Physiological Host Range Research Articles

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.

Torymus sinensis against the invasive chestnut gall wasp: Evaluating the physiological host range and hybridization risks of a classical biological control agent

BackgroundA common strategy to limit the negative impact of biological invasions is biological control through the release of specialized alien natural enemies. However, biological control plans are not without risks, which include parasitism of native hosts and hybridization with related native species, particularly those that are potential natural enemies of the invasive species. Here, we evaluate these potential risks resulting from the introduction of the parasitoid wasp Torymus sinensis (Hymenoptera: Torymidae) in Europe to control the invasive Asian chestnut gall wasp Dryocosmus kuriphilus (Hymenoptera: Cynipidae). ResultsWe found that, under laboratory conditions, the physiological host range of T. sinensis includes several native non-target species of Cynipidae, with oviposition observed on the galls of 8 of the 11 species tested. However, physiological host range of T. sinensis appears to be limited under field conditions, as we observed only one parasitized gall of Andricus curvator in the field. Regarding hybridization, inter-species mating between T. sinensis and its phylogenetically closest native Torymus species was not observed in the laboratory. Moreover, discordance between nuclear (ITS2) and mitochondrial (coxI) data does not support the presence of genetic introgression, suggesting that hybridization between T. sinensis and native Torymus species does not occur. In addition, we cite and discuss the unexpected presence of one individual of the related alien species Torymus beneficus in Spain. ConclusionOur results suggest that T. sinensis may negatively impact several non-target species, highlighting the need for careful monitoring of the extent of such undesired behaviour and its effects on the native fauna.

Retrospective host-specificity testing shows Trissolcus basalis (Wollaston) and the native Trissolcus oenone (Dodd) (Hymenoptera: Scelionidae) have overlapping physiological host ranges in New Zealand

Retrospective host range testing is essential for understanding the physiological host range of introduced biological control agents (BCAs) and updating forecasts of non-target risks. It is especially important to conduct this work if there was no host range testing prior to release of the agent. Trissolcus basalis Wollaston was released in New Zealand in 1949 against green vegetable bug (Nezara viridula [L.]), but host range testing was never undertaken, and subsequent work in the 1960s was only of a qualitative nature and remains incomplete. The host-parasitoid complex between New Zealand pentatomids, T. basalis, and the native pentatomid parasitoid Trissolcus oenone Dodd, is therefore poorly understood. We conducted no-choice oviposition tests between the two resident Trissolcus species and all available New Zealand pentatomid species to characterise the physiological (=fundamental) host ranges of these parasitoids. We present the results of the first retrospective host-specificity study on T. basalis in New Zealand. Our results show T. basalis attacks and develops in all nine pentatomid taxa we exposed it to (including the endemic alpine species Hypsithocus hudsonae Bergroth), while T. oenone attacks and develops in seven out of eight pentatomid species we tested it against (and its capacity to attack H. hudsonae remains unknown). Parasitism efficiencies for all treatments exceeded 60%, while development times were similar for both parasitoids regardless of host. We discuss the importance of physiological host range testing for understanding potential non-target effects. Trissolcus japonicus Ashmead (Hymenoptera: Scelionidae) was recently approved for release in New Zealand against brown marmorated stink bug Halyomorpha halys Stål (Hemiptera: Pentatomidae), subject to its potential establishment, and we examine our results in the context of potential competition between introduced parasitoids for non-target species.

Hydrotimetes natans as a suitable biological control agent for the invasive weed Cabomba caroliniana

