Sandra Kegley

Biology of Dendroctonus murrayanae (Coleoptera: Curculionidae: Scolytinae) in Idaho and Montana and Comparative Taxonomic Notes

Abstract We studied the biology of Dendroctonus murrayanae Hopkins (Coleoptera: Curculionidae: Scolytinae) in lodgepole pine, Pinus contorta Douglas, in Idaho and Montana. The beetle was not a primary agent of tree mortality. Susceptible host trees were physically damaged, had thin foliage, or were otherwise predisposed to infestation. Beetles attacked individual trees, not in groups, near ground level and at low density. Life stages and their behavior are described. Egg galleries were constructed upward and usually had short spurs. Mating occurred in the egg gallery. Eggs were laid in an elongated group, not in niches, in a shallow excavation along only one side of the egg gallery. Larvae aggregated in a communal chamber, feeding side by side, but separated before pupation. D. murrayanae has four instars. One annual generation is indicated, overwintering as larvae. D. murrayanae occurred in some trees with Pseudips (=Ips) mexicanus (Hopkins), Ips pini (Say), and Hylurgops porosus (LeConte) but seldom with the mountain pine beetle, Dendroctonus ponderosae Hopkins. No natural enemy or commensal insect was observed in brood chambers. A new character on the frons is described and the relationship of D. murrayanae and the spruce beetle, Dendroctonus rufipennis (Kirby), is discussed.

Comparative Efficacy of Adult and Larval Sampling for Detection of the Root-Boring Insects Agapeta zoegana (Lepidoptera: Cochylidae) and Cyphocleonus achates (Coleoptera: Curculionidae) Released for Biological Control of Spotted Knapweed

Abstract In biological control projects, establishment of released natural enemies is a key step and must be efficiently detected. We studied the relative efficacy of larval versus adult sampling to detect establishment on spotted knapweed, Centaurea maculosa Lamarck, of the two root feeding insects Agapeta zoegana L. and Cyphocleonus achates (Fahraeus). Larval sampling was based on excavation and dissection of plant roots. Adult sampling consisted of either sighting adults along transects at release sites or collection of adults by sweep netting. Recovery rates for A. zoegana were higher through adult visual sampling (54.8%) than through larval sampling via root dissection (43.0%). Adult visual sampling required less time (30 min/site) than did root dissection (130 min/site). Sweep net sampling, although having the lowest detection rate (38.1%), required even less time (10 min/site) and was the most effective method per unit time. In contrast, for C. achates, larval sampling was the most effective method, with a recovery rate of 35.6%, compared with 8.9% for adult visual sampling. Sweep netting was more effective than visual sampling, with a detection rate of 18.1%. Adult visual sampling required less time (44 min/site) than did root dissection (130 min/site). Sweep net sampling, although having the lowest detection rate (18.1%), required even less time (10 min/site) and was the most effective method per unit time. However, other factors such as weather, travel time, and training levels needed for sampling make root sampling a more effective method, in a larger sense, for both of these insects.

Observations on the Biology of Dryocoetes betulae (Coleoptera: Curculionidae) in Paper Birch in Northern Idaho

Abstract We describe the biology and life stages of the birch bark beetle, Dryocoetes betulae Hopkins, and report its second known occurrence in Idaho. One annual generation was observed with broods overwintering as larvae and sexually immature adults. The species is polygamous with a ratio of 1.8 females per male. Two females (rarely three) joined a male after he entered the bark, and each female created a 3- to 4-cm-long egg gallery with short lateral spurs. Eggs were laid in niches along each side of the main gallery. Larvae have three instars. No hymenopterous parasitoid was found; however, two apparent predators, Rhizophagus dimidiatus Mannerheim, and a clerid, Thanasimus undatulus (Say), were present in galleries. Two mites, Histiostoma sp. and Proctolaelaps n. sp., also occurred in galleries, and a nematode of the Order Rhabditida occurred in the midgut of larvae and adult D. betulae. An ambrosia beetle, Trypodendron betulae Swaine, also infested the basal stems apart from D. betulae. Stems of infested trees were infected with a root rot fungus, Armillaria ostoyae (Romagnesi) Herink. Several generations of beetles infested the basal portion of stems of either decadent or recently dead paper birch. This behavior preserves a scarce host resource and is enhanced by a relatively low fecundity and ability to establish new galleries without flight dispersal.

Efficacy of Verbenone and Green Leaf Volatiles for Protecting Whitebark and Limber Pines From Attack by Mountain Pine Beetle (Coleoptera: Curculionidae: Scolytinae)

ABSTRACT To develop safe and effective methods to protect whitebark pines, Pinus albicaulis Engelmann, and limber pines, Pinus flexilis James, from attack by mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), we compared verbenone and verbenone plus green leaf volatiles (GLVs) for prevention of beetle attack. We used two strategies: area-wide protection where semiochemical-releasing flakes are dispersed over the forest floor, and individual tree tests where flakes are applied to tree trunks. The area-wide bioassays were conducted by applying verbenone- and GLV-releasing flakes without stickers to the forest floor on 0.81-ha plots dominated by whitebark pines in the State of Washington with four replicates. We conducted individual tree bioassays by applying the same formulations with stickers to whitebark and limber pines in Montana and Colorado, respectively. In all three situations, both verbenone-alone and verbenone plus GLVs significantly increased the proportion of trees escaping mass attack by beetles, but the two formulations were not significantly different from one another. Despite a lack of significance at a Bonferroni-adjusted &agr; = 0.05, adding GLVs gave slightly greater absolute levels of tree protection in most cases. Monitoring traps placed in the area-wide treatments in Washington showed similar outcomes for numbers of beetles trapped: both treatments had significantly fewer beetles than controls, and they were not significantly different from one another. At peak flight, however, plots with GLVs combined with verbenone had roughly 40% fewer beetles than plots with verbenone alone. GLVs are considerably cheaper than verbenone, so tests of higher application rates may be warranted to achieve enhanced tree protection at reasonable cost.

