Attack Density Research Articles

WITHIN-TREE DYNAMICS OF MASS ATTACK BY DENDROCTONUS PSEUDOTSUGAE (COLEOPTERA: SCOLYTIDAE) ON ITS HOST

AbstractThe within-tree scale dynamics of mass attack by the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, on its host were investigated and quantified. Seven similarly sized Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco (Pinaceae), infested as part of several pheromone-induced infestations, were monitored over an entire attack season. Ninety percent of the attacks on mass-attacked trees occurred within 3 weeks of colonization; the remaining 10% occurred gradually over the remaining 7 weeks of the attack season. Vertical attack distribution followed a Gaussian form that shifted upwards on the bole with increasing attack density. The change in attack pattern associated with increasing attack density was investigated for the central vertical portion of the bole, where most attacks occurred, and where the vertical pattern was least variable. At low density, attacks were randomly distributed. As density increased, the distance between attacks decreased, eventually resulting in a uniform distribution.

Susceptibility of Fire-damaged Pine trees (Pinus pinaster and Pinus nigra) to Attacks by Ips sexdentatus and Tomicus piniperda (Coleoptera: Scolytidae)

During 1997 and the spring of 1998, a study to observe the colonization of burnt pine forests by bark beetles in the Castilla y Le6n region was carried out. Ferreras de Abajo is a reforested area of 640 ha of Pinus pinaster Ait. burnt in VI 1996 and located in the province of Zamora. The second locality: Rioseco de Tapia belongs to the province of Le6n, with 234 ha of Pinus nigra Arn. burnt in V, 1996. In each locality a sampling area of 900 m 2 was chosen and two kind of trees were marked: 12 'red' trees, entirely burnt and 12 'yellow' trees, partly burnt. The main objective of this study was to find out the species of bark beetles that colonize burnt pine trees two consecutive years after a wild fire, the sequence and distribution of attacks, attack density, and the life cycles of the two most representative species.

Impacts of Tomicus minor on distribution and reproduction of Tomicus piniperda (Col., Scolytidae) on the trunk of the living Pinus yunnanensis trees

This study investigated the impacts of Tomicus minor on Tomicus piniperda when the two Tomicus species coexist in the trunks of living Yunnan pine (Pinus yunnanensis L.) trees growing in the Kunming region, in south‐western China. Tomicus piniperda mostly locates in the mid‐ and upper trunks of Yunnan pine tree; whereas T. minor mainly attacks the mid‐ and lower trunks. In the mid‐trunk area from 1.0 to 5.0 m above ground, there are overlapping attack zones for the two Tomicus species, which accounts for an average of 80% of the entire zone occupied by T. piniperda and an average of 70% of the zone occupied by T. minor. In correspondence with their attack distributions, the average attack densities of the two species varied with height along the trunk, with 165.3 egg galleries per m2 at a height of 6 m for T. piniperda, and 138.2 egg galleries per m2 at the 1 m height for T. minor. It is suggested that T. minor adjusts its attack pattern with respect to T. piniperda, and thereby minimizes interspecific competition. No remarkable difference of average T. piniperda egg gallery length was found between the zone in which only T. piniperda occurred and the zone in which T. piniperda and T. minor coexisted; this is suggested to be due to low host quality in the upper trunk region where only T. piniperda was present. The number of T. piniperda larval galleries was highest when only T. piniperda was present, and decreased as T. piniperda and T. minor coexisted, particularly in the case when the density of T. piniperda was less than that of T. minor. Average larval density was 1649 larval galleries per m2 where only T. piniperda occurred. However, when T. piniperda coexisted with T. minor, T. piniperda larval density averaged 1010 per m2 when T. piniperda density was higher than T. minor, and averaged 442 per m2 when T. piniperda density was less than T. minor, which led to the conclusion that T. minor makes a negative impact on T. piniperda reproduction when the two Tomicus species jointly colonize the same trunk of Yunnan pine tree.

