Beetle Frass Research Articles

Environmental monitoring for invasive fungal pathogens of ʽŌhiʽa (Metrosideros polymorpha) on the Island of Hawaiʽi

The invasive rust Austropuccina psidii was detected in the Hawaiian Islands in 2005 and has become widely established throughout the archipelago in both native and introduced species of Myrtaceae. Initial predictions about the impacts of the fungus on native ʽōhiʽa lehua (Metrosideros polymorpha), a keystone native tree, have not materialized, but there is ongoing concern that introductions of new genotypes of the fungus could lead to widespread mortality with catastrophic effects on native ecosystems. By contrast, two recently emergent Ascomycete pathogens, Ceratocystis lukuohia (Ceratocystis wilt of ‘ōhi‘a) and C. huliohia (Ceratocystis canker of ‘ōhi‘a), collectively known to cause Rapid ʽŌhiʽa Death (ROD), are causing significant mortality in native forests on Hawaiʻi and Kauaʻi Islands, but pathways of spread are still incompletely understood. We used a network of passive environmental samplers for collecting windblown urediniospores of Austropuccina to evaluate the effectiveness of environmental monitoring to detect seasonal and landscape-scale differences in airborne propagules of this rust on Hawai`i Island. The samplers were also used to determine if windborn ambrosia beetle frass or spores of Ceratocystis can spread long distances. We found frequent detections and regional and seasonal differences in numbers of samplers that were positive for urediniospores of Austropuccinia, but little evidence of long-distance airborne dispersal of the ROD-causing fungi. The simple, inexpensive platform for sampling airborne fungal spores that we used may have value as a monitoring tool for detecting spread of airborne fungal pathogens, evaluating habitats for suitability for restoration efforts, and for detecting new pathogen introductions, particularly new Austropuccinia genotypes both in Hawaiʻi and other parts of the world.

Ceratocystis lukuohia‐infested ambrosia beetle frass as inoculum for Ceratocystis wilt of ʻōhiʻa (Metrosideros polymorpha)

AbstractMetrosideros polymorpha (‘ōhi‘a) trees in Hawaiʻi are dying from two distinct diseases, collectively referred to as rapid ‘ōhi‘a death (ROD), caused by Ceratocystis lukuohia and Ceratocystis huliohia. Boring dust (frass) released when ambrosia beetles attack and colonize infected trees has been suspected as a transmission source. We sampled ambrosia beetle frass from six locations on Hawaiʻi Island and screened samples for Ceratocystis DNA and fungal viability. Ceratocystis DNA was detected in 79% of frass samples and 61% were viable. To assess the infectivity of C. lukuohia‐colonized frass, M. polymorpha seedlings were wound‐inoculated with frass in growth chamber trials. Wilt incidence was 40% in the first trial and 15% in the second. Frass particles naturally infested with C. lukuohia were treated with a cytoplasmic stain and microscopically examined; thick‐walled chlamydospores were found in all samples. The chlamydospores appeared to be derived from aleurioconidia. Ceratocystis survival in frass was assessed in a baiting experiment conducted under varying environmental regimes; viability decreased with increasing temperature, frass age and decreasing humidity. After 6 months, 90% of the samples exhibited viable C. lukuohia at the lowest temperatures. Results confirmed that C. lukuohia chlamydospores are the fungal inoculum within ambrosia beetle frass and can induce wilt when introduced to M. polymorpha wounds. Although ambrosia beetles or other insects may serve as vectors, the present work supports the hypothesis that Ceratocystis species may be dispersed in frass, which can inform ongoing efforts to manage ROD across Hawaiʻi's native forests.

Predicting interactions of the frass-associated yeast Hyphopichia heimii with Oleaeuropaea subsp. cuspidata and twig-boring bark beetles.