The aquatic macrophyte Cabomba caroliniana A. Gray is a major invasive weed in Australia and several other countries. A classical biological control program was initiated in Australia in 2003 and native range explorations in Argentina that year led to the discovery of the aquatic weevil Hydrotimetes natans Kolbe feeding on C. caroliniana, making it the first, and so far, only potential biological control agent for the weed. However, the program was discontinued because the largely unknown biology had made rearing of H. natans difficult under quarantine laboratory conditions. We report here key aspects of the biology and reproductive behaviour of H. natans that provided significant insights to successfully establish a laboratory colony when the program was restarted in 2016. In addition, we studied the physiological host range of H. natans and determined its risks to 15 non-target plant species. The preoviposition period of H. natans was 6.50 ± 0.85 days, and the development times of eggs and pupae were 7.65 ± 0.86 and 14.27 ± 0.51 days, respectively. Egg to adult development time was 46.52 ± 0.82 days with a larval development time of 25–27 days. A single female laid 123.13 ± 23.03 eggs in 24 weeks under non-limiting laboratory conditions. Oviposition was intermittent and age-dependent with 75% eggs oviposited within 8.54 weeks after adult eclosion; percent viability of these eggs was 55.62 ± 4.61. Females oviposited mostly on the apical tips followed by on the first few nodes from the tip. Adults survived a maximum of 521 days with a mean longevity of 235.16 ± 21.16 days and females remained reproductive for 211.00 ± 35.05 days. Field surveys and laboratory host-specificity studies demonstrated H. natans is adequately host-specific to C. caroliniana. No non-target effects were observed on Nymphaea, Victoria and Trithuria species. Brasenia schreberi indicated the possibility of lifecycle completion by H. natans in choice and no-choice trials but did not sustain a population in continuation trials. The risks to B. schreberi were deemed negligible and H. natans was approved for release in Australia.

Characterization of a novel bullet-shaped lytic bacteriophage against extensively drug-resistant Pseudomonas aeruginosa isolated from human and domestic sources.

Global spread and emergence of the extensively drug-resistant (XDR) strains of P. aeruginosa have become a concern, thus, searching for new alternative treatment approaches are required. This study was aimed to isolate and characterize a novel lytic phage against P. aeruginosa. Seventy XDR isolates of P. aeruginosa were collected from May to September 2018. Wastewater samples were used for isolation of lytic phage against XDR P. aeruginosa isolates. Host range, thermal and pH stability, adsorption rate, latent period, burst size and morphology of phage were determined following the standard protocols. Morphological characteristics of the phage revealed that it belonged to Podoviridae family and it was named vB-PaeP-007. Although the phage had a narrow host range, 47 out of 70 XDR isolates were susceptible to it. The adsorption rate, latent period and burst size of vB-PaeP-007 were approximately 89.80% in 8 min, 10 min and 93 phages per cell, respectively. Its lysis activity remained at a wide range of pH (4 up to 12) and temperature (– 20.00 up to 70.00 ˚C). Regarding the physiological features and host range of the vB-PaeP-007 phage, it could be a promising candidate for phage therapy and bio-controlling of infections from XDR isolates of P. aeruginosa in human and livestock storage centers.

Risk Analysis Frameworks Used in Biological Control and Introduction of a Novel Bayesian Network Tool.

Classical biological control, the introduction of natural enemies to new environments to control unwanted pests or weeds, is, despite numerous successful examples, associated with rising concerns about unwanted environmental impacts such as population decline of nontarget species. Recognition of these biosafety risks is globally increasing, and prerelease assessments of biological control agents (BCAs) have become more rigorous in many countries. We review the current approaches to risk assessment for BCAs as used in Australasia, Europe, and North America. Traditionally, these assessments focus on providing assurance about the specificity of a proposed BCA, generally via a list of suitable versus nonsuitable hosts determined through laboratory specificity tests (i.e., by determining the BCA's physiological host range). The outcome of interactions of proposed agents in the natural environment can differ from laboratory-based predictions. Potential nontarget host testing may be incomplete, additional ecological barriers under field conditions may limit encounters between BCA and nontargets or reduce attack levels, and BCAs could disperse to habitats beyond those used by the target species and adversely affect nontarget species. We advocate for the adoption of more comprehensive, ecologically-based, probabilistic risk assessment approaches to BCA introductions. An example is provided using a Bayesian network that can integrate information on probabilities and uncertainties of a BCA to spread and establish in new habitats, interact with nontarget species in these habitats, and eventually negatively impact the populations of these nontarget species. Our new model, Biocontrol Adverse Impact Probability Assessment, aims to be incorporated into a structured decision-making framework to support national regulatory authorities.

