Acibenzolar-S-methyl induces resistance against ambrosia beetle attacks in dogwoods exposed to simulated flood stress.

Xylosandrus spp. ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are important wood-boring pests of nursery trees weakened by abiotic and biotic stressors. Acibenzolar-S-methyl (ASM), a plant defense elicitor, was tested for inhibiting Xylosandrus spp. tunneling (i.e., attacks) into flood-stressed flowering dogwoods (Cornus florida L. (Cornales: Cornaceae)). Container-grown dogwoods were treated with ASM substrate drench + flooding, ASM foliar spray + flooding, ASM drench + no flooding, ASM foliar + no flooding, no ASM + flooding, or no ASM + no flooding at 3 days before flood stress in a completely randomized design under field conditions. Trees were flooded for 14 days and then drained and watered as needed. Attacks were counted every 2 days for 28 days. Plant tissue samples were collected at 7 and 14 days after flooding to determine ethanol content using solid-phase microextraction-gas chromatography-mass spectrometry. Trees were dissected to determine gallery formation and depth, fungal colonization, and the presence of eggs, larvae, and adults. The highest number of Xylosandrus beetle species attacks were recorded from plants exposed to no ASM + flooding, but attacks were reduced in ASM treated trees (drench or foliar) + flooding. Trees treated with drenches had fewer attacks than foliar sprays. Plants assigned to no flood had the fewest beetle attacks. Moreover, ASM reduced Xylosandrus spp. gallery formation and depth, fungal colonization, and presence of eggs, larvae, and adults. All flooded trees produced ethanol. In conclusion, ASM induced a plant defense response to Xylosandrus spp. tunneling in dogwoods under flood stress conditions.

Electrophysiological and Behavioral Responses of an Ambrosia Beetle to Volatiles of its Nutritional Fungal Symbiont.

Ambrosia beetles (Coleoptera: Scolytinae) cultivate their fungal symbiont within host substrates as the sole source of nutrition on which the larvae and adults must feed. To investigate a possible role for semiochemicals in this interaction, we characterized electrophysiological and behavioral responses of Xylosandrus germanus to volatiles associated with its fungal symbiont Ambrosiella grosmanniae. During still-air walking bioassays, X. germanus exhibited an arrestment response to volatiles of A. grosmanniae, but not antagonistic fungi Beauveria bassiana, Metarhizium brunneum, Trichoderma harzianum, the plant pathogen Fusarium proliferatum, or malt extract agar. Solid phase microextraction-gas chromatography-mass spectrometry identified 2-ethyl-1-hexanol, 2-phenylethanol, methyl benzoate and 3-methyl-1-butanol in emissions from A. grosmanniae; the latter two compounds were also detected in emissions from B. bassiana. Concentration-responses using electroantennography documented weak depolarizations to A. grosmanniae fungal volatiles, unlike the comparatively strong response to ethanol. When tested singly in walking bioassays, volatiles identified from A. grosmanniae elicited relatively weak arrestment responses, unlike the responses to ethanol. Xylosandrus germanus also exhibited weak or no long-range attraction to the fungal volatiles when tested singly during field trials in 2016-2018. None of the fungal volatiles enhanced attraction of X. germanus to ethanol when tested singly; in contrast, 2-phenylethanol and 3-methyl-1-butanol consistently reduced attraction to ethanol. Volatiles emitted by A. grosmanniae may represent short-range olfactory cues that could aid in distinguishing their nutritional fungal symbiont from other fungi, but these compounds are not likely to be useful as long-range attractants for improving detection or mass trapping tactics.

Symbiont selection via alcohol benefits fungus farming by ambrosia beetles.

