Field phenology of emerald ash borer (Coleoptera: Buprestidae) parasitoids in New York State.

Emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), has caused extensive mortality of ash across North America. Biological control offers a potential long-term management option, allowing for long-term survival of ash. Careful monitoring of populations of biocontrol agents is necessary to understand their relative impacts. Understanding the emergence and flight phenology of these species allows for the optimization of monitoring schemes and improves our understanding of host-parasitoid interactions. We used yellow pan trapping data to assess the adult phenology of both EAB and its associated native and introduced parasitoids in 3 New York counties. We monitored 2 introduced larval biocontrol agents, Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) and Spathius galinae Belokobylskij & Strazanac (Braconidae), for 3-4 years post-release, as well as the native parasitoid Phasgonophora sulcata Westword (Chalcididae). Results indicate a single discrete emergence event for both EAB and P. sulcata in all monitored counties, which is consistent with previously reported results. Our results also suggest there are 4 generations per year of T. planipennisi and 3 generations of S. galinae in the monitored counties. We recorded an additional generation of T. planipennisi that had not previously been reported in New York, and both T. planipennisi and S. galinae appeared to emerge earlier than previously documented.

Lifecycle of Anastatus orientalis (Hymenoptera: Eupelmidae) and synchrony with its host, the spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae).

Anastatus orientalis Yang & Choi (Hymenoptera: Eupelmidae), an egg parasitoid of spotted lanternfly, Lycorma delicatula (White) (Hemiptera: Fulgoridae), has been documented emerging from host eggs in both autumn and spring, at the beginning and end of the period that spotted lanternfly eggs are present in the field, suggesting parasitoid-host specificity and synchrony. This study was designed to test whether, under conditions that simulate native and introduced ranges of spotted lanternfly, (a) A. orientalis has 2 and only 2 generations per year, (b) A. orientalis adults sometimes emerge when only nontarget species would be available for parasitization, and (c) emerging parasitoid adults can parasitize unhatched host eggs in the spring. Parasitized spotted lanternfly eggs were collected in 2019 and 2020 from Beijing, China and in 2020 and 2021 from Yantai, China. They were shipped for laboratory study in growth chambers programmed to simulate temperature and daylength for collection locations in China and in the invaded range in Pennsylvania, United States. Anastatus orientalis had a flexible lifecycle depending on environmental conditions and possibly genetic makeup, with 1-3 generations per year, and parasitoid emergence was not always synchronous with host egg availability. Additionally, given the cooler temperatures in Pennsylvania, autumn parasitoid emergence was often delayed until late October or November, no progeny were produced, and parasitoid populations died out. Anastatus orientalis does not exhibit host synchrony characteristics that would make it a good candidate for a classical biological control program.

Establishment and impacts of emerald ash borer (Coleoptera: Buprestidae) parasitoids released at early- and post-invasion sites.

Forest stands infested by emerald ash borer (EAB), Agrilus planipennis Fairmaire, experience extensive mortality of mature ash trees. Post-invasion woodlands commonly have a small contingent of mature lingering ash, an orphaned cohort of seedlings/saplings, and low EAB densities. To protect regenerating ash against rebounding EAB populations, a suite of biocontrol agents are being reared and released. USDA APHIS guidelines currently recommend the release of parasitoids into forests prior to overstory ash mortality at sites containing a variety of ash size classes and low to moderate but building EAB densities. To understand if biocontrol establishment and control of EAB is feasible in post-invasion sites, we assessed the establishment of parasitoids in 6 post-invasion forest stands in 2 regions of NY and compared EAB mortality in these stands to 2 regions where releases were conducted during the early-invasion phase. Results of parasitoid trapping indicates Tetrastichus planipennisi Yang established under both release strategies. Spathius galinae Belokobylskij & Strazanac was only released in post-invasion stands, where it was established successfully. Artificial EAB cohorts were established and life tables were constructed at 3 sites per region. EAB mortality due to T. planipennisi parasitism was similar under both release strategies 2 yr after release in post-invasion stands versus 8 yr after release in early-invasion stands. Combined mortality from T. planipennisi and woodpecker predation resulted in consistently low EAB reproductive rates. Future biocontrol releases could target forests identified as economically or ecologically important, regardless of whether EAB populations are increasing or have collapsed following initial invasion.

