RESUMO
Laurel wilt (LW) is a vascular disease caused by the fungus Harringtonia lauricola (previously Raffaelea lauricola) and transmitted by its primary vector, the redbay ambrosia beetle (Xyleborus glabratus, RAB), both of which were first detected in the United States (US) in 2002, likely introduced from their native range in Asia (Fraedrich et al. 2008; Harrington et al. 2008). LW has since spread across the southeastern US causing the death of millions of native redbay, sassafras, silk bay, swamp bay and other native Lauraceae species (Hughes et al. 2017). Detection of LW on the deciduous understory shrub northern spicebush (Lindera benzoin) was previously reported in South Carolina (Fraedrich et al. 2016) and Louisiana (Olatinwo et al. 2021) and is hereby confirmed in Kentucky and Tennessee. Spicebush plants displaying typical LW symptoms were observed in September 2020 on a property spanning the KY/TN border (Christian Co., KY and Montgomery Co., TN). Several dense stands of spicebush exhibited leaf wilt, early fall leaf coloration, dead leaves on branches, and black streaks of discolored xylem. LW was already confirmed on sassafras in the area (Loyd et al. 2020), and there were abundant dead sassafras nearby. Ambrosia beetle boring dust was observed and callow female RABs emerged from containerized bolts of spicebush collected from the site, indicating that the vector used spicebush as a brood host. Samples of spicebush sapwood tissue collected from two symptomatic plants were plated onto CSMA (cycloheximide-streptomycin malt extract agar) medium. The cultures were grown at room temperature in ambient light, and a fungus was recovered and further transferred onto MEA (malt extract agar) and PDA (potato dextrose agar) media. The morphology of the two fungal isolates, referred to as LW415 and LW416, matched the typical white mucoid growth and ovoid conidia of H. lauricola (Harrington et al. 2008). DNA was extracted from conidia harvested from two-week-old MEA cultures using a modified method of Dreaden et al. (2014). The identity of the fungus was confirmed by performing PCR with the H. lauricola-specific microsatellite primer sets IFW and CHK (Dreaden et al. 2014, Parra et al. 2020). A positive amplification product was obtained for LW415 and LW416 for both primer sets, validating their identification as H. lauricola. To confirm pathogenicity, four spicebush seedlings (mean height 22.5 cm; mean ground line diameter 3.3 mm) were inoculated: two with H. lauricola isolate LW415 grown on PDA for two weeks at room temperature in the dark, and two were mock-inoculated with sterile PDA as a control. A scalpel was used to nick the spicebush stem at a bud about 5 cm above groundline, and a 3 mm2 agar plug was placed in the wound and wrapped with parafilm. The spicebush seedlings were maintained in a growth chamber with an average temperature of 24°C and a 15 h photoperiod. Wilt symptoms were evident on inoculated seedlings after two weeks, while the control plants remained healthy. Four weeks post-inoculation, black staining of the vascular tissue was present in the symptomatic seedlings, and a fungus matching the morphology of H. lauricola was consistently recovered, while no fungus was isolated from the control plants. These results provide additional evidence that northern spicebush populations may be threatened by LW and could serve as a reservoir for the pathogen and vector (Gramling 2010). The spread of LW and RAB on spicebush may gain importance as preferred hosts (e.g., sassafras) are killed.
RESUMO
The Asiatic oak weevil, Cyrtepistomus castaneus Roelofs (Coleoptera: Curculionidae), is a nonnative defoliator of trees in the Fagaceae family in the United States but has not been studied on Castanea species in the southern Appalachian Mountains. Planted trees of Castanea dentata (Marsh.) Borkh. (Fagales: Fagaceae), Castanea mollissima Blume (Fagales: Fagaceae), and four hybrid breeding generations were evaluated in 2012 for insect defoliation and C. castaneus abundance and frequency. Defoliation was visually assessed throughout the growing season at two sites in the southern Appalachian Mountains (western North Carolina and eastern Tennessee). C. castaneus abundance and frequency were monitored on trees using beat sheets and emergence was recorded from ground traps. Asiatic oak weevils were more abundant and more frequently collected on American chestnut (Ca. dentata) and its most closely related BC3F3 hybrid generation than on the Asian species Ca. mollissima. In most months, C. castaneus colonization of hybrid generations was not significantly different than colonization of parental species. Frequency data for C. castaneus suggested that adults were distributed relatively evenly throughout the study sites rather than in dense clusters. Emergence of C. castaneus was significantly higher under a canopy dominated by Quercus species than under non-Quercus species or open sky. C. castaneus emergence began in May and peaked in late June and early July. These results may be useful for resource managers trying to restore blight-resistant chestnut to the Southern Appalachians while minimizing herbivory by insect pests.
