Intercepted Scolytidae (Coleoptera) at U.S. ports of Entry: 1985–2000

Since 1985, the U.S. Department of Agriculture, Animal and Plant Health Inspection Service has maintained the 'Port Information Network' (PIN) database for plant pests intercepted at the U.S. ports of entry. As of August 2001, PIN contained 6825 records of beetles (Coleoptera) in the family Scolytidae that had been intercepted during the years 1985–2000 from countries outside of North America. Of the 6825 scolytid interceptions, 2740 (40%) were identified to the species level, 2336 (34%) to only the genus level, and 1749 (26%) were identified to only the family level. Of the 49 identified scolytid genera, the 10 most common were Hypothenemus (821 interceptions), Pityogenes (662), Ips (544), Coccotrypes (520), Orthotomicus (461), Hylurgops (327), Hylurgus (266), Tomicus (194), Dryocoetes (166), and Hylastes (142). The 10 most common identified species were Pityogenes chalcographus (565 interceptions), Orthotomicus erosus (385), Hylurgops palliatus (295), Ips typographus (286), Hylurgus ligniperda (217), Ips sexdentatus (157), Tomicus piniperda (155), Hylastes ater (75), Hypothenemus hampei (62), and Polygraphus poligraphus (48). Of these 10 species, H. palliatus, H. ligniperda, and T. piniperda are known to be established in the continental U.S. The scolytids were intercepted from 117 different countries; the top 12 countries were Italy (1090 interceptions), Germany (756), Spain (457), Mexico (425), Jamaica (398), Belgium (352), France (261), China (255), Russia (247), India (224), U.K. (151), and Portugal (150). The scolytids were intercepted in 35 U.S. states and 97 port cities. In general, there was a positive relationship between the number of scolytid interceptions from individual countries and the value of the imports from those countries. Overall, 73% of the scolytids were found in solid wood packing materials, 22% in food or plants, and 5% in other or unspecified materials. The products most commonly associated with scolytid-infested wood packing materials were tiles, marble, machinery, steel, parts, ironware, granite, aluminum, slate, and iron. The food products and plants that were commonly infested with scolytids included nutmeg, palms, coffee beans, kola nuts, and macadamia nuts.     

Estimating risks for spruce bark beetle (Ips typographus (L.)) damage using pheromone‐baited traps and trees

The risk for damage associated with spruce bark beetle attacks on living trees was estimated in 12 forest districts in the Nordic countries during three years. Pheromone‐baited traps and trees were used. Five groups of three traps were deployed annually on fresh spruce clear‐fellings in each district. The mean catches within districts and years ranged from 950 to 46000 beetles per trap group. The standard error averaged 15 % of the mean catch. One tree was baited annually at each of five other sites in each district. The mean number of trees colonized by Ips typographus in each district and year ranged from 0 to 5 per site. The standard error was high, averaging 44% of the mean. Inventories of tree mortality within the districts yielded values ranging from 0 to 150 killed trees per km of spruce forest edge. There was a strong linear correlation between mean catches in traps and log‐transformed tree mortality (r=0.82). The correlation between colonization success at tree‐baiting sites and tree mortality was weaker (r=0.59), owing to one deviant observation. The results indicate that pheromone traps and baited trees may be used to assess the risk for damage caused by Ips typographus.     

After‐effects of drought did not predispose young Picea abies to infection by the bark beetle‐transmitted blue‐stain fungus Ophiostoma polonicum

The defence of Norway spruce against a combined attack of the bark beetle Ips typographus and its associated blue‐stain fungi is based upon a) constitutive resin stored in ducts of the bark and sapwood, and b) induced resinosis in reaction zones surrounding the point of infection. Empirically, beetle epidemics are associated with external stresses, drought being a particularly prominent factor. An attempt was made to mechanistically explain the apparent link between drought and infestations, through studying after‐effects of drought on the induced defence in stressed trees. In the field, 3–5.5 m tall trees were exposed to artificial drought over three growth seasons to investigate whether this treatment would predispose them to fungal infection in a fourth season when drought was absent. Pre‐dawn xylem water potentials down to ‐1.85 MPa and a considerable foliage depletion were recorded. In the fourth season, the trees were inoculated with Ophiostoma polonicum, a pathogenic associate of Ips typographus. No difference in susceptibility could be seen between drought stressed trees and unstressed controls. Carbohydrate concentrations of foliage and branch bark were slightly enhanced and mineral nutrient concentrations strongly reduced in stressed trees.     