Bark beetles are destructive insect pests known to form symbioses with different fungal taxa, including yeasts. The aim of this study was to (1) determine the prevalence of the rare yeast Hyphopichia heimii in bark beetle frass from wild olive trees in South Africa and to (2) predict the potential interaction of this yeast with trees and bark beetles. Twenty-eight culturable yeast species were isolated from frass in 35 bark beetle galleries, including representatives of H. heimii from nine samples. Physiological characterization of H. heimii isolates revealed that none was able to degrade complex polymers present in hemicellulose; however, all were able to assimilate sucrose and cellobiose, sugars associated with an arboreal habitat. All isolates were able to produce the auxin indole acetic acid, indicative of a potential symbiosis with the tree. Sterol analysis revealed that the isolates possessed ergosterol quantities ranging from 3.644 ± 0.119 to 13.920 ± 1.230mg/g dry cell weight, which suggested that H. heimii could serve as a source of sterols in bark beetle diets, as is known for other bark beetle-associated fungi. In addition, gas chromatography-mass spectrometry demonstrated that at least one of the isolates, Hyphopichia heimii CAB 1614, was able to convert the insect pheromone cis-verbenol to the anti-aggregation pheromone verbenone. This indicated that H. heimii could potentially influence beetle behaviour. These results support the contention of a tripartite symbiosis between H.heimii, olive trees, and bark beetles.

Population genetic structure of Raffaelea quercus‐mongolicae indicates a recent fungal introduction event to Jeju Island from inland areas of South Korea

AbstractRaffaelea quercus‐mongolicae, a mycangial symbiont of a wood‐boring ambrosia beetle, Platypus koryoensis (Coleoptera: Curculionidae: Platypodidae), has been associated with the mass mortality of Korean oak trees in South Korea. Systemic wilt from the inoculation of oak trees with R. quercus‐mongolicae has caused significant damage to forest ecosystems in the country. Despite the continued spread of this fungus across the country since the first discovery of the disease, little is known regarding its biology. During a recent survey carried out to investigate the status of oak wilt diseases on Jeju Island, South Korea, visible signs of bark beetle attack, including bark beetle frass and galleries, were consistently observed in Quercus serrata, and R. quercus‐mongolicae was successfully recovered from the trees. To determine whether the pathogen was introduced from inland areas of the country to Jeju Island, the genetic diversity and population structure of R. quercus‐mongolicae isolates collected from various geographical regions and hosts in the country were investigated using a combination of eight microsatellite markers designed from the genome of the fungus in this study. The results showed lower levels of genetic diversity for the population from Jeju Island compared to those from inland areas of the country. This suggests that a limited number of individuals were recently introduced to Jeju Island, resulting in a new disease problem in the area.

Geographic distribution of Ovavesicula popilliae in the United States and sensitivity of visual diagnosis compared with qPCR detection

The Japanese beetle (Popillia japonica) is one of the most destructive invasive pests in North America, causing significant economic impact to many fruit crops, turfgrass and the nursery industry. A microsporidian pathogen of Japanese beetle, Ovavesicula popilliae, discovered in 1985, proliferates in the Malpighian tubules of larvae and adults, disrupting waste-removal, mineral filtering, and fluid balance in heavily infected individuals. Most infected larvae do not survive from fall to spring, and egg production by infected females is reduced by 50%.Ovavesicula popilliae is promising as a classical biological control agent for Japanese beetle, but outside of surveys completed in Connecticut and Michigan little is known about its geographic distribution in North America. The objective of this research is to obtain a better understanding of the distribution of O. popilliae in North America. Japanese beetles were collected at 59 locations in a total of 19 different states in the USA for pathogen analysis. Overall, the proportion of Japanese beetle adults infected by O. popilliae was much greater in Michigan, Ohio, Tennessee and four states in the northeastern USA compared with sites located west of the Mississippi River (18.6 ± 13.3% and 0.6 ± 1.2%, respectively). Nucleotide sequences of the gene encoding a small subunit of nuclear ribosomal RNA (ssrDNA), obtained from GenBank for O. popilliae was used to develop a highly specific qPCR test for O. popilliae DNA. A subsample of 110 individual Japanese beetles were visually diagnosed first, then analyzed via qPCR. Visual diagnosis and qPCR detection agreed for 80.9% of the beetles tested. The qPCR assay is more sensitive than visual diagnosis (56 visually positive, 73 qPCR positive), is highly specific for O. popilliae, and will be useful for detecting the pathogen in large batches of beetles, or in beetle frass.