Assuntos
Fagaceae/parasitologia , Gorgulhos/fisiologia , Animais , Região dos Apalaches , Folhas de Planta/parasitologia , Densidade Demográfica , Árvores/fisiologiaRESUMO
The hemlock woolly adelgid Adelges tsugae Annand (Hemiptera: Adelgidae), is a non-native invasive pest that has caused widespread decline and mortality of eastern hemlock (Tsuga canadensis (L.) Carr. (Pinales: Pinaceae)) and Carolina hemlock (T. caroliniana Engelm.) in the eastern United States. Our preliminary experiments evaluated the utility of a rain-down technique to induce artificial infestations of A. tsugae on hemlock seedlings en masse. Experiments were conducted in PVC (1 m3) cages topped with poultry wire for placement of A. tsugae-infested branches, and with 1 m(2) gridded glue sheets and/or hemlock seedlings placed below to capture adelgid abundance, distribution, and infestation rate data. In the March 2011 experiment, the density of progrediens crawlers (adelgid nymphs, first instars) that rained down inside the PVC cages was significantly higher in the high ovisac treatment compared to the low ovisac treatment, with an estimated 513,000 and 289,000 crawlers per m(2) falling beneath each treatment, respectively. Resulting A. tsugae infestation rates on Carolina hemlock seedlings placed inside the cages did not differ between the treatments but were at or above established damage threshold densities for the adelgid. Infestation rates on eastern hemlock seedlings that were placed in cages nine days after the experiment started were below damage threshold levels and did not differ between the treatments. In the May 2011 experiment, the density of sistens crawlers raining down was substantially lower, with 17,000 and 33,000 falling per m(2) in the low and high ovisac treatments, respectively. Resulting infestation rates on Carolina hemlock seedlings were extremely low and well below damage threshold levels. Although A. tsugae crawlers were well distributed across the 1 m(2) gridded glue sheets placed at the bottom of each cage, hot spots of unusually high crawler density did occur in both experiments. This rain-down technique shows potential for use in an operational tree-breeding program where screening large numbers of hemlock seedlings for resistance to A. tsugae is required.
Assuntos
Hemípteros/fisiologia , Doenças das Plantas/parasitologia , Tsuga/parasitologia , Animais , Equipamentos e Provisões , Interações Hospedeiro-Parasita , Ninfa/fisiologiaRESUMO
In 2009, we determined the effects of the enantiomeric composition of the kairomone, α-pinene, on trap catches of arboreal beetles (Coleoptera) in stands of eastern pine trees with resin dominated by (+)-α-pinene. We hypothesized that the responses of beetles would correlate with the predominant enantiomer of α-pinene found in host pines. Lures of (+)-, racemic (±), and (-)-α-pinene were added separately to ethanol-baited multiple-funnel traps. Species such as Monarthrum mali (Fitch), Dendroctonus terebrans (Olivier), Ips grandicollis (Eichhoff), and Pachylobius picivorus (Germar) (Coleoptera: Curculionidae) showed a preference for traps co-baited with (-)-α-pinene. α-Pinene enhanced attraction of Hylastes salebrosus Eichhoff, Hylastes porculus Erickson and Hylastes tenuis Eichhoff (Coleoptera: Curculionidae) to ethanol-baited traps with no effects from enantiomeric composition of α-pinene. The attraction of the ambrosia beetles, Xyleborinus saxesenii (Ratzeburg) and Dryoxylon onoharaense (Murayama) (Coleoptera: Curculionidae) to ethanol-baited traps was interrupted by the addition of α-pinene, regardless of enantiomeric composition. Species such as Xylosandrus germanus (Blandford), Cnestus mutilatus (Blandford) and Stenoscelis brevis (Boheman) (Coleoptera: Curculionidae) were unaffected by the presence of α-pinene. Trap catches of some species of longhorn beetles and bark beetle predators (Coleoptera: Cerambycidae, Cleridae, Elateridae, Histeridae, and Trogossitidae) were increased by the addition of α-pinene, although results varied by location. Platysoma spp. (Coleoptera: Histeridae) showed a marked preference for traps co-baited with (+)-α-pinene in Florida and Georgia. In summary, we found that the enantiomeric composition of α-pinene in hosts was not a good predictor of enantiomeric preferences by beetles.