Physiological host range of Trissolcus mitsukurii, a candidate biological control agent of Halyomorpha halys in Europe

The invasive stink bug Halyomorpha halys, native to East Asia, is a severe agricultural pest of worldwide importance, and chemical insecticides are largely sprayed for its control. Negative impact and failures of chemical pest management led to consider classical biological control as one of the most promising methods in a long-term perspective. The Asian egg parasitoid Trissolcus japonicus is the main candidate biocontrol agent of H. halys, but more recently a second species, Trissolcus mitsukurii, which shares the area of origin with H. halys, has drawn special attention after adventive populations were found in Europe. Despite its recent detection, intentional release or redistribution are bound to approval of national petitions, which requires detailed risk analyses. With the aim of providing a contribution for the future development of a risk assessment for release purposes, here we present the first study on the physiological (fundamental) host range of T. mitsukurii in Europe. Tests conducted on different hemipterans common to Southern Europe, using three different experimental designs, revealed a oligophagous host range, limited to Pentatomoidea and comparable with the host range displayed by T. japonicus under similar laboratory conditions. In addition to its coevolved host H. halys, T. mitsukurii successfully parasitized the majority of tested pentatomid species and one scutellerid, although with highly variable emergence rates. Notably high parasitization rates were detected on H. halys, Acrosternum heegeri and Dolycoris baccarum. Host egg sizes positively affected parasitoid size and female egg load. Although T. mitsukurii might be a promising biological control agent of H. halys in Europe, further studies (e.g., chemical ecology, field parasitism) are needed for assessment of non-target risks.

Trissolcus kozlovi in North Italy: Host Specificity and Augmentative Releases against Halyomorpha halys in Hazelnut Orchards

Simple SummaryThe Asian brown marmorated stink bug, Halyomorpha halys, is an invasive crop pest introduced into Europe in the 2000s. Due to its high harmfulness, and the increased chemical use for its control in the invaded areas, research has focused on biological control. In North Italy, the native parasitoid Trissolcus kozlovi emerged from field-collected H. halys eggs and proved to successfully parasitize H. halys eggs in the laboratory. Therefore, since little is known on T. kozlovi, this study aimed at assessing its physiological host range on 12 bug species in the laboratory, as well as its potential as a biological control agent of H. halys in the field by releases in two hazelnut orchards. In the laboratory, among the tested bug species, only Nezara viridula was an unsuitable host. On all others, T. kozlovi was able to develop, even if at different levels, suggesting that it is as oligophagous as Trissolcus japonicus, with which it shares many similarities. In the field, T. kozlovi was found to parasitize H. halys eggs, but only immediately after field releases. Therefore, further field surveys are required to assess its favorably environmental conditions and its possible interaction with T. japonicus, currently present in Italy.Trissolcus kozlovi (Hymenoptera: Scelionidae) emerged from field-laid eggs of Halyomorpha halys (Hemiptera: Pentatomidae) in North Italy, and it emerged in significantly higher numbers from fresh H. halys eggs compared to other native scelionids. Since few data on T. kozlovi are available, its host-specificity and some biological traits were investigated in laboratory tests, and its impact after augmentative releases was evaluated in two hazelnut orchards. Among the 12 tested bug species (Hemiptera: Pentatomidae, Scutelleridae), only Nezara viridula was an unsuitable host, while the highest offspring proportions were obtained from Arma custos, Pentatoma rufipes, and Peribalus strictus, followed by Acrosternum heegeri and Palomena prasina. Furthermore, when reared on P. strictus, T. kozlovi showed a high longevity as well as a high adaptation to H. halys eggs. In both hazelnut orchards, T. kozlovi emerged from H. halys eggs after field releases, but it was not found in the next two years. The physiological host range of T. kozlovi was quite similar to that of T. japonicus, and probably T. kozlovi has just begun to attack H. halys as a new host. This aspect needs to be further investigated, as well as its favorable environmental conditions, its distribution and also its possible interaction with T. japonicus, currently present in Italy.

