Oak Borer Research Articles

Current and Future Insect Threats to Oaks of the Midwest, Great Lakes, and Northeastern United States and Canada

Increasing temperatures, prolonged drought, the increased severity and intensity of storms, and other effects of climate change are being felt globally, and long-lived forest tree species may struggle in their current ranges. Oaks (Quercus spp.) have evolved a range of adaptations to dry and hot conditions and are believed to be a “climate change winner” by increasing their suitable habitat. However, a mixture of life history traits and increasing susceptibility to herbivores and xylovores as well as secondary pathogen infections still put oaks at risk of decline. Oak species found in the Midwestern, Great Lakes, and Northeastern United States and Canada are important keystone species with high ecological and economical importance. They are also vulnerable to existing, new, and emerging threats that have the potential to cause mortality across entire stands quickly. Current examples of insect threats include the Lymantria dispar (spongy moth), Agrilus bilineatus (twolined chestnut borer), and Nitidulidae (sap beetles) as disease vectors. Examples of emerging insects of concern include Cynipidae (oak gall wasps) and Enaphalodes rufulus (red oak borer). This study describes these insects, explains their mechanisms of action and the effects on oaks, and explores mitigation strategies for each.

Current Problems of Forest Protection (25–27 October 2022, Katowice Poland)

Forestry is one of the sectors particularly affected by the threats posed by changing climatic conditions. This is reflected in the deterioration of the health status of stands due to the synergistic effect of numerous abiotic and biotic factors. Current forest health problems are due to dynamic, negative changes in the forest environment. While the amount of precipitation remains at a similar level, its distribution varies throughout the year and, in particular, the lack of soil moisture during the growing season leads to the weakening of trees, including the main forest-forming species in Poland such as Pinus sylvestris. The weakening of trees, in turn, leads to species of insect pests that were previously considered secondary becoming primary pests, such as Ips acuminatus. It is likely that weakening of trees also favours increased occurrence of parasitic plants such as Viscum album ssp. austriacum or Loranthus europaeus. Infestations of the hemiparasitic, xylem-secreting pine mistletoe are of great interest because they are spreading rapidly throughout Europe. Drought in forests is not only a long-term water shortage, but also a situation in which plant-fungal relationships are disrupted. Reduced water availability leads to a number of negative changes in the soil and the mycobiota that live there, affecting entire ecosystems. The effects of climate change and increased international trade are leading to the spread of pathogenic fungi and other harmful organisms whose range was previously restricted to the south of our continent. Unfavourable abiotic and biotic factors leading to weakening of oak stands in the western part of Poland have resulted in activation of new pests like Mediterranean oak borer. Intensification of transport and shortening of its duration, as well as climatic changes, favour the introduction of various organisms, including bark beetles (Scolytinae). In Poland, cyclic insect outbreaks are one of the most important problems in forest protection. Developing methods to monitor, prevent outbreaks and control the density of insect populations below harmful levels can be a challenge to consider. Finding an innovative system for applying insecticides to control spruce bark beetle could also be an interesting solution, where insects attracted to pheromones die after contact with the insecticide. Contact with the insecticide has a dual effect: either directly when the tree is treated, or when the bark beetle attempts to invade the tree. Opportunities for the use of biostimulants in forestry and is an attractive way to regenerate plants after negative stressors such as frost, drought or damage caused by improper use of pesticides, as well as the negative effects of diseases and pests. It acts indirectly by stimulating leaf, stem and root development and improving nutrient uptake. The effects of chemical treatments on fungal biodiversity in forests should be studied using powerful molecular tools such as NGS.

First Report of Biscogniauxia mediterranea on Quercus emoryi in Southern Arizona.