Biology of Scolytus subscaber (Coleoptera: Curculionidae: Scolytinae) in Grand Fir in Idaho

ABSTRACT We studied the biology of Scolytus subscaber LeConte (Coleoptera: Curculionidae: Scolytinae) in grand fir, Abies grandis (Douglas) Lindley, in northern Idaho. Presented are new Idaho distribution records, description of the mature larva and adult, biological features, characteristics of infestation and galleries, and natural control factors. The beetle has one generation per year, taking flight in July to infest live branches in the crowns of mature trees. The uniquely shaped egg gallery deeply scores the wood; its two arms curve inward like the Greek letter &egr;. Eggs are laid along the outer edge of the gallery; hatched larvae mine hidden in the phloem for a short distance after which they mine next to the sapwood where they overwinter. A cerambycid, Tetropium abietis Fall, occurred often in the larger diameter portion of branches infested with S. subscaber. A scolytid, Scolytus abietis Blackman, also infested branches but not those containing S. subscaber. Mortality factors included a braconid parasitoid, Ecphylus arcuatus Muesebeck, on larvae and the flooding of egg galleries with resin evidently caused by defensive response of the host tree to a staining fungus, Spicaria anomala (Corda) Harz., carried by the beetle. In addition, we point out errors and lack of documentation concerning the identity, biology, and behavior of S. subscaber in secondary published sources.

Effects of Climate Change on Ecological Disturbance in the Northern Rockies

Disturbances alter ecosystem, community, or population structures and change elements of the biological and/or physical environment. Climate changes can alter the timing, magnitude, frequency, and duration of disturbance events, as well as the interactions of disturbances on a landscape, and climate change may already be affecting disturbance events and regimes. Interactions among disturbance regimes, such as the co-occurrence in space and time of bark beetle outbreaks and wildfires, can result in highly visible, rapidly occurring, and persistent changes in landscape composition and structure. Understanding how altered disturbance patterns and multiple disturbance interactions might result in novel and emergent landscape behaviors is critical for addressing climate change impacts and for designing land management strategies that are appropriate for future climates. This chapter describes the ecology of important disturbance regimes in the Northern Rockies region, and potential shifts in these regimes as a consequence of observed and projected climate change. We summarize five disturbance types present in the Northern Rockies that are sensitive to a changing climate—wildfires, bark beetles, white pine blister rust (Cronartium ribicola), other forest diseases, and nonnative plant invasions—and provide information that can help managers anticipate how, when, where, and why climate changes may alter the characteristics of disturbance regimes.

Biology of Scolytus piceae (Coleoptera: Curculionidae: Scolytinae) in Northern Idaho and Notes on Comparative Anatomical Features of the Larva

Abstract The forests of the northern Rocky Mountains are hosts of nine species of Nearctic conifer-infesting bark beetles of the genus Scolytus Geoffroy. One of these, Scolytus piceae Swaine (Coleoptera: Curculionidae), infests spruces across the continent including Picea engelmannii Parry (Pinaceae) in Idaho. Mature larvae overwintered before transforming to adults, which infested new hosts in early June. Scolytus piceae most commonly infested shaded out lower branches of mature live spruce. In sporadic wind-felled spruce, the beetle infested the terminal portion of branches throughout the crown, whereas another Scolytinae, Polygraphus rufipennis (Kirby), infested the thicker bark basal portion of the same branches. This niche separation resulted from difference in time of their dispersal flight and ability of S. piceae to colonize thin bark by engraving the underlying sapwood. Population recruitment of S. piceae was low in shaded out lower branches, in balance with this limited host resource. Features of the head of S. piceae larvae differed from that reported in literature, including the mandible dentition, antennal field, and pattern of setae on the postlabium.

Biology of Pityophthorus pulchellus tuberculatus (Coleoptera: Curculionidae: Scolytinae) in Lodgepole Pine in Northern Idaho

Abstract The twig beetle, Pityophthorus pulchellus tuberculatus Eichhoff, infests dead branches of pines in western United States and Canada, including lodgepole pine, Pinus contorta Douglas, in northern Idaho. Adult broods overwintered in their host and emerged and colonized new hosts in late April. Males initiated galleries and were joined by up to seven females, each of which constructed an egg gallery radiating from a central chamber. Galleries had an average of 4.7 egg niches each with an egg that was large relative to the mother beetle. Two larval instars were recognized. Dentition of larval mandibles differed in shape from that in literature. Mature larvae pupated either in a cell excavated on the wood surface or in a cell below the wood surface. First-generation adults mined extensively in the inner bark and wood before emerging to infest new trees in late June. Their progeny became adults beginning in early August and likewise mined and fed on the inner bark and wood before overwintering. Predacious beetles present as larvae in the galleries included Enoclerus lecontei (Wolcott) (Coleoptera: Cleridae) and Lasconotus sp. (Coleoptera: Zopheridae). Parasitoid Hymenoptera reared from infested trees were Cosmophorus pityophthori Rohwer (Braconidae), Phasmidiasta n. sp. (Braconidae), Spathius sp. (Braconidae), Acerocephala n. sp. (Pteromalidae), Metacolus fasciatus Girault (Pteromalidae), Rhaphitelus maculatus Walker (Pteromalidae), Rhopalicus sp. (Pteromalidae), and an unidentified pteromalid.