophiostoma europhioides, Ophiostoma pseudotsugae.

Probability of infestation and extent of mortality associated with the Douglas-fir beetle in the Colorado Front Range

Infested and uninfested areas within Douglas fir, Pseudotsuga menziesii (Mirb.) Franco, stands affected by the Douglas-fir beetle, Dendroctonus pseudotsugae Hopk. were sampled in the Colorado Front Range, CO. Classification tree models were built to predict probabilities of infestation. Regression trees and linear regression analysis were used to model amount of tree mortality in terms of basal area killed in infested stands. Classification trees had cross-validation estimates of classification accuracy ranging from 0.55 to 0.63. The data suggests that Douglas-fir beetle-attacked stands contain a high percentage of the basal area represented by Douglas-fir, high tree densities, and poor growth during the last 5 years prior to attack. Trees prone to attack by the Douglas-fir beetle within infested points also exhibited reduced growth rates. Tree and linear regression analysis indicate that initial amount of Douglas-fir basal area can be used as a predictor variable for the amount of basal area affected.

Pheromone-Baited Traps for Dendroctonus Pseudotsugae(Coleoptera: Scolytidae): Influence of Selected Release Rates and Trap Designs

Several different aggregation pheromone release rates and trap designs were evaluated for trapping the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins. Frontalin:seudenol release rates of 160:80,80:40,40:20, 20:10, 10:5,and 1:0.5 mg/ d, respectively, with a constant ethanol release rate of 88 mg/d at 24°C were tested in multiple-funnel traps. The highest Douglas-fir beetle catches occurred at release rates of 20:10 and 10:5 mg/ d. There were significantly fewer catches at higher and lower release rates. The percentage of male Douglas-fir beetles increased significantly with increasing release rates up to a plateau at 80:40 mg/d. Catches of Thanasimus undatulus (Say) (Coleoptera: Cleridae), a predator, increased consistently with higher release rates. Multiple-funnel traps caught significantly more Douglas-fir beetles than slotted-panel traps for both total numbers and number per unit area of trapping surface. There was no difference between the 2 trap types in selectivity for Douglas-fir beetles relative to T. undatulus. Placing metal screens with 6- or 12-mm openings above the collection cup to filter intercepted insects or providing a strip of metal screen with 1.5-mm openings to serve as an escape route for predators from the collection cup in multiplefunnel traps resulted in capture of a significantly higher ratio of Douglas-fir beetles to predators. These results will contribute to the development of more efficient trapping programs to lessen the impact of Douglas-fir beetle outbreaks.

Growth and virulence of <i>Ceratocystis rufipenni</i> and three blue-stain fungi isolated from the Douglas-fir beetle

Growth and virulence of <i>Ceratocystis rufipenni</i> and three blue-stain fungi isolated from the Douglas-fir beetle

Using Aggregation and Antiaggregation Pheromones of the Douglas-Fir Beetle to Produce Snags for Wildlife Habitat

Abstract Pheromone baits for the Douglas-fir beetle were applied alone and in combination with the antiaggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), to test potential treatments for creating snags to improve wildlife habitat. All baited trees were attacked by beetles following both treatments. However, more unbaited trees were attacked on plots without MCH than on plots with MCH. One year after treatment, more of the attacked trees were dead on plots without MCH than on plots with MCH. Bark beetle pheromones can be used effectively to create snags for improving wildlife habitat, but to achieve specific objectives treatments must be prescribed based on knowledge of the expected beetle population densities. West. J. Appl. For. 12(2):00-00.

Using Pheromone-Baited Traps To Control the Amount and Distribution of Tree Mortality During Outbreaks of the Douglas-Fir Beetle

Abstract Multiple-funnel traps baited with strong aggregation pheromone lures were placed throughout three 259 ha plots in northeastern Oregon during an outbreak of the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins. Mean numbers (± SEM) of Douglas-fir beetles collected per plot for the entire flight periods of 1992 and 1993 were 277,921 ± 40,447 and 268,834 ± 37,088, respectively. Mean numbers (± SEM) of the most abundant predator, Thanasimus undatulus (Say), collected per plot in 1992 and 1993 were 43,527 ± 3,553 and 35,652 ± 3,514, respectively. Douglas-fir beetle-caused tree mortality was concentrated around the trap sites in the treated plots, even though traps were located an average of 40 m from the nearest host tree. Managers can influence the spatial distribution of tree mortality during an outbreak by selective placement of traps across the landscape. Selective trap placement, plus the removal of trapped beetles from the population, may reduce tree mortality within the general area. For. Sci. 43(1):65-70.

