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Understanding how native hyperparasitoids are attuned to novel hosts has practical implications for the classical biological control of invasive pest insects. This research focuses on both host size and female parasitoid body size to examine their joint effects on host evaluation and offspring performance. The parasitoid is Cheiloneurus nankingensis, which is native to Asia and an obligate gregarious hyperparasitoid attacking Aenasius arizonensis, which parasitizes the mealybug Phenacoccus solenopsis invasive to Asia. There was a quadratic 'dome-shaped' relationship between mealybug body size and both antenna-tapping and ovipositor-drilling frequencies and durations. Parasitoid body size did not affect these behaviors, except having a slight negative effect on ovipositor-drilling duration. Offspring egg-to-adult development time was similar for both large and small females when attacking large mealybugs, but it was longer for large females compared to small ones when attacking small mealybugs. Brood size at eclosion increased with both mealybug size and female size. Brood sex ratio (percent males) decreased with mealybug size while remaining unaffected by female size. The body size of adult offspring and their longevity increased with mealybug size while remaining unaffected by female size. These findings imply that mealybug size is much more relevant than female size to host examination behaviors and both aspects of size exert separate effects on brood allocation but an interaction to affect offspring developmental time. [ABSTRACT FROM AUTHOR]

The prickly pear cochineal, Dactylopius opuntiae Cockerell (Hemiptera: Dactylopiidae) and the cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) have become invasive pests of cactus and tomato in the Mediterranean region. In prospects for biological control possibilities, we assessed life history and population growth parameters of Cryptolaemus montrouzieri (Coleoptera: Coccinellidae) on both insects using age-stage two-sex life tables. Results revealed that the preadult development was longer on D. opuntiae (female: 33.41 ± 0.93 days and male: 33.17 ± 3.35 days) than on P. solenopsis (female: 27.85 ± 0.63 days and male: 28.15 ± 0.54 days). The total life cycle was longer on D. opuntiae (female: 85.05 ± 2,15 days and male: 80.78 ± 20 days) than on D. solenopsis (female: 77.85 ± 2.36 days and male: 76.15 ± 1.84 days). Fecundity was significantly higher on the cotton mealybug with 60.1 ± 5.61 eggs/female (18.9 ± 0.85 oviposition days) versus 37.41 ± 2.57 eggs/female on the prickly pear cochineal (12.95 ± 0.45 oviposition days). All life table parameters of the predator were significantly higher when fed on the cotton mealybug with a net reproductive rate (R0) of 30,0 ± 9.6421 offspring/female, an intrinsic rate of increase (r) of 0,0770 ± 0.0042 day−1, a finite rate of increase (λ) of 1,080 ± 0.00512 day−1. Projections of population growth and structure showed that 1.5 generations could be completed on both cochineals over a period of 60 days. The largest adult size of C. montrouzieri was observed when reared on P. solenopsis, reaching approximately 3,000 individuals. These data are important for the development and implementation of biological control and integrated pest management programmes targeting these invasive scales. [ABSTRACT FROM AUTHOR]

The release of biological control agents has been an important means of controlling invasive species for over 150 years. While these releases have led to the sustainable control of over 250 invasive pest and weed species worldwide, a minority have caused environmental harm. A growing recognition of the risks of biological control led to a focus on risk assessment beginning in the 1990s along with a precipitous decline in releases. While this new focus greatly improved the safety of biological control, it came at the cost of lost opportunities to solve environmental problems associated with invasive species. A framework that incorporates benefits and risks of biological control is thus needed to understand the net environmental effects of biological control releases. We introduce such a framework, using native biodiversity as the common currency for both benefits and risks. The model is based on interactions among four categories of organisms: (1) the biological control agent, (2) the invasive species (pest or weed) targeted by the agent, (3) one or more native species that stand to benefit from the control of the target species, and (4) one or more native species that are at risk of being harmed by the released biological control agent. Conservation values of the potentially benefited and harmed native species are incorporated as well, and they are weighted according to three axes: vulnerability to extinction, the ecosystem services provided, and cultural significance. Further, we incorporate the potential for indirect risks to native species, which we consider will result mainly from the ecological process of agent enrichment that may occur if the agent exploits but does not control the target pest or weed. We illustrate the use of this framework by retrospectively analyzing the release of the vedalia beetle, Novius (= Rodolia) cardinalis, to control the cottony cushion scale, Icerya purchasi, in the Galapagos Islands. While the framework is particularly adaptable to biological control releases in natural areas, it can also be used in managed settings, where biological control protects native species through the reduction of pesticide use. [ABSTRACT FROM AUTHOR]

Ash trees (Fraxinus spp.) were commonly planted street trees in urban environments prior to the arrival of emerald ash borer (EAB), Agrilus planipennis Fairmaire, in the 1990 s and its subsequent impacts. Insecticide treatments can provide consistent control of EAB and are used to protect high-value trees; however, control only lasts a few years before reapplication is needed. An EAB biological control program seeks to provide long-term control and several parasitoids have been released to that end, including the larval parasitoids Tetrastichus planipennisi Yang (Eulophidae) and Spathius galinae Belokobylskij (Braconidae). In 2015, we released parasitoids in three cities (Syracuse NY, Naperville IL, Boulder CO) while city arborists were simultaneously treating high-value street trees with insecticides. We hypothesized parasitoids would be able to establish on EAB in untreated trees and spread throughout the cities while treated trees remained healthy. We also hypothesized EAB densities would fall as non-treated ash died and would not subsequently rebound as insecticide treatments were removed from street trees due to the parasitism of biocontrol agents. Three-hundred trees were selected for monitoring in each city: 100 untreated, 100 treated, and 100 temporarily treated. Tetrastichus planipennisi successfully established in all three cities, while S. galinae established in Syracuse and Boulder. Untreated trees rapidly declined as expected while treated trees remained healthy. During the study subsets of trees were removed from the treatment cycle as EAB densities fell (≤ 10 larvae/m2). Minor canopy decline was present in 2021–2023 in trees from which treatment was removed, with median crown classes declining from 1 to 2. Despite this shift, most of these trees remained un-infested (∼ 75 %) and retained healthy canopies. Trees that did become infested had high apparent parasitism and low EAB densities. Due to the high value of urban trees, we recommend managers continue monitoring trees and consider selectively reinstating insecticide treatments on trees that start to decline and/or are subject to additional urban stressors.

