Stephen P. Cook

Nitrogen Concentration in Mountain Pine Beetle Larvae Reflects Nitrogen Status of the Tree Host and Two Fungal Associates

ABSTRACT Individual lodgepole pines (Pinus contorta) were fertilized with urea at nitrogen (N) inputs equivalent to 0, 315, or 630 kg/ha. Four months after application of the fertilizer, inner bark tissue N concentrations were significantly higher in the trees that had received the low dose (315 kg/ha) fertilization treatment than in the control trees; trees that had received the high-dose treatment (630 kg/ha) were intermediate and not significantly different from either of the other treatments. There was a significant positive correlation between N concentration in inner bark tissue and larval mountain pine beetle, Dendroctonus ponderosae (Coleoptera: Curculionidae, Scolytinae). In vitro studies on synthetic growth media examined effects of temperature and N concentration on N concentration of two common fungal associates of the mountain pine beetle (Ophiostoma clavigerum and Ophiostoma montium). Increasing N concentration in growth media significantly increased fungal N concentrations in both O. clavigerum and O. montium. Furthermore, N concentration was consistently higher in O. clavigerum than in O. montiun. Neither species had sufficient growth at 30°C, nor did O. clavigerum at 15°C, to test N concentration. However, for O. montium, increasing temperatures decreased fungal N concentrations. There was no correlation between N concentration of O. clavigerum and growth temperature. Potential impacts of ingestion of the fungal species by developing mountain pine beetle larvae-infesting trees under various environmental conditions such as increasing temperatures are discussed.

Defence syndromes in lodgepole – whitebark pine ecosystems relate to degree of historical exposure to mountain pine beetles

Warming climate is allowing tree-killing bark beetles to expand their ranges and access naïve and semi-naïve conifers. Conifers respond to attack using complex mixtures of chemical defences that can impede beetle success, but beetles exploit some compounds for host location and communication. Outcomes of changing relationships will depend on concentrations and compositions of multiple host compounds, which are largely unknown. We analysed constitutive and induced chemistries of Dendroctonus ponderosaes primary historical host, Pinus contorta, and Pinus albicaulis, a high-elevation species whose encounters with this beetle are transitioning from intermittent to continuous. We quantified multiple classes of terpenes, phenolics, carbohydrates and minerals. Pinus contorta had higher constitutive allocation to, and generally stronger inducibility of, compounds that resist these beetle-fungal complexes. Pinus albicaulis contained higher proportions of specific monoterpenes that enhance pheromone communication, and lower induction of pheromone inhibitors. Induced P. contorta increased insecticidal and fungicidal compounds simultaneously, whereas P. albicaulis responses against these agents were inverse. Induced terpene accumulation was accompanied by decreased non-structural carbohydrates, primarily sugars, in P. contorta, but not P. albicaulis, which contained primarily starches. These results show some host species with continuous exposure to bark beetles have more thoroughly integrated defence syndromes than less-continuously exposed host species.

Diversity of the beetle (Coleoptera) community captured at artificially-created snags of Douglas-fir and Grand fir

Snags are dead standing trees that have been killed by such forces as fire, wind, lightning, insects/disease, drought and/or flooding. Snag management includes such practices as protecting/maintaining existing snags and artificially creating additional snags. Snags can be used by the insect community that occurs on a site. The objective of the current study was to describe and compare the abundance, species composition and diversity of the beetle community captured adjacent to artificially created snags of Douglas-fir, Pseudotsuga menziesii var. glauca Franco, and Grand fir, Abies grandis (Douglas) Lindley. Beetle populations directly adjacent to the artificially created snags were monitored throughout the season using Lindgren-funnel traps placed directly adjacent to snags. A total of 27,428 beetles from 28 families were captured from May through September, 2002. Significantly more beetles were captured adjacent to the Douglas-fir snags than the Grand fir snags. Beetle capture was highest in late May and lowest in early August. Family richness of the captured beetle community was similar at traps adjacent to the Douglas-fir and Grand fir snags but family diversity was lower at traps adjacent to the Douglas-fir snags. A single species, Hylastes nigrinus (Mannerheim) (Curculionidae: Scolytinae), dominated the early capture peak. Ten genera of scolytids and at least 14 species were captured. An additional 10 genera (16 species) of other curculionids were captured. The population of these other curculionids was similar in abundance, richness and diversity at both the Douglas-fir and Grand fir snags. There were 12 species (7 genera) of Buprestidae captured and the total population was also similar adjacent to both snag species. The Cerambycidae captured during the study represented 26 species, with species richness and diversity being higher adjacent to the Grand fir snags.