Pathogenicity to Douglas-fir of <I>Ophiostoma pseudotsugae</I> and <I>Leptographium abietinum</I>, fungi associated with the Douglas-fir beetle

Pathogenicity to Douglas-fir of <I>Ophiostoma pseudotsugae</I> and <I>Leptographium abietinum</I>, fungi associated with the Douglas-fir beetle

Pathogenicity to Douglas-fir ofOphiostoma pseudotsugaeandLeptographium abietinum, fungi associated with the Douglas-fir beetle

Pole-size Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) were inoculated with two fungi (Ophiostoma pseudotsugae (Rumb.) von Arx and Leptographium abietinum (Peck) Wingf.) associated with the Douglas-fir beetle (Dendroctonus pseudotsugae Hopkins) to evaluate their pathogenicity. Pruning the lowermost 30% of the live crown had no effect on host tree defenses. Inoculation with O. pseudotsugae produced significantly longer lesions in the phloem and resulted in a significantly greater percentage of necrotic phloem than inoculation with L. abietinum. The percentage of occluded sapwood was also greater following O. pseudotsugae inoculations, but the difference was not statistically significant. Individual lesion lengths declined significantly with increasing inoculation density, but the total percentage of necrotic phloem increased significantly. Both fungi appeared to be better adapted to grow in sapwood than in phloem. None of the inoculated trees were dead after 5 months, but some were chlorotic with less than 30% functional sapwood within the inoculation band. The results suggest that these fungi may assist the Douglas-fir beetle in overcoming the defenses of live trees. Resume : Des Douglas taxifoliOs (Pseudotsuga menziesii (Mirb.) Franco) au stade de perchis ont OtO inoculOs avec deux champignons, Ophiostoma pseudotsugae (Rumb.) von Arx et Leptographium abietinum (Peck) Wingf., associOs au dendroctone du Douglas taxifoliO (Dendroctonus pseudotsugae Hopkins) dans le but diOvaluer leur pathogOnOcitO. Le fait diOlaguer 30% de la cime dans sa partie infOrieure niavait pas dieffet sur les rOactions de dOfense de lihUte. Liinoculation avec O. pseudotsugae a causO des lOsions significativement plus longues dans le phlome et un pourcentage significativement plus OlevO de phlome nOcrotique quiavec L. abietinum. Le pourcentage de bois diaubier obstruO Otait Ogalement plus OlevO dans le cas des inoculations avec O. pseudotsugae mais la diffOrence niOtait pas statistiquement significative. La longueur des lOsions diminuait significativement avec liaugmentation de la densitO des inoculations mais le pourcentage total de phlome nOcrotique augmentait de faAon significative. Les deux champignons semblaient mieux adaptOs pour se dOvelopper dans le bois diaubier que dans le phlome. Aucun des arbres inoculOs niOtait mort aprs 5 mois mais certains Otaient chlorosOs et avaient moins de 30% de bois diaubier fonctionnel dans la zone diinoculation. Les rOsultats suggrent que ces champignons pourraient aider le dendroctone du Douglas taxifoliO ‡ surmonter les dOfenses des arbres vivants. (Traduit par la ROdaction)

Mortality of Douglas-fir After Operational Semiochemical Baiting for Douglas-fir Beetle (Coleoptera: Scolytidae)

Abstract Effects of an operational application of synthetic Douglas-fir beetle (Dendroctonus pseudotsugae Hopkins) attractants applied to Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) trees have not been well documented. Baits, containing a 1:1 mixture of frontalin and alpha-pinene, were deployed over 64 acres in an area application at the rate of 2 baits/ac. Baited trees, and unbaited Douglas-firs surrounding the bait centers, were selected for measurements. All baited trees were attacked along with 42.3% of the surrounding unbaited Douglas-firs. Attacked trees were significantly larger than unattacked trees and were closer to the bait centers. The percentage of trees attacked was not influenced by cardinal direction from the bait center. Approximately 97% of the baited trees were either moderately or heavily attacked. Almost 60% of the moderately and heavily attacked unbaited Douglas-firs were within 33 ft of the bait centers. A model to predict probability of infestation of unbaited trees surrounding the bait center was developed. West. J. Appl. For. 12(1):16-20.