Translocation and Efficacy of a Neem-Based Insecticide in Lodgepole Pine Using Ips pini (Coleoptera: Scolytidae) as an Indicator Species

Recent research suggests that mountain pine beetles, Dendroctonus ponderosae Hopkins, may be controlled on pine using systemic applications of extracts from seeds of the neem tree, Azadirachta indica A. Jussieu. We investigated the extent of translocation of neem extracts in the bole of lodgepole pines, Pinus contora variety latifolia Engelmann. Because attacks by D. ponderosae do not always occur high on the bole of standing trees, the pine engraver, Ips pini Say, was used as an indicator species. A proprietary emulsifiable concentrate formulation of neem seed extract containing 20,000 ppm azadirachtin was applied into a basal axe frill around the root collar of lodgepole pines. After 1 wk the trees were felled and the logs were baited at 3, 9, and 15 m from the base with the pheromone ispdienol to induce attack by I. pini. Six weeks later, bolts were removed from the trees at the bait positions and held for a further 16 wk in rearing. At 3 and 9 m from the base, populations of I. pini (emerged and remaining under the bark) were significantly reduced by 87 and 77%, respectively, indicating that the active ingredients translocated at least 9 m up the bole and persisted for at least 6 wk. Numbers of emergence holes also were significantly reduced by 89, 88, and 63% at 3, 9, and 15 m, suggesting that the translocation extended beyond 9 m. Neem treatment had no impact on gallery construction and attack density, but significantly reduced the number of progeny per egg gallery. Unlike the currently used systemic arsenical, neem extracts would pose no toxicity to vertebrates and would have a short residual activity in the environment. There would be little chance of resistance developing because of neem's multiple modes of action and the fact that very few infested trees in a given year would ever be treated.

Susceptibility of defoliated Scots pine to spontaneous and induced attack by Tomicus piniperda and Tomicus minor

In 1990–1991, Diprion pini extensively defoliated Scots pine (Pinus sylvestris L.) trees in Lauhanvuori National Park in southwestern Finland. Many trees lost all their foliage, while others had ca. 10% foliage left after the second year of defoliation. Outside the national park, many nearby stands were also heavily defoliated in 1990, but were sprayed with diflubenzuron (Dimilin®) in 1991. This protected the current year needles, corresponding to ca 30% of full foliage. In spring 1992, pine trees with 0, 10, 30 and 100% foliage remaining (10 small and 10 large trees in each category) were baited with pine bolts to induce stem attacks by pine shoot beetles. All baited trees were attacked by Tomicus piniperda and some by T. minor. The attacks failed in all these trees except those that were totally defoliated and some of the small trees with 10% foliage left. Many unbaited trees escaped attack entirely, but only totally defoliated trees were successfully colonized (i.e. produced brood). Attack densities and brood production figures peaked in baited, large and totally defoliated trees. None of the measures (cambial electrical resistance, resin flow, induced lesion length by fungal inoculation, amount of hydrocarbons or phenolic compounds) used to describe tree vigour at the time of attack gave better information than the estimated remaining foliage. We conclude that the risk for beetle-induced mortality following defoliation is a function of remaining needle biomass and beetle pressure. Even at high beetle densities (as was simulated by baiting of trees), trees with 10% of the foliage remaining were able to defend themselves against attacking pine shoot beetles.

Scramble competition in the southern pine beetle, Dendroctonus frontalis

Abstract.1. The nature of intraspecific competition was investigated in the southern pine beetle, Dendroctonus frontalis, a highly destructive pest of pine forests in the southern U.S.A. Data were analysed from an observational study of naturally‐attacked trees, and from field experiments where attack density was manipulated by adding different numbers of beetles to caged trees.2. The effect of attack density on gallery construction, oviposition, brood survival, and the overall rate of increase was examined, and a flexible model of intraspecific competition used to classify the type of competition (contest or scramble) at different points in the life cycle.3. The results of these analyses suggest that contest competition occurs during gallery construction and oviposition, in accord with previous work on D. frontalis. Strong scramble competition occurs later on in development, however, and the overall competitive process is better characterized as scramble competition, similar to other bark beetles. Trees with attack densities sufficiently high to produce significant competition are common in the field.

Semiochemical-Induced Competition Between Dendroctonus rufipennis and Two Secondary Species, Ips tridens and Dryocoetes affaber (Coleoptera: Scolytidae)

We investigated the hypothesis that interspecific interactions between the spruce beetle, Dendroctonus rufipennis Kirby, and 2 secondary species, Ips tridens Mannerheim and Dryocoetes affaber Mannerheim, adversely affect species beetle progeny production and survival. In field experiments in the British Columbia interior, attack by the secondary species was induced by placing pheromone baits on felled trees just after spruce beetle attack. Spruce beetle attack densities, gallery length per square meter, and progeny densities were significantly reduced in trees that were baited with D. affaber pheromones or D. affaber and I. tridens pheromones. Resource exploitation and synomonal interference with subsequent spruce beetle attacks were the primary competitive mechanisms. No evidence for direct interference was found. Because the impact of the secondary species was not pronounced, semiochemical-induced competitive displacement of the spruce beetle after it has established would not be practical for retarding the development of, or suppressing, beetle outbreaks.