LepNet: The Lepidoptera of North America Network

The Lepidoptera of North America Network, or LepNet, is a digitization effort recently launched to mobilize biodiversity data from 3 million specimens of butterflies and moths in United States natural history collections (http://www.lep-net.org/). LepNet was initially conceived as a North American effort but the project seeks collaborations with museums and other organizations worldwide. The overall goal is to transform Lepidoptera specimen data into readily available digital formats to foster global research in taxonomy, ecology and evolutionary biology.

Bumble bee (Hymenoptera: Apidae) community structure on two sagebrush steppe sites in southern Idaho

Abstract Although sagebrush, Artemisia spp., does not require an insect pollinator, there are several native species of bumble bees, Bombus spp. (Hymenoptera: Apidae), that are present in sagebrush steppe ecosystems where they act as pollinators for various forbs and shrubs. These native pollinators contribute to plant productivity and reproduction. We captured 12 species of bumble bees (437 individuals) at two sites during this study. The three most commonly captured species of Bombus at the first site (Red Mountain in the Targhee-Caribou National Forest) were B. rufocinctus Cresson, B. fervidus and B. melanopygus Nylander. Bombus fervidus dominated the trap catch at the second site (Lave Lake Land and Livestock) followed by B. rufocinctus and B. californicus consanguineus Smith. When numerous species of bumble bees co-occur on a given site, the community must have some mechanism for partitioning the available resources for the coexistence to occur. Along with temporal separation that was demonstrated by monthly differences in the capture of several of the individual species of bumble bees at both study sites, differences in capture of individual species of bumble bees was influenced by trap color. The differences observed among the species of Bombus we captured at the two sites may serve to limit competitive interactions among some of the species. Further, more bumble bees were captured in traps placed in the plots with the lowest percentage of sagebrush in the canopy. The results suggest that sagebrush steppe habitats can harbor a diverse community of native bumble bees and that multiple Bombus species can coexist on these sites. To maintain these diverse bumble bee communities, some portion of the sites should be managed to have little to no sagebrush in the canopy.

Examining olfactory and visual cues governing host-specificity of a weed biological control candidate species to refine pre-release risk assessment

In weed biological control programs, pre-release host-specificity testing relies traditionally on no-choice and choice feeding, oviposition, and development tests. Rarely have they included detailed examination of behavioral responses to olfactory and visual cues of biological control candidates, although a better understanding of the mechanisms underlying host recognition may explain potential discrepancies between choice and no-choice tests, and/or between tests conducted in the lab versus field conditions. We investigated how the seed-feeding weevil, Mogulones borraginis, distinguishes its host plant, Cynoglossum officinale, from three native confamilial non-target species in North America. In behavioral bioassays, M. borraginis responded to olfactory and visual cues individually and, to an even greater extent, to both plant cue modalities when offered simultaneously. In tests with the combined cues, M. borraginis was attracted to C. officinale but responded with indifference or was repelled by non-target plants. In electrophysiological experiments, we identified that M. borraginis responded to ten volatile compounds and four wavelengths of lights from inflorescences of C. officinale. We propose that studies of responses to multimodal plant cues can advance our understanding of how biocontrol candidate species discriminate among host plants and closely related non-target species, thereby increasing the accuracy of environmental safety assessments pre-release.

Comparison of trap types for surveying insect communities in Idaho sagebrush steppe ecosystems

Abstract Insects represent an abundant and diverse group of community members throughout terrestrial ecosystems. Because of their abundance and diversity, insects can be useful for monitoring and assessing change and disturbance within ecosystems. However, to utilize insects as indicators of change, the individual insect components present within ecosystems must be identified. We compared the use of several passive (non-baited) trap types on two sagebrush steppe sites in southern Idaho. Species of insects in 12 orders were captured at the two sites, with the most abundant numbers captured in the orders Microcoryphia, Hemiptera, Diptera, Coleoptera and Hymenoptera. A combined total of 23,579 insects were captured during the 3, 5-day sample periods, of which 3342 were beetles (Coleoptera). Pitfall traps and Japanese beetle traps provided the most information on abundance and richness of both the overall insect and beetle communities present on the sites. Blue Japanese beetle traps proved very effective at capturing beetles, especially members of the Melyridae. Monthly comparisons indicated that different taxa may be best sampled during different months, but more individuals were captured in June versus May at both sites and June captures provide the highest numbers for ordinal and beetle family richness at both sites.