Optimal Dose of an Antiaggregation Pheromone (3-Methylcyclohex-2-en-1-one) for Protecting Live Douglas-Fir from Attack by Dendroctonus pseudotsugae (Coleopera: Scolytidae)

The Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, anti aggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), was applied to stands of Douglas-fir, Pseudotsuga menziesii (Mirabel) Franco, at high risk for infestation to determine the lowest effective dose for protecting live trees. MCH was applied at rates of 50, 100, and 150 bubble capsules per hectare (20, 40, and 60 g/ha, respectively) in 1994, and 15, 30, and 50 bubble capsules per hectare (6, 12, and 20 g/ha, respectively) in 1995. Mean release rates throughout the beetle flight periods in 1994 and 1995 were 1.63 and 1.23 milligrams per capsule per day, respectively. For both years, catches of Douglas-fir beetles in pheromone-baited traps located at the plot centers were significantly lower on all MCH-treated plots compared with untreated plots, but there were no differences among the 3 doses of MCH. In contrast, NCR had no effect on the numbers of 3 predators [Thanasimus undatulus (Say), Enoclerus sphegeus F., and Temnochila chlorodia (Mannerheim)] collected in the traps during either year. In 1994, the percentage of Douglas-fir ≥20 cm diameter at breast height (abh) that were mass attacked was significantly lower on MCH-treated plots compared with the untreated control, and all 3 doses were equally effective. In 1995, there were no significant differences in the percentage of mass-attacked trees among the treatments. These results demonstrate that MCH applied at rates as low as 20 g/ha (50 bubble capsules per hectare) can reduce the probability that high-risk Douglas-fir will become infested.

EFFICACY OF AN ANTIAGGREGATION PHEROMONE FOR REDUCING DOUGLAS-FIR BEETLE, DENDROCTONUS PSEUDOTSUGAE HOPKINS (COLEOPTERA: SCOLYTIDAE), INFESTATION IN HIGH RISK STANDS

AbstractThe Douglas-fir beetle (Dendroctonus pseudotsugae) antiaggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), was applied to stands at high risk for infestation. The MCH was applied in a bubble capsule formulation to plots ranging from 2.1 to 2.6 ha in size at rates of 45–76 g/ha. Catches of Douglas-fir beetles in attractant-baited Lindgren funnel traps located at the plot centers were significantly lower on MCH-treated plots compared with untreated plots. In contrast, catches of the most abundant predator, Thanasimus undatulus (Say), were unaffected by the MCH treatment. The percentage of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] trees ≥20 cm dbh that were mass attacked was significantly lower on treated plots (0.2%) compared with untreated plots (8.5%). MCH alone was effective in reducing the probability of Douglas-fir beetle infestations occurring in high risk stands.

The Candida antarctica lipase B catalysed kinetic resolution of seudenol in non-aqueous media of controlled water activity

For further investigation of the kinetic resolutions in transesterification reactions with the highly enantioselective Candida antarctica lipase B, an easy to study model reaction with one typical substrate, the Douglas Fir Beetle pheromone 3-methyl-2-cyclohexen-1-ol (Seudenol), was developed. The influence of the nature of the solvent and thermodynamic water activity was studied. Initial rates showed constant or progressively increasing values with increasing water activity. Enantioselectivity depended on the choice of solvent and descended in most cases with increasing water activity. No general correlations of enantioselectivity or activity with physicochemical constants of the solvent were found. However, at a water activity of 0.11 a tendency toward optimum hydrophobicity (i.elog P ≈ for enantioselectivity was observed. Enantiomeric ratios were in the range 8–32.