Competitive Exclusion of Dendroctonus rufipennis Induced by Pheromones of Ips tridens and Dryocoetes affaber (Coleoptera: Scolytidae)

We tested the feasibility of competitive exclusion as a potential management tactic for the spruce beetle, Dendroctonus rufipennis Kirby, using pre-attack baiting with pheromones of 2 secondary species, Ips tridens Mannerheim and Dryocoetes affaber Mannerheim. Spruce beetle attack densities, gallery lengths per square meter, and progeny densities were significantly reduced by up to 78% in individual felled trees baited with the I. tridens pheromones (+/-)-ipsdienol and (-)-cis-verbernol, and the D. affaber pheromones (+/-)-exo-and (+)-endo-brevicomin, or pheromones of both secondary species. A simplified D. affaber bait consisting of only (+/-)-endo-brevicomin also significantly reduced spruce beetle attacks, resource exploitation, and progeny production. Baiting with I. tridens pheromones also reduced spruce beetle attack and success in simulated patches of windthrown trees. Resource exploitation and indirect interference by synomonal inhibition of spruce beetle attack are the most likely competitive mechanisms invoked. Competitive exclusion of the spruce beetle may provide an alternative management tactic where traditional methods based on tree removal, widespread harvesting, and the use of insecticides are not feasible.

Resource partitioning of four sympatric bark beetles depending on swarming dates and tree species

The niche relationships among bark beetle species attacking pines in northern Spain were studied at three localities with respect to tree species ( Pinus radiata and P. sylvestris) and swarming time. Four bark beetle species were found attacking the trees, but not all four species were present at all sites: Tomicus piniperda, Ips sexdentatus, Orthotomicus erosus and Pityogenes bidentatus. Niche width and overlap were affected by resource availability, arrival sequence and attack density. In general, T. piniperda showed the widest niche breadth and was the first swarming species. The largest niche overlaps were found at the sites where the resource was less limiting. The niche overlap between T. piniperda and O. erosus depended mainly on the swarming time. The portion of the niche of O. erosus occupied by T. piniperda was greater than that of T. piniperda occupied by O. erosus at the site in which T. piniperda swarmed first. In general, the bark species appeared segregated from each other, bark thickness being a good segregating factor.

Hydrogen Absorption into Aluminum Alloy 2024-T3 During Exfoliation and Alternate Immersion Testing

Exfoliation and alternate immersion corrosion were investigated in Al alloy 2024-T3 (UNS A92024) uptake during exposure and to correlate it with corrosion characterization. Characterization involved determination of weight loss, pitting density, and maximum depth of attack. Hydrogen uptake was determined by subsequent hydrogen evolution during heating. In both accelerated corrosion tests, pitting developed into intergranular corrosion and intergranular attack. Hydrogen penetrated through Al 2024-T3. In the exfoliation test, hydrogen concentration correlated well with the increase in available surface area during intergranular attack. There was indirect evidence that the first portions of hydrogen absorbed were arrested chemically inside the specimen. Free hydrogen (which evolves with mild heating) started to build up only after all active sites were occupied.

Multiscale experimental analysis of aggregative responses of mobile predators to infaunal prey

Aggregative responses of predatory birds and fish to their prey are stronger at some spatial scales than others. In waders feeding on benthic invertebrates, aggregative responses decrease in strength at scales less than 100 m. However, decoupling of predator density or consumption rate from prey density at smaller spatial scales has not been tested experimentally. Three wader species (an endemic species, South Island Pied Oystercatcher Haematopus ostralegus finschi Martens, and the migratory species Red Knot, Calidris canutus rogersi (Mathews) and Eastern Bar-tailed Godwit, Limosa lapponica baueri Naumann) were abundant on an intertidal sandflat in Manukau Harbour, New Zealand before, during and after an experiment in which densities of their bivalve prey ( Macomona liliana Iredale) were manipulated on a small scale (0.5-m×0.5-m plots) within a 250-m×500-m study site. Faecal dropping analysis was used to confirm the diet of South Island Pied Oystercatchers and Red Knot, and to determine the diet of Bar-tailed Godwits. Based on knowledge of the foraging behaviour of these waders, we predicted the following responses to the experimentally-induced increases in bivalve density: 1. waders would discover and then focus their foraging on plots with experimentally elevated densities of Macomona liliana; 2. wader density within the study site would increase during the course of the experiment; and 3. wader density would then decrease when experimental plots were removed. To test these predictions the density and rate of prey attack by waders were measured before, during and after the density-manipulation experiment. Although the waders discovered the experimental aggregations of prey, there was no response at the scale of the plot, or at the larger scale of the study site. This study is the first experimental verification of no response by waders to small-scale increases in prey patchiness, where larger scale changes in patchiness were controlled. We hypothesize that a lower limit on the spatial scale of aggregative response is set by the mobility of prey relative to the predator—the patch structure of a relatively immobile prey will change on a much smaller scale than that of a highly mobile prey, and their respective predators become adapted accordingly.