In 2019, a decline of Quercus emoryi (Emory oak) was observed on the Coronado National Forest located in southeastern Arizona. Symptoms associated with oak mortality included crown die-back and large cankers revealing charcoal-like stromal growth. Trunks and root collars showed girdling and many affected trees also displayed evidence of gold-spotted oak borer activity. Initial surveys in stands identified clusters of severe infections. Samples with black perithecia and stromal tissue were collected from symptomatic hosts. Morphological characterization of the fungus was completed on fresh perithecial tissue. Stromata were pulvinate and black showing embedded perithecial bumps, with ostioles visible from the surface of the stroma. Asci were short stipitate and cylindrical with visible oil drops, 6.6 to 9.4 (mean: 8.8) × 139.8 to 179.9 μm (mean: 166.4). Ascospores were smooth ovoid, brown to dark brown, with narrowed and round ends, 6.9 to 9.1 (mean: 7.7) × 13.8 to 25.9 μm (mean: 16.5). Colonies grown on ½ strength potato dextrose agar (½ PDA) (Korhonen 1980) at 25°C for 14 days were whitish-grey when viewed from the top and darkened embedded spheres were visible from the bottom. Single-spored cultures were isolated by dissecting the hymenium and placing in distilled water. The suspension was streaked onto ½ PDA plates and incubated for 12 hours, and pure cultures were grown on ½ PDA. DNA was isolated from a mycelial scrape and extracted using a 10% Chelex solution (Safaee 2017). The internal transcribed spacer region was amplified with the ITS1/ITS4 primers (White et al. 1990) and PCR products were sequenced at Eurofins Scientific (Lewisville, KY). Isolates (BSS1, BSS2, BSS3, BSS4) were compared to other Biscogniauxia mediterranea sequences in the NCBI database (MG098274, EF026134) and had 100% sequence identity. Pathogenicity assays were conducted using 8-year-old Emory oaks in a greenhouse. The oaks were drought stressed and watered at 50% pot capacity for two months prior to inoculation. Each tree received approximately 2400 ml of water every two weeks for the remainder of the experiment. Eight trees were wounded three times with a 5mm corer. A 5mm plug of mycelium of isolate BSS2 was used to inoculate wounds. Four trees were used as controls and inoculated with ½ PDA plugs. Wounded and inoculated areas were assessed after three months. All eight trees exhibited dark necrotic tissue in the vascular cambium and lesions ranged from 11.4 - 25.8 mm in length and were 3.9 - 13.3 mm wide. The controls exhibited no fungal sign, lesions, or necrotic tissues. The pathogen B. mediterranea was recovered from 13 of the 24 total inoculations and its identity was confirmed with ITS sequencing. Mortality and die-back caused by Biscogniauxia spp. are commonly associated with drought-stressed trees, with increasingly hot and dry conditions routinely noted as inciting factors (Desprez Loustau et al.). Emory oaks are among the dominant tree species in much of the Madrean oak woodlands of the southwestern US and Mexico and provide vital ecological and cultural services. As southwestern states continue to experience hotter and drier, conditions, it is likely Emory oak will become increasingly susceptible to die-back and mortality due to this Biscogniauxia species (Southern et al.).

Indirect effects mediate direct effects of climate warming on insect disturbance regimes of temperate broadleaf forests in the central U.S.