Response of Dendroctonus pseudotsugae (Coleoptera: Scolytidae) and Thanasimus undatulus (Coleoptera: Cleridae) to Traps with Different Semiochenricms

The attractiveness of frontalin alone and in combinations with ethanol, MCOL (1-methylcyclohex-2-en-1-01), and seudenol (3-methylcyclohex-2-en-l-ol) to the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, and associated predators was determined in northeastern Oregon. All three alcohols significantly increased attractiveness of frontalin to the Douglas-fir beetle. Seudenol was most attractive followed by ethanol and MCOL, respectively. Seudenol plus ethanol was the only combination of alcohols that significantly increased attractiveness of frontalin more than that of seudenol alone. There was no increase in attractiveness to the Douglas-fir beetle with addition of MCOL to a lure containing ethanol or seudenol, or both. Seudenol significantly In creased the percentage of male Douglas-fir beetles trapped, but ethanol had the opposite effect. MCOL had no significant effect on the sex ratio of trapped Douglas-fir beetles. Thanasimus undatulus (Say) was the only predator caught in appreciable numbers. Seudenol significantly increased the number of T. undatulus caught in the traps compared with the oilier alcohols. These results suggest that the combination of frontalin, seudenol, and ethanol is the most effective lure tested for trapping the Douglas-fir beetle.

Reduction of Douglas-fir beetle infestation of high-risk stands by antiaggregation and aggregation pheromones

A combination of antiaggregation and aggregation pheromones was tested for protecting stands of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) at high risk for infestation by the Douglas-fir beetle (Dendroctonuspseudotsugae Hopkins). The antiaggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), was applied in a bubble capsule formulation to the perimeter of 1-ha circular plots at a rate of 60 g/plot. Treated plots also had three or four clusters of four Lindgren funnel traps baited with frontalin, seudenol, 1-methylcyclohex-2-en-1-ol, and ethanol located outside of the plot but within 160 m of the boundary. Mean (±SE) accumulated catches in all traps per plot were 73 658 ± 19 721 Douglas-fir beetles and 12 892 ± 2 513 Thanasimusundatulus (Say), a predator of the Douglas-fir beetle. The mean percentage of Douglas-fir trees ≥20 cm DBH that were mass attacked was reduced by 80% within the treated plots compared with the untreated plots. However, there was an eightfold increase in the percentage of trees mass attacked in the area outside the treated plots in the vicinity of the funnel traps. The net effect of the treatment was to concentrate mass-attacked trees within a limited area outside of the protected stand. Our results indicate that Douglas-fir beetle antiaggregation and aggregation pheromones can be used effectively to reduce the probability of infestation in small, high-value stands.

Blue-stain fungi and their transport structures on the Douglas-fir beetle

Parent and preflight-adult Douglas-fir beetles (Dendroctonuspseudotsugae Hopk., Coleoptera: Scolytidae) were collected from felled Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) trees. Fungi isolated from the beetles included blue-stain fungi, such as Ophiostomapseudotsugae (Rumbold) von Arx, Leptographiumterebrantis Barras & Perry, and Leptographiumabietinum (Peck) Wingfield; other ascomycetes, such as Graphium spp. and Leptographium spp.; yeasts; and unidentified basidiomycetes. All fungal cultures derived from parent beetles, preflight adults, beetle eggs, larvae, frass, and bark from galleries had yeasts present. Ophiostomapseudotsugae was isolated from 67% of the parent females, 19% of the parent males, and 100% of the preflight adults of both sexes collected from their pupal cells. Rinsing the beetles with 70% ethanol prior to fungus isolations reduced the frequency of all fungi, except yeasts. Parent and preflight adult beetles (of both sexes) were examined with a scanning electron microscope, where spores of O. pseudotsugae were visible in shallow pits on the elytra of both male and female beetles. Spores of other fungi were observed in shallow pits on elytra and in much smaller but deeper pits on the scutellum of both sexes. The results indicate a close association between Douglas-fir beetles and fungi, accompanied by anatomical differentiation on the beetles that allows the dissemination of blue-stain fungi to new Douglas-fir hosts and substrates.