Ambrosia Beetle Host Selection Among Logs of Douglas Fir, Western Hemlock, and Western Red Cedar with Different Ethanol and -Pinene Concentrations

Logs from Douglas fir, Pseudotsuga menziesii; western hemlock, Tsuga heterophylla; and western red cedar, Thuja plicata, were left in the forest through winter. In April, segments from these logs were removed and randomly positioned adjacent to one another allowing ambrosia beetles to select their preferred host. In early June the tissues of Douglas fir and western hemlock logs contained significantly higher ethanol concentrations and ambrosia beetle (Trypodendron lineatum and Gnathotrichus spp.) densities than logs of western red cedar. Low beetle attack densities in western red cedar were probably a consequence of low ethanol concentrations. Although Douglas fir tissues produced significantly higher ethanol concentrations than western hemlock, the beetles did not effectively discriminate between these two conifer species. Ethanol and α-pinene were significant covariates for the ambrosia beetle densities. α-Pinene concentrations were highest in the phloem of western red cedar, intermediate in Douglas fir, and nearly absent in western hemlock. α-Pinene did not synergize the beetle's response to ethanol or to ethanol + pheromone during host selection, and it may have functioned as a deterrent.

Dynamics of trophical niches of the winter pine shoot moth (Rhyacionia buoliana schiff., Lepidoptera: Tortricidae) and response of the protective system of the scots pine to the affection

From the position of trophical niche concept, the process of forming of an infestation spot of the winter pine shoot moth in a space of a pine stand as well as the process of degradation of this spot was studied. It was shown that the process begins with the emergance of separate microspots in a stand. With increasing age of the affected stand, the area of these microspots grows, and they unite themselves in lager ones together with growing pest density. The process of growth of both the area and the density continues to an age of 15 years of the pine stands. After that, the reverse process of degradation begins when the area and density decreases. On all the stages of the process, a distribution of density of the pest attacks on trees has contagious character, and stabilisation of an affected ecosystem is finished at the age of 20–30 years.

The influence of ethylene on primary attraction of the olive beetle,Phloeotribus scarabaeoides (Bern.) (Col., Scolytidae)

Two experiments have been carried out to verify the effect of ethylene on the primary attraction ofPhloeotribus scarabaeoides under both laboratory and field conditions. The experiments were based on the enhancement of ethylene production by olive branches and trunks after the application of (2-chloroethyl)phosphonic acid. Under laboratory conditions, the beetles' response was strongly stimulated on the treated branches. Under field conditions, the treatment aided the location of the olive wood by the flying beetles, and the attack density was significantly greater in the treated wood at the end of the experiment.

Regionally‐specific bioactivity of two new pheromones for Dendroctonus rufipennis (Kirby) (Col., Scolytidae)

Abstract: 1‐Methyl‐2‐cyclohexen‐1‐ol (MCOL) was shown for the first time to occur in the frass produced by female spruce beetles, Dendroctonus rufipennis (Kirby). MCOL and 4‐methylene‐6,6‐dimethylbicyclo[3.1.1]hept‐2‐ene (verbenene) were evaluated in five geographic locations for attractiveness to spruce beetles. In trapping experiments (±)‐ or (+)‐ MCOL enhanced attraction to a standard blend of α‐pinene with frontalin in two Alaska locations. (+)‐MCOL was attractive and (‐)‐MCOL inhibitory in south‐central British Columbia, and (+)‐, (‐)‐ and (±)‐MCOL were all weakly attractive in one of three experiments in southeastern British Columbia and northern Alberta. Verbenene was attractive only in combination with the standard blend plus MCOL in Alaska. In comparison with the standard bait, tree baits incorporating (±)‐ or (+)‐MCOL caused higher numbers of trees to be attacked in the interior Alaska locations and (+)‐ MCOL had the same effect in south‐central British Columbia. Density of attack on attacked trees was unaffected. (±)‐ or (+)‐MCOL could improve the operational efficacy of tree baits in Alaska, and (+)‐MCOL could be used in south‐central British Columbia. Our results indicate that for wide‐ranging scolytid species, operational evaluation of new semiochemicals should be regionally specific.