Abstract Climate warming directly affects insect disturbance regimes by altering temperature‐dependent population development. Indirect effects of climate change on insect disturbance may mediate or accelerate direct effects via vegetation feedback (e.g. host tree demographic dynamics). However, such indirect effects have rarely been incorporated in predicting insect disturbance regimes. We included both direct and indirect effects in a forest landscape modelling framework to simulate red oak borer [ROB, Enaphalodes rufulus (Coleoptera: Cerambycidae)] disturbance regimes under a warming climate from 2000 to 2150 in the Central Hardwood Forests, U.S. We quantified effect sizes and relative importance of direct effects and indirect effects of warming climate on the ROB disturbance using a factorial experimental design and two‐way ANOVA. Both direct and indirect effects acted positively in the short and medium term (e.g. 0–100 years) while the effect size of indirect effects changed over time from positive (+30.9 kha) to negative (−17.3 kha) and mediated the positive direct effects in the long term (e.g. 100–150 years). Direct effects had greater influence than indirect effects on ROB disturbed areas in the short term (e.g. <50 years), whereas indirect effects were more important (ω2 = 0.38 vs. 0.26) in the long term. This was because the host tree abundance significantly declined over time under warming climates, which decreased the forest susceptibility to ROB and thus overrode the outbreak‐promoting effects of warming climates in the long term. Synthesis and applications. This study reveals indirect effects of warming climates mediate direct effects on insect disturbance regimes by altering primary host tree demographic dynamics. We highlight that indirect effects are important in understanding insect disturbance regimes under warming climates as they may mediate or even reverse the expectation of increased insect disturbance. Long‐term predictions of insect disturbance without considering indirect effects may overestimate its impacts under warming climates. Our findings also indicate that different management interventions are required at different time‐scales to maintain oak forests' health and sustainability in the U.S. central temperate broadleaf forests.

Рост и состояние смешанных древостоев лесных насаждений Каменной Степи

By now, a vast amount of experimental material has been accumulated in the field of protective afforestation of the Central Chernozem Region of Russia, which allows estimating the stability and longevity of various trees and shrubs in different environmental conditions. Good growth and high vitality of woody vegetation largely depend on growing conditions and are determined primarily by the relationship between species (individuals within a species) when they are placed in the forest area and the type of terrain. The researchdifferent combinations in tree and shrub mixing schemes and unequal location by types of terrain. The study was carried out in mature (115–118-year-old) forest strips laid out by the staff of the Kamennaya Steppe experimental forestry G.F. Morozov and N.A. Mikhailov on the territory of the Kamennaya Steppe (Voronezh region, Talovsky district) using archival materials, scientific works of the authors of this article and the employees of the Department of Agroforestry. A comparative analysis of the materials of forest survey work carried out in protective forest plantations created according to the tree-shrub type of mixing on different types of terrain revealed an excess of biometric indicators of tree species growing on the upland type of terrain over those on the slope. It is shown that the initial percentage of participation of English oak is a significant, but not always decisive factor in the creation of oak plantations. They can also be grown with a smaller proportion of this species in the culture, but in this case, timely thinning will be of paramount importance. Over time, there have been significant changes in the composition of plantations, the number of trees and their valuation indicators. There are no viable ash and elm specimens left in the upper tier of the stands. They are severely damaged by stem pests. Certain tree species are damaged by the following pests: common ash by large ash bark beetle (Hylesinus crenatus) and ash bark beetle (Hylesinus fraxini); elm species by cambium-feeding beetles (large elm bark beetle (Scolytus scolytus), European elm bark beetle (Scolytus multistriatus), and pygmy elm bark beetle (Scolytus pygmaeus); English oak by gold pit oak splendour beetle (Chrysobothris affinis), oak borer (Agrilus angustulus), longhorn beetle (Plagionotus detritus), and European oak bark beetle (Scolytus intricatus). The predominant number of trees of all tree species belongs to the categories of limited viable and inviable.

Improving trapping methods for buprestid beetles to enhance monitoring of native and invasive species