Aerially applied methylcyclohexenone-releasing flakes protect Pseudotsuga menziesii stands from attack by Dendroctonus pseudotsugae

We tested methylcyclohexenone (MCH), an anti-aggregation pheromone for the Douglas-fir beetle (Dendroctonus pseudotsugae), for protection of Douglas-fir (Pseudotsuga menziesii) stands by applying MCH-releasing polymer flakes by helicopter twice during summer 2006 to five 4.05-ha plots in the State of Washington, USA. Five similar plots served as untreated controls. We assessed D. pseudotsugae flight into study plots using baited pheromone traps, and tallied D. pseudotsugae attack rates on all P. menziesii trees in 2005 and 2006. We also measured stand basal area and incorporated that as an explanatory variable in the analysis. Significantly fewer D. pseudotsugae were trapped in treated plots than in control plots, and significantly fewer P. menziesii trees were attacked in treated plots than in control plots. The attack rate in untreated stands was nearly 10 times that of treated plots, and stands with higher basal area were significantly more likely to be attacked by D. pseudotsugae than were stands of lower basal area. Attack rates in 2006 and 2005 were significantly correlated, regardless of treatment.     

Protection of spruce from colonization by the bark beetle, Ips perturbatus, in Alaska

Field bioassays were conducted in south-central Alaska in a stand of Lutz spruce, Picea × lutzii, to determine whether a semiochemical interruptant (verbenone and trans-conophthorin) and/or a defense-inducing plant hormone (methyl jasmonate, MJ) could be used to protect individual standing trees from bark beetle attack. During two experiments (initiated in May 2004 and 2005, respectively), attacks by Ips perturbatus on standing trees were induced by using a three-component aggregation pheromone (ipsenol, cis-verbenol, and ipsdienol) and prevented by using the interruptant. In 2005, treatments from 2004 were repeated and additional treatments were evaluated by using MJ spray or injection with and without the interruptant. Aggregation began before 3 or 7 June, and attack density was monitored through 3 or 16 August. During both years, tree mortality caused by I. perturbatus was recorded twice (in August, and in May of the following year). In both experiments, attack density was greatest on trees baited with the three-component attractive pheromone, but was significantly reduced by addition of the semiochemical interruptant to trees baited with the attractant. There were no significant differences in attack density between attractant + interruptant-treated trees and unbaited trees. In 2004, mortality was highest among attractant-baited trees, whereas addition of the interruptant significantly reduced the level of initial (10 week post-treatment) and final (54 week post-treatment) mortality. In 2005, no significant reduction in attack density occurred on trees baited with the attractant when MJ was sprayed or injected. The highest initial (10.6 week post-treatment) and final (49.4 week post-treatment) mortality was observed among trees that had been injected with MJ and baited with the attractant. Mortality at the final assessment was significantly lower in all other treatment groups. As in 2004, addition of the interruptant to attractant-baited trees significantly reduced the level of final mortality compared to attractant-baited trees. MJ was not attractive or interruptive to I. perturbatus or associated bark beetles in a flight trapping study. However, MJ-treated trees (sprayed or injected) exuded copious amounts of resin on the bark surface. Anatomical analyses of felled trees from four treatment groups [Tween (solvent)-sprayed, MJ-sprayed, Tween-injected, and MJ-injected + attractant baited] showed that treatment with MJ increased the number and size of resin ducts produced following treatment. These analyses also revealed a reduction in radial growth in MJ-treated trees. Our results show that during both years, treatment with a simple, two-component interruptant system of verbenone and trans-conophthorin significantly reduced I. perturbatus attack density and tree mortality on attractant-baited trees and provided a full year of protection from bark beetle attack.     

Potential for Nonhost Volatiles as Repellents in Integrated Pest Management of Ambrosia Beetles

