[Show abstract][Hide abstract] ABSTRACT: To investigate natural enemies of emerald ash borer (EAB),
Fairmaire (Coleoptera: Buprestidae), in northeastern China, we conducted field surveys of ash (
Linnaeus (Oleaceae)) trees in semi-natural forests and plantations at variable EAB densities from 2008 to 2013. Our surveys revealed a complex of natural enemies including eight hymenopteran parasitoids and two apparently parasitic Coleoptera, woodpeckers, and several undetermined mortality factors. Parasitoid complex abundance and its contribution to EAB mortality varied with the time of year, type of ash stands, and geographic regions. The egg parasitoid
Zhang and Huang (Hymenoptera: Encyrtidae) and the larval parasitoid
Yang (Hymenoptera: Eulophidae) were frequently observed in Jilin, Liaoning, and Heilongjiang provinces and in Beijing, but not in Tianjin.
Yang (Hymenoptera: Braconidae), however, was more prevalent near Beijing and further south in Tianjin. Larvae of two species of apparently parasitic beetle,
Laporte (Coleoptera: Cleridae) species and
Mannerheim (Coleoptera: Trogossitidae), were also recovered attacking overwintering EAB in Liaoning Province, with
species being a dominant mortality agent (~13%). Our findings support the need to consider the geographic origin of insect natural enemies for EAB biocontrol, as well as an expanded foreign exploration for EAB natural enemies throughout its native range in Asia.
Full-text · Article · Dec 2015 · The Canadian Entomologist
[Show abstract][Hide abstract] ABSTRACT: Host-specificity determination prior to the introduction of non-native natural enemies is a critical component of the risk assessment for modern classical biocontrol programs. In the present study, we assessed the host specificity of a newly described parasitoid, Spathius galinae Belokobylskij and Strazanac, which is native to Northeast Asia, for classical biocontrol of the invasive emerald ash borer (EAB), Agrilus planipennis Fairmaire, in North America. Along with foreign exploration for natural enemies of EAB in 2010 and 2012, we surveyed ash (. Fraxinus spp.) wood-boring insects and their parasitoids from artificially stressed Oriental ash (. F. rhynchophylla Hance) trees in natural forest stands in the Primorskiy Kray region of Russia. Once colonies of S. galinae were established in U.S. quarantine, we tested the parasitoid against 15 species or groups of North American wood-boring insects that were selected along a continuum from closely related taxa (e.g., Agrilus spp. in the family Buprestidae in Coleoptera) to distantly related ones in Lepidoptera and Hymenoptera. While three of the tested insects, Neoclytus acuminatus Fabricius, Podosesia spp. and Hylesinus fraxini Panzer attack ash as their main host, the rest attack non-ash trees such as birch, maple and oak. Results from our field survey in Russia showed that S. galinae did not attack bark beetles (. Hylesinus spp.) or longhorned beetles (Cerambycidae) that coexisted with EAB on infested ash trees. In quarantine laboratory studies, S. galinae did not attack 14 species or groups of non-target wood-boring insects infesting both ash and/or non-ash trees such as birch, maple or red oak. The only non-target attack was on the goldspotted oak borer (GSOB), Agrilus auroguttatus Schaeffer, infesting red oak. The rate of parasitism on GSOB was significantly lower than on EAB under laboratory conditions that favored parasitism. These findings indicate that the host specificity of S. galinae is restricted within the host genus (. Agrilus).
Full-text · Article · Oct 2015 · Biological Control
[Show abstract][Hide abstract] ABSTRACT: First detected in North America in 2002, the emerald ash borer (EAB) (
Fairmaire; Coleoptera: Buprestidae), an invasive phloem-feeding beetle from Asia, has killed tens of millions of ash (
Linnaeus; Oleaceae) trees. Although few parasitoids attack EAB in North America, three parasitoid species were found attacking EAB in China: the egg parasitoid
Zhang and Huang (Hymenoptera: Encyrtidae) and two larval parasitoids
Yang (Hymenoptera: Eulophidae) and
Yang (Hymenoptera: Braconidae). In 2007, classical biological control of EAB began in the United States of America after release of these three species was approved. In 2013, release of the larval parasitoids was approved in Canada. Research continues at study sites in Michigan, United States of America where the establishment, prevalence, and spread of
have been monitored since 2008. However, establishment of
remains unconfirmed in northern areas, and its release is now restricted to regions below the 40th parallel. In 2015, approval for release of
Belokobylskij (Hymenoptera: Braconidae), an EAB larval parasitoid from the Russian Far East, may be granted in the United States of America. Researchers are guardedly optimistic that a complex of introduced and native natural enemies will regulate EAB densities below a tolerance threshold for survival of ash species or genotypes in forested ecosystems.