Pre‐emptive host‐specificity testing of Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) reveals high parasitism levels against the endemic New Zealand alpine shield bug in laboratory no‐choice tests

AbstractBrown marmorated stink bug (BMSB), Halyomorpha halys (Hemiptera: Pentatomidae), is a serious horticultural pest causing considerable damage to local production and international supply chains as it spreads around the world. The samurai wasp, Trissolcus japonicus (Hymenoptera: Scelionidae), is well recognised as the most promising classical biological control against BMSB. The wasp has been conditionally approved for release in New Zealand in the event the stink bug establishes here. Previous host range testing showed that all available non‐target New Zealand pentatomids except a single exotic species were accepted for oviposition and that the parasitoid was capable of parasitising the eggs of two native pentatomids at proportions similar to BMSB. Only one New Zealand species of pentatomid, the endemic alpine shield bug Hypsithocus hudsonae, was not previously tested owing to the difficulty of collecting it from the field. Here we report the results of no‐choice oviposition tests between H. hudsonae and T. japonicus, conducted in containment, to complement previous physiological host range testing of this parasitoid in New Zealand. Parasitoids emerged from 14 out of 15 egg masses, and in total, from 78 out of 83 eggs (94%). The mean sex ratio was 89% female, and no males emerged from six egg masses. H. hudsonae is confirmed as a physiological host for T. japonicus, and this finding is discussed in relation to the strengths and limitations of physiological host range studies.

Combining physiological host range, behavior and host characteristics for predictive risk analysis of Trissolcus japonicus

Halyomorpha halys is an Asian pentatomid that has recently invaded several countries worldwide, where it has become a severe pest. Classical biological control focused on the scelionid egg parasitoid Trissolcus japonicus appears to be the most promising long-term solution. However, non-target risks need to be included in cost/benefit analyses. Physiological host range tests were conducted by offering T. japonicus females a single hemipteran egg for short (2 h) and long (24 h) exposure periods, and recording the behavior and parasitization acceptance/success during the short exposures. Of the 16 different hemipteran species tested in no-choice experiments, 9 species were accepted and suitable for T. japonicus development. Among pentatomids, Palomena prasina and Rhaphigaster nebulosa were accepted at rates comparable to H. halys, while species accepted at lower rates included Acrosternum heegeri, Carpocoris mediterraneus, C. purpeiripennis, Dolycoris baccarum, Piezodorus lituratus and Peribalus strictus. The other 7 hemipterans tested, including two coreids and one reduviid, were never parasitized. The use of a short-term exposure of 2 h revealed no differences with the 24-h exposure that has been widely used in physiological host range testing. Thus, T. japonicus oligophagy observed in other studies was confirmed by using our extremely simplified laboratory protocol. Moreover, the host egg morphology was correlated with the acceptance rates, permitting us to propose a new predictive approach for non-target studies. However, further research with more complex experimental designs that account for environmental conditions is needed to confirm laboratory predictions of host specificity under actual field conditions.

Host Kairomones Influence Searching Behavior of Trissolcus japonicus (Hymenoptera: Scelionidae), a Parasitoid of Halyomorpha halys (Heteroptera: Pentatomidae).

The brown marmorated stink bug, Halyomorpha halys (Stål), is a highly polyphagous species native to Asia that has become a serious invasive agricultural and nuisance pest across North America and Europe. Classical biological control host range evaluations have revealed egg parasitoid Trissolcus japonicus (Ashmead) to be the primary candidate biocontrol agent for field release against H. halys. However, these evaluations only provide us with the physiological host range of T. japonicus. Other Trissolcus species have demonstrated that contact kairomones from different host species elicit varied responses in the parasitoids' host foraging behaviors. To assess T. japonicus response to host kairomones, mated naive females were exposed to leaf surfaces contaminated with adult kairomones from its preferred host, H. halys, or from a native nontarget host, Podisus maculiventris (Say) (Heteroptera: Pentatomidae). Red maple, apple, and soybean were used as plant substrate treatments. The wasp's residence time on the leaf surface, linear walking velocity, and angular walking velocity were observed and measured using Noldus EthoVision XT tracking software. Within each leaf treatment, T. japonicus displayed stronger behavioral responses on leaves contaminated with contact kairomones from H. halys. The parasitoid resided on H. halys contaminated leaves for approximately twice as a long as it did on P. maculiventris contaminated leaves. Further, both species' kairomones elicited significant decreases in parasitoid walking velocity on all tested substrate types. Overall, our study suggests that kairomone-based behavioral studies can be used to further evaluate the host specificity of T. japonicus and can be an invaluable supplement to classical biocontrol host range testing regimes.