Exploration for Asian longhorned beetle parasitoids in Korea using an improved sentinel log trap.

The Asian longhorned beetle (ALB), Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), is a destructive invasive woodboring insect pest, and efforts are being made to find parasitoids for ALB biological control. Through a four-year survey in Korea using a sentinel log trap associated with host chemical cues potentially important for host finding by parasitoids, two parasitoid species were discovered attacking ALB. One species is Spathius ibarakius Belokobylskij & Maetô, which is known to also parasitize citrus longhorned beetle, Anoplophora chinensis (Forster). The other parasitoid species, whose offspring were dead before imago, could not be morphologically identified at the adult stage. We attempted molecular and morphological identification of the larvae/pupae of the unidentified parasitoid; however, only superfamily-level identification was possible. The parasitism rate recovered in the logs was 0.3% by the unidentified parasitoid in Gapyeong-gun in 2019, while it reached 29.2% by S. ibarakius in Busan city in 2022. Future efforts for exploring ALB natural enemies in the pest's native range may focus on parasitoids with high parasitism rates.

Title: Exploration des parasitoïdes du longicorne asiatique en Corée à l'aide d'un piège à bûche sentinelle amélioré. Abstract: Le longicorne asiatique (LA), Anoplophora glabripennis (Motschulsky) (Coleoptera : Cerambycidae), est un insecte ravageur envahissant et destructeur du bois, et des efforts sont déployés pour trouver des parasitoïdes pour la lutte biologique contre lui. Au cours d'une étude de quatre ans en Corée utilisant un piège à bûche sentinelle associé à des signaux chimiques de l'hôte potentiellement importants pour la détection de l'hôte par les parasitoïdes, deux espèces de parasitoïdes ont été découvertes attaquant le longicorne. Une espèce est Spathius ibarakius Belokobylskij & Maetô, qui est connue pour parasiter également le longicorne des agrumes, Anoplophora chinensis (Forster). Les autres espèces de parasitoïdes, dont les descendants sont morts avant l'imago, n'ont pu être identifiées morphologiquement au stade adulte. Nous avons tenté une identification moléculaire et morphologique des larves/pupes du parasitoïde non identifié, mais seule une identification au niveau de la superfamille a été possible. Le taux de parasitisme observé dans les bûches était de 0,3 % par le parasitoïde non identifié à Gapyeong-gun en 2019, tandis qu'il atteignait 29,2 % par S. ibarakius dans la ville de Busan en 2022. Les efforts futurs pour explorer les ennemis naturels du capricorne dans l'aire de répartition naturelle du ravageur pourraient se concentrer sur les parasitoïdes à taux de parasitisme élevés.

Effects of transgenerational photoperiod experience on the reproduction and development of Anastatus orientalis, an egg parasitoid of the spotted lanternfly.

Transgenerational experience can affect a range of natural enemies' life-history traits and can be involved in the control of developmental plasticity. As a major egg parasitoid of the spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), the wasp Anastatus orientalis (Hymenoptera: Eupelmidae) is effective at suppressing its host populations. The reproductive and developmental traits of A. orientalis is known to depend on photoperiod conditions, but transgenerational photoperiodic effects have yet to be evaluated. To evaluate the transgenerational photoperiodic effects on A. orientalis, we assessed wasp adult longevity, female fecundity, sex ratio, and diapause rate over three consecutive generations under different experimental photoperiods (L16:D8, L12:D12, and L8:D16), using Antheraea pernyi (Lepidoptera: Saturniidae) eggs as hosts. The results suggest that transgenerational experience significantly impacts several biological parameters of progeny. All parasitoids entered a diapause under the long photoperiod condition (i.e., L16:D8), after which the number of female parasitoids and fecundity of the 2nd and 3rd generations increased significantly as compared to the 1st generation. With the long photoperiod conditions, the female ratio rose from 68.1% (1st generation) to 86.0% (3rd generation) and the progeny per females increased from 35.8 to 75.7. However, adult longevity of females and males were shortened significantly. With the intermediate photoperiod (L12:D12) conditions, fecundity and sex ratio of the 2nd and 3rd generations increased significantly as compared to the 1st generation. With the short photoperiod (L8:D16) conditions, there were no significant differences in fecundity among three generations, but sex ratio of the 2nd and 3rd generations increased significantly as compared to the 1st generation. These results on transgenerational photoperiodic effects can be applied to improve laboratory rearing efficiency of parasitoids and to better understand population dynamics in the field across a latitudinal gradient.