As the globalisation of trade increases, so does the spread of arthropod pests, leading to a growing focus on biosecurity preparedness. One approach to this is pre-emptive biological control, involving the importation of classical biological control (CBC) agents for risk assessments and acquiring approval for their release prior to the expected arrival of their target pests. This aims to mitigate the economic and/or environmental consequences of a delayed biological control response to pest invasions. Guidelines to assess the feasibility of pre-emptive biological control for high priority pests were recently developed. Emerald ash borer (EAB), Agrilus planipennis, is an invasive woodboring pest of ash (Fraxinus spp.) in North America, European Russia and Ukraine, and is spreading westward into Europe, threatening the future of European ash (Fraxinus excelsior). We applied the aforementioned guidelines to assess the feasibility of pre-emptive biological control in Europe using four EAB parasitoids, already released in North America for CBC. Three of the parasitoids; Oobius agrili, Spathius galinae, and Tetrastichus planipennisi, were found suitable for pre-emptive biological control. The fourth parasitoid, Spathius agrili, was found to have limited establishment in new environmental conditions, and was therefore deemed less suitable for pre-emptive biological control of EAB in Europe. This assessment can inform scientists and regulators in Europe on the most promising EAB parasitoids that should be considered for pre-emptive applications for importation and risk assessment to acquire pre-approval for immediate release should the target pest subsequently be discovered. In turn, this study contributes to the development of biosecurity preparedness against EAB’s imminent spread throughout Europe.

The identity and diversity of Kordyana species on three native species of Commelinaceae in Australia were studied following surveys in 2020–2022 for Kordyana brasiliensis, which had been deliberately released as a biocontrol agent for the environmental weed Tradescantia fluminensis. Three new species of Kordyana are described from Australia based on DNA sequence analysis of the ITS and LSU rDNA regions, morphology, host associations, and geographic distributions. Two new species, Kordyana spectabilis on Aneilema acuminatum and Kordyana luteoalba on Pollia crispata, occur in shaded rainforest habitats in eastern Australia. The third new species, Kordyana occidentalis on Commelina ensifolia, occurs in forests and woodlands of the Kimberley region of Western Australia. Morphological descriptions are provided for these three new species of Kordyana as well as for the conidial stage of K. brasiliensis. [ABSTRACT FROM AUTHOR]

The southern tip of North America coalesces into one of the world's largest freshwater wetlands, the Everglades, Florida, USA. Though this region is much like an island, home to high biodiversity and endemism, it is also the site of a century of development and associated landscape-scale species invasions. Melaleuca quinquenervia (hereafter melaleuca), a tree native to tropical Australia, was planted extensively throughout south Florida as street trees, levee stabilizers, and later to reduce standing water in marshy areas. Through extensive cooperation with the United States Department of Agriculture's Australian Biological Control Laboratory, several biological control agents were released, three of which later successfully established. Herein we examine evidence that plant community shifts determined from vegetation surveys and remotely sensed images reflect changes from melaleuca-dominated wetlands (before management) to native communities (after management). Melaleuca-dominated community types decreased from 1990 to 2020 by more than 99%. Vegetation surveys also reflect an increase in cypress wetlands, pinelands, and open water wetlands, all of which were dominated by melaleuca in previous decades. We also found the normalized difference vegetation index (NDVI) increased in melaleuca-invaded wetlands during peak infestations but decreased again after communities recovered to sawgrass-dominated wetlands. These responses are concomitant with the development of integrative management techniques for melaleuca that include mechanical, chemical, and biological control. Our results confirm previous findings that biological control likely augments conventional management methods by limiting recovery of invasive species. [ABSTRACT FROM AUTHOR]

The contributions in this Special Issue originate from a Symposium "Classical biological control of weeds and arthropods: Evaluation of social, economic and ecological benefits" presented at the 26th International Congress of Entomology, held in Helsinki, Finland in 2022. Following an opening article analyzing agent and target traits associated with greater success odds in weed biological control, a perspective article summarizing how biological control programs are currently assessed and how they may be evaluated going forward frames the articles in the Special Issue. Articles assess different dimensions of success for selected weed and arthropod biocontrol programs either on the individual project level or through summaries of recent projects for geographic regions. Success dimensions include economic, ecological and socio-economic benefits. Included are also several articles that summarize or propose the use of innovative tools to improve biological control as a discipline going forward. Overall, this Special Issue portrays a status quo of biological control characterized by thoughtful analyses of project outcomes and recommendations to improve outcome assessments and increase the odds of success. As such, an optimistic prognosis for biological control is provided. [ABSTRACT FROM AUTHOR]

Invasive insect pests are a significant and accelerating threat to agricultural productivity, they degrade wilderness areas, and reduce quality of life in urban zones. Introduction biological control, the introduction, release, and establishment of host-specific efficacious natural enemies, is an effective management tool for permanently suppressing invasive pest populations over vast areas, often to levels that may no longer cause economic or environmental damage. However, introduction biological control programs are reactive: they are only initiated after an invasive pest has established, spread, and is causing damage that requires mitigation. Host specificity and host range testing of natural enemies for use in an introduction biological control program against an invasive pest can take years to complete. During this time, the target pest population continues to increase, invades new areas, and inflicts damage. Proactive biological control research programs identify prior to their establishment pest species that have high invasion potential and are likely to cause economic or environmental damage once established. Natural enemies are selected, screened, and if sufficiently host-specific, approved for release in advance of the anticipated establishment of the target pest. Following detection of the target pest and determination that incipient populations cannot be eradicated, natural enemies already approved for release are liberated into infested areas. This proactive approach to introduction biological control could significantly reduce project development time post-invasion, thereby lessening opportunities for pest populations to build, spread, and cause damage. [ABSTRACT FROM AUTHOR]

Simple Summary: Privets (Ligustrum spp.) are popular hedge shrubs that escape from gardens and cause negative impacts by invading forests in the United States. The narrow host specificity of the seed-feeding weevil, Ochyromera ligustri, suggests that this weevil could be considered a fortuitous biological control agent of privets. To find out the host range of this weevil, time-consuming experiments involving rearing and dissections are often conducted. Herein, we developed PCR primers to rapidly and accurately detect the presence of the weevil in privet fruits. We confirmed that the novel PCR primers specifically work for O. ligustri even with a small quantity of DNA, which was 0.01 ng. Using the newly developed PCR-based detection saves time and labor in research related to the detection and impact of this weevil. Ligustrum spp. (Oleaceae) have become invasive species in the US and negatively affect native plant diversity and richness in forests. Ochyromera ligustri (Coleoptera: Curculionidae) is considered a potential biological control agent in the US because adults feed on the foliage and larvae are seed-feeders of Ligustrum spp. To discover the relationships between O. ligustri and Ligustrum spp., fruit dissections or rearing and field observations are required. In the current research project, novel PCR primers were developed to rapidly detect the DNA of O. ligustri in molecular analyses without rearing and observation. The developed PCR primers worked even with 0.01 ng of DNA and did not amplify the DNA of the other five curculionid species tested. When the novel primers were tested with three Ligustrum spp. species common in the southeastern US, the DNA of O. ligustri was detected from all three species. We expect that the novel primers will be utilized to find out the presence and impact of O. ligustri on Ligustrum spp rapidly and accurately. [ABSTRACT FROM AUTHOR]

Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) and Trissolcus mitsukurii (Ashmead) (Hymenoptera: Scelionidae) are Asian egg parasitoids that are considered important natural enemies of the brown marmorated stink bug Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). These species are expanding their geographic distribution outside their native area, which suggests investigating their adaptability to environmental conditions. In a laboratory experiment, we investigated the life table parameters of these two egg parasitoid species under four constant temperatures, i.e., 16, 21, 26 and 31 °C. Results showed that the longevity of T. japonicus was higher than that of T. mitsukurii at all temperatures considered. The net reproductive rate (Ro) of T. japonicus was higher than that of T. mitsukurii at 26 and 31 °C. However, the intrinsic rate of increase (rm) at 26 and 31 °C was similar between the two species, and at 21 °C, T. mitsukurii exhibited a higher intrinsic and finite rate of increase. The two species complete their development at 16 °C, but with the lowest performances. Results suggest a higher increase of T. mitsukurii population when mean temperatures are equal to 21 °C, while the population increase of T. japonicus is expected to be favoured at higher temperatures.

The lineage G1 of Ganaspis brasiliensis is a larval parasitoid of the worldwide pest Drosophila suzukii and one of its most effective natural enemies in the native area. Because of its high degree of host specificity, G. brasiliensis G1 is considered a suitable species for introduction in areas invaded by D. suzukii following a classical biological control approach. Indeed, the release of the parasitoid is currently implemented in the USA and Italy. G1 females attack only host larvae developing in ripening fresh fruits on the plant and not larvae that develop in decaying fruits. To date, virtually no information is available on the cues regulating the foraging behavior of G1. In this study, we therefore aimed to find out whether chemical cues are exploited by G1 females to: (i) locate host fruits; (ii) locate suitable host larvae within infested fruit; (iii) discriminate between infested fresh fruits and infested rotting ones. We used a model system composed of blueberries and D. suzukii tested in two-choice olfactometer bioassays (with D. suzukii-infested fruits, healthy fruits, and pure air as odor targets), followed by the collection and the characterization of volatile organic compounds (VOCs) released by the tested targets. The results showed a clear time-dependent choice made by G1 females of infested versus healthy fruits related to the concomitant development of D. suzukii larvae and fruit degradation. Attraction to infested fruits was recorded during the early stages of infestation, followed by a repellent phase coinciding with fruits largely degraded by larval feeding. We found that the attractiveness of G. brasiliensis G1 towards fruits infested by young larvae was associated with the detection of VOCs released by the infested blueberries, and host’s cuticular hydrocarbons. Conversely, the repellence of older and deteriorated fruits hosting developed D. suzukii larvae was associated with the detection of a fermentation compound produced by microorganisms likely carried inside the fruit by the flies. The response of G1 females to the temporal dynamics of chemical cues emitted by the fruit–host larvae complex was consistent with the high degree of specificity of the parasitoid towards the ripening host fruits and towards D. suzukii.

Abstract Puccinia abrupta var. partheniicola, the so-called winter rust of parthenium weed (Parthenium hysterophorus), an invasive alien weed in India, was rediscovered at an epiphytotic scale in February 2023 following a prolonged period of presumed absence in the field. Disease incidence was 80–90% in large tracts of P. hysterophorus stands along the roadsides in an area of 5 km2 near Attibele–Sarjapura road (948A) in Anekal taluk of Bengaluru Urban district in Karnataka. Pycnial, aecial or telial stages of the rust were not found. The morphological parameters of uredinia and urediniospores completely matched those originally described, thus confirming the fungal identity. The significance of this rust epiphytotic to P. hysterophorus biocontrol in India is discussed together with the planned follow-up activities.

As the increasing globalisation of trade generates an escalating spread of arthropod pests, eradication has gained traction as a viable approach to avoiding the growing long-term management costs. The Sterile Insect Technique (SIT) involves releasing sexually sterile insects into the wild population and has been employed for environmentally friendly eradication. Alternatively, classical biological control (CBC) comprises the importation and release of natural enemies. Although generally used for long-term management, evidence suggests a synergistic impact could be exerted on pest populations when combined with SIT, potentially improving eradication outcomes. It is possible that sterile parasitoids, which would not bear the risk of irreversible non-target impacts associated with conventional CBC releases, could be accepted by regulatory agencies as a safe option to be used as a synergistic component of eradication. We investigated the post-irradiation behaviour and fitness of the egg parasitoid Trissolcus basalis to determine whether irradiation-induced sterility may reduce its efficacy. In comparing sterile and non-sterile parasitoids, there were no observable differences in searching behaviour, no significant differences in the number of egg masses found and parasitised, nor longevity. It is possible that sterile parasitoid release could contribute to an eradication programme without detrimental effects. [ABSTRACT FROM AUTHOR]

Although classical biological controls aim to permanently minimize numbers of invasive pests using exotic natural enemies, few long-term studies have been conducted on this subject. In this study, we investigated the population dynamics of the chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), and an introduced parasitoid, Torymus sinensis Kamijo (Hymenoptera: Torymidae), over 40 years (1982–2023) at a site at which the parasitoid was first released (Tsukuba City, Ibaraki Prefecture) in Japan. Because the gall formation rate per 100 chestnut buds, an indicator of pest density, had decreased from 42.5 to 0.7% in the first 10 years after the release, the biocontrol program was deemed successful. However, further research showed fluctuations in the pest density over the next 30 years. It usually remained at low levels but occasionally increased dramatically, with three peaks exceeding the economic injury level (30%). Simultaneously, an indicator of parasitoid density (the number of parasitoids emerging from 100 galls × the gall formation rate) also fluctuated, in synchronization with the pest density indicator. These results suggest that T. sinensis has played an important role in suppressing D. kuriphilus at the releasing site over 40 years. [ABSTRACT FROM AUTHOR]

New strategies are urgently needed to control Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), one of the most destructive pests of tomato crops. Originating from South America, it is spreading rapidly and has evolved resistance to most common insecticides making it highly challenging to control. Regarding biological control, the parasitoid Necremnus tutae Ribes & Bernardo (Hymenoptera: Eulophidae) is widely present around the Mediterranean basin and has adapted to the invader playing a substantial role in its control. In addition, the neotropical parasitoid Dolichogenidea gelechiidivoris Marsh (Hymenoptera: Braconidae) has established accidentally following its host in Spain and Algeria and a classical biological control program using this species is ongoing in Sub-Saharan Africa. Understanding the trophic connections between D. gelechiidivoris, N. tutae, the targeted host T. absoluta and potential non-target hosts is essential to assess their value as augmentative or classical biological control agents and to promote their establishment in conservation biocontrol. We conducted host-specificity tests in the laboratory using four European leafminer species to evaluate the specificity of these two parasitoids to T. absoluta. We then assessed their affinity for T. absoluta by exposing sentinel plants with the alternative host Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) inside and around greenhouses and measuring each parasitoid species' field parasitism rate. Our results show that of the four non-target species tested in the laboratory, N. tutae attacked three, while D. gelechiidivoris attacked only P. operculella. In the greenhouse, N. tutae did not prefer P. operculella or T. absoluta, whereas D. gelechiidivoris preferred the latter. The mean parasitism rate of T. absoluta over the three-month monitoring period in the greenhouses reached 27 % for N. tutae and 35 % for D. gelechiidivoris. We discuss the importance of host affinity for understanding potential non-target effects and the value a natural enemy can have as biological control.