Mutualism is not restricted to tree‐killing bark beetles and fungi: the ecological stoichiometry of secondary bark beetles, fungi, and a scavenger

1. All bark beetles are in symbiosis with fungi. Although obligate mutualisms with fungi are common with tree‐killing bark beetles (primaries), fungi associated with non‐tree‐killing bark beetles (secondaries) are usually dismissed as commensals.2. Using an ecological stoichiometric approach, we show secondaries are also involved in nutrition‐based mutualisms, some of which appear obligate, and that differences in symbiont provisioning efficiency have a potent effect on beetle carbon (C): nitrogen (N): phosphorus (P) ratios.3. Some secondary beetles have high P contents and require efficient P provisioning via fungi, while others have low P contents that may allow them to exploit less efficient fungi or a broader range of species with variable efficiencies. A co‐occurring scavenger that feeds on nutrient‐poor bark beetle frass (excrement/boring residues) exhibited the lowest phosphorus content yet recorded for an invertebrate.4. Our results generally support the growth‐rate hypothesis that posits differences in C:P and N:P ratios in consumers are due to differential allocation of P to P‐rich RNA to support growth. However, while the beetle species that accumulated the most biomass was considerably enriched in P and that with the least biomass was P‐poor, one beetle species that was P‐rich was also small possibly due to limitation by an element other than P.5. Our results indicate that fungi are important to a broader range of bark beetles than previously recognised. Additional research is needed to describe how these various symbioses influence forest ecosystems via differential effects of fungi on host beetle fitness.

Decontamination of Ceratocystis Pathogens Responsible for Rapid ʻŌhiʻa Death

Rapid ʻōhiʻa death (ROD) is caused by two recently described species of Ceratocystis, C. lukuohia and C. huliohia. These fungi are decimating ʻōhiʻa lehua (Metrosideros polymorpha), the keystone native tree species of Hawaiʻi. Viable Ceratocystis propagules can persist in ambrosia beetle frass (Coleoptera: Scolytinae), and movement of the frass may play a key role in the spread of the disease. In order to prevent the spread of ROD, we developed effective and practical surface (e.g., tools and shoes) decontamination methods to be used by researchers, managers, and the public alike. We first tested different household and laboratory disinfectants on the Ceratocystis fungi in culture, and then we applied the effective culture disinfectants to contaminated ambrosia beetle frass. Laboratory-grade ethanol (70, 80, and 95%), Clorox bleach (10%, 0.825% active ingredient [a.i.]), and isopropanol (70 and 91%), were all equally effective at decontaminating cultured C. lukuohia and C. huliohia. Although all concentrations of isopropanol (50, 70, and 90%) and ethanol (50, 70, and 90%) were effective disinfectants of Ceratocystis-contaminated frass, treatments of frass with up to 20% Clorox bleach (1.2% a.i.) were not completely adequate at killing the fungus. These data reveal that bleach is not a sufficient ROD disinfectant when frass is present, and isopropanol or ethanol are the more reliable options.

Presence and viability of Ceratocystis lukuohia in ambrosia beetle frass from Rapid ʻŌhiʻa Death‐affected Metrosideros polymorpha trees on Hawaiʻi Island

AbstractRapid ʻŌhiʻa Death (ROD) is a fungal disease of ʻōhiʻa lehua (Myrtaceae: Metrosideros polymorpha) caused by Ceratocystis lukuohia and C. huliohia. ROD is the aetiological agent of widespread mortality of this important tree on Hawaiʻi Island, but its epidemiology remains unclear. We investigated the prevalence and viability of C. lukuohia in ambrosia beetle frass in ROD‐affected ʻōhiʻa trees. A total of 200 frass traps were placed onto C. lukuohia‐infected ʻōhiʻa at four locations on the east side of Hawaiʻi Island. Frass was collected and screened for the presence of C. lukuohia DNA using a diagnostic qPCR assay. In addition, frass samples were screened for viability by carrot baiting. All trapped beetles were of the genus Xyleborus, with the majority being the non‐native X. ferrugineus. Of the frass samples tested, 62% contained C. lukuohia DNA and 17% of carrot baits were positive for the fungus. These results indicate that ambrosia beetle frass releases C. lukuohia into the environment. We discuss the potential role infested frass could play in the ROD pathosystem.