Cryptic genetic diversity and associated ecological differences of Anastatus orientalis, an egg parasitoid of the spotted lanternfly.

Anastatus orientalis, native to northern China, is an egg parasitoid wasp of the spotted lanternfly (Lycorma delicatula) and is being tested as a potential biological control agent for invasive L. delicatula in the United States. As a component of these evaluations, live A. orientalis collected from Beijing and Yantai in China were reared in containment in the U.S. These specimens showed different responses in diapause behaviors to rearing conditions used previously by other researchers. To understand the primary mechanism potentially driving discrepancies in important life history traits, we used molecular tools to examine the genetic composition of A. orientalis from China and from South Korea, where the parasitoid has been introduced to aid in the population management of invasive L. delicatula. Molecular analysis of mitochondrial DNA recovered six haplotype groups, which exhibit biased frequency of abundance between collection sites. Some haplotypes are widespread, and others only occur in certain locations. No apparent pattern is observed between wasps collected from different years or emergence seasons. Uncorrected genetic distances between haplotype groups range from 0.44% to 1.44% after controlling for within-group variation. Genetic variance of A. orientalis is characterized by high levels of local diversity that contrasts with a lack of a broad-scale population structure. The introduced Korean population exhibits lower genetic diversity compared to native populations. Additionally, we created iso-female lines for major haplotype groups through laboratory rearing. Differences in diapause behavior were correlated with mitochondrial haplotype. Our results indicate that the observed life history traits in A. orientalis have a genetic base.

Assessing the host range of Anastatus orientalis, an egg parasitoid of spotted lanternfly (Lycorma delicatula) using Eastern U.S. non-target species.

The spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), an invasive planthopper discovered in Pennsylvania, U.S. in 2014, has spread to many surrounding states despite quarantines and control efforts, and further spread is anticipated. A classical (importation) biological control program would contribute to the long-term management of L. delicatula in the eastern U.S. In its native range of China, Anastatus orientalis (Hymenoptera: Eupelmidae), an egg parasitoid, causes significant mortality. Anastatus orientalis consists of multiple haplotypes that differ in important biological parameters. To delineate the physiological host range of A. orientalis Haplotype C, we completed no-choice and choice testing. No-choice testing of non-target eggs from 36 insect species spanning six orders and 18 families showed that physiologically this haplotype of A. orientalis can develop in a variety of host species eggs from the families Coreidae, Fulgoridae, Pentatomidae, and Saturniidae. Ten of the 16 species that were attacked in the no-choice tests were also attacked in the choice tests. The production of progeny on non-target egg masses was significantly lower than on the controls (L. delicatula egg masses run simultaneously) in the no-choice and choice tests. For the non-target species that were attacked and resulted in female wasp progeny, these females were able to produce their own progeny at the same rate as control females that were reared from the L. delicatula eggs. Larger host eggs corresponded to an increased female-biased sex ratio of the progeny, suggesting that gravid females select them for fertilized eggs. Results from these studies suggest that A. orientalis Haplotype C prefers to parasitize L. delicatula egg masses but is capable of developing in some non-target species.

Male-produced pheromone of Spathius agrili, a parasitoid introduced for the biological control of the invasive emerald ash borer, Agrilus planipennis.