Ganaspis Foerster includes several cryptic species that are important larval parasitoids of the invasive pest Drosophila suzukii (Matsumura), spotted-wing drosophila (SWD). Drosophila suzukii , native to Asia, was first discovered in 2008 in North America and Europe, becoming a devastating pest of soft-skinned fruit crops. Biological control could be among the safest, most environmentally benign, and cost-effective methods for long-term and landscape-level management of this invasive pest. Foreign exploration in East Asia discovered several major larval D. suzukii parasitoids. One of them was initially described as Ganaspis brasiliensis (Ihering) and consisted of 2 major genetic groups (G1 and G3). The groups are now recognized as 2 different species, Ganaspis kimorum Buffington and Ganaspis lupini Buffington. The more host-specific species G. kimorum was selected and approved for field release in the United States in 2021 and has been widely released since 2022. Here, we provide a comprehensive overview of the parasitoid's taxonomy, current known distribution, biology, ecology, mass-rearing methods, and biological control potential. [ABSTRACT FROM AUTHOR]

Plant species have been introduced increasingly into non‐native ranges, where many have become exotic weeds with adverse impacts on native ecosystems, as well as on farming and other livelihoods. In biological control, the classical or inoculative approach is the one most commonly used for the management of invasive alien weeds and is based on the use of co‐evolved natural enemies from the native range to control the invasive weed. Typically, the inundative or mycoherbicide approach targets problematic weeds using local plant pathogens that, in the case of introduced species, have 'jumped' onto the exotic host. The leaf‐spot fungus, Mycosphaerella polygoni‐cuspidati, co‐evolved with its host, Reynoutria (Fallopia) japonica (Japanese knotweed), in Japan and has a unique history of being investigated both as a classical biological control agent and a mycoherbicide against this highly invasive weed in the United Kingdom and North America. Here, we highlight our research on M. polygoni‐cuspidati as part of a biological control programme for Japanese knotweed and review the potential of mycoherbicides using exotic pathogens for the management of invasive alien weeds. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Climate change poses uncertainties in the effectiveness of classical biological control (CBC), and there is a lack of information on the establishment of natural enemy populations under present and future climatic conditions. The objective is to explore current traces of two alien predators (Neoseiulus californicus and Neoseiulus fallacis; introduced for the CBC program in the 1980s) and their future expansion under climate change in Taiwan. RESULTS: The results indicated that N. californicus was present in alpine orchards (e.g., Lishan and Meifeng) but N. fallacis was not found. Under current climate condition, most areas in Taiwan were deemed highly suitable for N. californicus, but not for N. fallacis, which may explain the outcomes of the CBC program. With intensifying climate change, the ranges of both species are projected to contract to varying extents in Taiwan but expand in some countries. CONCLUSION: The findings from this study can provide insights for evaluating and developing future CBC programs worldwide, and can help predict the implications of climate change on biological control efforts. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Native to Asia, Drosophila suzukii (Matsumura) is currently undergoing a rapid distribution expansion in Europe, America, and parts of Africa and has become a major economic pest of cultivated berry and stone fruits. Understanding the occurrence of D. suzukii and its associated parasitoids in its native range is crucial for effectively manage this invasive pest. In our study, traps baited with sugar vinegar wine were used to monitor the population dynamics of D. suzukii in four waxberry orchards in Fujian province, China, from May 2020 to April 2022. Additionally, parasitoids were sampled using sentinel traps baited with SWD-infested banana from May to June 2022. Four sites survey in Fujian indicated that D. suzukii population peak once per year. This peak occurred either in mid-May or mid-to late June, coinciding with the ripening period of waxberry fruit at the corresponding sites. During the waxberry ripening period, the percentages of D. suzukii adults captured in the four sites were female-bias, and the relative abundance of D. suzukii captured in Fuzhou was greater than that in other sample sites. Moreover, four parasitoid species, namely, Leptopilina japonica Novković & Kimura (Hymenoptera: Figitidae), Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae), Trichopria drosophilae (Perkins) (Hymenoptera: Diapriidae), and Asobara sp. (Hymenoptera: Braconidae) were identified based on morphology. Trichopria drosophilae was numerically dominated in the traps, and it was the only species that emerged from recovered banana slices under laboratory conditions. This study represents the first investigation on the occurrence of D. suzukii and its associated parasitoids in southeastern China. Our findings provide important clues for improving the efficacy of parasitoid-based IPM program in combating this pest, particularly in regions invaded by D. suzukii flies. [ABSTRACT FROM AUTHOR]

Abstract Background Farmer perceptions are highly important in influencing on-farm pest management decision-making. Biological control is extremely sustainable in the smallholder production context, but in Sub Saharan Africa (SSA) few attempts using this pest control method for arthropod pests have been successful, with one of the key reasons cited as poor involvement of farming communities and extension in the dissemination of information. Although farmers’ knowledge and attitudes are hugely important for the successful implementation of biological control, they are often disregarded. Papaya mealybug (Paracoccus marginatus) (PMB) has rapidly spread and established in suitable areas across Kenya becoming a serious pest. The objective of this study is to determine smallholder farmers’ knowledge, attitudes and practices towards biological control; farmers’ willingness to reduce their chemical pesticide use; and levels of support for a classical biological control initiative for PMB management. Methods Household surveys were conducted covering 383 farming households (148 women) in four papaya producing counties in Kenya alongside key informant interviews with eight extension agents and thirty agro-dealers, and eight focus group discussions. Results Although some farmers demonstrated awareness of the concept of biological control they lacked knowledge, experience and technical support from extension or agro-dealers. Reasons for not using biological control included inadequate awareness and concerns over efficacy and safety. Farmers expressed high levels of interest and willingness to support biological control, and were willing to reduce their chemical pesticide use to help conserve, and support the establishment of natural enemies. County, perception of biological as safe, training in IPM and gender were all highly significant factors determining farmers willingness to support biological control. Conclusions Previously, poor attention has been paid to farmer perceptions and participation in biological control, which has resulted in limited success in developing countries. With high levels of interest and willingness to support biological control, the next step is to engage with farming communities impacted by PMB. By building awareness and capacity, and developing a management plan with farmers that will support the release and establishment of the biological control agent, Acerophagus papayae, long-term, sustainable control of PMB in Kenya is possible.

