Assessing potential hybridization between a hypothetical gene drive-modified Drosophila suzukii and nontarget Drosophila species.

Genetically engineered gene drives (geGD) are potentially powerful tools for suppressing or even eradicating populations of pest insects. Before living geGD insects can be released into the environment, they must pass an environmental risk assessment to ensure that their release will not cause unacceptable harm to non-targeted entities of the environment. A key research question concerns the likelihood that nontarget species will acquire the functional GD elements; such acquisition could lead to reduced abundance or loss of those species and to a disruption of the ecosystem services they provide. The main route for gene flow is through hybridization between the geGD insect strain and closely related species that co-occur in the area of release and its expected dispersal. Using the invasive spotted-wing drosophila, Drosophila suzukii, as a case study, we provide a generally applicable strategy on how a combination of interspecific hybridization experiments, behavioral observations, and molecular genetic analyses can be used to assess the potential for hybridization

Models for the practitioner: Predicting the efficient biocontrol of Tuta absoluta under different management scenarios

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most destructive pests of solanaceous crops. One possible biological control strategy is the augmentative release of parasitoids. However, parasitoid intervention efficacy is highly sensitive to the release timing and intensity. Virus-based biopesticides are additional control means since they are highly selective and can be combined with natural enemies. We developed a stage-structured population model, validated with results from a semi-field experiment, to investigate and predict the population dynamics of the pest T. absoluta and one of its parasitoids, Necremnus tutae Ribes & Bernardo (Hymenoptera: Eulophidae). The aim of the study was to assess the best release parameters of N. tutae to control the pest in four different management scenarios: without any other control method, with a biopesticide (PhopGV, Baculoviridae), with the natural presence of the parasitoid, and when combining the natural presence of the parasitoid with a biopesticide. Moreover, in each scenario, two growing seasons of different lengths were compared. To achieve the same control level, 3–45% fewer parasitoids are necessary in a long growing season than in a shorter one. Biopesticide applications reduce the number of required parasitoids by 66% and 78%, whereas the natural presence of parasitoids reduces it by 11% and 17% for short and long growing seasons, respectively. On average, with biopesticide application, the parasitoid intervention can be delayed by a month and remains efficient. These findings highlight the importance of mathematical models in applied pest management drawing precise predictions crucial for efficient control.JA was financed by the CERCA Programme of the Generalitat de Catalunya.info:eu-repo/semantics/publishedVersio

Entomopathogens and Parasitoids Allied in Biocontrol: A Systematic Review

Biological pest control is an environmentally friendly alternative to synthetic pesticides, using organisms such as viruses, bacteria, fungi, and parasitoids. However, efficacy is variable and combining different biocontrol agents could improve success rates. We conducted a systematic review of studies combining a parasitoid with an entomopathogenic microorganism, the first of its kind. We searched in Web of Science and extracted data from 49 publications matching the pre-defined inclusion criteria. Combinations of 36 hymenopteran parasitoids with 17 entomopathogenic microorganisms used to control 31 target pests were found. Trichogramma pretiosum and Encarsia formosa were the most frequently studied parasitoids, while Beauveria bassiana, Metarhizium anisopliae, Lecanicillium muscarium, Bacillus thuringiensis var. kurstaki, the Spodoptera exigua multiple nucleopolyhedrovirus, and the Spodoptera frugiperda multiple nucleopolyhedrovirus were the main microbial agents assessed. Out of 49 parasitoid–microorganism combinations assessed in the laboratory experiments, thirty-eight were reported as compatible and six as incompatible. Timing and dosage of biopesticides played a crucial role, with later application and appropriate dosage minimizing adverse effects on parasitoid development. More research is needed to assess compatibility and efficacy under real-world conditions. Our review provides valuable insights for researchers and practitioners to optimize the combined use of micro- and macroorganisms for effective pest control

Insight into the host-specificity of a native and a newly introduced parasitoid of Tuta absoluta and prospect for biological control

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.JA was funded by the Horizon Europe project ADOPT-IPM (Project 101060430) and from the CERCA Program of the Generalitat de Catalunya.info:eu-repo/semantics/publishedVersio

A parasitoid wasp allied with an entomopathogenic virus to control Tuta absoluta

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a major threat to worldwide tomato production, and sustainable management methods are needed. Betabaculovirus phoperculellae (PhopGV) and the parasitoid wasp Necremnus tutae Ribes & Bernardo (Hymenoptera: Eulophidae) were identified as promising biocontrol agents of this pest. Since the virus is most effective against first instar larvae, whereas the parasitoid targets older ones, combining both agents could result in increased pest control. We conducted a replicated semi-field experiment to evaluate the control efficacy of N. tutae and PhopGV when used alone and in combination against T. absoluta and their compatibility over an entire growth period. Combining the two agents achieved the highest larval (−24 %) and crop damage (−29 %) reduction cumulated over the entire experiment. However, there was no significant additive effect of the two agents. At the end of the trial, which coincided with the emergence of the third generation of T. absoluta adults, using the virus alone resulted in the strongest reduction of adult density (−78 %), followed by the virus-parasitoid combination (−59 %). No negative effect of the virus was recorded on the parasitoid population. Our results demonstrate the compatibility and potential of N. tutae and PhopGV to reduce population growth and crop damage of T. absoluta under semi-field conditions. While more research is needed, our findings provide important insights into an innovative combination of biocontrol agents, thereby contributing to more sustainable agriculture.This research was partly financed by Andermatt Biocontrol Switzerland. JA was supported by the CERCA Program of the Generalitat de Catalunya.info:eu-repo/semantics/publishedVersio