The braconid wasp, Spathius agrili, has been released in the U.S. as a biocontrol agent for the invasive emerald ash borer (Coleoptera: Buprestidae: Agrilus planipennis), a destructive pest of ash trees (Fraxinus spp.). We identified and synthesized seven male-specific volatile compounds. Three of these, dodecanal, (4R,11E)-tetradecen-4-olide, and (Z)-10-heptadecen-2-one, were the key behaviorally active components in flight tunnel bioassays. Male specificity was demonstrated by gas chromatographic comparison of male and female volatile emissions and whole body extracts. Identifications were aided by coupled gas chromatographic-mass spectrometric (GC-MS) analysis, microchemical reactions, NMR, chiral GC analysis, and GC and MS comparison with authentic standards. Both the racemic and chiral forms of the γ-lactone, as well as both E- and Z-isomers were synthesized. Flight tunnel behavioral tests showed positive male and female S. agrili responses to both natural pheromone and synthetic blends, with upwind flight and landing on the source. Large field-cage tests, using yellow sticky traps baited with pheromone, captured approximately 50% of the released male and female wasps in 24-h periods. The use of pheromone-baited traps in the field could simplify the current detection method for determining parasitoid establishment (i.e., laboriously felling and peeling ash trees for recovery of S. agrili from infested EAB larvae).

Mortality of Emerald Ash Borer Larvae in Small Regenerating Ash in New York Forests.

Despite a robust biocontrol program against emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), parasitoid populations cannot build quickly enough to save mature ash trees. The future of ash as a viable component of North American forests depends on survival of immature ash that were too small to be attacked during the initial outbreak. This study was designed to quantify impacts of established introduced parasitoids and native woodpeckers on the population growth of emerald ash borer infesting regenerating ash saplings in white ash forests. Most emerald ash borer larvae were killed by Tetrastichus planipennisi Yang and woodpeckers in the fourth instar. Life-table analyses revealed that the estimated net reproductive rate of emerald ash borer was R0 = 4.2 in eastern New York and R0 = 0.0 in western New York. Without mortality from parasitoids and woodpeckers, R0 values would have been 16.4 and 7.9 in eastern and western New York, respectively. We monitored the health of mature and sapling ash trees from 2012 to 2017 and found that large trees were significantly more likely to be infested with emerald ash borer and to die than smaller trees. Fifty-four percent to 81% of ash saplings contained no living emerald ash borer, and the density of emerald ash borer at all sites was very low (< 4/m2). This study adds to the growing body of evidence that emerald ash borer biocontrol is contributing to population control and can help promote survival of young ash trees as forests recover from emerald ash borer outbreaks.

Development of rearing methodology for the invasive Spotted Lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae).

Lycorma delicatula, White (Hemiptera: Fulgoridae), spotted lanternfly, is a univoltine, phloem-feeding, polyphagous and invasive insect in the USA. Although a primary host for this species is Ailanthus altissima, tree of heaven, L. delicatula also feeds on a wide range of hosts important to the USA including cultivated grapevines. Due to the need for classical or augmentative biological control programs to reduce impacts of L. delicatula across invaded areas, we developed a laboratory-based rearing protocol for this invasive species. Here, we evaluated the use of A. altissima apical meristems, epicormic shoots, and fresh foliage cut from A. altissima as a food source for rearing newly hatched L. delicatula. On these sources of plant material <20% of L. delicatula developed into adults and no oviposition occurred. However, when young, potted A. altissima trees were used as a food source, >50% of L. delicatula nymphs developed to the adult stage under natural daylengths and temperatures ranging from 20-25°C. The addition of wild grapevine, Vitis riparia, did not increase survivorship or reduce development time. To elicit mating and oviposition, adults were provided with A. altissima logs as an oviposition substrate and maintained under shortened daylengths and reduced nighttime temperatures (12L:12D and 24°C:13°C). This resulted in 2.12 egg masses deposited per female, which was 4× more than when adults were maintained in standard rearing conditions (16L:8D and 25°C). Based on these experiments, we present a protocol for reliably rearing L. delicatula under laboratory and/or greenhouse conditions.