Animal-microbe mutualisms are typically maintained by vertical symbiont transmission or partner choice. A third mechanism, screening of high-quality symbionts, has been predicted in theory, but empirical examples are rare. Here we demonstrate that ambrosia beetles rely on ethanol within host trees for promoting gardens of their fungal symbiont and producing offspring. Ethanol has long been known as the main attractant for many of these fungus-farming beetles as they select host trees in which they excavate tunnels and cultivate fungal gardens. More than 300 attacks by Xylosandrus germanus and other species were triggered by baiting trees with ethanol lures, but none of the foundresses established fungal gardens or produced broods unless tree tissues contained in vivo ethanol resulting from irrigation with ethanol solutions. More X. germanus brood were also produced in a rearing substrate containing ethanol. These benefits are a result of increased food supply via the positive effects of ethanol on food-fungus biomass. Selected Ambrosiella and Raffaelea fungal isolates from ethanol-responsive ambrosia beetles profited directly and indirectly by (i) a higher biomass on medium containing ethanol, (ii) strong alcohol dehydrogenase enzymatic activity, and (iii) a competitive advantage over weedy fungal garden competitors (Aspergillus, Penicillium) that are inhibited by ethanol. As ambrosia fungi both detoxify and produce ethanol, they may maintain the selectivity of their alcohol-rich habitat for their own purpose and that of other ethanol-resistant/producing microbes. This resembles biological screening of beneficial symbionts and a potentially widespread, unstudied benefit of alcohol-producing symbionts (e.g., yeasts) in other microbial symbioses.

Thiamethoxam Differentially Impacts the Survival of the Generalist Predators, Orius insidiosus (Hemiptera: Anthocoridae) and Hippodamia convergens (Coleoptera: Coccinellidae), When Exposed via the Food Chain.

Insect predators are seldom considered during toxicological trophic assessments for insecticide product development. As a result, the ecological impact of novel insecticides on predators is not well understood, especially via the food chain, i.e., when their prey is exposed to insecticides. Neonicotinoids are systemic insecticides widely used in agriculture to control herbivorous insects, but their effects on predatory insects via the food chain have not been well characterized. In this study, we documented the time-course effects of the neonicotinoid thiamethoxam on the survival of two predators, the insidiosus flower bug Orius insidiosus (Say) and the convergent lady beetle Hippodamia convergens Guérin-Méneville, when preying upon the aphids Aphis glycines Matsumura (Hemiptera: Aphididae), Aphis gossypii Glover (Hemiptera: Aphididae), and Myzus persicae (Sulzer) (Hemiptera: Aphididae). Aphids were exposed to thiamethoxam-treated or untreated plants every week over the course of 5 wk. After transferring aphids to Petri dishes, predators were allowed to feed on aphids. We found that the survival of the insidiosus flower bug, but not the convergent lady beetle, was reduced after consuming aphids reared on thiamethoxam-treated plants compared to untreated plants. Survival reduction of the insidiosus flower bug was observed only during the first weeks after thiamethoxam application; no reduction occurred 28 d after treatment or beyond. These results demonstrate that a systemic application of thiamethoxam could be compatible with convergent lady beetles and insidiosus flower bugs, if the time of predator release does not coincide with thiamethoxam activity. These findings are critical for the development of future pest control programs that integrate biological and chemical control.

Movement of Xylosandrus germanus (Coleoptera: Curculionidae) in Ornamental Nurseries and Surrounding Habitats.

Some exotic ambrosia beetles are damaging pests in ornamental nurseries. Xylosandrus germanus (Blandford) is the most problematic ambrosia beetle in Ohio nurseries. Movement of X. germanus in nurseries has not been characterized, and knowledge is lacking on whether infestations originate from within nurseries or surrounding habitats. Flight activity of X. germanus was monitored in nurseries and adjacent wooded areas to determine the source of beetles infesting nurseries, and characterize their movement within nurseries. Ethanol-baited bottle traps were positioned within wooded areas adjacent to commercial nurseries and within nurseries at various distances from the nursery woodlot interface. Flight activity of overwintered X. germanus occurred in wooded areas adjacent to nurseries before occurrence within nurseries. There was a direct relationship between degree-days and the distance from woodlots when X. germanus were first found in traps in spring, with earlier captures closest to wooded areas and latest ones furthest away into the nursery. X. germanus appeared to move into nurseries from adjacent wooded areas, with numbers trapped within nurseries decreasing with distance away from wooded areas. Trees in the interior of nurseries would appear to be subjected to less attack pressure than trees near the nursery border. Intercepting beetles as they move into nurseries might be an effective strategy to reduce attack pressure on valuable trees.