Laboratory and Field Evaluation of Tebufenozide, Diflubenzuron, and Bacillus thurengiensis var kurstaki for Suppression of Douglas-fir Tussock Moth (Orgyia pseudotsugata (Mcdunnough)) in Idaho: A Case Study

The insect growth regulator tebufenozide (MIMIC 2LV) was tested to examine its impact on the Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough) (Lepidoptera: Lymantriidae). Laboratory tests gave an estimated concentration of 1.26 ppm of the compound to achieve 50% population mortality (LC50) for second-instar O. pseudotsugata. At the highest concentration tested, tebufenozide resulted in significant larval mortality within 7 d with an estimated time to 50% population mortality (LT50) of 6.3 d. A field comparison oftebufenozide with diflubenzuron (Dimilin 4L) and Bacillus thurengiensis var. kurstaki (Btk, FORAY 48B) was also conducted. There was no significant difference in larval mortality within field plots that were treated with diflubenzuron (42.4%) or Btk (44.8%). Larval mortality in the tebufenozide-treated plots (56.8%) was also similar to the mortality in the diflubenzuron and Btk treatments. All three treatments resulted in more larval mortality than that measured in untreated controlplots (11.2%). Both tebufenozide and diflubenzuron treatments resulted in significantly more mortality (55.0% and 40.0%, respectively) to larvae-fed treated foliage 3 wk after application than was measured for larvae-fed foliage from untreated trees (11.0%). There was no significant difference among the treatments in the percentage of host trees in the overstory that sustained >25% defoliation, and all three treatments resulted in less defoliation than was measured in the control plots. There was no significant difference among the treatments in the percentage of host trees in the understory that sustained >25% defoliation.

Anatomical defenses against bark beetles relate to degree of historical exposure between species and are allocated independently of chemical defenses within trees: Resin ducts of lodgepole and whitebark pine

Conifers possess chemical and anatomical defences against tree-killing bark beetles that feed in their phloem. Resins accumulating at attack sites can delay and entomb beetles while toxins reach lethal levels. Trees with high concentrations of metabolites active against bark beetle-microbial complexes, and more extensive resin ducts, achieve greater survival. It is unknown if and how conifers integrate chemical and anatomical components of defence or how these capabilities vary with historical exposure. We compared linkages between phloem chemistry and tree ring anatomy of two mountain pine beetle hosts. Lodgepole pine, a mid-elevation species, has had extensive, continual contact with this herbivore, whereas high-elevation whitebark pines have historically had intermittent exposure that is increasing with warming climate. Lodgepole pine had more and larger resin ducts. In both species, anatomical defences were positively related to tree growth and nutrients. Within-tree constitutive and induced concentrations of compounds bioactive against bark beetles and symbionts were largely unrelated to resin duct abundance and size. Fewer anatomical defences in the semi-naïve compared with the continually exposed host concurs with directional differences in chemical defences. Partially uncoupling chemical and morphological antiherbivore traits may enable trees to confront beetles with more diverse defence permutations that interact to resist attack.

Insects emerging from novel species of host trees attacked by mountain pine beetle, Dendroctonus ponderosae Hopkins, 1902 (Coleoptera: Curculionidae: Scolytinae), in the University of Idaho Arboretum

Abstract. A naturally-occurring infestation of mountain pine beetle, Dendroctonus ponderosae Hopkins, 1902 (Coleoptera: Curculionidae: Scolytinae), in the Shattuck Arboretum on the campus of the University of Idaho, Moscow, was found to be attacking non-native conifers. The arboretum had experienced a prior infestation in similar tree species in the late 1960s (Furniss & Schenk 1969). Infested trees were harvested, and an approximately 0.3-m section of each tree was cut from a height of 10 m on the bole and maintained under laboratory conditions. All insects that emerged from the bolts were collected and identified. In the current infestation, trees successfully attacked by mountain pine beetle included jack pine (Pinus banksiana Lamb.), Austrian pine (P. nigra L.), red pine (P. resinosa Sol. Ex Alton), pitch pine (P. rigida Mill.), eastern white pine (P. strobus L.), Scots pine (P. sylvestris L.), Norway spruce (Picea abies H. Karst.) and white spruce (P. glauca (Moench) Voss). A total of 777 mountain pine beetle were captured as they emerged from the bolts, and emergence densities of the beetle were similar across tree species. Insects from three orders, 15 families and 27 species emerged from the bolts. Species richness of the emerged insect assemblages were similar across tree species. Shortleaf pine had the largest number of emerged species of insects captured, followed by white spruce and eastern white pine.