Assuntos
Monoterpenos Bicíclicos , Besouros , Controle de Insetos , Monoterpenos , Animais , Monoterpenos/farmacologia , Besouros/efeitos dos fármacos , Feromônios/farmacologia , Estereoisomerismo , Gorgulhos/efeitos dos fármacos , Pinus/química , Etanol/farmacologiaRESUMO
In 2007-2008, we examined the flight responses of Monochamus titillator (F.) complex [M. titillator, Monochamus carolinensis (Olivier), and any possible hybrids], Monochamus scutellatus (Say), Monochamus clamator (LeConte), Monochamus obtusus Casey, and Monochamus mutator LeConte (Coleoptera: Cerambycidae) to multiple-funnel traps baited with and without host volatiles and bark beetle pheromones. Experiments were conducted in mature pine (Pinus) stands in Alberta (Canada), and Arkansas, Arizona, California, Florida, Idaho, Michigan, Montana, New Hampshire, North Carolina, Ohio, Oregon, Tennessee, Utah, and Wisconsin (United States). At each location, traps were deployed in 10 replicate blocks of four traps per block. The trap treatments were: 1) blank control; 2) ipsenol and ipsdienol; 3) ethanol and alpha-pinene; and 4) a quaternary blend of ipsenol, ipsdienol, ethanol, and alpha-pinene. All five species or species complex of Monochamus preferred traps baited with the quaternary blend over all other treatments. The consistency of these results across such a large geographic area suggests that similar selection pressures may be acting on Monochamus spp. in pine forests, regardless of variation in stand composition and climatic conditions. Our results suggest that multiple-funnel traps baited with the quaternary blend ofipsenol, ipsdienol, ethanol, and alpha-pinene may be highly effective for monitoring various Monochamus spp. in pine forests of North America, and may have utility in trapping and detection programs in North America and overseas.
Assuntos
Besouros/efeitos dos fármacos , Etanol/farmacologia , Monoterpenos/farmacologia , Feromônios/farmacologia , Monoterpenos Acíclicos , Alberta , Álcoois/farmacologia , Animais , Monoterpenos Bicíclicos , Controle de Insetos , Octanóis/farmacologia , Pinus/química , Especificidade da Espécie , Estados UnidosRESUMO
Following the adventive arrival, subsequent spread, and ensuing impact of Adelges tsugae Annand (Hemiptera: Adelgidae), the hemlock woolly adelgid (HWA) in the eastern United States, a robust initiative was launched with the goal of decreasing ecosystem impacts from the loss of eastern hemlock (Pinales: Pinaceae). This initiative includes the use of biological control agents, including Laricobius spp. (Insecta: Coleoptera). Laboratory production of these agents is limited by subterranean mortality and early emergence. Therefore, the subterranean survivorship and timing of emergence of a mixture of Laricobius spp. was investigated. PVC traps internally lined with a sticky card and covered with a mesh screen were inserted into the soil to measure the percent emergence of adults based on the number of larvae placed within. The number of emerged adults in the field and laboratory-reared larval treatments was adjusted based on emergence numbers in the control and used as the response variable. Independent variables included in the final model were: treatment (field-collected vs. laboratory-reared), organic layer depth (cm), soil pH, and April-to-December mean soil moisture. No differences were found in survivorship between field-collected and laboratory-reared treatments. As pH and organic layer increased survivorship decreased, significantly. Although the majority of emergence occurred in the fall, emergence also occurred in spring and summer. The occurrence of spring and summer emergence and low survivorship (17.1 ± 0.4%) in the field across all treatments suggests that these are characteristics of Laricobius spp. field biology in their introduced range and not artifacts of the laboratory rearing process.