A weevil sex pheromone serves as an attractant for its entomopathogenic nematode predators

Diaprepes abbreviatus is an invasive pest of citrus in the USA from the Caribbean. Entomopathogenic nematodes (EPNs) are used as biological control agents in citrus agroecosystems against D. abbreviatus. EPNs respond to herbivore-induced volatiles from citrus roots to assist in the location of insect hosts. Here, we investigated EPN response to the male-produced sex pheromone of D. abbreviatus. In the laboratory, we used two-choice tests to investigate the behavioral response of Steinernema diaprepesi, Heterorhabditis indica, Steinernema riobrave, and the plant parasitic nematode, Tylenchulus semipenetrans, to the synthetic sex pheromone of D. abbreviatus, as well as its natural source, beetle frass. Nematodes were not attracted by volatiles of citrus plant origin or carvacrol, a non-pheromone volatile associated with beetle frass. S. diaprepesi and H. indica were attracted to the frass and the pheromone of D. abbreviatus. The response of S. diaprepesi to the pheromone was greater than that of H. indica at all doses tested; the greatest response from both species occurred at 0.12 and 1.2 ng of pheromone/μL of solvent. Deploying the pheromone in a citrus grove increased the mortality of caged Diaprepes larvae as compared to control larvae deployed with solvent alone. Also, more EPNs were found in the soil surrounding the pheromone-baited larvae than the surrounding controls.

Soil Biology Research across Latitude, Elevation and Disturbance Gradients: A Review of Forest Studies from Puerto Rico during the Past 25 Years

Progress in understanding changes in soil biology in response to latitude, elevation and disturbance gradients has generally lagged behind studies of above-ground plants and animals owing to methodological constraints and high diversity and complexity of interactions in below-ground food webs. New methods have opened research opportunities in below-ground systems, leading to a rapid increase in studies of below-ground organisms and processes. Here, we summarize results of forest soil biology research over the past 25 years in Puerto Rico as part of a 75th Anniversary Symposium on research of the USDA Forest Service International Institute of Tropical Forestry. These results are presented in the context of changes in soil and forest floor biota across latitudinal, elevation and disturbance gradients. Invertebrate detritivores in these tropical forests exerted a stronger influence on leaf decomposition than in cold temperate forests using a common substrate. Small changes in arthropods brought about using different litterbag mesh sizes induced larger changes in leaf litter mass loss and nutrient mineralization. Fungi and bacteria in litter and soil of wet forests were surprisingly sensitive to drying, leading to changes in nutrient cycling. Tropical fungi also showed sensitivity to environmental fluctuations and gradients as fungal phylotype composition in soil had a high turnover along an elevation gradient in Puerto Rico. Globally, tropical soil fungi had smaller geographic ranges than temperate fungi. Invertebrate activity accelerates decomposition of woody debris, especially in lowland dry forest, but invertebrates are also important in early stages of log decomposition in middle elevation wet forests. Large deposits of scoltine bark beetle frass from freshly fallen logs coincide with nutrient immobilization by soil microbial biomass and a relatively low density of tree roots in soil under newly fallen logs. Tree roots shifted their foraging locations seasonally in relation to decaying logs. Native earthworms were sensitive to disturbance and were absent from tree plantations, whereas introduced earthworms were found across elevation and disturbance gradients.

Cryptaphelenchus varicaudatus n. sp. (Rhabditida: Ektaphelenchinae) from Tehran Province, Iran.

Cryptaphelenchus varicaudatus n. sp. is described and illustrated. It was isolated from bark samples of dead or dying pine (Pinus spp.) trees with bark beetle frass and galleries, in Tehran province. The new species has 275- to 367-µm-long females (a medium-sized species) with distinctly annulated cuticle having three bands in lateral fields, lip region continuous with body contour, delicate knobbed stylet, monodelphic-prodelphic reproductive system with distinct spermatheca, short postvulval uterine sac (PUS), transverse vulval slit with raised posterior lip and body narrowing behind it, sclerotized vagina, simple intestine ending in a blind sac, having no rectum but vestigial anus in some specimens, and distal body end tip (tail tip) with variation in morphology (shape), from sharply or slightly pointed to bluntly rounded. Males of the new species are common, but less frequent than females, characterized by shorter body (235-278 µm long) compared to females, their posterior body end more ventrally bent, arcuate separate spicules with well-developed wide condyles, distinct rostrum having sharp, attenuated tip. The precloacal single supplement (P1) and the distally located pair of caudal papillae close to tail tip were only observed. The new species is morphologically compared with the species of the genus having short PUS and similar body end morphology. In molecular phylogenetic analyses using 1520- and 698-nt-long sequences of small subunit (SSU) and large subunit (LSU) rDNA D2/D3 fragments, the new species formed a clade with two currently available GenBank-derived, unspecified isolates/sequences in SSU and three other isolates/sequences in LSU trees, respectively.