AbstractMost of the current understanding of the orientation and communication of jewel beetles arose from research on the Asian emerald ash borer (EAB), Agrilus planipennis, which has become one of the most destructive invasive forest insect pests in history following its introduction to North America and European Russia. From a European perspective, a number of jewel beetles have a high invasive risk similar to that of the emerald ash borer, including the potential threat of the bronze birch borer Agrilus anxius, the goldspotted oak borer Agrilus auroguttatus, and the twolined chestnut borer Agrilus bilineatus. Native jewel beetles expanding their geographic range include the cypress jewel beetle Ovalisia festiva and the black-banded oak borer Coraebus florentinus. Other native species are increasing in their importance, including the flathead oak borer Coraebus undatus, the two-spotted oak borer Agrilus biguttatus, the flatheaded beech borer Agrilus viridis and Agrilus cuprescens. Commonly used prism and multi-funnel trap designs and other promising experimental trap designs have been tested and compared in the US and in Europe. One factor considered has been colouration, typically purple and green. Another is olfactory attraction, both to plant volatiles and extracts such as (Z)-3-hexenol, Manuka oil, Phoebe oil and Cubeb oil, and also to pheromones such as (Z)-3-lactone, for emerald ash borer. Field observations have been made of mating and host-finding behaviours of oak buprestids based upon visual stimuli in North America and Europe. By using pinned dead EAB models, visual mating approaches have been observed by males of Agrilus biguttatus, Agrilus sulcicollis and Agrilus angustulus, which is a behaviour similar to that previously observed in EAB. Green plastic-covered branch-traps significantly out-performed other trap designs and caught more Agrilus jewel beetles if an artificial visual decoy that copies a beetle body was included. A higher fidelity decoy offered the same distinctive light-scattering pattern as real resting EAB females and elicited the full sequence of stereotypical male mating flight behaviour of EAB and A. biguttatus from up to 1 m away. An optimization of visual, olfactory and other possible stimuli has likely not yet been achieved. More sophisticated trap designs could lead to more sensitive detection capabilities with increased selectivity.

Two chiral types of randomly rotated ommatidia are distributed across the retina of the flathead oak borer Coraebus undatus (Coleoptera: Buprestidae).

Jewel beetles are colorful insects, which use vision to recognize their conspecifics and can be lured with colored traps. We investigated the retina and coloration of one member of this family, the flathead oak borer Coraebus undatus using microscopy, spectrometry, polarimetry, electroretinography and intracellular recordings of photoreceptor cell responses. The compound eyes are built of a highly unusual mosaic of mirror-symmetric or chiral ommatidia that are randomly rotated along the body axes. Each ommatidium has eight photoreceptors, two of them having rhabdomeres in tiers. The eyes contain six spectral classes of photoreceptors, peaking in the UV, blue, green and red. Most photoreceptors have moderate polarization sensitivity with randomly distributed angular maxima. The beetles have the necessary retinal substrate for complex color vision, required to recognize conspecifics and suitable for a targeted design of color traps. However, the jewel beetle array of freely rotated ommatidia is very different from the ordered mosaic in insects that have object-directed polarization vision. We propose that ommatidial rotation enables the cancelling out of polarization signals, thus allowing stable color vision, similar to the rhabdomeric twist in the eyes of flies and honeybees.

Spatial patterns of within-treeEnaphalodes rufulus(Coleoptera: Cerambycidae) attacks during outbreak conditions in the Ozark National Forest in Arkansas, United States of America

AbstractEnaphalodes rufulus(Haldeman) (red oak borer; Coleoptera: Cerambycidae) is a native wood borer that colonises and develops in oaks (QuercusLinnaeus; Fagaceae) across southeastern Canada and the eastern United States of America. It is rarely considered a pest because it normally occurs at low population density levels in stressed or dying oak trees. In the late 1990s and early 2000s there was a large, historically unique outbreak ofE.rufulusin the Ozark mountains of Arkansas and Missouri, United States of America. This outbreak provided an opportunity to investigate within-tree spatial distribution of attacks during unusually high insect population levels. Fifty trees from northern Arkansas were felled and destructively sampled. The locations of attack sites by femaleE.rufuluswere standardised across varying heights and diameters for comparison across trees. Attack sites showed a significant clustered pattern within trees. Attack sites were aggregated towards the lower and middle bole, and on the south-facing side of trees. This pattern has been seen in other insects, including wood borers, and is potentially related to differences in temperature. These patterns of ovipositional behaviour in outbreak situations have implications forE.rufulusresource partitioning and facultative intraguild predation among larvae.