Effects of rearing conditions on reproduction of Spathius agrili (Hymenoptera: Braconidae), a parasitoid of the emerald ash borer (Coleoptera: Buprestidae).

Spathius agrili Yang (Hymenoptera: Braconidae) can be successfully reared on emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), larvae feeding in chambers drilled in small ash twigs that are wrapped with floral tape. Females maintained in groups with males for one week can receive enough sperm for production of female progeny throughout their lives. Volatiles released by emerald ash borer adults feeding on ash foliage increased parasitoid fecundity over ash foliage alone or no stimulus. The temperature at which the parasitoids were reared ranged from 20 to 25 degrees C in a daily cycle; however, raising the daily maximum temperature to 28 degrees C did not affect parasitoid longevity or fecundity. Adult females lived between 12 and 127 d, with an average of 60.8 +/- 4.5 d. Males lived slightly longer, with an average of 66 +/- 4.5 d. The first clutch of eggs was laid when the female was between 2 and 42 d old, with the average preoviposition period lasting 11.4 +/- 1.4 or 19.5 +/- 2.0 d in 2007 and 2009 trials, respectively. A higher proportion of the emerald ash borer larvae were feeding and thus attractive to parasitoids in the 2009 trial, and female S. agrili laid an average of 9.5 +/- 1.0 clutches containing 5.4 +/- 0.2 eggs, for an average of 51.2 eggs per female. Approximately three quarters of the progeny were female. The number of eggs per clutch was significantly greater when deposited on larger emerald ash borer larvae, further highlighting the need for quality larvae in rearing. Chilling S. agrili pupae at 10 degrees C to stockpile them for summer release was not successful; chilling resulted in lower survival and lower fecundity of emerging progeny. Female S. agrili proved capable of attacking emerald ash borer larvae through even the thickest bark of an ash tree that was 30-cm diameter at breast height. Even emerald ash borer larvae that were creating overwintering chambers in the outer sapwood of the tree were successfully attacked, suggesting that S. agrili could be reared on field collected logs infested with emerald ash borer.

Field-cage methodology for evaluating climatic suitability for introduced wood-borer parasitoids: preliminary results from the emerald ash borer system.

Field-cage methods were developed to evaluate the abilities of Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) and Spathius agrili Yang (Hymenoptera: Braconidae), biocontrol agents of Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), to parasitize, develop and overwinter following three late-season releases at both a northern (Michigan) and a southern (Maryland) location within the current North American range of A. planipennis. In August, September and October of 2009, five young green ash trees were selected at each location. Tetrastichus planipennisi and S. agrili were each randomly assigned to one of two cages attached to each tree, surrounding separate sections of trunk in which late-instar A. planipennis had been inserted. The following April, the caged trunk sections were dissected to determine the fate of each A. planipennis larva and the developmental stages of all recovered parasitoid progeny. At both locations, T. planipennisi and S. agrili were able to parasitize hosts and successfully overwinter (i.e., reach adulthood the following spring). For T. planipennisi, successful parasitism (i.e., parasitoid progeny reached adulthood) occurred for all caged releases in Maryland, but only for the August and September releases in Michigan. At both locations, percent parasitism by T. planipennisi was higher in August and September than in October. For S. agrili, successful parasitism occurred for all caged releases in Maryland, but only for the August release in Michigan. In Maryland, percent parasitism by S. agrili in August and September was higher than in October. The caging method described here should be useful in determining the climatic suitability of other regions before proceeding with large-scale releases of either species and may have utility in other wood-borer parasitoid systems as well.

Exploratory Survey of Spotted Lanternfly (Hemiptera: Fulgoridae) and Its Natural Enemies in China.