A population survey of Beauveria bassiana in the microhabitat of the red turpentine beetle, Dendroctonus valens, in Chinese pine forests

Field survey of the entomopathogenic fungus Beauveria bassiana in association with the red turpentine beetle, Dendroctonus valens, was undertaken in three pine plantations in Northern China. In total, 88 strains of B. bassiana sensu lato were isolated from the soil, bark, beetle frass, living adult and cadaver samples and soil was proved to be an important inoculum reservoir for fungal entomopathogens. Of these, 77 isolates were included for genetic diversity analysis by PCR for inter-simple sequence repeats (ISSR). Genetic diversity and population structure analysis of the isolates from three sites and five niches demonstrated high genetic diversity and heterogeneity between and/or within populations. Wright's statistics revealed a high gene flow rate (4.529) among the three populations, especially among the soil-derived isolate subpopulations. Low variation was mainly caused (94.8%) by variation among different substrates, suggesting the importance of microhabitat substrates on genetic diversity of B. bassiana. Phylogenetic variation was not associated with geographic distance.

The effects of α‐cellulose extraction and blue‐stain fungus on retrospective studies of carbon and oxygen isotope variation in live and dead trees

Tree-ring carbon and oxygen isotope ratios from live and recently dead trees may reveal important mechanisms of tree mortality. However, wood decay in dead trees may alter the δ(13)C and δ(18)O values of whole wood obscuring the isotopic signal associated with factors leading up to and including physiological death. We examined whole sapwood and α-cellulose from live and dead specimens of ponderosa pine (Pinus ponderosa), one-seed juniper (Juniperous monosperma), piñon pine (Pinus edulis) and white fir (Abies concolor), including those with fungal growth and beetle frass in the wood, to determine if α-cellulose extraction is necessary for the accurate interpretation of isotopic compositions in the dead trees. We found that the offset between the δ(13)C or δ(18)O values of α-cellulose and whole wood was the same for both live and dead trees across a large range of inter-annual and regional climate differences. The method of α-cellulose extraction, whether Leavitt-Danzer or Standard Brendel modified for small samples, imparts significant differences in the δ(13)C (up to 0.4‰) and δ(18) O (up to 1.2‰) of α-cellulose, as reported by other studies. There was no effect of beetle frass or blue-stain fungus (Ophiostoma) on the δ(13)C and δ(18)O of whole wood or α-cellulose. The relationships between whole wood and α-cellulose δ(13)C for ponderosa, piñon and juniper yielded slopes of ~1, while the relationship between δ(18)O of whole wood and α-cellulose was less clear. We conclude that there are few analytical or sampling obstacles to retrospective studies of isotopic patterns of tree mortality in forests of the western United States.

Endozoochory by beetles: a novel seed dispersal mechanism

Due in part to biophysical sized-related constraints, insects unlike vertebrates are seldom expected to act as primary seed dispersers via ingestion of fruits and seeds (endozoochory). The Mediterranean parasitic plant Cytinus hypocistis, however, possesses some characteristics that may facilitate endozoochory by beetles. By combining a long-term field study with experimental manipulation, we tested whether C. hypocistis seeds are endozoochorously dispersed by beetles. Field studies were carried out over 4 years on six populations in southern Spain. We recorded the rate of natural fruit consumption by beetles, the extent of beetle movement, beetle behaviour and the relative importance of C. hypocistis fruits in beetle diet. The tenebrionid beetle Pimelia costata was an important disperser of C. hypocistis seeds, consuming up to 17·5 % of fruits per population. Forty-six per cent of beetles captured in the field consumed C. hypocistis fruits, with up to 31 seeds found in individual beetle frass. An assessment of seeds following passage through the gut of beetles indicated that seeds remained intact and viable and that the proportion of viable seeds from beetle frass was not significantly different from that of seeds collected directly from fruits. A novel plant-animal interaction is revealed; endozoochory by beetles may facilitate the dispersal of viable seeds after passage through the gut away from the parent plant to potentially favourable underground sites offering a high probability of germination and establishment success. Such an ecological role has until now been attributed only to vertebrates. Future studies should consider more widely the putative role of fruit and seed ingestion by invertebrates as a dispersal mechanism, particularly for those plant species that possess small seeds.