Freilandtest zur Attraktivität von Monoterpenen und Ethanol für den Borkenkäfer Tomicus piniperda L (Col., Scolytidae)

Abstract: Field investigations into the attraction of Tomicus piniperda L. (Col., Scolytidae) to monoterpens and ethanol. In northern German pine forests, ethanol and various monoterpenes have been tested in flight‐barrier slot traps and in combination with both trap trees felled 4 weeks before baiting and standing pines debarked at the same time near the ground by forming a 20‐cm‐wide barkless girdle around the stem. The host volatiles ethanol (et), (‐)‐α‐Pinene (ap), (‐)‐β‐Pinene (bp), terpinolene (tp) and the pheromones myrtenol (my) and transverbenol (tv), separately tested in traps, totally failed to lure Tomicus piniperda during the main flight period from 17th to 28th April, 1994. In combination however, these volatiles, except bp + et and tv + et, have been successful in slot traps, but at a very low level compared to some combinations at trap trees in the same pine stand. In traps, the combination my + bp + tp + et caught most (5 + 13 specimen in two replicates), but the differences with respect to my + tv + bp (9 + 4), to bp + tp + et (3 + 8), or to ap + et (2 + 8) are not significant (χ2 test for equality of frequencies in k classes). Additional monoterpene‐combinations on trap trees did not enhance the number of boring (entrance) holes: trap trees without any additional volatiles (untreated control) had 308 holes (two replicates: 83 + 225), trap trees with additional host volatiles (bp + tp + et) showed 285 (134 + 151) holes, but trap trees with pheromones combined with β‐Pinene (my + tv + bp) showed 25 (19 + 6) entrance holes only. This strong reduction in attack density points to a repellent effect of these pheromones when applied to trap trees. The standing pines which have been to be weakened by the narrow debarked girdle and treated the same way as the trap trees were not attacked at all. Thus, the main attractive components must come from trees more weakened than can result from this way of debarking, i.e. from felled (or windthrown) trees and, of course, from logs.These findings again reveal that aggregation pheromones do not play a substantial part in the chemical host‐recognition system of T. piniperda compared to the evident strong attraction of uninfested logs. The obvious question concerning the biological meaning of the existing pheromones such as transverbenol and myrtenol should lead to investigations into an eventual short‐distance communication system, e.g. for mate‐finding or — more likely — for spacing. The latter would demand a repellent effect of these pheromones, as observed in the trap‐tree experiment. The use of host volatiles in practical forest protection — if at all — will probably be restricted to trap‐based monitoring systems and biological control: the most economic and promising volatile combination is obviously ap + et, and this is also the case with respect to Swedish findings, according to which ap + et‐baited logs had much less offspring of T. piniperda than unbaited logs had, as a result of the effect of lured predators and competitors.

ENANTIOMERIC COMPOSITION AND RELEASE RATES OF exo-BREVICOMIN INFLUENCE AGGREGATION OF THE WESTERN BALSAM BARK BEETLE, DRYOCOETES CONFUSUS SWAINE (COLEOPTERA: SCOLYTIDAE)

AbstractField experiments demonstrated that the western balsam bark beetle, Dryocoetes confusus, responded best to multiple-funnel traps baited with mixtures of (+)- and (−)-exo-brevicomin. (±)-exo-Brevicomin released at 0.8 mg per 24 h performed as well as or better than release rates of from 0.2 to 1.0 mg per 24 h in terms of the number of baited trees which were mass attacked (80%), average attack density, and average number of trees attacked within a 10-m radius of baited trees. Baiting more than one tree in a spot resulted in an intensification of attack on baited trees and increased the number of trees attacked within 10 m of each spot.