The host-specific beetle Neogalerucella calmariensis was introduced to North America to control Lythrum salicaria, and in some areas has persisted in high population densities despite decimation of target plants. We hypothesised that egg predation might contribute to the survival of the beetles. In small-scale laboratory experiments, we investigated the likelihood of egg cannibalism at different N. calmariensis life stages. Neither neonates nor adults cannibalised eggs, however late instar larvae readily preyed on eggs of conspecifics. Pupal weights of larvae that cannibalised eggs were larger than those fed only leaf material suggesting that egg cannibalism may be associated with a fitness benefit. [ABSTRACT FROM AUTHOR]

Cryptostegia grandiflora and C. madagascariensis (Apocynaceae) are the only two species of this Madagascan plant genus. Both have been transported around the world as ornamentals due to their attractive flowers and based on a perceived potential as sources of rubber - hence, the common name rubber vine - because of their copious latex, which also contains toxic cardiac glycosides. As a result of their vigorous growth and ability to climb over and smother vegetation, both species have become invasive, posing an actual or potential threat to native ecosystems in many tropical and sub-tropical countries, as well as to human and animal health. Classical biological control (CBC), or the introduction of co-evolved natural enemies to control an invasive alien species in its exotic range, has successfully been used to tackle C. grandiflora in northern Queensland, Australia. This strategy is currently being evaluated for its suitability to manage C. madagascariensis in north-eastern Brazil using the same Madagascan rust fungus, Maravalia cryptostegiae, released as a CBC agent in Australia. For CBC to be successful, it is critical to understand the taxonomy of the invader as well as the origin(s) of its weedy biotype(s) in order to select the best-matched co-evolved natural enemies. Based on an exhaustive search in published and unpublished sources, we summarise the taxonomy and uses of these rubber vines, follow their historical movements and track their earliest records and current weed status in more than 80 countries and territories around the world. [ABSTRACT FROM AUTHOR]

Spathius galinae is a larval parasitoid native to the Russian Far East that was approved for release in the United States in 2015 for biological control of the emerald ash borer (EAB), Agrilus planipennis , an invasive beetle from Asia responsible for widespread mortality of ash trees (Fraxinus spp.) in North America. From 2015 to 2017, 1,340–1,445 females of S. galinae along with males were released into each release plot, paired with a nonrelease control plot (1–12.5 km apart), at 6 postinvasion forested sites containing abundant pole-sized ash trees in Michigan. By 2018, S. galinae had spread to all but one control plot. Based on the first year that S. galinae was found in trees in each control plot and the distances of those trees to the parasitoid release point within each site, we estimated that S. galinae spread at 3.7 (±1.9) km per year after its initial releases in 2015. The proportion of sampled trees with S. galinae broods, brood densities within sampled trees, and parasitism of EAB larvae increased sharply in both control and release plots after the last field releases in 2017, with the highest parasitism rates (42.8–60.3%) in 2020. Life table analysis showed that S. galinae alone reduced EAB's net population growth rate by 35–55% across sites from 2018 to 2020. These results demonstrate that S. galinae has established an increasing population in Michigan and now plays a significant role in reducing EAB populations in the area. [ABSTRACT FROM AUTHOR]

Climate suitability analyses based on ecological niche modeling provide a powerful tool for biological control practitioners to assess the likelihood of establishment of different candidate agents prior to their introduction in the field. These same analyses could also be performed to understand why some agents establish more easily than others. The release of three strains of Aphalara itadori (Shinji) (Hemiptera: Pysllidae), each from a different source locality in Japan, for the biological control of invasive knotweed species, Reynoutria spp. Houtt. (Caryophyllales: Polygonaceae), provides an important opportunity to compare the utility of climate suitability analyses for identifying potential climate‐based limitations for successful biological control introductions. Here, we predict climate suitability envelopes for three target species of knotweed in Europe and two target species of knotweed in North America and compare these suitability estimates for each of these species to the source localities of each A. itadori strain. We find that source locality of one strain, the Kyushu strain, has little‐to‐no suitability compared to other locations in Japan based on knotweed records from Europe, supporting an earlier study based on North American Japanese knotweed records. The source locality of a second strain, the Murakami strain, was predicted to have medium‐to‐high suitability based on records of knotweeds from North America. In contrast, European records of Reynoutria × bohemica Chrtek & Chrtková and Reynoutria sachalinensis (F. Schmidt) Nakai predicted no suitability for this locality compared to other locations in Japan, while European records for Reynoutria japonica Houtt. predicted low suitability. The source locality of the final strain, the Hokkaido strain, was predicted as having medium‐to‐high suitability based on knotweed records of all examined species from both North America and Europe. [ABSTRACT FROM AUTHOR]

Arrival, establishment, and further dispersal of non‐native natural enemies are considered essential for a successful biological control programme, while among the factors that may determine the success of such a programme, genetic diversity of the introduced population plays an important role in the establishment of a non‐native species.The Chinese parasitoid wasp Torymus sinensis Kamijo (Hymenoptera: Torymidae) was initially released in Europe in Italy to control biologically the Asian chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), and reduce the damage induced on sweet chestnut (Castanea sativa Miller). In the following years, T. sinensis was then released in numerous other European countries as a biological control agent of D. kuriphilus. Its presence has also been reported beyond the countries of release due to rapid natural dispersal.To assess the post‐release genetic diversity of D. kuriphilus, we screened T. sinensis populations from six European countries and tested the possibility of these populations suffering from frequently observed genetic effects that could threaten its successful establishment in Europe.Our results exhibit that T. sinensis populations have suffered neither from the Allee effect nor from genetic bottleneck after their release and establishment in Europe, something that increases the possibility to effectively control D. kuriphilus in Europe. [ABSTRACT FROM AUTHOR]

The release of Tamarixia triozae (Burks) (Hymenoptera: Eulophidae), a parasitoid of the potato psyllid, Bactericera cockerelli (Šulc) (Hemiptera: Triozidae), resulted in the successful establishment of the parasitoid in New Zealand. The parasitoid was released at more than 30 sites by the final year of the three-year study throughout New Zealand. Its continued presence over the three-year study was confirmed in two regions (Hawke's Bay and Canterbury). At one site in Canterbury, the parasitoid was released only in the first summer of this study (Nov. 2017–Feb. 2018). It was recovered from potato psyllid infested African boxthorn (Lycium ferocissimum Miers) foliage in the second and third summers at this site, demonstrating the parasitoid's ability to survive over successive winters. We found T. triozae parasitized nymphs at 24 sites of the 86 potato psyllid host plant sites surveyed within a 25 km radius of known release sites in Hawke's Bay. The parasitoid was found up to 24 km from the nearest known release site in Hawke's Bay. In Canterbury, the parasitoid was found up to 0.6 km from a known release site. Parasitism rates of 13.7–15.6% were estimated based on two post-release survey methods employed in this study. The parasitoid also feeds on psyllid nymphs so its establishment may lead to helping to reduce or delay potato psyllid populations from reaching damaging levels. Long-term monitoring is needed to determine the consequences of importing T. triozae on populations of potato psyllid. [ABSTRACT FROM AUTHOR]