Plant Pathogenic Fungi Associated with Coraebus florentinus (Coleoptera: Buprestidae) Attacks in Declining Oak Forests

The black-banded oak borer, Coraebus florentinus, is an emerging pest of oak trees in the western Mediterranean region. Larvae of the insect are xylophagous and progressively excavate an annular gallery that interrupts sap flow, resulting in the death of the attacked branches. Until now, limited information has been available regarding the ecological interactions between C. florentinus and the main plant pathogenic fungi involved in the etiology of oak decline. Knowledge of these interactions is important in understanding their impact in natural ecosystems and developing appropriate management strategies. Therefore, in this study, we characterized the fungal communities occurring in the exoskeleton of adults and larvae of C. florentinus and associated with the necrotic wood tissues surrounding the branch galleries of declining oak trees. A total of 29 fungal species were identified based on DNA sequence data and morphological features, of which 14 were from symptomatic woody tissues, six from insect exoskeleton, and nine from both insects and symptomatic wood tissues. The most frequent fungal species, Cryphonectria naterciae (15.9% of isolates), Dothiorella iberica (11.3%), and Diplodia corticola (9.9%), were isolated from both insect and gallery systems. All three species are well-known oak pathogens and are reported here, for the first time, to be associated with C. florentinus. At the same time, 89.6% of the fungal taxa were isolated from one or two sites, highlighting the site-dependence of fungal community assemblages.

Integrated management of the charcoal disease by silviculture, chemical and biological methods in forest parks

ABSTRACTBiscogniauxia mediterranea (De Not.) Kuntze, is a widespread fungus, causes outbreaks of Charcoal disease on cork oak and dieback thousands oak trees in recent years in Iran. Yet no efficient and effective management methods have been found to control the disease. The present study aimed to provide a suitable method for charcoal disease management through silviculture operations, systemic pesticides and biological compounds. The results showed that, simultaneous implementation of silvicultural practices (scarification+sanitation), use of systemic fungicides and Trichoderma compounds, reduce the number and depth of cankers, increase callus thickness, and ultimately improve health of the diseased trees. But disease severity and fungi activity were increased when scarification operation implements alone. The greatest effectiveness of the treatments and health condition improvement of the diseased trees was observed 12 months after applying the treatments. Then, preventive and therapeutic effectiveness of the treatments reduced over time. Sanitation and scarification practices can increase soil permeability and also destroy the larvae, pupa or adult insects and oak borer beetles that play an important role in disease outbreaks. Therefore, simultaneous implementation of sanitation and scarification practices with application of biological and systemic compounds can reduce primary source of pathogen inoculum and help trees to recover their health.

Effect of Contact Insecticides Against the Invasive Goldspotted Oak Borer (Coleoptera: Buprestidae) in California.

The goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), was linked in 2008 to ongoing tree mortality in oak woodlands of southern California. Mortality of coast live oak, Quercus agrifolia Née, and California black oak, Q. kelloggii Newb., continues as this exotic phloem borer spreads in southern California. Management options are needed to preserve high-value oaks and maintain management objectives. From 2009 to 2012, we tested four contact insecticide formulations in four experiments against A auroguttatus in California. The impact of contact insecticides was evaluated ∼<1, 8, and 12 mo postapplication against A auroguttatus adults in no-choice leaf-feeding or walking bioassays. At <1 mo postapplication, bifenthrin, carbaryl, lambda-cyhalothrin, and permethrin all reduced adult survival and feeding in leaf-feeding and walking bioassays. At 8 mo postapplication, only bifenthrin reduced adult feeding, but had no effect on survivorship. At 12 mo postapplication, adult A auroguttatus survived fewer days and fed less in leaf-feeding bioassays with bifenthrin, carbaryl, and permerthin. These results support the annual application of contact insecticides prior to A auroguttatus' flight period to reduce adult leaf maturation feeding and activity on the bark surface (e.g., oviposition), but additional studies are needed to show these contact treatments can prevent tree mortality from this invasive species.