Rare excitatory amino acid from flowers of zonal geranium responsible for paralyzing the Japanese beetle.

The Japanese beetle (JB), Popillia japonica, exhibits rapid paralysis after consuming flower petals of zonal geranium, Pelargonium x hortorum. Activity-guided fractionations were conducted with polar flower petal extracts from P. x hortorum cv. Nittany Lion Red, which led to the isolation of a paralysis-inducing compound. High-resolution-MS and NMR ((1)H, (13)C, COSY, heteronuclear sequential quantum correlation, heteronuclear multiple bond correlation) analysis identified the paralytic compound as quisqualic acid (C(5)H(7)N(3)O(5)), a known but rare agonist of excitatory amino acid receptors. Optical rotation measurements and chiral HPLC analysis determined an L-configuration. Geranium-derived and synthetic L-quisqualic acid demonstrated the same positive paralytic dose-response. Isolation of a neurotoxic, excitatory amino acid from zonal geranium establishes the phytochemical basis for induced paralysis of the JB, which had remained uncharacterized since the phenomenon was first described in 1920.

Eliminating explanations for Maladera formosae (Coleoptera: Scarabaeidae) preponderance in sandy soil.

Most field corn in the United States receives a neonicotinoid seed treatment for the management of early-season, soil-dwelling insect pests. Grubs of Maladera formosae (Brenske) (Coleoptera: Scarabaeidae) have been reported feeding on young field corn with both low and high rates of clothianidin seed treatments in Indiana, Michigan, and Ohio. Anecdotally, these infestations are restricted to sandy soils in the region. The purpose of this study was to (1) evaluate whether grub populations in corn are restricted to sandy soils, (2) assess whether soil type influences M. formosae survival, and (3) determine whether soil type affects clothianidin uptake by the plant, possibly explaining the observed differences in M. formosae abundance by soil type. We observed nearly 10-times more grubs in sand (>80% sand content) than loam (<80% sand content) soil within a single corn field. Grub survival to adult was not influenced by soil type. We then compared the concentrations of clothianidin seed treatment in the roots and shoots of corn seedlings grown in either sand or loam soil over time. Similar amounts of the active ingredient were found in the roots and shoots of corn grown in both soil types. Within 2 week, the clothianidin concentrations in both soil types had significantly declined in roots and shoots and were no different from the no-insecticide control. These findings suggest that factors other than insecticide exposure contribute to the higher abundance of M. formosae larvae in sand relative to loam soils, even within the same field.

Influence of Ethanol Grade on Captures of Ambrosia Beetles in Tree Fruit Orchards, Ornamental Nurseries, and Lumber Yards.

Ambrosia beetles, particularly invasive species within the tribe Xyleborini, such as Xylosandrus germanus (Blandford, 1894), pose significant threats to various ecosystems and managed habitats worldwide. Monitoring these invaders is vital for effective pest management, typically accomplished through ethanol-baited traps. We compared trap efficacy using denatured ethanol versus absolute ethanol in orchards, tree nurseries, and lumber yards in northeastern Ohio, USA, finding that absolute ethanol traps captured significantly more X. germanus. Analysis revealed acetone, ethanol, and methyl isobutyl ketone in the denatured ethanol, likely impacting trap efficacy. Our study underscores the importance of using pure denatured ethanol without acetone for effective monitoring, especially for X. germanus. Exotic xyleborines dominated trap captures across various habitats, emphasizing the need for tailored pest management strategies. Further research is warranted to explore the chemical ecology of ambrosia beetles and the influence of ethanol impurities on trap effectiveness.

Monitoring attack and flight activity of Xylosandrus spp. (Coleoptera: Curculionidae: Scolytinae): the influence of temperature on activity.