In Australia there are five weedy Sporobolus grass (WSG) species that heavily impact agricultural industries and native biodiversity. WSG have been the subject of several efforts to find host-specific pathogens with potential for classical and inundative biocontrol. Most of these studies are only discussed in unpublished reports or theses, so in this paper we synthesise the available peer-reviewed and 'grey' literature that discuss classical, augmentative and inundative biocontrol of WSG in Australia using fungal pathogens. We consider the hundreds of fungal pathogens previously isolated from Sporobolus hosts on an international and national scale. Of the pathogens investigated for WSG biocontrol previously, the only promising classical biocontrol agent was a smut fungus (Ustilago sporoboli-indici) from South Africa that is now present in Queensland and New South Wales, Australia. Its method of introduction to Australia is unknown. We hence discuss the history and potential for augmentative biocontrol of WSG using U. sporoboli-indici. Next, we summarise inundative biocontrol efforts. Several ascomycetes isolated from Australian WSG populations have been tested in this regard, including species of Nigrospora, Fusarium, Curvularia, Microdochium, Pestalotiopsis, and Neopestalotiopsis. However, a lack of host-specificity or efficacy subsequently precluded their further development, and potential improvements on those inundative biocontrol studies are discussed. Finally, we discuss a collection of endemic fungal taxa isolated from diseased Sporobolus in Australia, which are currently undergoing virulence, pathogenicity, and host-specificity screening as potential inundative biocontrol agents for WSG. Our intention is that the lessons learned from previous studies and summarised herein, will support ongoing development of WSG biocontrol agents in Australia, and more broadly, weed biocontrol using plant pathogens anywhere in the world. [ABSTRACT FROM AUTHOR]

The olive psyllid, Euphyllura olivina, is a newly invasive species to California with the potential to become an economical pest if it reaches the olive production regions of Californias Central Valley. Here, we report on surveys undertaken in California to assess the psyllids current distribution and the occurrence of parasitism. Additionally, we present results of foreign collections of its parasitoids and initial non-target studies of a possible biological control agent, the Mediterranean parasitoid Psyllaephagus euphyllurae. The current distribution of the psyllid appears to be limited to the California coast between Monterey and San Diego; there have been no reports of infestations on olives in the major production areas of central and northern California. Psyllaephagus euphyllurae was the major primary parasitoid found in our foreign collections. The potential non-target impact of P. euphyllurae was tested on three native North American psyllid species: Neophyllura arctostaphyli, Euglyptoneura nr. robusta, and Calophya nigrella. No P. euphyllurae developed on the non-target species during no-choice tests. Behavioral observations in choice tests confirmed no attack on the non-target hosts, although the parasitoid did remain longer on N. arctostaphyli-infested manzanita plants, and revealed no host feeding behavior.

Abstract Background There is a consensus that the conservation of natural enemies is the most important biological control strategy, but it has also been the least attended. The reason is simple: there is a strong contradiction between modern agriculture and biological control. Various strategies have been proposed for the conservation of natural enemies, among others, protection against pesticides and establishment of nectar plants as alternative food. Less attention has been paid to the conservation of alternative hosts for natural enemies. Main body Natural enemies are not exclusive to pests, on the contrary, numerous species require alternative prey and hosts for their prevalence. Their conservation is a strategy widely referenced in scientific literature; however, this idea is not consistent with the studies developed. From 1973 to 2021, only 21 studies that emphasized the use of alternative hosts were recorded. Most focused on single phytophagous–natural enemy species, and little attention was given to the plant–phytophagous relationship. For example, Asclepias curassavica (Apocynaceae) hosts more than nine species of specialist phytophagous; and they, in turn, attracted 24 species of natural enemies. Although different studies demonstrate the potential of alternative hosts, some presume an adverse or doubtful effect on pest control; for example, additional vegetation in agroecosystems could act as a source, but also as a sink for natural enemies. This analysis tries to fit biological control to the modern agricultural paradigm, and not the other way around, as suggested by ecological theory. We support the idea that conservation biological control should be directed toward the conservation of multiple species, with the aim of controlling not only pest, but also the self-regulation of the agroecosystem. The path that should be followed by the study and application of alternative hosts as a strategy of biological control by conservation is discussed. Conclusion The wide diversity of non-pest insect species suggests an enormous potential for their exploitation as alternative hosts. The evaluation of host plants of specialized phytophagous species could improve biological control and reduce the risk of pests for crops. This strategy would partly fill the huge gap that exists in modern agroecosystems in terms of biological diversity.

The Nagoya Protocol for access and benefit sharing (ABS) attaches significance to India since the country exchanges classical biological control agents to manage invasive alien species. Classical biological control differs from commercial biological control in that it involves the use of co-evolved, host specific natural enemies from the host's native region to control the host wherever invasive. The national Biological Diversity Act is responsible for implementing ABS in India. It stipulates the means for use of biological resources for various purposes including research and commerce. However, commercial use of bioresources as biological control agents is not included. ABS regulates the exchange of research results using biological resources and related intellectual property rights. India is yet to implement the Nagoya Protocol effectively due to certain gaps in the Biological Diversity Act concerning some of the key provisions in the protocol that need to be addressed. However, some examples of the application of ABS measures for export of biological resources are discussed here. For export of biological control agents from India, collaborative research with the recipient country is necessary and is governed by the Ministry of Agriculture and Farmers' Welfare. Multiplication of biological control agents for commercial use and release is governed by ABS regulations. For importation of biological control agents into India, the exporting country regulations apply, and the Plant Protection Advisor grants permission. To implement the Nagoya Protocol effectively in India, we recommend that: (1) user country policies include clauses that discourage misuse of biological resources, (2) the consent of local communities be sought before accessing biological resources instead of just 'consulting' them, (3) ABS provisions are clearly stated, including what is covered and what is not covered under the Biological Diversity Act, (4) ABS provisions be made more flexible to facilitate compliance, and (5) the roles and responsibilities of each agency involved in ABS implementation be clearly defined. [ABSTRACT FROM AUTHOR]

