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

Improved Learning Outcomes in Labview for Undergraduate Students with Lego Mindstorms NXT Kit

International audienceIn the literature, several educational programs for undergraduate students in control engineering are based on a project-based learning. This paper belongs to this trend to teach the graphical-based computer language LabVIEW for measurement, data acquisition and control. The aim is to improve the student skills in the use of this software by means of a suitable methodology based on team to team competition using Modeling & Simulation. It is included in a program for undergraduate student bringing them to obtain a professional degree at the Technological Institute of the University of Bordeaux. Three different educational sessions are compared where different methodologies of teaching LabVIEW and finite state machine have been proposed to improve the learning outcomes. After a discussion on a standard solution for the project, the assessment of created programs was analyzed to establish the learning experiences in term of LabVIEW user and developer

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

Contribution à la caractérisation de l'état écologique de masses d'eaux de transition de type " estuaire "à partir du cas de la Gironde

This methodological note expounds a first approach for the characterization of estuarine fish assemblages using data sets available about the haline part of the Gironde estuary. It then undertakes to compare it with other large French and European estuaries.Cette note méthodologique présente une première approche pour la caractérisation des assemblages ichtyologiques estuariens, à partir des jeux de données disponibles sur l'estuaire halin de la Gironde puis entreprend une comparaison avec d'autres grands estuaires français ou européens

Sex Ratio of Small Hive Beetles: The Role of Pupation and Adult Longevity

The sex ratio of sexually reproducing animal species tends to be 1:1, which is known as Fisher’s principle. However, differential mortality and intraspecific competition during pupation can result in a biased adult sex ratio in insects. The female-biased sex ratio of small hive beetles (SHBs) is known from both laboratory and field studies, but the underlying reasons are not well understood. Here, we used laboratory mass and individual pupation to test if differential mortality between sexes and/or intraspecific interactions can explain this sex ratio. The data show a significant female-biased adult sex ratio in both mass and individual rearing, even when assuming that all dead individuals were males. Our results therefore suggest that neither differential mortality during pupation nor intraspecific interactions are likely to explain the female-biased sex ratio of freshly emerged adult SHBs. We regard it as more likely that either competition during the larval feeding stage or genetic mechanisms are involved. In addition, we compared our data with previously published data on the sex ratio of both freshly emerged and field-collected SHBs to investigate possible gender differences in adult longevity. The data show a significantly greater female bias in the sex ratio upon emergence, compared to field-collected SHBs, suggesting that adult females have a shorter longevity

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

Data from: Bees and flowers: how to feed an invasive beetle species

Invasive species may exploit a wide range of food sources, thereby fostering their success and hampering mitigation, but the actual degree of opportunism is often unknown. The small hive beetle (SHB), Aethina tumida, is a parasite of honeybee colonies endemic to sub-Saharan Africa. SHBs have now spread on all habitable continents and can also infest colonies of other social bees. To date, the possible role of solitary bee nests as alternative hosts is unknown. Similarly, flowers as possible alternative food sources are not well understood. Here, we show that SHBs can complete an entire life cycle in association with nests of solitary bees Megachile rotundata. The data also show that flowers can serve as alternative food sources. These results support the opportunistic nature of this invasive species, thereby generating further obstacles for mitigation efforts in the field. It also suggests that SHB invasions may result in more serious consequences for endemic bee fauna than previously thought. This provides further motivation to slow down the global spread of this pest, and to improve its management in areas, where it is established