Assuntos
Besouros , Hemípteros , Cicutas (Apiáceas) , Animais , Agentes de Controle Biológico , Besouros/fisiologia , Ecossistema , Hemípteros/fisiologia , Comportamento Predatório , Estações do Ano , Sobrevivência , TsugaRESUMO
A predator, Laricobius osakensis Montgomery and Shiyake (Coleoptera: Derodontidae), is being mass-produced and released for the biological control of the invasive hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae). To better understand and predict the seasonality of this predator in North America, the development and reproduction of L. osakensis were evaluated at constant temperatures ranging from 5 to 22°C. The predicted seasonal biology was compared with data from field collections. L. osakensis did not complete development from egg to adult at the two lowest temperatures tested, 5 and 8°C, but did so at the highest temperature of 22°C. The minimum development thresholds were estimated for eggs (4.2°C), first (1.8°C), second (5.5°C), third (4.6°C), and fourth instar (4.1°C), prepupa (3.6°C), and pupa (7.5°C). Oviposition rates were significantly greater at 5 and 10°C than at 20 and 25°C. Head capsule width significantly increased for each of the four larval instars with a mean of 0.19, 0.26, 0.35, and 0.44 mm, respectively. Laboratory and field data were used to develop a phenology forecasting model to predict the occurrence of all developmental stages of L. osakensis. This model will allow land managers to more accurately predict the optimal timing for L. osakensis larval sampling throughout its established range.
Assuntos
Besouros , Hemípteros , Animais , Feminino , Larva , Oviposição , Comportamento Predatório , TemperaturaRESUMO
Efficient separation of insects from plant material for quantification and collection is an important component of entomological research. This paper reports on a novel, easily replicable container designed to efficiently collect two different biological control agents dispersing from hemlock (Tsuga spp.) foliage infested with the invasive hemlock woolly adelgid (HWA), Adelges tsugae Annand (Hemiptera: Adelgidae). The container utilizes a simplified Berlese-style funnel design to collect Laricobius spp. (Coleoptera: Derodontidae) larvae dropping from the foliage into a removable bottom jar, a central jar to house the foliage sample, and a removable top jar to collect adult silver flies (Leucopis spp., Diptera: Chamaemyiidae) emerging from puparia on the twigs. The efficacy of two designs (with and without a funnel leading to the top collection jar) was evaluated using western hemlock [Tsuga heterophylla (Raf.) Sarg.] foliage naturally colonized with HWA and the two predator genera. All Laricobius larvae were effectively collected in the bottom jar, and the addition of an inverted funnel leading to the top collection jar increased the proportion of Leucopis flies reaching the target jar from 60% to 94%. This 'Lari-Leuco' container is presented as a research and motoring tool to benefit the integrated pest management program for HWA in eastern North America and for potential use in simultaneously separating ascending and descending life stages in other insect-plant or predator-prey systems.
Assuntos
Besouros , Dípteros , Hemípteros , Animais , Comportamento Predatório , TsugaRESUMO
Formulations of entomopathogenic (insect-killing) fungi represent alternatives to synthetic insecticides in the management of forest and shade tree insects. We evaluated bark spray applications of the entomopathogen Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) strain GHA (BotaniGardES), permethrin insecticide (Astro), and water (control) on colonization of black walnut (Juglans nigra L.) (Fagales: Juglandaceae) bolts by the walnut twig beetle (Pityophthorus juglandis Blackman) (Coleoptera: Curculionidae), vector of the fungus that causes thousand cankers disease. Treated bolts were baited with a P. juglandis aggregation pheromone lure and deployed in infested walnut trees. Bark application of permethrin prevented P. juglandis colonization of the phloem. Although treatment of bolts with the B. bassiana suspension did not reduce P. juglandis colonization or short-term emergence relative to the control treatment, it increased the B. bassiana infection rate from 25 to 62% of emerged adults. Results suggest that commercial applications of B. bassiana strain GHA may help augment natural levels of infection by this entomopathogen in the eastern United States, and support continued exploration of entomopathogens for biological control of the walnut twig beetle.