Influence of the Rearing Host on Biological Parameters of Trichopria drosophilae, a Potential Biological Control Agent of Drosophila suzukii

Trichopria drosophilae is a pupal parasitoid that can develop in a large number of drosophilid host species including the invasive pest Drosophila suzukii, and is considered a biological control agent. We investigated the influence of the rearing host on the preference and performance of the parasitoid, using two different strains of T. drosophilae, reared on D. melanogaster or D. suzukii for approximately 30 generations. Host switching was employed to assess the impact of host adaptation on T. drosophilae performance. In a no-choice experimental setup, T. drosophilae produced more and larger offspring on the D. suzukii host. When given a choice, T. drosophilae showed a preference towards D. suzukii, and an increased female ratio on this host compared to D. melanogaster and D. immigrans. The preference was independent from the rearing host and was confirmed in behavioral assays. However, the preference towards D. suzukii increased further after a host switch from D. melanogaster to D. suzukii in just one generation. Our data indicate that rearing T. drosophilae for several years on D. melanogaster does not compromise its performance on D. suzukii in the laboratory. However, producing a final generation on D. suzukii prior to release could increase its efficacy towards the pest.publishe

Few indirect effects of baculovirus on parasitoids demonstrate high compatibility of biocontrol methods against Tuta absoluta

BACKGROUND Combining different biocontrol agents, particularly micro- and macroorganisms, can contribute to new and sustainable pest control approaches. Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most destructive pests of solanaceous crops. An emerging management strategy consists of biological control using microbial insecticides such as baculoviruses, but with limited efficacy. Thanks to their high target specificity, baculoviruses can be used simultaneously with natural enemies such as parasitoids for improved control of T. absoluta. However, potential indirect nontarget effects of baculoviruses on parasitoids can result from overlapping resource requirements. We assessed whether ovipositing parasitoid females discriminated against virus-treated hosts and examined the outcome of within-host competition between the hymenopteran parasitoids Necremnus tutae (Reuter) (Eulophidae) and Dolichogenidea gelechiidivoris Marsch (Braconidae), and the Phthorimaea operculella granulovirus (PhopGV, Baculoviridae) that infects T. absoluta larvae. RESULTS Female D. gelechiidivoris discriminated against virus-treated hosts, whereas N. tutae did not. We found few indirect virus-related effects depending on the species, the sex, and the time of virus treatment. Effects were ambivalent for D. gelechiidivoris offspring and ranged from increased male longevity when infection occurred before parasitization to reduced emergence and male longevity when infection occurred after parasitization. N. tutae offspring showed a longer development time and shorter male longevity when they developed in virus-treated hosts. CONCLUSION The virus had a low impact on parasitoid offspring. In rare cases, adverse effects were detected; however, the low magnitude of these effects is unlikely to reduce the fitness of parasitoid offspring, therefore both parasitoids seem compatible with the baculovirus for control of T. absoluta.info:eu-repo/semantics/acceptedVersio

Räuberische Gegenspieler der Kirschessigfliege

Die Kirschessigfliege (Drosophila suzukii), kurz KEF, wurde erstmals im Jahr 2011 in der Schweiz beobachtet und ist seitdem ein regelmässig auftretender Schädling in Beeren-, Steinobst- und Rebkulturen

Assessing potential hybridization between a hypothetical gene drive-modified Drosophila suzukii and non-target Drosophila species

Genetically engineered gene drives (geGD) are potentially powerful tools for suppressing or even eradicating populations of pest insects. Before living geGD insects can be released into the environment, they must pass an environmental risk assessment (ERA) to ensure that their release will not harm valued and protected entities of the environment. A key research question concerns the likelihood that non-target species will acquire the functional GD elements; such acquisition could lead to the loss of those species and to a disruption of the ecosystem services they provide. The main route for gene flow is through hybridization between the GD insect strain and closely related species that co-occur in the area of release. Using the invasive spotted-wing drosophila, Drosophila suzukii, as a case study, we demonstrate how a combination of interspecific hybridization experiments, behavioral observations, and molecular genetic analyses can be used to assess the potential for hybridization.Funding provided by: AgroscopeCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100022575Award Number

A parasitoid wasp allied with an entomopathogenic virus to control Tuta absoluta

The South American tomato leafminer, Tuta absoluta, is a major threat to tomato production worldwide. In a semi-field experiment, we assessed the efficacy of the parasitoid wasp Necremnus tutae and the Phthorimaea operculella granulovirus (PhopGV), used alone and in combination, in controlling T. absoluta. The parasitoid, used alone and in combination with PhopGV resulted in significantly reduced numbers of T. absoluta adults. Both agents, used alone and in combination, caused a significant and similar damage reduction. Releasing N. tutae in sufficient quantities at the right time could keep the pest under control. However, combining it with PhopGV might provide more flexibility in the timing of application. Further research should be conducted to determine the appropriate doses of N. tutae and PhopGV when applied at different times and on different population densities of T. absoluta