The USA has been actively involved in classical biological control projects against invasive insect pests and weeds since 1888. Classical (importation) biological control relies upon natural enemies associated through coevolution with their target species at their geographic origin to also provide long-term, self-sustaining management where the pest/weed has become invasive. Biological control agents are a form of genetic resources and fall under the purview of the 1993 Convention on Biological Diversity (CBD) and its Nagoya Protocol (NP), which entered into force in 2014 to address equitable sharing of benefits arising from utilization of genetic resources. Safe and effective classical biological control agents have historically been shared among countries experiencing problems with invasive species. However, a feature of the Nagoya Protocol is that countries are expected to develop processes governing access to their genetic resources to ensure that the benefits are shared equitably—a concept referred to as "access and benefit sharing" (ABS). Although the USA is not party to the CBD nor the NP, US biological control programs are affected by these international agreements. Surveying, collecting, exporting and importing of natural enemies may be covered by new ABS regulatory processes. Challenges of ABS have arisen as various countries enact new regulations (or not) governing access to genetic resources, and the processes for gaining access and sharing the benefits from these resources have become increasingly complex. In the absence of an overarching national US policy, individual government agencies and institutions follow their own internal procedures. Biological control practitioners in the USA have been encouraged in recent years to observe best practices developed by the biological community for insect and weed biological control. [ABSTRACT FROM AUTHOR]

National idiosyncrasies in the adoption of the Nagoya Protocol (NP) and implementation of access and benefit sharing (ABS) have created obstacles for many research-based activities that require access to genetic resources. This is particularly true for disciplines such as classical and augmentative biological control. As a provider of biological control genetic resources worldwide, South America plays an important role in this context. The status of adoption of the NP in South America is reviewed, analysing the number of internationally recognised certificates of compliance, and examining the number of certificates issued in South America to access biological control genetic resources. We also summarise the common problems associated with access and export of biological control genetic resources through the experience of a non-governmental organisation in Argentina, the Fundación para el Estudio de Especies Invasivas (https://en.fuedei.org/). Finally, we provide some communication and awareness-raising activities to persuade policy makers on the importance of facilitating the exchange of biocontrol genetic resources and ABS regulations in South America. [ABSTRACT FROM AUTHOR]

The Nagoya Protocol on Access and Benefit Sharing (ABS) was implemented to further develop the third objective of the Convention on Biological Diversity, the fair and equitable sharing of benefits arising out of the utilization of genetic resources. Interpretation of this agreement is wide-ranging and there is concern that if ABS measures are poorly implemented biological control and the resultant public good will be greatly impeded. The ethos of multilateral use and exchange of genetic resources used in classical biological control will be particularly affected. In the spirit of the fair and equitable sharing of benefits arising out of the utilization of genetic resources, we propose a simple practical solution in the form of an international agreement on the use and exchange of classical biological control genetic resources. [ABSTRACT FROM AUTHOR]

Abstract Climate suitability analyses based on ecological niche modeling provide a powerful tool for biological control practitioners to assess the likelihood of establishment of different candidate agents prior to their introduction in the field. These same analyses could also be performed to understand why some agents establish more easily than others. The release of three strains of Aphalara itadori (Shinji) (Hemiptera: Pysllidae), each from a different source locality in Japan, for the biological control of invasive knotweed species, Reynoutria spp. Houtt. (Caryophyllales: Polygonaceae), provides an important opportunity to compare the utility of climate suitability analyses for identifying potential climate‐based limitations for successful biological control introductions. Here, we predict climate suitability envelopes for three target species of knotweed in Europe and two target species of knotweed in North America and compare these suitability estimates for each of these species to the source localities of each A. itadori strain. We find that source locality of one strain, the Kyushu strain, has little‐to‐no suitability compared to other locations in Japan based on knotweed records from Europe, supporting an earlier study based on North American Japanese knotweed records. The source locality of a second strain, the Murakami strain, was predicted to have medium‐to‐high suitability based on records of knotweeds from North America. In contrast, European records of Reynoutria × bohemica Chrtek & Chrtková and Reynoutria sachalinensis (F. Schmidt) Nakai predicted no suitability for this locality compared to other locations in Japan, while European records for Reynoutria japonica Houtt. predicted low suitability. The source locality of the final strain, the Hokkaido strain, was predicted as having medium‐to‐high suitability based on knotweed records of all examined species from both North America and Europe.

Ligustrum spp. (Oleaceae) have become invasive species in the US and negatively affect native plant diversity and richness in forests. Ochyromera ligustri (Coleoptera: Curculionidae) is considered a potential biological control agent in the US because adults feed on the foliage and larvae are seed-feeders of Ligustrum spp. To discover the relationships between O. ligustri and Ligustrum spp., fruit dissections or rearing and field observations are required. In the current research project, novel PCR primers were developed to rapidly detect the DNA of O. ligustri in molecular analyses without rearing and observation. The developed PCR primers worked even with 0.01 ng of DNA and did not amplify the DNA of the other five curculionid species tested. When the novel primers were tested with three Ligustrum spp. species common in the southeastern US, the DNA of O. ligustri was detected from all three species. We expect that the novel primers will be utilized to find out the presence and impact of O. ligustri on Ligustrum spp rapidly and accurately.

The intentional introduction of exotic species through classical biological control programs provides unique opportunities to examine the consequences of population movement and ecological processes for the genetic diversity and population structure of introduced species. The weevils Neochetina bruchi and N. eichhorniae (Coleoptera: Curculionidae) have been introduced globally to control the invasive floating aquatic weed, Eichhornia crassipes, with variable outcomes. Here, we use the importation history and data from polymorphic microsatellite markers to examine the effects of introduction processes on population genetic diversity and structure. We report the first confirmation of hybridization between these species, which could have important consequences for the biological control program. For both species, there were more rare alleles in weevils from the native range than in weevils from the introduced range. N. eichhorniae also had higher allelic richness in the native range than in the introduced range. Neither the number of individuals initially introduced nor the number of introduction steps appeared to consistently affect genetic diversity. We found evidence of genetic drift, inbreeding, and admixture in several populations as well as significant population structure. Analyses estimated two populations and 11 sub-clusters for N. bruchi and four populations and 23 sub-clusters for N. eichhorniae, indicating divergence of populations during and after introduction. Genetic differentiation and allocation of introduced populations to source populations generally supported the documented importation history and clarified pathways in cases where multiple introductions occurred. In populations with multiple introductions, genetic admixture may have buffered against the negative effects of serial bottlenecks on genetic diversity. The genetic data combined with the introduction history from this biological control study system provide insight on the accuracy of predicting introduction pathways from genetic data and the consequences of these pathways for the genetic variation and structure of introduced species.