Assuntos
Beauveria , Besouros , Inseticidas , Juglans , Gorgulhos , Animais , Permetrina , Controle Biológico de Vetores , Casca de PlantaRESUMO
The redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), and its fungal symbiont, Raffaelea sp., are new introductions to the southeastern United States responsible for the wilt of mature redbay, Persea borbonia (L.) Spreng., trees. In 2006 and 2007, we investigated the seasonal flight activity of X. glabratus, its host associations, and population levels at eight locations in South Carolina and Georgia where infestations ranged from very recent to at least several years old. Adults were active throughout the year with peak activity in early September. Brood development seems to take 50-60 d. Wood infested with beetles and infected with the Raffaelea sp. was similar in attraction to uninfested redbay wood, whereas both were more attractive than a nonhost species. Sassafras, Sassafras albidium (Nutt.) Nees, another species of Lauraceae, was not attractive to X. glabratus and very few beetle entrance holes were found in sassafras wood compared with redbay. Conversely, avocado, Persea americana Mill., was as attractive to X. glabratus as swampbay, P. palustris (Raf.) Sarg., and both were more attractive than the nonhost red maple, Acer rubrum L. However, avocado had relatively few entrance holes in the wood. In 2007, we compared X. glabratus populations in areas where all mature redbay have died to areas where infestations were very active and more recent. Trap catches of X. glabratus and numbers of entrance holes in trap bolts of redbay were correlated with the number of dead trees with leaves attached. Older infestations where mature host trees had been eliminated by the wilt had low numbers of beetles resulting in trap catches ranging from 0.04 to 0.12 beetles per trap per d compared with 4-7 beetles per trap per d in areas with numerous recently dead trees. Our results indicate beetle populations drop dramatically after suitable host material is gone and provide hope that management strategies can be developed to restore redbay trees. The lack of attraction of X. glabratus to sassafras suggests that spread of X. glabratus may slow once it is outside the range of redbay.
Assuntos
Comportamento Animal , Besouros/fisiologia , Interações Hospedeiro-Parasita , Persea/parasitologia , Estações do Ano , Animais , Besouros/microbiologia , Voo Animal , Geografia , Insetos Vetores , Doenças das Plantas/microbiologia , Densidade Demográfica , South Carolina , Especificidade da EspécieRESUMO
The walnut twig beetle (Pityophthorus juglandis Blackman) (Coleoptera: Curculionidae) is a regulated pest in the United States due to its causal role in thousand cankers disease of walnut trees, including the commercially valuable eastern black walnut (Juglans nigra L.). Several state quarantines designed to limit spread of P. juglandis regulate movement of kiln-dried walnut lumber that contains bark. Previous research demonstrated that P. juglandis will enter and re-emerge from bark of kiln-dried, J. nigra slabs subjected to extreme beetle pressure (baited with a pheromone lure and hung in infested J. nigra trees). This study evaluated P. juglandis bark colonization of both kiln-dried and fresh J. nigra slabs, varying the presence of aggregation pheromone and relative proximity to a beetle source. Wood treatment, slab location, and pheromone presence all significantly affected P. juglandis colonization, as assessed by subsequent beetle emergence. When placed on the ground directly beneath infested trees, kiln-dried slabs were not colonized, and fresh slabs were colonized only when baited with the pheromone lure (6/14 replicates). When placed in crowns of infested trees, kiln-dried slabs were colonized only when baited with pheromone (3/14 replicates), whereas fresh slabs were colonized with and without pheromone (14/14 and 1/13 replicates, respectively). Timing of emergence indicated that beetles did not reproduce in kiln-dried bark. Results suggest that the risk of kiln-dried walnut bark becoming colonized by the P. juglandis during movement of commercial wood products is very low. This information may be useful to government agencies that administer quarantines regulating the transport of walnut lumber.