Semiochemical-based mass trapping of the striped ambrosia beetle, Trypodendron lineatum (Olivier) (Coleoptera: Scolytidae), has been the cornerstone of an integrated pest management (IPM) programme for ambrosia beetles on the British Columbia coast since 1981. However, there is no available tactic of protecting logs from attack that could be incorporated into the IPM programme. We tested nonhost volatiles (NHVs) from the bark of angiosperm trees for their ability to disrupt catches of T. lineatum in multiple-funnel traps baited with the aggregation pheromone lineatin. In one set of experiments, a blend of 1-hexanol and benzyl alcohol caused 77.9% and 80.0% reduction in captures of males and females, respectively, and in another a blend of methyl salicylate and salicylaldehyde caused reductions of 65.0% for males and 66.9% for females. All four NHVs combined caused reductions in captures for males and females of 82.3% and 81.4%, respectively, not much greater than to the blend of 1-hexanol and benzyl alcohol. However, because both blends were active alone, their redundancy when combined lends confidence to the selection of the four-component blend for operational testing. Although disruption was increased when a 16-component NHV blend was tested, or when (±)–(E)-conophthorin was added to the four-component blend, addition of more compounds to the four-component blend was not considered operationally or economically justifiable. When deployed from low-density polyethylene tubes stapled along the length of pheromone-baited conifer logs, this blend caused prolonged and significant reductions in landing by T. lineatum and also by Gnathotrichus sulcatus (LeConte) and G. retusus (LeConte) (Coleoptera: Scolytidae). However, attacking beetles generally overcame the NHV treatment by the end of the flight period, leading to similar attack densities on treated and control logs. Therefore, we recommend that further operational investigations explore using repellent NHVs in combination with disruptive visual, tactile or gustatory stimuli.     

Non-Host Volatiles Disrupt the Response of the Stenographer Bark Beetle, Ips sexdentatus (Coleoptera: Scolytidae), to Pheromone-Baited traps and Maritime Pine Logs

Non-host volatiles (NHV) were tested on antennae of Ips sexdentatus with coupled gas chromatographic-electroantennographic detection (GC-EAD). Significant antennal responses were found to aggregation pheromone components, ipsdienol and amitinol, an attraction inhibitor, verbenone, and non-host bark volatiles extracted from Betula pendula, including trans-conophthorin (tC) and alcohols. The tC, a blend of three green leaf alcohols (C6-alcohols), and a blend of two bark alcohols (C8-alcohols) were tested in combination for their ability to disrupt the attraction of the stenographer bark beetle to pheromone-baited traps, unbaited and pheromone-baited maritime pine logs. The strongest disruptive effect resulted from the addition of the tC combined with the blends of NHV alcohols at high release rate, achieving an 83% reduction in trap catches, 89% reduction of attacks on unbaited pine logs, and 60% on baited logs. It is proposed that the two types of NHV have an additive effect, tC playing a major role in pheromone disruption while the alcohols would interrupt host specific signals. The results suggest that I. sexdentatus uses both bark and green leaf volatiles from non-host tree species in the host selection process. These NHV are promising disruptants, which could be used to prevent stenographer bark beetle attacks on log piles or standing trees in forest. A mixture of conifers and broad-leaved species would also disturb olfactory guided host selection supporting the assumption that more diverse forests are less prone to pest insect outbreaks.     

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 β-pinene, 3-carene, -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.     

Larssoniella duplicati n.sp. (Microsporidia, Unikaryonidae), a newly described pathogen infecting the double-spined spruce bark beetle, Ips duplicatus (Coleoptera, Scolytidae) in the Czech Republic

Larssoniella duplicati n.sp. infects the midgut muscularis, the Malpighian tubules, and the ovaries of adult Ips duplicatus (Sahlb.) in the Czech Republic. The microsporidian attacks up to 50% of the population. Oval spores of two sizes, 3–3.5×1.5–2 and 2–2.5×1.5 μm have the polar filament coiled in 6/7 coils, representing primary and environmental spores, respectively. In early sporogony the young spores produce long electron dense threads and tubules of secretions, which remain fixed around the spore and avoid their free release during dissection of infected hosts. The microsporidian was not found in associated bark beetles such as Ips typographus (L.), or I. amitinus (Eichh.) and others.     

Interactions between<Emphasis Type="Italic"> Orthotomicus erosus</Emphasis> (Woll.) (Col., Scolytidae) and the Argentine ant<Emphasis Type="Italic"> Linepithema humile</Emphasis> (Mayr) (Hym., Formicidae)

Interactions occurring between Orthotomicus erosus, an economically important pine bark beetle in Portugal, and the aggressive Argentine ant Linepithema humile were investigated. Tri-trophic experimental enclosures consisting of Pinus pinaster logs, O. erosus adults and L. humile workers were set up in the field and in the laboratory. Interactions between ants and scolytids were observed and quantified in terms of the bark beetles success in colonizing the logs. The presence of L. humile did not influence the ability of O. erosus to colonize the logs, apparently due to the difficulties met by the ants in handling the bark beetles and to their inability to injure them. Thus, although abundant in many pine stands in Portugal and in spite of its aggressiveness, L. humile does not seem to affect populations of O. erosus.