Wood-boring ambrosia beetles (Coleoptera: Curculionidae: Scolytinae), including Xylosandrus spp., are key pests in ornamental nurseries. Knowledge of their activity in spring is important for nursery growers to effectively time their protective sprays. We measured the reliability of ethanol-baited bottle traps for monitoring emergence of overwintered Xylosandrus spp. in ornamental nurseries. Detection of initial flight activity by traps was compared with initial attacks on ethanol-injected trap trees. To develop tools for forecasting Xylosandrus germanus (Blandford) activity, the relationships between temperature and their attack and flight activity were examined, and the bloom sequence of ornamental plants was examined as phenological indicators of X. germanus emergence in Ohio. Captures of X. germanus coincided with attacks on trap trees on seven of eight occasions over 2 yr in four nurseries. Xylosandrus crassiusculus (Motshulsky) were detected in only one nursery and captures coincided with attacks each year. There was a strong relationship between maximum daily temperatures 20 and 21degrees C and X. germanus attack and flight activity. No attack or flight activity were detected in a monitoring period unless there were 1 or 2 d of at least 20 degrees C. Emergence of X. germanus always began after and within 6 d of full bloom on Cornelian cherry dogwood, and usually after and within 4 d of first bloom on Norway maple and full bloom on border forsythia. The traps or phenological indicators can be used by growers to monitor emergence of X. germanus to time their initial protective sprays. The relationship between X. germanus activity and temperature can be used by growers to make decisions on timing subsequent treatments.

Ethanol injection of ornamental trees facilitates testing insecticide efficacy against ambrosia beetles (Coleoptera: Curculionidae: Scolytinae).

Exotic ambrosia beetles are damaging pests in ornamental tree nurseries in North America. The species Xylosandrus crassiusculus (Motshulsky) and Xylosandrus germanus (Blandford) are especially problematic. Management of these pests relies on preventive treatments of insecticides. However, field tests of recommended materials on nursery trees have been limited because of unreliable attacks by ambrosia beetles on experimental trees. Ethanol-injection of trees was used to induce colonization by ambrosia beetles to evaluate insecticides and botanical formulations for preventing attacks by ambrosia beetles. Experiments were conducted in Ohio, Tennessee, and Virginia. Experimental trees injected with ethanol had more attacks by ambrosia beetles than uninjected control trees in all but one experiment. Xylosandrus crassiusculus and X. germanus colonized trees injected with ethanol. In most experiments, attack rates declined 8 d after ethanol-injection. Ethanol-injection induced sufficient pressure from ambrosia beetles to evaluate the efficacy of insecticides for preventing attacks. Trunk sprays of permethrin suppressed cumulative total attacks by ambrosia beetles in most tests. Trunk sprays of the botanical formulations Armorex and Veggie Pharm suppressed cumulative total attacks in Ohio. Armorex, Armorex + Permethrin, and Veggie Pharm + Permethrin suppressed attacks in Tennessee. The bifenthrin product Onyx suppressed establishment of X. germanus in one Ohio experiment, and cumulative total ambrosia beetle attacks in Virginia. Substrate drenches and trunk sprays of neonicotinoids, or trunk sprays of anthranilic diamides or tolfenpyrad were not effective. Ethanol-injection is effective for inducing attacks and ensuring pressure by ambrosia beetles for testing insecticide efficacy on ornamental trees.

Acute toxicity of plant essential oils to scarab larvae (Coleoptera: Scarabaeidae) and their analysis by gas chromatography-mass spectrometry.

Larvae of scarab beetles (Coleoptera: Scarabaeidae) are important contaminant and root-herbivore pests of ornamental crops. To develop alternatives to conventional insecticides, 24 plant-based essential oils were tested for their acute toxicity against third instars of the Japanese beetle Popillia japonica Newman, European chafer Rhizotrogus majalis (Razoumowsky), oriental beetle Anomala orientalis (Waterhouse), and northern masked chafer Cyclocephala borealis Arrow. Diluted solutions were topically applied to the thorax, which allowed for calculating LD50 and LD90 values associated with 1 d after treatment. A wide range in acute toxicity was observed across all four scarab species. Of the 24 oils tested, allyl isothiocyanate, cinnamon leaf, clove, garlic, and red thyme oils exhibited toxicity to all four species. Allyl isothiocyanate was the most toxic oil tested against the European chafer, and among the most toxic against the Japanese beetle, oriental beetle, and northern masked chafer. Red thyme was also comparatively toxic to the Japanese beetle, oriental beetle, European chafer, and northern masked chafer. Interspecific variability in susceptibility to the essential oils was documented, with 12, 11, 8, and 6 of the 24 essential oils being toxic to the oriental beetle, Japanese beetle, European chafer, and northern masked chafer, respectively. Analysis of the active oils by gas chromatography-mass spectrometry revealed a diverse array of compounds, mostly consisting of mono- and sesquiterpenes. These results will aid in identifying active oils and their constituents for optimizing the development of plant essential oil mixtures for use against scarab larvae.