An invasive population of spotted lanternfly (SLF), Lycorma delicatula White, was first noted in North America in Pennsylvania in 2014, and by September 2020 populations had spread to six additional states. To develop a biocontrol program to aid in the management of the pest, exploratory surveys for SLF natural enemies in its native range were carried out in 27 provinces and other administrative regions of China from 2015 to 2019. Naturally laid egg masses were collected and sentinel SLF egg masses were deployed to attract egg parasitoids, and yellow sticky traps were used to collect SLF nymphs to discover and determine the parasitism rates of nymphal parasitoids. Results show that SLF is widely distributed in China (22 provinces and regions) and that the population densities in northeast China are higher than in southern and western China. An egg parasitoid, Anastatus orientalis Yang (Hymenoptera: Eupelmidae), and a nymphal parasitoid, Dryinus sinicus Olmi (Hymenoptera: Dryinidae), were collected. Anastatus orientalis was reared from SLF eggs in seven provinces in China with parasitoid emergence rates ranging from 4.0 to 15.5% (or 17.6 to 37.3% if including only egg masses that had at least some parasitism). There were significant differences in parasitoid emergence rates between sites associated with factors including habitat and host plants. Dryinus sinicus was discovered in eight cities across six provinces. The percentage of SLF nymphs parasitized by D. sinicus were 31.1, 23.3, and 0% in Tai'an, Shandong Province, Beijing City, and Yan'an, Shaanxi Province, respectively. These two parasitoids are promising natural enemies that are being considered as potential biocontrol agents of invasive populations of SLF.

Life History and Rearing of Anastatus orientalis (Hymenoptera: Eupelmidae), an Egg Parasitoid of the Spotted Lanternfly (Hemiptera: Fulgoridae).

To support efforts to manage and contain spotted lanternfly (SLF), Lycorma delicatula White (Hemiptera: Fulgoridae), research is being conducted to develop classical biological control methods. To date, two potential biocontrol agents from China have been identified: an egg parasitoid, Anastatus orientalis, and a nymphal parasitoid, Dryinus sinicus Olmi (Hymenoptera: Dryinidae). The research detailed here focuses on investigating the biology and rearing of A. orientalis to assess its potential efficacy in a biocontrol program and optimize its rearing. Female wasps lived significantly longer than male wasps (68 and 23 d, respectively) and females produced an average of 94 total progeny that successfully emerged as adults, with most progeny produced between weeks one and four of the females' lives. The sex ratio of the progeny, with no re-mating, was initially highly female-biased but became progressively more male-biased, likely due to sperm depletion. There was no evidence of additional mortality to SLF eggs from wasp host feeding, but the data were highly variable and the sample size was small. There was high parasitoid emergence when oviposition conditions mimicked mid-September Beijing temperature and photoperiod; however, there was little emergence under 25°C and long-day conditions because most progeny entered a diapause. Storage of parasitized eggs in 5°C chill lowered parasitoid emergence rates. Lastly, there was no evidence that storing field-collected SLF egg masses in 5°C for 10 mo prior to parasitization affected parasitism rates. These findings inform our rearing protocol for A. orientalis and facilitate our testing of this species as a potential biological control agent for SLF.

The biology and ecology of the emerald ash borer, Agrilus planipennis, in China.

The biology, ecology, and life cycle of the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), were studied using regular inspection in the forest and observations in the laboratory. Results indicated that A. planipennis are mostly univoltine in Tianjin, China. They overwintered individually as mature larvae in shallow chambers excavated in the outer sapwood. In late July, some full-grown larvae began to build overwintering chambers, and all larvae entered the sapwood for dormancy by early November. A. planipennis pupated in the overwintering chamber from early April to mid May the following year, and the average pupal duration was about 20 days. In late April, some newly eclosed adults could be found in the pupal cells, but they had not yet emerged from the tree. Adults began to emerge in early May, with peak flight occurring in mid May. The average longevity of adults was about 21 days and the adult stage lasted through early July. The adults fed on ash foliage as a source of nutrition. Mating was usually conducted and completed on the leaf or trunk surfaces of ash trees. Oviposition began in mid May and eggs hatched on average in 15.7 days. The first instar larvae appeared in early June. The larval stage lasted about 300 days to complete an entire generation. The emerald ash borer had four larval instars on velvet ash, Fraxinus velutina (Scrophulariales: Oleaceae). The major natural control factors of A. planipennis were also investigated, and preliminary suggestions for its integrated management are proposed.