Full-text · Article · Jun 2015 · The Canadian Entomologist
[Show abstract][Hide abstract] ABSTRACT: The emerald ash borer Agrilus planipennis Fairmaire is a serious invasive forest pest of ash (Fraxinus) trees in North America. Life tables were constructed for both experimentally established cohorts and wild populations of A. planipennis on healthy host trees from 2008 to 2011 in six forests in central Michigan.Life table analysis showed that the net population growth rates (R0) for the experimental cohorts (16.0 ± 2.9) and associated wild A. planipennis (19.4 ± 1.9) were the highest for the first study period (2008–2009) at three Ingham Co. sites but decreased to 4.7 ± 0.9 and 4.6 ± 0.4, respectively, for the second (2009–2010) study period at the same sites. By contrast, R0 values of both experimental cohorts (5.7 ± 2.2) and associated wild A. planipennis populations (11.3 ± 2.5) were intermediate in the third (2010–2011) study period at different sites in the Gratiot and Shiawassee Cos.The sudden decrease in R0 of both experimental and wild A. planipennis cohorts in the Ingham Co. sites corresponded with increases in parasitism by hymenopteran parasitoids Atanycolus spp. (native) and Tetrastichus planipennisi Yang (introduced), as well as an increase in woodpecker predation, indicating the role of these natural enemies in regulation of the pest's population dynamics.
Full-text · Article · May 2014 · Agricultural and Forest Entomology
[Show abstract][Hide abstract] ABSTRACT: The emerald ash borer (EAB), Agrilus planipennis, is an invasive beetle that has killed millions of ash trees (Fraxinus spp.) since it was accidentally introduced to North America in the 1990s. Understanding how predators such as woodpeckers (Picidae) affect the population dynamics of EAB should enable us to more effectively manage the spread of this beetle, and toward this end we combined two experimental approaches to elucidate the relative importance of woodpecker predation on EAB populations. First, we examined wild populations of EAB in ash trees in New York, with each tree having a section screened to exclude woodpeckers. Second, we established experimental cohorts of EAB in ash trees in Maryland, and the cohorts on half of these trees were caged to exclude woodpeckers. The following spring these trees were debarked and the fates of the EAB larvae were determined. We found that trees from which woodpeckers were excluded consistently had significantly lower levels of predation, and that woodpecker predation comprised a greater source of mortality at sites with a more established wild infestation of EAB. Additionally, there was a considerable difference between New York and Maryland in the effect that woodpecker predation had on EAB population growth, suggesting that predation alone may not be a substantial factor in controlling EAB. In our experimental cohorts we also observed that trees from which woodpeckers were excluded had a significantly higher level of parasitism. The lower level of parasitism on EAB larvae found when exposed to woodpeckers has implications for EAB biological control, suggesting that it might be prudent to exclude woodpeckers from trees when attempting to establish parasitoid populations. Future studies may include utilizing EAB larval cohorts with a range of densities to explore the functional response of woodpeckers.
[Show abstract][Hide abstract] ABSTRACT: Competition for food, mates, and space among different individuals of the same insect species can affect density-dependent regulation of insect abundance or population dynamics. The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a serious invasive pest of North American ash (Fraxinus spp.) trees, with its larvae feeding in serpentine galleries between the interface of sapwood and phloem tissues of ash trees. Using artificial infestation of freshly cut logs of green ash (Fraxinus pennsylvanica Marshall) and tropical ash (Fraxinus uhdei [Wenzig] Lingelsh) with a series of egg densities, we evaluated the mechanism and outcome of intraspecific competition in larvae of A. planipennis in relation to larval density and host plant species. Results from our study showed that as the egg densities on each log (1.5-6.5 cm in diameter and 22-25 cm in length) increased from 200 to 1,600 eggs per square meter of surface area, larval survivorship declined from ≈68 to 10% for the green ash logs, and 86 to 55% for tropical ash logs. Accordingly, larval mortality resulting from cannibalism, starvation, or both, significantly increased as egg density increased, and the biomass of surviving larvae significantly decreased on both ash species. When larval density was adjusted to the same level, however, larval mortality from intraspecific competition was significantly higher and mean biomasses of surviving larvae was significantly lower in green ash than in tropical ash. The role of intraspecific competition of A. planipennis larvae in density-dependent regulation of its natural population dynamics is discussed.
Full-text · Article · Nov 2013 · Environmental Entomology
[Show abstract][Hide abstract] ABSTRACT: A new parasitoid reared from Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), Sclerodermus pupariae n. sp. (Hymenoptera: Bethylidae), is described from China. S. pupariae was reared from A. planipennis in China attacking velvet ash (Fraxinus velutina Torr.), a tree native to North America. Life-history studies of S. pupariae in the field and laboratory indicated it is a gregarious idiobiont ectoparasitoid of pupa and larva of A. planipennis and has up to five generations per year. Parasitism rate in the field was 13%. Adult wasps reared from single host pupa or mature larva ranged from 24 to 56 individuals. Based on laboratory rearing, the emerging adult female to male ratio was 22:1. The new parasitoid species has a high potential as a biocontrol agent for emerald ash borer. Diagnosis of the new species with comparisons to Sclerodermus harmandi (Buysson) and a key to Sclerodermus known in China are provided.
Preview · Article · Sep 2012 · Annals of the Entomological Society of America
[Show abstract][Hide abstract] ABSTRACT: 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).
Full-text · Article · Mar 2012 · Journal of Chemical Ecology
[Show abstract][Hide abstract] ABSTRACT: 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.
Full-text · Article · Oct 2011 · Journal of Insect Science
[Show abstract][Hide abstract] ABSTRACT: 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.
No preview · Article · Apr 2011 · Journal of Economic Entomology