A preliminary study on the use of trap‐trees baited with ethylene for the integrated management of the olive beetle, Phloeotribus scarabaeoides (Bern.) (Col., Scolytidae)

AbstractRecent studies have established the importance of ethylene in the primary attraction of the olive beetle, Phloeotribus scarabaeoides. In light of this, two experiments were carried out in an olive grove in Granada province, Spain, these experiments utilized the increase of natural levels of ethylene produced by olive trees after the application of 2‐(chloroethyl)phosphonic acid. In the first experiment, a significant attraction of the emerging beetles for the treated trees was noted. The second experiment constitutes a first step in the use of poisoned ethylene‐baited trees in the integrated management of P. scarabaeoides. A barrier of trap‐trees sprayed with a mixture of 2‐(chloroethyl)phosphonic acid and lambda cyalothrine‐A had been set‐up along the edge of two selected plots of the olive grove. A significant reduction in the density of attacks and beetle population density has been observed in the zone located behind the barrier of trap‐trees. A decrease in the efficacy of the experimental set‐up was noted at the end of August. The factors influencing changes in density of beetle attack and population on the trees throughout the summer are discussed.

Wound reactions of Scots pine (Pinus sylvestris L) to attacks by Tomicus piniperda L. and Ips sexdentatus Boern. (Col., Scolytidae)

AbstractBark beetles Tomicus piniperda and Ips sexdentatus were artificially inserted in Scots pines. Attacks were also provoked in other trees by attractants. Resin flow corresponding to each introduction was measured in the case of artificial insertions. In all cases, gallery length, reaction zone length and the total quantity of induced resin contained in the whole reaction were measured 5–6 weeks after insertions or attacks. The attempt of gallery construction (beginning of gallery boring) and the beginning of oviposition were also noted in each case, as well as the presence of associated fungi.Resin flow discouraged T. piniperda, but not I. sexdentatus, to attempt a gallery construction. For the two beetle species, however, it played no role after gallery boring had started. Although tree induced reaction was present during gallery elongation, at least in the case of T. piniperda, it was not clear if it played a role in stopping gallery elongation and in failure of oviposition. Few beetles were killed by resin flow or by tree reaction. The existence of oviposition was not related to attack density, tree characteristics or presence of fungi. Fungi were involved in the development of the induced reaction in response to I. sexdentatus attacks, but not in response to T. piniperda attacks. When expressing reaction zone length or resin quantity as a function of gallery length, galleries where oviposition had begun were clearly separated from those where it had not. For galleries where oviposition did not occur, reaction zone length was always correlated with gallery length for T. piniperda, and not for I. sexdentatus, but in the latter case the correlations existed when considering only galleries without fungi. Accumulation of induced resin was always correlated with gallery length for the two species. Therefore, a tree's induced reaction is not basically a defense reaction. The results corroborate the hypothesis that it is a wound reaction induced by mechanical stress due to gallery boring, and amplified by fungi when they are effective. For T. piniperda, the beetle boring activity seems to be the only way to exhaust tree response capacity.

Attack Densities of Tomicus pintiperda and Ips pini (Coleoptera: Scolytidae) on Scotch Pine Logs in Michigan in Relation to Felling Date

Established populations of an exotic bark beetle, the larger pine shoot beetle [Tomicus piniperda (L.)], were first reported in Ohio in July 1992. Subsequent surveys through July 1994 have found T. piniperda in six states in the United States and in one Canadian Province in the Great Lakes region. One-meter-long trunk sections were cut from Scotch pine (Pinus sylvestris L.) trees felled from February through July 1993 in a forested site in southern Michigan, laid horizontally, allowed to undergo natural attack by bark beetles and associates, and later dissected. In southern Michigan in 1993, T. piniperda initiated spring flight in late March; the pine engraver [Ips pini (Say)], a native pine bark beetle, initiated spring flight about one month later in late April. Tomicus piniperda attacks (galleries) were found in logs cut during February through May. Attack densities of T. piniperda were highest in February-cut logs, and declined with subsequent felling dates. The highest T. piniperda attack density recorded for an entire log section was 263 attacks/m2 of bark area on one of the February-cut logs. Ips pini attack densities tended to increase with later felling dates. When I. pini attacked logs that had already been colonized by T. piniperda, I. pini galleries were mostly found on the upper log surface. When I. pini attacked logs with few or no T. piniperda, I. pini galleries were found on all log surfaces. By initiating spring flight several weeks before I. pini, T. piniperda is able to colonize much of the susceptible pine material and thereby may lower I. pini populations.