Floral Transmission ofErwinia tracheiphilaby Cucumber Beetles in a WildCucurbita pepo

Cucumber beetles, Acalymma vittatum (F.) and Diabrotica undecipunctata howardi (Barber), are specialist herbivores of cucurbits and the vector of Erwinia tracheiphila (E.F. Smith) Holland, the causative agent of wilt disease. Cucumber beetles transmit E. tracheiphila when infected frass falls onto leaf wounds at the site of beetle feeding. We show that E. tracheiphila also can be transmitted via the floral nectaries of Cucurbita pepo ssp. texana L. Andres (Texas gourd). Under field conditions, we found that beetles aggregate in flowers in the late morning, that these beetles chew the anther filaments that cover the nectaries in male flowers thereby exposing the nectary, and that beetle frass accumulates on the nectary. We use real-time polymerase chain reaction to show that most of the flowers produced during the late summer possess beetle frass containing E. tracheiphila. Greenhouse experiments, in which cultures of E. tracheiphila are deposited onto floral nectaries, show that Texas gourds can contract wilt disease through the floral nectaries. Finally, we use green fluorescent protein-transformed E. tracheiphila to document the movement of E. tracheiphila through the nectary into the xylem of the pedicel before the abscission of the flower. Together, these data show that E. tracheiphila can be transmitted through infected frass that falls on or near the floral nectaries. We hypothesize that the concentration of frass from many beetles in the flowers increases both exposure to and the concentration of E. tracheiphila and plays a major role in the dynamics of wilt disease in both wild populations and cultivated squash fields.

Macadamia Quick Decline Caused by Phytophthora tropicalis is Associated with Sap Bleeding, Frass, and Nectria in Hawaii.

Macadamia quick decline (MQD) has been a persistent problem since 1986 when it started killing productive 14- to 36-year-old macadamia trees in the Hilo, HI area. Fungi including Nectria regulosa, Xylaria arbuscula, Phellinus gilvus, and Acremonium recifei have been attributed to MQD and could kill twigs on healthy macadamia trees after artificial inoculation (3). The oomycete originally called Phytophthora capsici and later reclassified as P. tropicalis was also considered to be involved in the MQD complex (3). However, the primary causal agent has never been determined and the issue continues to perplex the industry. Between 2005 and 2006, a mature macadamia field on the Waiakea Experiment Station planted with cv. HAES 333 began to experience a high frequency of MQD. Trees exhibiting dull green, yellow, or brown leaves within the tree canopy were observed. Sap bleeding from the trunk, Ambrosia beetles, and Nectria fruiting bodies were consistently associated with MQD. Disease incidence was 22%. Of 21 infected trees, 53% died within an average period of 6.8 months. Four branch samples were collected from four trees showing browning of leaves, sap bleeding, Ambrosia beetles, and Nectria, and seven P. tropicalis isolates were recovered from diseased tissue on water agar or V8 agar media. No other microorganisms were isolated from diseased branches. On the basis of the morphological characteristics described by Aragaki and Uchida (1), the isolates were identified as P. tropicalis. The morphological identification was confirmed by molecular analysis of the 5.8S subunit and flanking internal transcribed spacers (ITS1 and ITS2) of rDNA amplified from DNA extracted from single-zoospore cultures with the ITS1/ITS4 primers (2,4) and sequenced (GenBank No. FJ849839). Pathogenicity tests were conducted on four 12-year-old macadamia trees in the field. A 4 × 104 zoospore/ml suspension of P. tropicalis isolate L1 was injected into branches of cv. HAES 344 to incite MQD signs and symptoms. Branches inoculated with P. tropicalis started showing the initial sign of MQD, excessive sap bleeding, within 36 days postinoculation (dpi). The presence of Ambrosia beetle frass and the appearance of orange fruiting bodies of Nectria were visible within 110 dpi. No symptoms were noted on the four control tree branches inoculated by the same method but with sterilized distilled water. P. tropicalis was reisolated from the symptomatic macadamia branches, fulfilling Koch's postulates. To our knowledge, this is the first report of P. tropicalis as the primary causal agent of MQD and its association with sap bleeding, Ambrosia beetles, and a saprotrophic species of Nectria. After completion of our research, Ko (3) reported that the MQD P. capsici was P. tropicalis, supporting our finding in this study. Quick decline of macadamia trees continues to be a serious problem in Hawaii. Minimizing tree loss in mature orchards is critical for maintaining the economic viability of Hawaii's macadamia industry. Understanding the biology of this pathosystem will enable the development of control and prevention strategies.