Ecología y fitosanidad de los encinos (Quercus spp.) en la Sierra Fría, Aguascalientes, México

Durante los años 2007, 2008 y 2009 se condujo un estudio para evaluar la distribución y abundancia de las especies de encinos (Quercus spp), los factores ambientales que afectan su distribución y la identificación de los patógenos e insectos asociados a la declinación y muerte de estos árboles en la Sierra Fría, Aguascalientes. Para evaluar la distribución y abundancia se realizaron 60 inventarios de la vegetación en 60 sitios de muestreo distribuidos al azar utilizando parcelas de 600 m2. Para la identificación de los fitopatógenos se hicieron 28 transectos, revisando 100 árboles en cada uno. Para la identificación de los insectos asociados con la declinación de los encinares se instalaron trampas de emergencia sobre el fuste de árboles con síntomas de ataque de insectos barrenadores y se tomaron muestras de fuste, las cuales se observaron en laboratorio. Se identificaron 10 especies de encinos, siendo la altitud, el relieve, la exposición del sitio y la fisiografía las variables que influyeron sobre su distribución y abundancia. Se identificaron los fitopatógenos Phellinus robustus, P. gilvus, P. everhartii, Ganoderma lucidum e Hypoxylon thouarsianum, siendo el último el más ampliamente distribuido. Se identificó al barrenador Crioprosopus magnificus infestando encinos vivos. La información obtenida contribuye al manejo de la Sierra Fría y se sugiere profundizar en estos estudios.

Evaluation of the host specificity of Spathius galinae (Hymenoptera: Braconidae), a larval parasitoid of the emerald ash borer (Coleoptera: Buprestidae) in Northeast Asia

Host-specificity determination prior to the introduction of non-native natural enemies is a critical component of the risk assessment for modern classical biocontrol programs. In the present study, we assessed the host specificity of a newly described parasitoid, Spathius galinae Belokobylskij and Strazanac, which is native to Northeast Asia, for classical biocontrol of the invasive emerald ash borer (EAB), Agrilus planipennis Fairmaire, in North America. Along with foreign exploration for natural enemies of EAB in 2010 and 2012, we surveyed ash (Fraxinus spp.) wood-boring insects and their parasitoids from artificially stressed Oriental ash (F. rhynchophylla Hance) trees in natural forest stands in the Primorskiy Kray region of Russia. Once colonies of S. galinae were established in U.S. quarantine, we tested the parasitoid against 15 species or groups of North American wood-boring insects that were selected along a continuum from closely related taxa (e.g., Agrilus spp. in the family Buprestidae in Coleoptera) to distantly related ones in Lepidoptera and Hymenoptera. While three of the tested insects, Neoclytus acuminatus Fabricius, Podosesia spp. and Hylesinus fraxini Panzer attack ash as their main host, the rest attack non-ash trees such as birch, maple and oak. Results from our field survey in Russia showed that S. galinae did not attack bark beetles (Hylesinus spp.) or longhorned beetles (Cerambycidae) that coexisted with EAB on infested ash trees. In quarantine laboratory studies, S. galinae did not attack 14 species or groups of non-target wood-boring insects infesting both ash and/or non-ash trees such as birch, maple or red oak. The only non-target attack was on the goldspotted oak borer (GSOB), Agrilus auroguttatus Schaeffer, infesting red oak. The rate of parasitism on GSOB was significantly lower than on EAB under laboratory conditions that favored parasitism. These findings indicate that the host specificity of S. galinae is restricted within the host genus (Agrilus).

Native and introduced range surveys for egg parasitoids of Agrilus auroguttatus, an invasive pest of native oaks in California

The invasive goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), has caused extensive mortality to indigenous oaks in southern California. This woodborer is native to southern Arizona where low population densities may, in part, be due to the presence of co-evolved natural enemies. Surveys were conducted in Arizona and California from June to August 2013 by deploying sentinel egg masses in an attempt to attract, collect and identify potential egg parasitoids of this beetle that could be used for a classical biological control programme in California. In total, 18,052 A. auroguttatus eggs were deployed throughout the native and introduced range. Parasitoids did not attack any eggs deployed in Arizona or California. The inability to detect egg parasitoids could be explained by the following: (1) host-specific egg parasitoids of A. auroguttatus do not exist, (2) surveying time did not coincide with peak activity of egg parasitoids or (3) surveying methods were insufficient at detecting egg parasitoids.