Assuntos
Distribuição Animal , Cadeia Alimentar , Temperatura Alta , Juglans/fisiologia , Gorgulhos/fisiologia , Madeira/análise , Animais , Quimiotaxia , Herbivoria , Feromônios/farmacologia , Casca de Planta/fisiologia , Gorgulhos/efeitos dos fármacosRESUMO
The redbay ambrosia beetle, Xyleborus glabratus Eichhoff, is the principal vector of laurel wilt disease in North America. Lures incorporating essential oils of manuka plants ( Leptospermum scoparium J. R. Forster & G. Forster) or cubeb seeds ( Piper cubeba L.f.) are the most effective in-flight attractants to date. Using grids of traps baited with these essential oil lures, we evaluated 1) the effect of trap distance from a source beetle population on beetle captures, 2) the feasibility of trapping out low-density beetle populations, and 3) the effect of trap spacing on beetle captures. In the first experiment, increasing trap distance up to 300 m from a source X. glabratus population had little effect on beetle captures. In a second experiment conducted in a study area with very low beetle densities, trapping for 5 mo prior to deploying freshly cut, uninfested redbay bolts had no effect on subsequent attack densities. In a third experiment, numbers of X. glabratus captured in traps in the center of a grid of nine traps spaced 1 or 5 m apart were compared with lone baited or unbaited traps 30 m away. Relative to the more distant traps, the grid of baited traps neither increased captures in the unbaited center trap nor decreased captures in the baited center trap, regardless of spacing. The results suggest that the effective trapping distance of essential oil lures for X. glabratus is <1 m, and that newer, more attractive lures will be needed to be useful in managing X. glabratus populations.
RESUMO
From 2010 through 2013, adult emergence and seasonality of Laricobius nigrinus Fender, an introduced predatory species native to western North America, as well as hybridization with the native species Laricobius rubidus (LeConte), were evaluated using emergence traps and beat-sheet sampling in areas of previous release against hemlock woolly adelgid, Adelges tsugae Annand. The shortest emergence period of adult L. nigrinus was 7 wk beginning 22 October 2010, and the longest emergence was 15 wk beginning 17 October 2012. Native L. rubidus also were collected from emergence traps placed on the ground surface and beat-sheet samples all 3 yr, with emergence of L. rubidus initiating later than L. nigrinus each season. Seasonality of both Laricobius species was similar across a 44-mo study period. Adult L. nigrinus were present from October through April, and larvae of Laricobius spp. were collected from February to May. The average number of L. nigrinus from emergence traps was significantly greater than the average number of beetles collected from beat-sheet samples in 2010, while the converse was observed during 2012. Hybridization between L. nigrinus and L. rubidus was documented from 10.75% of specimens collected during 2010 and 2011, indicating periodic interbreeding between the introduced and native species. These findings suggest emergence trapping may be a useful method to assess establishment, population densities, and seasonality of Laricobius species in areas of release to enhance their use in management of A. tsuage.
Assuntos
Besouros/fisiologia , Cadeia Alimentar , Hemípteros , Estações do Ano , Animais , Besouros/genética , Besouros/crescimento & desenvolvimento , Hemípteros/fisiologia , Hibridização Genética , Larva/crescimento & desenvolvimento , Larva/fisiologia , Dinâmica Populacional , Pupa/crescimento & desenvolvimento , Pupa/fisiologia , TennesseeRESUMO
The predatory species Laricobius nigrinus (Fender) and Laricobius osakensis (Shiyake and Montgomery) (Coleoptera: Derodontidae) have been released for biological control of hemlock woolly adelgid (Adelges tsugae; Hemiptera: Adelgidae) in eastern North America. L. osakensis is native to Japan, whereas L. nigrinus is endemic to the Pacific Northwest of the United States and Canada. After release, L. nigrinus was found to hybridize with the native eastern species, Laricobius rubidus (LeConte). The purpose of this study is to observe prey location behaviors of these three Laricobius species and L. nigrinus × L. rubidus (Ln × Lr) hybrids. Olfactometer bioassays were used to test response to host odors of adelgid-infested eastern hemlock, uninfested eastern hemlock, and uninfested eastern white pine. Predators reacted in the olfactometer more quickly when adelgid-infested foliage was included as a choice. L. nigrinus preferred infested eastern hemlock over uninfested eastern white pine, and L. rubidus preferred uninfested eastern white pine over uninfested eastern hemlock. Laricobius hybrids did not show a preference for foliage types known to be primary adelgid hosts (eastern hemlock and eastern white pine). Unequal preference by species of Laricobius for host trees of different adelgid prey could therefore be maintaining Laricobius species barriers despite hybridization. L. osakensis for this study were reared in the laboratory, whereas other species in this study were collected from the field, yet still were attracted to infested and uninfested eastern hemlock. This species also responded most quickly in the olfactometer, which is encouraging for successful biological control with this species.