Physiological host range of Trissolcus japonicus in relation to Halyomorpha halys and other pentatomids from California

Brown marmorated stinkbug (BMSB), Halyomorpha halys Stal (Hemiptera: Pentatomidae), is native to Asia and an invasive urban and agricultural pest in the US. In California (CA), BMSB has been recorded attacking specialty crops such as almonds and peaches. The egg parasitoid Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), a key BMSB natural enemy native to Asia, is a candidate for classical biological control efforts targeting BMSB in CA and other parts of the US Trissolcus japonicus cannot be introduced deliberately into CA for BMSB control without US federal regulatory agency approval which is contingent on better understanding of its host range and specificity. Consequently, the host specificity and physiological host range of T. japonicus was evaluated under laboratory quarantine conditions by exposing eggs of BMSB and non-target pentatomid hosts (native and other exotic species) found in CA to T. japonicus. No-choice and binary-choice experiments provided female T. japonicus with equal unrestricted access to eggs of BMSB and non-target pentatomids. In addition to BMSB, eggs from six of ten resident pentatomid species found in CA were parasitized by T. japonicus. However, T. japonicus attack and emergence rates were consistently higher on BMSB when compared to non-target species. These results suggest that T. japonicus is oligophagous, but BMSB is a superior reproductive host compared to non-target pentatomid species that were evaluated. The implications of these findings for classical biological control efforts targeting BMSB in CA are discussed.

Experimental assessment of the biosafety of Trissolcus japonicus in New Zealand, prior to the anticipated arrival of the invasive pest Halyomorpha halys

Despite numerous interceptions at the border, the brown marmorated stink bug (BMSB), Halyomorpha halys Stal (Hemiptera: Pentatomidae), is not yet established in New Zealand. Nevertheless, a classical biocontrol programme using the egg parasitoid Trissolcus japonicus Ashmead (Hymenoptera: Scelionidae) has been initiated in anticipation of its likely arrival. The potential host range of the parasitoid in New Zealand was investigated by importing parasitised BMSB eggs into quarantine from Newark, DE, USA. Egg masses of seven species of Pentatomidae, including one sub-species, were individually exposed to naive mated female T. japonicus in no-choice laboratory experiments. The results showed that predatory Cermatulus nasalis nasalis, C. nasalis hudsoni and Oechalia schellenbergii, and the phytophagous Monteithiella humeralis, Dictyotus caenosus, Glaucias amyoti, and Cuspicona simplex are all within the physiological host range of T. japonicus, although not all appeared to be equally susceptible to parasitism. No development or emergence of T. japonicus from eggs of the cosmopolitan pentatomid plant pest Nezara viridula were observed. The likely ecological consequences of releasing T. japonicus in New Zealand are discussed, as is the subsequent decision of New Zealand’s Environmental Protection Authority to approve release of the parasitoid once BMSB arrives in New Zealand.

Variation in physiological host range in three strains of two species of the entomopathogenic fungus Beauveria.

