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.

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. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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.

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.