Biology and behavior of Spathius agrili, a parasitoid of the emerald ash borer, Agrilus planipennis, in China.

Spathius agrili Yang (Hymenoptera: Braconidae) is a gregarious larval ectoparasitoid of the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) and is a recently described species. Both pest and parasitoid are native to China. In Tianjin City, China, S. agrili typically exhibited 3-4 generations per year, overwintering as a prepupa in a cocoon inside the host gallery. The multiple generations of S. agrili overlapped with its host, as did the emergence dates of the overwintering generation. From a single host, 1-18 S. agrili successfully developed to the adult stage (average 8.4), but in all cases the host was killed. The sex ratio (female: male) of the parasitoid adults emerging from field-collected cocoons was 2:1, whereas the sex ratio of parasitoids reared from field collected eggs and larvae was greater than 3:1. On average, adult females lived 29.1 d, and males lived 23.6 d when fed with 20% honey solution, significantly longer than without a nutritional supplement. Sexual reproduction is the normal mode of reproduction, but in the laboratory females did reproduce parthenogenetically, producing only males. The average fecundity was 23.3 eggs per female in the laboratory. S. agrili developed through five larval instars, and the larvae fed gregariously on the host hemolymph. The generation time from egg to adult wasp was 27-28 d at 22-26 degrees C. Natural parasitism rates were as high as 60%, and in October they reached over 90% in some stands. This study showed that S. agrili is a promising agent for biocontrol of A. planipennis.

Phenology of Emerald Ash Borer (Coleoptera: Buprestidae) and Its Introduced Larval Parasitoids in the Northeastern United States.

Biological control offers a long-term and sustainable option for controlling the destructive forest pest emerald ash borer (EAB), Agrilus planipennis Fairmaire, in North America. Three larval parasitoids, Spathius agrili Yang (Hymenoptera: Braconidae), Tetrastichus planipennisi Yang (Eulophidae), and Spathius galinae Belokobylskij & Strazanac, have been introduced to North America from the native range of EAB (northeastern Asia). While T. planipennisi appears to be persisting where it has been introduced in northern United States, S. agrili failed to establish in northeastern states. The more recently identified parasitoid S. galinae was recovered from the Russian Far East and climate matching suggests it should be suited for release in colder climates. We collected data on the phenology of EAB and its introduced larval parasitoids from colonies established in an insectary, growth chambers, and field-caged trees in Syracuse, New York to determine whether asynchrony between parasitoids and EAB or climate could impact establishment and persistence. Phenological data indicated EAB has one and 2-yr life cycles in New York, with parasitoid-susceptible EAB larvae available spring to fall for parasitism. Insectary and growth chamber studies indicated S. galinae and T. planipennisi were synchronous with EAB phenology, and field studies suggested both species could overwinter in northeastern climates. Spathius agrili was asynchronous with EAB phenology and climate, emerging when fewer parasitoid-susceptible EAB larvae were available and temperatures were not optimal for survival. Our results suggest S. galinae and T. planipennisi are suited for biological control of EAB at the northern limits of its range in North America.

Optimizing Parasitoid and Host Densities for Efficient Rearing of Ontsira mellipes (Hymenoptera: Braconidae) on Asian Longhorned Beetle (Coleoptera: Cerambycidae).

Ontsira mellipes Ashmead is a gregarious larval ectoparasitoid of woodboring cerambycids. It is native to North America but can readily attack the exotic Asian longhorned beetle, Anoplophora glabripennis (Motschulsky). This study aimed to develop an efficient rearing system for this parasitoid, as a potential novel association biocontrol agent for the beetle, by investigating the effects of different densities of host (two, three, or four larvae) and parasitoid (one, two, three, four, five, six, seven, and eight female wasps) on Ontsira's parasitization efficiency and reproductive outcomes. Results showed that overall parasitism and total numbers of parasitized hosts or progeny produced increased with host and/or parasitoid densities, but the number of parasitized hosts or progeny produced per female parasitoid decreased with parasitoid density at each given host density. Nonlinear regression indicated a consistent pattern of mutual interference as parasitoid density increased. Additional experiments showed that superparasitism (indirect interference) did not occur probably because the parasitoid detects hosts through vibration cues from host feeding and attacked (thus paralyzed) hosts are no longer detectable. Thus, the interference probably results from direct or exploitative competition. Interestingly, female parasitoids responded to increased parasitoid density with a significant increase in clutch size. Overall, per capita parasitization efficiency or reproductive outcomes were optimized at a low parasitoid-host ratio but with large group size of hosts and parasitoids. Therefore, an optimal combination of exposing three or four parasitoids to four hosts is proposed for efficient mass-rearing of this parasitoid.