Background: There is a consensus that the conservation of natural enemies is the most important biological control strategy, but it has also been the least attended. The reason is simple: there is a strong contradiction between modern agriculture and biological control. Various strategies have been proposed for the conservation of natural enemies, among others, protection against pesticides and establishment of nectar plants as alternative food. Less attention has been paid to the conservation of alternative hosts for natural enemies. Main body: Natural enemies are not exclusive to pests, on the contrary, numerous species require alternative prey and hosts for their prevalence. Their conservation is a strategy widely referenced in scientific literature; however, this idea is not consistent with the studies developed. From 1973 to 2021, only 21 studies that emphasized the use of alternative hosts were recorded. Most focused on single phytophagous–natural enemy species, and little attention was given to the plant–phytophagous relationship. For example, Asclepias curassavica (Apocynaceae) hosts more than nine species of specialist phytophagous; and they, in turn, attracted 24 species of natural enemies. Although different studies demonstrate the potential of alternative hosts, some presume an adverse or doubtful effect on pest control; for example, additional vegetation in agroecosystems could act as a source, but also as a sink for natural enemies. This analysis tries to fit biological control to the modern agricultural paradigm, and not the other way around, as suggested by ecological theory. We support the idea that conservation biological control should be directed toward the conservation of multiple species, with the aim of controlling not only pest, but also the self-regulation of the agroecosystem. The path that should be followed by the study and application of alternative hosts as a strategy of biological control by conservation is discussed. Conclusion: The wide diversity of non-pest insect species suggests an enormous potential for their exploitation as alternative hosts. The evaluation of host plants of specialized phytophagous species could improve biological control and reduce the risk of pests for crops. This strategy would partly fill the huge gap that exists in modern agroecosystems in terms of biological diversity. [ABSTRACT FROM AUTHOR]

Candidate biological control agents of invasive insect pests are increasingly being found in new geographic regions as a result of unintentional introductions. However, testing the degree of genetic differentiation among adventive and native-range populations of these agents is rarely done. We used reduced-representation sequencing of genomic DNA to investigate the relationships among laboratory lines of Trissolcus japonicus (Ashmead) (Hymenoptera, Scelionidae), an egg parasitoid and biological control agent of the brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera, Pentatomidae). We compared sequences from multiple adventive populations in North America (Canada, USA) and Europe (Switzerland) with populations sourced from part of its native range in China. We found considerably more genetic variation among lines sourced from adventive populations than among those within native populations. In the Pacific Northwest of North America (British Columbia, Canada and Washington State, USA), we found preliminary evidence of three distinct genetic clusters, two of which were highly dissimilar from all other lines we genotyped. In contrast, we found that other adventive lines with close geographic proximity (two from Ontario, Canada, three from Switzerland) had limited genetic variation. These findings provide a basis for testing biological differences among lines that will inform their use as biological control agents, and provide evidence to support a hypothesis of several independent introductions of T. japonicus in western North America from different source areas. [ABSTRACT FROM AUTHOR]

• Tetrastichus planipennisi successfully established in three urban locations. • Spathius galinae successfully established at two of three urban locations. • Canopy health experienced only minor decline once insecticide treatments were halted. • EAB densities did not appear to rapidly increase in the presence of both parasitoids. Ash trees (Fraxinus spp.) were commonly planted street trees in urban environments prior to the arrival of emerald ash borer (EAB), Agrilus planipennis Fairmaire, in the 1990 s and its subsequent impacts. Insecticide treatments can provide consistent control of EAB and are used to protect high-value trees; however, control only lasts a few years before reapplication is needed. An EAB biological control program seeks to provide long-term control and several parasitoids have been released to that end, including the larval parasitoids Tetrastichus planipennisi Yang (Eulophidae) and Spathius galinae Belokobylskij (Braconidae). In 2015, we released parasitoids in three cities (Syracuse NY, Naperville IL, Boulder CO) while city arborists were simultaneously treating high-value street trees with insecticides. We hypothesized parasitoids would be able to establish on EAB in untreated trees and spread throughout the cities while treated trees remained healthy. We also hypothesized EAB densities would fall as non-treated ash died and would not subsequently rebound as insecticide treatments were removed from street trees due to the parasitism of biocontrol agents. Three-hundred trees were selected for monitoring in each city: 100 untreated, 100 treated, and 100 temporarily treated. Tetrastichus planipennisi successfully established in all three cities, while S. galinae established in Syracuse and Boulder. Untreated trees rapidly declined as expected while treated trees remained healthy. During the study subsets of trees were removed from the treatment cycle as EAB densities fell (≤ 10 larvae/m2). Minor canopy decline was present in 2021–2023 in trees from which treatment was removed, with median crown classes declining from 1 to 2. Despite this shift, most of these trees remained un-infested (∼ 75 %) and retained healthy canopies. Trees that did become infested had high apparent parasitism and low EAB densities. Due to the high value of urban trees, we recommend managers continue monitoring trees and consider selectively reinstating insecticide treatments on trees that start to decline and/or are subject to additional urban stressors. [ABSTRACT FROM AUTHOR]

• Emerald ash borer is a key biosecurity threat to European ash forests. • Pre-emptive biological control could improve preparedness for its arrival. • Three parasitoids were deemed suitable for pre-emptive biological control in Europe. • European countries should conduct pre-emptive risk assessment for these parasitoids. As the globalisation of trade increases, so does the spread of arthropod pests, leading to a growing focus on biosecurity preparedness. One approach to this is pre-emptive biological control, involving the importation of classical biological control (CBC) agents for risk assessments and acquiring approval for their release prior to the expected arrival of their target pests. This aims to mitigate the economic and/or environmental consequences of a delayed biological control response to pest invasions. Guidelines to assess the feasibility of pre-emptive biological control for high priority pests were recently developed. Emerald ash borer (EAB), Agrilus planipennis , is an invasive woodboring pest of ash (Fraxinus spp.) in North America, European Russia and Ukraine, and is spreading westward into Europe, threatening the future of European ash (Fraxinus excelsior). We applied the aforementioned guidelines to assess the feasibility of pre-emptive biological control in Europe using four EAB parasitoids, already released in North America for CBC. Three of the parasitoids; Oobius agrili , Spathius galinae , and Tetrastichus planipennisi , were found suitable for pre-emptive biological control. The fourth parasitoid, Spathius agrili , was found to have limited establishment in new environmental conditions, and was therefore deemed less suitable for pre-emptive biological control of EAB in Europe. This assessment can inform scientists and regulators in Europe on the most promising EAB parasitoids that should be considered for pre-emptive applications for importation and risk assessment to acquire pre-approval for immediate release should the target pest subsequently be discovered. In turn, this study contributes to the development of biosecurity preparedness against EAB's imminent spread throughout Europe. [ABSTRACT FROM AUTHOR]

Globally, governments spend significant amounts of money attempting to prevent or mitigate the negative impacts of invasive species using different strategies, including classical biological control for species that are widespread in the landscape. Arriving at the point of biocontrol release requires significant investment of time and funds for research and testing, and success of the biocontrol agent is uncertain. We present a numerical model designed to assist in this process. The model is based on well-established equations of population growth and spread. Technical feasibility of a biocontrol programme is assessed based on the population parameters for the pest and biocontrol agent.