Knowledge of the host range of a biocontrol agent (BCA) is fundamental. Host range determines the BCA’s economic potential, as well as the possible risk for non-target organisms. Entomopathogenic fungal strains belonging to the genus Beauveria are widely used as BCA, but our knowledge of their physiological host range is only partial. The aim of this study was to improve our understanding of the physiological host range of three Beauveria strains belonging to two species, B. hoplocheli and B. bassiana. We performed laboratory mortality bioassays to assess their pathogenicity and virulence against nine insect pests, belonging to three orders: Lepidoptera, Coleoptera and Diptera. Mortality rate, mean survival time and mycosis rate were used to estimate virulence. Pathogenicity was assessed as the capacity to cause a disease and induce mortality. Virulence was assessed as the severity of the disease based on mortality rate, mean survival time and mycosis rate. The results of this study revealed significant differences in the physiological host range of the three Beauveria strains tested. The three strains were pathogenic to all Diptera and Lepidoptera species tested. In the case of the Coleoptera, only the B. hoplocheli strain was pathogenic to the white grub Hoplochelus marginalis and only the B. bassiana strains were pathogenic to Alphitobius diaperinus. The B. hoplocheli strain was less virulent on Lepidoptera and Diptera than the two B. bassiana strains. The latter both exhibited very similar virulence patterns. The fact that B. hoplocheli and B. bassiana strains have different host ranges means that they can be used as BCA to target different pests. Impacts on non-target insects across multiple orders cannot be ruled out in the absence of ecological host range studies.

Host-Acceptance Behavior of Trissolcus japonicus (Hymenoptera: Scelionidae) Reared on the Invasive Halyomorpha halys (Heteroptera: Pentatomidae) and Nontarget Species

Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) is an egg parasitoid wasp from East Asia. It is considered to be an important natural enemy of the brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). Ongoing efforts to evaluate the physiological host range of this potential classical biological control agent have demonstrated that the wasp can parasitize at least 11 genera of nontarget Pentatomoidea in North America in no-choice tests. However, factors such as host-acceptance behavior that might affect nontarget parasitism in the field are poorly understood. We evaluated the preference of T. japonicus females provided with egg clusters of H. halys, Thyanta custator accerra McAtee (Hemiptera: Pentatomidae), Podisus maculiventris (Say) (Hemiptera: Pentatomidae), and Euschistus variolarius (Palisot de Beauvois) (Hemiptera: Pentatomidae) when wasps were reared on the target pest, H. halys, and the nontarget species, T.c. accerra and P. maculiventris. When reared on H. halys, T. japonicus showed a strong preference for H. halys, and frequently rejected nontarget hosts after inspection. When T. japonicus was reared on nontarget hosts, females showed reduced host-specificity, but were significantly smaller and produced a lower number of offspring. These results suggest that innate host-acceptance behavior is likely to reduce parasitism on some nontarget Pentatomoidea which T. japonicus will encounter in the field. Future efforts should be made to examine the ability of the wasp to reproduce long term on nontarget species when H. halys eggs are limited.

Infection of Drosophila suzukii with the obligate insect-pathogenic fungus Entomophthora muscae

Physiological constraints restrict specialist pathogens from infecting new hosts. From an applied perspective, a narrow host range makes specialist pathogens interesting for targeting specific pest insects since they have minimal direct effects on non-target species. Entomopathogenic fungi of the genus Entomophthora are dipteran-specific but have not been investigated for their ability to infect the spotted wing drosophila (SWD; Drosophila suzukii) a fruit-damaging pest invasive to Europe and America. Our main goal was to study whether SWD is in the physiological host range of the entomophthoralean species E. muscae. We investigated pathogenicity and virulence of E. muscae towards its main natural host, the housefly Musca domestica, and towards SWD. We found that E. muscae readily infected and significantly reduced survival of SWD by 27.3% with the majority of flies dying 4–8 days post-exposure. In comparison with SWD, infection of the natural host M. domestica resulted in an even higher mortality of 62.9% and larger conidial spores of E. muscae, reflecting the physiological constraints of the pathogen in the atypical host. We demonstrated that pathogens of the E. muscae species complex that typically have a narrow natural host range of one or few dipteran species are able to infect SWD, and we described a new method for in vivo transmission and infection of an entomophthoralean fungus to SWD.

Host specificity of Asian Chrysochus Chevr. in Dej. (Coleoptera, Chrysomelidae: Eumolpinae) and their potential use for biological control of invasive Vincetoxicum species

Three Asian leaf beetles of the genus Chrysochus were investigated as potential biological control agents of Vincetoxicum rossicum and V. nigrum, invasive weeds in northeastern North America. Chrysochus chinensis and Ch. globicollis were collected from a field host in a different genus and subtribe. Preliminary no-choice laboratory tests with Ch. goniostoma showed that its physiological host range is too broad. Based on these data, we are not considering these three species as potential biological control agents of invasive Vincetoxicum species.