PITYOPHTHORUS ORARIUS BRIGHT (COLEOPTERA: SCOLYTIDAE) IN A NORTHERN CALIFORNIA DOUGLAS-FIR SEED ORCHARD: EFFECT OF CLONE, TREE VIGOR, AND CONE CROP ON RATE OF ATTACK

AbstractThe geographic range of the Douglas-fir twig beetle, Pityophthorus orarius Bright, was extended beyond the original provenance of southern British Columbia to northern California. A survey of 457 Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] trees in 1985 revealed that those with heavy cone crops were more likely to be infested by twig beetles than were those with a light crop. Furthermore, attack rates differed among clones. A second survey done in 1987 confirmed the importance of clone and cone crop in attack rate. In this survey, stressed trees were attacked at a higher rate than unstressed trees. Beetle distributions appeared clumped in both surveys, possibly because of semio-chemicals or oviposition behavior.

Dendroctonus pseudotsugae hopkins (Coleoptera: Scolytidae): Production of and response to enantiomers of 1-methylcyclohex-2-en-1-ol

Female Douglas-fir beetles,Dendroctonus pseudotsugae, produced an average 45∶55 mixture of the (S)-(-)- and (R)-(+)-enantiomers of 1-methylcyclohex-2-en-1-ol (MCOL). The (S)-(-)∶(R)-(+) ratio of 3-methylcyclohex-2-en-1-ol (seudenol) produced by this population of females was 34∶66. Lindgren funnel traps baited with (R)-(+)-MCOL attracted significantly more males and females than (S)-(-)-MCOL-baited traps, which captured significantly more beetles than unbaited controls. The combined effect of the enantiomers was additive, rather than synergistic. Either enantiomer of MCOL increased catches by frontalin-baited traps. Racemic MCOL can be used for trapping Douglas-fir beetles in south-central British Columbia.

Mortality of Douglas-Fir after Two Semiochemical Baiting Treatments for Douglas-Fir Beetle (Coleoptera: Scolytidae)

In May 1989, a study was conducted in southwestern Idaho to test the hypothesis that infestations of Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, would not differ among plots containing five semiochemical baits per 0.4 ha, two semiochemical baits per 0.4 ha, and control plots containing no baits. On average, 5.8 times and 6.4 times more trees were infested on the plots with two- or five-bait treatments, respectively, compared with the control plots. The average number of infested trees did not differ significantly between baited plots. However, means in baited plots differed significantly from means in the control plots

The role of the Douglas-fir beetle and wood borers in the decomposition of and nutrient release from Douglas-fir logs

The role of insects in the decomposition of and nutrient release from Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) logs was studied in the Cedar River Watershed near Seattle, Washington. In April 1976, two large-diameter (average diameter at breast height, 41.7 cm) and two small-diameter (average diameter at breast height 26.3 cm) trees were felled. Three pairs of 91 cm length sections were cut from each tree. Half the sections were covered with window screening to prevent insect entry. The number of Douglas-fir beetle (Dendroctonuspseudotsugae Hpk.) attacks on each section, as well as the frass production, were monitored. After 10 years, decomposition rates were determined by mass loss. Douglas-fir beetles attacked large-diameter (23 attacks/m2) and small-diameter (27 attacks/m2) log sections at similar rates. Total frass production was also similar (33.6 g•m−2 for large logs and 32.6 g•m−2 for small logs). Large-diameter unscreened log sections tended to decompose faster (k = 0.050 per year) than small diameter unscreened logs (k = 0.026 per year) owing to the presence of wood borers (Monochamusscutellatus (Say)) in the larger logs. Screening of logs to reduce insect attack tended to reduce the rate of decomposition. A brown rotting fungus (Oligoporusplacentus (Fr.) Gilb. and Ryv.) fruited on unscreened large-diameter logs. Wood borers had a greater influence on log decomposition than Douglas-fir beetles. Frass produced by the Douglas-fir beetle contributed very little to litter fall and nutrient cycling. After 10 years there was a net release of N, P, K, Ca, and Mn from decomposing logs. Only Mg was immobilized in large-diameter logs.