Host Overwintering Phenology and Climate Change Influence the Establishment of Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae), a Larval Parasitoid Introduced for Biocontrol of the Emerald Ash Borer.

Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is one of the most serious forest pests in the United States. Ongoing research indicates that establishment of larval parasitoids depends upon the season-long availability of host stages susceptible to parasitism. We monitored emerald ash borer overwintering stages at 90 sites across 22 states to: 1) produce a model of the percentage of emerald ash borer overwintering as non-J larvae; 2) link that model to establishment of Tetrastichus planipennisi; and 3) explore changes to our model under climate change scenarios. Accumulated growing degree days (GDD) is an important predictor of the proportion of emerald ash borer overwintering as non-J larvae (1-4 instar larvae under the bark; available to parasitoids emerging in spring) versus J-larvae (fourth-instar larvae in pupal chambers in the outer wood; unavailable to parasitoids). From north to south, the availability of non-J emerald ash borer larvae in the spring decreases as accumulated GDD increases. In areas where the model predicted >46-75%, >30-46%, >13-30%, or ≤13% of emerald ash borer overwintering as non-J larvae, the probability of establishment of T. planipennisi was 92%, 67%, 57%, and 21%, respectively. We determined that 13% of emerald ash borer overwintering as non-J larvae was the lowest threshold for expected T. planipennisi establishment. Additional modeling predicts that under climate change, establishment of T. planipennisi will be most affected in the Central United States, with areas that are currently suitable becoming unsuitable. Our results provide a useful tool for the emerald ash borer biological control program on how to economically and successfully deploy emerald ash borer biological control agents.

Discovery of Parasitoids of Anoplophora glabripennis (Coleoptera: Cerambycidae) and Their Seasonal Abundance in China Using Sentinel Host Eggs and Larvae.

Asian longhorned beetle, Anoplophora glabripennis (Motschulsky), is a high-risk invasive forest pest worldwide. We surveyed Asian longhorned beetle parasitoid guilds and their seasonal abundance using field-deployed sentinel host logs infested with Asian longhorned beetle eggs or newly hatched (early-instar) larvae in three different sites of China (Beijing City, Shanghai City, and Jilin Province) from 2015 to 2018. Our survey detected 12 species of hymenopteran parasitoids (four Pteromalidae, three Braconidae, two Eupelmidae, one Eurytomidae, one Ichneumonidae, and one Bethylidae) attacking sentinel Asian longhorned beetle larvae or eggs deployed in these sites. Total parasitism by all the parasitoid species varied with different sites and across different years of the survey (averaging 7-16% in Beijing, 4-11% in Shanghai, and 0-0.2% in Jilin Province). In addition, the seasonal pattern of parasitism also differed among different sites, with parasitism peaking in July in the northern site (Beijing, 19%) and June in the southern site (Shanghai, 16%). Among all the parasitoid species recovered, Oxysychus sp. (Hymenoptera: Pteromalidae) was the most abundant parasitoid species in both Beijing and Shanghai (with 42-66% relative abundance and an average of 6% Asian longhorned beetle parasitism). The second most abundant species was Bracon planitibiae Yang, Cao et Gould (Hymenoptera: Braconidae), which accounted for 35% of the species collected and caused an average of 5% Asian longhorned beetle parasitism. Relevance of our findings to Asian longhorned beetle biocontrol is discussed.