Assuntos
Comportamento de Escolha , Besouros/fisiologia , Hemípteros , Odorantes , Comportamento Predatório , Olfato , Tsuga/parasitologia , Animais , Bioensaio , Agentes de Controle Biológico , Quimera , PinusRESUMO
The invasive redbay ambrosia beetle, Xyleborus glabratus, is the primary vector of Raffaelea lauricola, a symbiotic fungus and the etiologic agent of laurel wilt. This lethal disease has caused severe mortality of redbay (Persea borbonia) and swampbay (P. palustris) trees in the southeastern USA, threatens avocado (P. americana) production in Florida, and has potential to impact additional New World species. To date, all North American hosts of X. glabratus and suscepts of laurel wilt are members of the family Lauraceae. This comparative study combined field tests and laboratory bioassays to evaluate attraction and boring preferences of female X. glabratus using freshly-cut bolts from nine species of Lauraceae: avocado (one cultivar of each botanical race), redbay, swampbay, silkbay (Persea humilis), California bay laurel (Umbellularia californica), sassafras (Sassafras albidum), northern spicebush (Lindera benzoin), camphor tree (Cinnamomum camphora), and lancewood (Nectandra coriacea). In addition, volatile collections and gas chromatography-mass spectroscopy (GC-MS) were conducted to quantify terpenoid emissions from test bolts, and electroantennography (EAG) was performed to measure olfactory responses of X. glabratus to terpenoids identified by GC-MS. Significant differences were observed among treatments in both field and laboratory tests. Silkbay and camphor tree attracted the highest numbers of the beetle in the field, and lancewood and spicebush the lowest, whereas boring activity was greatest on silkbay, bay laurel, swampbay, and redbay, and lowest on lancewood, spicebush, and camphor tree. The Guatemalan cultivar of avocado was more attractive than those of the other races, but boring response among the three was equivalent. The results suggest that camphor tree may contain a chemical deterrent to boring, and that different cues are associated with host location and host acceptance. Emissions of α-cubebene, α-copaene, α-humulene, and calamenene were positively correlated with attraction, and EAG analyses confirmed chemoreception of terpenoids by antennal receptors of X. glabratus.
Assuntos
Lauraceae/química , Lauraceae/parasitologia , Terpenos/isolamento & purificação , Gorgulhos/fisiologia , Animais , Feminino , Cromatografia Gasosa-Espectrometria de Massas/métodos , Lauraceae/classificação , Feromônios/isolamento & purificação , Extratos Vegetais/química , Olfato , Estados UnidosRESUMO
The redbay ambrosia beetle (Xyleborus glabratus Eichhoff) is an invasive pest and vector of the pathogen that causes laurel wilt disease in Lauraceous tree species in the eastern United States. This insect uses olfactory cues during host finding, but use of visual cues by X. glabratus has not been previously investigated and may help explain diameter-related patterns in host tree mortality. The objective of this study was to determine whether X. glabratus females visually detect silhouettes of tree stems during host finding and are more likely to land on large diameter stems than smaller ones. Three field experiments were conducted in which stem silhouettes (black cylinders or standing nonhost pines) of varying diameters and identical capture surface areas were baited with essential oil lures. The Log10-transformed number of X. glabratus trapped per week increased as a function of silhouette diameter in 2011 and 2012, using artificial silhouette diameters ranging 2-18 and 3-41 cm, respectively. When lures and capture surfaces were attached to standing pines ranging 4-37 cm in diameter, a positive relationship between Log10(X. glabratus trap catch) and stem diameter was modeled using nonlinear quadratic plateau regression and indicated a diameter above which visual attraction was not enhanced; however, there was not a maximum diameter for enhanced X. glabratus attraction that was generally consistent across all experiments. These results 1) indicate that X. glabratus incorporates visual information during host finding, 2) help explain diameter-related patterns of redbay (Persea borbonia (L.) Sprengel) mortality observed during laurel wilt epidemics, and 3) are applicable to the management of this forest pest.