Preharvest quarantine treatments of chlorantraniliprole, clothianidin, and imidacloprid-based insecticides for control of Japanese beetle (Coleoptera: Scarabaeidae) and other scarab larvae in the root zone of field-grown nursery trees.

Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae), is an important quarantine pest of nurseries. Nursery plant movement from P. japonica-infested regions is regulated by the U.S. Domestic Japanese Beetle Harmonization Plan (DJHP), which classifies states by risk categories. Treatments for category 2 states include preharvest soil surface treatment of nursery plants grown in field soil using Discus SC, Marathon (1G or 60 WP), or Flagship (0.22G or 25 WG). In this study, Discus, Marathon 60 WP, or Flagship 0.22G DJHP standards were compared with labeled rates of non-DJHP-approved insecticides, including neonicotinoids clothianidin (Arena 50WDG), generic imidacloprid (Quali-Pro Imidacloprid 2 F T&O Insecticide, Mallet 2 F T&O Insecticide, and Lada 2 F Insecticide), and imidacloprid + bifenthrin (Allectus SC), as well as the anthranilic diamide, chlorantraniliprole (Acelepryn Insecticide). Arena provided 100% P. japonica control in May, June, and July over four test years, but had one larva recovered during August in two of those 4 yr. Acelepryn did not provide DJHP-acceptable P. japonica control. During July, Allectus provided 100% P. japonica control in three of four test years, but had four larvae in one test year. Other treatments tested only during July, which provided 100% P. japonica control, included Discus (five tests); Marathon, Quali-Pro, and Mallet (two tests); and Lada and Flagship (one test). Generic imidacloprid 2 F formulations were equivalent in P. japonica control to DJHP-approved insecticides. Insecticides generally performed poorly on other scarabs or curculionid larvae. The study supports Arena, Allectus, and generic imidacloprid 2 F products as suitable candidates for the DJHP.

Attraction of Myzus persicae (Hemiptera: Aphididae) to Volatiles Emitted From the Entomopathogenic Fungus Beauveria bassiana.

Beauveria bassiana (Balsamo) Vuillemin infects a wide variety of insects, including the green peach aphid, Myzus persicae (Sulzer). Volatiles emitted from B. bassiana can act as semiochemical attractants or repellents, with most responses reported to date resulting in insects avoiding B. bassiana. Since insects can detect 'enemy-specific volatile compounds', we hypothesized the preference behavior of M. persicae would be influenced by volatile emissions from B. bassiana. We conducted Petri dish and Y-tube olfactometer bioassays to characterize the preference of M. persicae to B. bassiana strain GHA. During Petri dish bioassays, more apterous and alate M. persicae were recorded in the vicinity of agar colonized by B. bassiana compared to agar, or Fusarium proliferatum (Matsushima) Nirenberg and Ambrosiella grosmanniae Mayers, McNew, & Harrington as representatives of nonentomopathogenic fungi. Petri dish bioassays also determined that apterous and alate M. persicae preferred filter paper saturated with 1 × 107, 1 × 106, and 1 × 105B. bassiana conidia/ml compared to Tween 80. Y-tube bioassays documented that more apterous and alate M. persicae oriented upwind to volatiles from B. bassiana mycelia compared to agar. Apterous and alate Myzus persicae were also preferentially attracted to 1 × 107 and 1 × 106B. bassiana conidia/ml compared to Tween-80 during Y-tube bioassays. These results complement a previous finding that the mosquito Anopheles stephensi (Diptera: Culicidae) Liston is attracted to volatiles from B. bassiana. Future studies aimed at characterizing the olfactory mechanism leading to the attraction of M. persicae to B. bassiana could aid in optimizing lure-and-kill strategies.