Development rate, consumption, and host fidelity ofNeostauropus alternus(Walker, 1855) (Lepidoptera: Notodontidae)

The Asian shrub Rhodomyrtus tomentosa (Aiton) Hasskarl (Myrtaceae) is an invasive weed in Florida and Hawaii, U.S.A. Surveys for natural enemies of this exotic shrub in Hong Kong, China resulted in the development of a laboratory colony and host range testing of Neostauropus alternus (Walker, 1855) as a potential biological control agent of R. tomentosa. Twelve critical test plant species were presented to larvae of N. alternus. Complete development was limited to R. tomentosa, the ornamentally important Myrtus communis Linneaus (Myrtaceae), and the Florida natives Myrcianthes fragrans (Small) (K.A. Wilson) (Myrtaceae) and Morella cerifera (Linneaus) Small (Myricaceae). Total development time was more than ten days faster with R. tomentosa versus M. communis and M. cerifera, with the latter species requiring an extra larval instar to reach the pupal stage. Consumption rates were similar among R. tomentosa and M. cerifera, but due to the longer development time, larvae consumed two-fold more leaf material on M. cerifera. Despite an apparent larval survival and development preference for R. tomentosa, it is clear that the physiological host range of N. alternus includes M. cerifera and M. communis. The generalized feeding patterns exhibited in this research indicate that additional resources dedicated to the development of N. alternus as a biological control agent of R. tomentosa in Florida are unwarranted.

Development Rate, Consumption, and Host Specificity ofCarea varipes(Lepidoptera: Nolidae)

The Asian shrub Rhodomyrtus tomentosa is an invasive weed in Florida and Hawaii, USA. Surveys for natural enemies of this exotic shrub in Hong Kong, China, resulted in the development of a laboratory colony and initial host range testing of Carea varipes Walker as a potential biological control agent of R. tomentosa . Twelve critical test plant species were presented to C. varipes larvae, but complete development was limited to R. tomentosa , the ornamental Myrtus communis , and the Florida native Morella cerifera . Total development time was >10 d faster when held with R. tomentosa and M. communis versus M. cerifera , with the latter species requiring an extra larval instar to reach the pupal stage. Total consumption levels over an individual’s larval stage were similar among R. tomentosa and M. cerifera but, when the longer development time associated with the latter host is accounted for, consumption rates indicate that larvae consumed >2 times more leaf material when held with the Florida native. Despite an apparent preference for R. tomentosa , it is clear that the physiological host range of C. varipes includes the Florida native M. cerifera and the ornamentally important M. communis . The generalized feeding patterns exhibited in this research indicates that additional resources dedicated to the development of this species as a biological control agent are unwarranted.

Field study demonstrates that exotic parasitoids (Hymenoptera: Encyrtidae) of mealybugs (Hemiptera: Pseudococcidae) are absent from a native forest habitat in New Zealand

Laboratory-based, physiological host-range tests of classical biocontrol agents may be complemented by examining the ecological (realised) host-range of similar, previously established species. Sentinel long-tailed mealybugs (Pseudococcus longispinus (Targioni-Tozzetti)) on potted citrus plants, and two species of native mealybugs on potted native trees, were placed in pairs in an orchard and a native forest block 500 m away. Sentinel P. longispinus on citrus plants were also placed along transects anchored in each habitat and extending towards the other by 100–150 m. Parasitoids were reared from the retrieved mealybugs. P. longispinus in the orchard was regularly parasitized by four species of exotic Encyrtidae, but was never parasitized by them in the native forest even though the parasitoids were present in the surrounding environment. Sentinel native mealybugs were not parasitized by any species in either habitat, although native parasitoids (especially Errolium sp. (Hym: Platygastridae) and unidentified Hym: Aphelinidae) were collected from native mealybugs within the native forest.