Impact of the goldspotted oak borer, Agrilus auroguttatus, on the health of coast live oak before and after treatment with two systemic insecticides.

The invasive goldspotted oak borer, Agrilus auroguttatus, is threatening the health and survival of oak trees in San Diego County, California. From two sites in the core area of the infestation, we report a 2.5 year investigation of the impact of A. auroguttatus on coast live oak, Quercus agrifolia, before and after treatment with two systemic insecticides, emamectin benzoate (EB) and imidacloprid (IC). None of the 446 survey trees died during the study. The crown dieback rating of most trees at both study sites remained unchanged, regardless of insecticide treatment. A higher cumulative increase in the number of A. auroguttatus emergence holes was observed on trees that were previously infested and on trees with larger diameters. Over the 2.5 year period, the new infestation rates of initially uninfested trees across the untreated and treated groups were 50% (EB) and 32% (IC), and neither EB nor IC treatment affected cumulative increases in the number of emergence holes. EB-injected trees did not have significant annual increases in the number of A. auroguttatus emergence holes at either 1.5 or 2.5 years compared with that at 0.5 years, whereas untreated trees had significant annual increases. Although IC-injected trees had a significantly greater annual increment in the number of emergence holes than untreated trees during the last year of the study, treated trees had significant reductions in annual increases in emergence holes at both 1.5 and 2.5 years compared with that at 0.5 years. Untreated trees had no significant reduction in the annual increase in emergence holes at 1.5 and 2.5 years. A. auroguttatus preferentially attacked previously infested and larger (diameter at breast height > 15-30 cm) oak trees, but the attacks led to very gradual changes in the health of the trees. Both EB and IC provided minor suppressive effects on A. auroguttatus emergence. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Effects of mating on the termination of aggregation by the oak borer, Platypus quercivorus (Murayama) (Curculionidae: Platypodinae) during host colonization

We conducted a field experiment to determine whether logs bored by male Platypus quercivorus beetle were less attractive to conspecifics after beetles had mated. Bored (with male beetles) and unbored logs were placed in a beetle-infested forest and enclosed within a cage. For half of the bored logs, female beetles were released to mate with the male beetles. Log attractiveness was determined by assessing the number of beetles captured on adhesive paper placed on each cage enclosing the log. On the logs on which female beetles were released, the number of beetles captured decreased distinctly after release, and did not differ from the number captured on the unbored logs. In contrast, the number of beetles captured on logs with only unpaired males was higher than the number captured on the unbored logs. This result confirms that the attractiveness of logs bored by male P. quercivorus beetles declines after mating occurs. To our knowledge, this is the first evidence for the relaxation of aggregation pheromone following mating for beetles in the subfamily Platypodinae.

Goldspotted oak borer effects on tree health and colonization patterns at six newly-established sites

Newly-established populations of invasive wood-inhabiting insects provide an opportunity for the study of invasion dynamics and for collecting information to improve management options for these cryptic species. From 2011 to 2013, we studied the dynamics of the goldspotted oak borer Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), a new pest of oaks in southern California, at six sites that had been colonized recently. At all sites, the percentage of coast live oaks Quercus agrifolia Née, colonized by A. auroguttatus increased between 2011 (6–33%) and 2013 (23–40%), although beetle densities did not grow rapidly at most sites. From 2011 to 2013, there were minor changes in signs and symptoms of A. auroguttatus infestation (adult emergence holes, bark staining, and evidence of woodpecker foraging), except at one site where an outbreak occurred. At some sites, noticeable negative changes in oak crown health occurred 1 year prior to positive A. auroguttatus population growth. Among sites, most of the A. auroguttatus population density (66–93%) was produced by a small number of heavily-infested trees (= brood trees). Early identification and removal of brood trees in newly-invaded areas could slow the growth of A. auroguttatus populations.