Volatiles of fungal cultivars act as cues for host-selection in the fungus-farming ambrosia beetle Xylosandrus germanus.

Many wood-boring insects use aggregation pheromones during mass colonization of host trees. Bark beetles (Curculionidae: Scolytinae) are a model system, but much less is known about the role of semiochemicals during host selection by ambrosia beetles. As an ecological clade within the bark beetles, ambrosia beetles are obligately dependent on fungal mutualists for their sole source of nutrition. Mass colonization of trees growing in horticultural settings by exotic ambrosia beetles can occur, but aggregation cues have remained enigmatic. To elucidate this mechanism, we first characterized the fungal associates of the exotic, mass-aggregating ambrosia beetle Xylosandrus germanus in Southern Germany. Still-air olfactometer bioassays documented the attraction of X. germanus to its primary nutritional mutualist Ambrosiella grosmanniae and to a lesser extent another common fungal isolate (Acremonium sp.). During two-choice bioassays, X. germanus was preferentially attracted to branch sections (i.e., bolts) that were either pre-colonized by conspecifics or pre-inoculated with A. grosmanniae. Subsequent analyses identified microbial volatile organic compounds (MVOCs) that could potentially function as aggregation pheromones for X. germanus. To our knowledge, this is the first evidence for fungal volatiles as attractive cues during host selection by X. germanus. Adaptive benefits of responding to fungal cues associated with an infestation of conspecifics could be a function of locating a suitable substrate for cultivating fungal symbionts and/or increasing the likelihood of mating opportunities with the flightless males. However, this requires solutions for evolutionary conflict arising due to potential mixing of vertically transmitted and horizontally acquired symbiont strains, which are discussed.

Type and duration of water stress influence host selection and colonization by exotic ambrosia beetles (Coleoptera: Curculionidae).

Fungus-farming ambrosia beetles in the tribe Xyleborini tunnel into plants and trees to establish chambers for cultivating their nutritional fungal mutualists and rearing offspring. Some xyleborine ambrosia beetles preferentially infest and perform better in living but weakened trees. Flood stress predisposes horticultural tree crops to infestation, but the impact of drought stress has not been well studied. Our objectives were to compare the effects of flood stress vs. drought stress on host selection and colonization by xyleborine ambrosia beetles and to assess the duration of flooding. Container-grown Cornus florida L. trees were flood stressed using a pot-in-pot system to submerge the roots in water while drought-stressed conditions were imposed by withholding irrigation and precipitation. When experimental trees were held under field conditions for 14 days, 7.5 × more ambrosia beetles landed on stems of the flood-stressed than on the drought-stressed trees. During two additional experiments over 14 and 22 days, ambrosia beetles tunneled into the flood-stressed trees but not the drought-stressed or standard irrigation trees. By simultaneously deploying trees that were flood stressed for varying lengths of time, it was found that more tunnel entrances, and xyleborine adults and offspring were recovered from trees that were flooded for 1-16 days and 7-22 days than from trees that were flooded for 14-29 days and 28-43 days. These results indicate that acute and severe drought stress does not predispose C. florida to infestation, but flood stress and the duration of flooding influence ambrosia beetle host selection and colonization. Understanding the role of host quality on ambrosia beetle preference behavior will assist with predicting the risk of infestation of these opportunistic insects in horticultural tree crops.

Systemic insecticides reduce feeding, survival, and fecundity of adult black vine weevils (Coleoptera: Curculionidae) on a variety of ornamental nursery crops.