Studies on the Biology of a Bark Beetle Predator, Aulonium ruficorne (Coleoptera: Colydiidae)

Densities of adult Aulonium ruficorne Olivier were significantly higher when the beetle prey, Orthotomicus erosus (Wollaston), were in the first two instars. Under controlled conditions, adult longevity was 33.5 d. Female A. ruficorne were more abundant during bark beetle colonization and, later, during the bark beetles' larval stage. However, males outnumbered females during bark beetle oviposition. Eggs were laid under bark scales, in crevices, and in bark beetle frass. The egg distribution was mainly a function of the bark scale distribution and was independent of distance from egg tunnels. There are four or five larval instars. The thermal constant of A. ruficorne is 571 degree-days (lower temperature threshold, 11.3°C). The predator can feed on all immature stages of the bark beetles O. erosus and Pityogenes calcaratus Eichhoff. However, larvae and adults were recorded gnawing bark, and wood particles were observed inside the alimentary canal. In simulated pine tree systems, adults consumed 0.6–1.9 bark beetle eggs or neonates. The combined effect of adults and larvae suggest that this predator might reduce the population of the bark beetles by up to 90% during spring and autumn and by 30–50% during summer.

Sites of production and occurrence of volatiles in Douglas-fir beetle,Dendroctonus pseudotsugae hopkins

Volatiles were found to be distributed throughout adult Douglasfir beetles,Dendroctonus pseudotsugae Hopkins, suggesting that the hindgut may not be the sole site of production. The volatile content of individual beetles increased dramatically with feeding; qualitative changes reflected the different bark habitats of newly emerged and established beetles. All detected volatiles were also found in beetle frass. Myrcene was the predominant monoterpene of emergent beetles and α-pinene of fed beetles. Linalool and bornyl acetate occurred in significant amounts after feeding, and diacetone alcohol and sulcatol were also detected for the first time. The presence of sulcatol explains the reported cross-attraction withGnathotrichus spp.cis-Verbenol was also found to occur in addition totrans-verbenol. The volatile content of male beetles was similar to that of females but amounts of individual compounds were less. Acetic acid was found in both emerged and fed beetles and in lesser amounts in frass, suggesting that microbial metabolism could be a potential source of volatile production.

Blue-stain fungi in xylem of lodgepole pine: a light-microscope study on extent of hyphal distribution

In midsummer mountain pine beetles emerge from lodgepole pine trees and fly to unattacked trees. While chewing vertical egg galleries in the inner bark of the tree, they inoculate into it a blue-stain fungus complex. Initially, the fungi are confined to the beetle frass of the egg gallery, but they soon grow into the sapwood. The fungi spread radially via the parenchyma of the xylem rays. Once established in the xylem rays, fungal hyphae move into the tracheids of the axial water-conducting system. Here they occlude bordered-pit pairs and occasionally the entire lumen of the cell. Fungal hyphae also attack and destroy resin-duct epithelial cells. This may result in release of resin into surrounding tissues. Destruction of storage and water-conducting tissues in the tree trunk is detrimental to renewed shoot tip expansion the following spring.

THE FEEDING POTENTIAL OF CORTICEUS GLABER AND CORTICEUS PARALLELUS (COLEOPTERA: TENEBRIONIDAE), FACULTATIVE PREDATORS OF THE SOUTHERN PINE BEETLE, DENDROCTONUS FRONTALIS (COLEOPTERA: SCOLYTIDAE)

AbstractUnder laboratory conditions, Corticeus glaber (LeConte) and C. parallelus (Melsheimer) adults were facultative predators of southern pine beetle, Dendroctonus frontalis Zimmermann, eggs and first and second instar larvae. Southern pine beetle frass and blue stain fungus, Ceratocystis minor (Hedgecock) Hunt were also suitable for survival for both species of Corticeus. Loblolly pine (Pinus taeda L.) phloem was not utilized as a food source by either species. Corticeus spp. larvae were predators of D. frontalis eggs.