Field trapping of the flathead oak borer Coroebus undatus (Coleoptera: Buprestidae) with different traps and volatile lures.

The flathead oak borer Coroebus undatus F. (Coleoptera: Buprestidae) is one of the primary pests of cork oak Quercus suber L. in the Mediterranean region causing great economic losses to the cork industry. Very little is known about its biology and behavior and, so far, no control measures have been established. We present the results of a pilot study aimed to develop an efficient trapping method for monitoring this harmful pest. In a 3-year field study, purple-colored prism traps baited with a mixture of green leaf volatiles (GLVs) from the host have been shown the most effective combination to catch C. undatus adults (solely females) compared to other trap and lure types tested. Wavelength and reflectance measurements revealed that purple traps exhibit reflectance peak values similar to those found in the abdominal and elytral cuticle of both sexes, suggesting the involvement of visual cues for mate location in this species. The data presented are the first to demonstrate captures of adults of the genus Coroebus by an attractant-based trapping method.

Pyemotes tritici (Acari: Pyemotidae): a parasitoid of Agrilus auroguttatus and Agrilus coxalis (Coleoptera: Buprestidae) in the southwestern United States of America and southern Mexico

AbstractThe straw itch mite, Pyemotes tritici Lagrèze-Fossat and Montané (Acari: Pyemotidae), was discovered parasitising the goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), an invasive exotic species to California, United States of America, and the Mexican goldspotted oak borer, Agrilus coxalis Waterhouse (Coleoptera: Buprestidae), during surveys for natural enemies for a classical biological control programme for A. auroguttatus. Pyemotes tritici caused low levels of mortality to each species of flatheaded borer, but it will likely not be a good candidate for a biological control programme because it is a generalist parasitoid with deleterious human health effects.

Developing monitoring techniques for the invasive goldspotted oak borer (Coleoptera: Buprestidae) in California.

The goldspotted oak borer, Agrilus auroguttatus Schaeffer (Coleoptera: Buprestidae), is an invasive species that has colonized oak woodlands in southern California. To better define its seasonal flight activity, assist with forest and integrated pest management activities, and define the current distribution in California, an effective monitoring technique for A. auroguttatus is necessary. We assessed the efficacy of two colors of flight-intercept prism traps, the placement of these traps at three heights, and several commercially available lures [Manuka oil, Phoebe oil, and a green leaf volatile, (3Z)-hexenol] for monitoring the flight of adult A. auroguttatus. Landing rates and the densities of D-shaped emergence holes of A. auroguttatus adults were assessed on the lower stems of coast live oak, Quercus agrifolia Née, of varying size and crown health classes. Purple flight-intercept prism traps placed at heights of 3 m and 4.5 m caught significantly more female A. auroguttatus than green prism traps. In one experiment, males also responded at a significantly higher level to purple than to green prism traps placed at 3 m height. The addition of commercially available lures significantly enhanced male, but not female, A. auroguttatus trap catch when compared with unbaited control traps. There were no differences among male flight responses to the three lures. A. auroguttatus landing rates and emergence hole densities were significantly greater on the largest-diameter trees (>76.2 cm diameter at breast height) and on trees with severe crown thinning or complete crown collapse. The annual increment in emergence hole densities was also significantly greater on trees with severe crown thinning or complete crown collapse. In three trapping studies over multiple years in southern California, the adult flight period began as early as mid-May, peaked in mid-June to early July, and ended in early- to mid-September. To demonstrate the efficacy of the detection method for A. auroguttatus (unbaited purple traps at 3 m height), a delimitation survey conducted from 2009 to 2012 confirmed that the species was only present in San Diego Co., but that the distribution was expanding northward.