Systemic activity of the neonicotinoids clothianidin, dinotefuran, and thiamethoxam and the anthranilic diamide chlorantraniliprole was tested against adult black vine weevils, Otiorhynchus sulcatus (F.) (Coleoptera: Curculionidae), on Astilbe, Euonymus, Heuchera, Rhododendron, Sedum, and Taxus. Insecticide treatments were applied to the soilless substrate of containerized plants. Bioassays were conducted 12 or 13, 26, and 42 d after treatment (DAT) and ran for 7 d; and feeding, mortality, and weight gain or loss by weevils were evaluated. Foliage was removed from test plants and then placed in arenas with adult black vine weevils. The neonicotinoids reduced feeding and weight gain by adult black vine weevils on most plant species with residual activity 42 DAT on some plant species. At 12 DAT, mortality was caused by the three neonicotinoids on Astilbe and by thiamethoxam on Sedum; and at 26 DAT dinotefuran caused mortality on Astilbe. Chlorantraniliprole reduced feeding on Taxus at 12 DAT, with no activity detected in other bioassays. Another set of bioassays was conducted to examine survival and fecundity of adult black vine weevils during prolonged feeding on Heuchera and Taxus systemically treated with dinotefuran or thiamethoxam. Bioassay procedures were similar to those described above, except they ran continuously for 56 d. Prolonged feeding on dinotefuran and thiamethoxam treated Heuchera and Taxus resulted in high mortality of adult black vine weevils and reduced fecundity. These studies show that the systemic activity of neonicotinoids is influenced by plant species and that systemic neonicotinoids have the potential to suppress black vine weevil populations in containerized nursery crops.

Optimizing ethanol-baited traps for monitoring damaging ambrosia beetles (Coleoptera: Curculionidae, Scolytinae) in ornamental nurseries.

The exotic ambrosia beetles Xylosandrus crassiusculus (Motschulsky) and Xylosandrus germanus (Blandford) (Coleoptera: Curculionidae: Scolytinae) are serious pests in ornamental tree nurseries. To optimize bottle-traps as a monitoring system for X. crassiusculus and X. germanus in nurseries, we tested whether increasing the rate of commercial ethanol lures improved captures or early detection of these species. Experiments were conducted in Ohio (2008 and 2009) and Virginia (2008), two states that have experienced significant damage from X. crassiusculus, X. germanus, or both. There were four treatments: no-lure (unbaited control), 1-ethanol lure, 2-ethanol lures and 1 + 1-ethanol lures (one lure in the trap and one suspended 0.5 m above the trap). Captures of X. crassiusculus and X. germanus were higher in all ethanol treatments than unbaited controls, and were generally higher in treatments with two lures versus one. There was no difference in beetle captures between the 2-lure and 1 + 1-lure treatments. First detection of X. crassiusculus and X. germanus occurred more consistently in the treatments with two lures than one lure. Xyleborinus saxesenii (Ratzeburg), Anisandrus sayi Hopkins, Hypothenemus dissimilis Zimmermann, and Hypothenemus eruditus Westwood were also more attracted to traps baited with ethanol than unbaited controls. X. saxesenii was captured in higher numbers in the treatments with two lures than one in Virginia but not in Ohio. There was no difference in captures of the other species among ethanol treatments. The current research shows that ethanol release rates influence sensitivity of traps for detecting emergence of overwintered ambrosia beetles.

Species dependent influence of (-)-alpha-pinene on attraction of ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) to ethanol-baited traps in nursery agroecosystems.

Field-based trapping experiments were conducted in Ohio in 2003, 2004, and 2008 to determine the influence of (-)-alpha-pinene on the attraction of exotic and native ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) to ethanol-baited traps. In 2003 and 2004, we determined the effect of adding an (-)-alpha-pinene ultrahigh release lure (UHR; 2 g/d at 20 degrees C) to traps baited with an ethanol UHR lure (0.39 g/d). FewerAnisandrus (Xyleborus) sayi (Hopkins) and Xyleborinus saxeseni (Ratzeburg) were collected in 2003 and 2004 from traps baited with ethanol UHR plus (-)-alpha-pinene UHR compared with ethanol UHR. (-)-alpha-Pinene also reduced the attraction of Xyloterinus politus (Say) to ethanol-baited traps in 2004. Total captures of Xylosandrus germanus (Blandford) in 2003 were higher in traps baited with ethanol UHR plus (-)-alpha-pinene UHR than in traps with ethanol UHR alone but not in 2004. In 2008, captures were compared among traps baited with eight combinations of ethanol and (-)-a-pinene at both UHR and low release (LR) rates. Release rates for ethanol LR and (-)-alpha-pinene LR were 0.027 and 0.0015 g/d, respectively. (-)-alpha-Pinene UHR and (-)-alpha-pinene LR reduced the attractiveness of ethanol UHR to A. sayi and X. saxeseni. Ethanol UHR was also more attractive than ethanol LR to A. sayi and X. germanus. These findings demonstrate traps baited with ethanol alone are more effective than ethanol plus (-)-alpha-pinene for monitoring ambrosia beetle flight activity in ornamental nurseries. Ethanol release rate is also an important consideration for monitoring purposes.

Comparative efficacy of plant-derived essential oils for managing ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) and their corresponding mass spectral characterization.

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) pose a significant challenge to producers of ornamental nursery stock. Conventional insecticides are commonly used for management purposes, but plant-derived essential oils also may discourage ambrosia beetles from initiating attacks. To identify promising commercially available products, field-based efficacy trials were conducted in Ohio in 2009 and 2010 with the following products: Armorex (Soil Technologies), Cinnacure (Proguard, Inc.), EcoTrol (EcoSMART Technologies, Inc.), and Veggie Pharm (Pharm Solutions, Inc.). Potted Magnolia virginiana L. were first injected with 75 ml of 5% ethanol to ensure ambrosia beetle pressure on experimental trees. Mixtures of each product (10% in water) and a water control were applied until runoff and attacks occurring under field conditions were quantified at 1, 4, 7, and 14 d after treatment (DAT). Ambrosia beetle attacks generally increased over time but at differing rates depending on the particular treatment. In 2009, Armorex and Veggie Pharm were associated with the lowest cumulative attacks 14 DAT. In 2010, Armorex and Cinnacure were associated with the fewest attacks 14 DAT. Solid phase microextraction-gas chromatography-mass spectrometry was used to characterize the volatile compounds associated with each product. Allyl isothiocyanate, a compound with known repellent and insecticidal properties, was unique and predominant in Armorex. These experiments identified commercially available botanicals containing plant essential oils with activity against ambrosia beetles, along with demonstrating the usefulness of ethanol-injection to ensure ambrosia beetle pressure under field conditions. Characterizing the constituents of efficacious botanically based products could also lead to the development of improved botanical insecticides.

Colonization of Trees by Ambrosia Beetles (Coleoptera: Curculionidae: Scolytinae) Is Influenced by Duration of Flood Stress.

The ambrosia beetles Xylosandrus germanus (Blandford) and Xylosandrus crassiusculus (Motschulsky) bore into flood-stressed trees to establish colonies, but the influence of flooding duration on colonization is unknown. This relationship was examined by flooding trees for various time periods and evaluating colonization. In one experiment, X. germanus bored into 20 dogwood (Cornus florida L.) trees during a 3-d flood treatment. Ten trees dissected that season had no offspring present in tunnels; the remaining trees appeared healthy and bloomed the following spring. In another experiment, dogwood trees were flooded for 3 or 7 d and then dissected to assess colonization. The incidence of superficial (short unbranched) and healed (callus tissue in entrance) tunnels was greater in the 3-d trees, while the incidence of tunnels with X. germanus or offspring was greater in the 7-d trees. Four experiments (three in Ohio and one in Virginia) had flood treatments of 0 (nonflooded), 3, 5, 7, and 10 d. Numbers of tunnel entrances, tunnels with X. germanus, and incidence of tunnels with offspring or live foundresses tended to increase as flood duration increased on apple (Malus × domestica Borkh.), dogwood, and redbud (Cercis canadensis L.) in Ohio and redbud in Virginia. Nonflooded trees in Ohio had no boring activity, but ambrosia beetles bored into three nonflooded trees in Virginia. Indicators of unsuccessful colonization, such as superficial tunnels and healing, decreased as flood duration increased. These results suggest tree crops may recover from boring by ambrosia beetles following short-duration flood events, and not necessarily require culling.