Host range patterning of parasitoid wasps Aphidiinae (Hymenoptera: Braconidae)

Acute toxicity effects of pesticides on beneficial organisms - Dispelling myths for a more sustainable use of chemicals in agricultural environments

Agricultural practitioners, researchers and policymakers are increasingly advocating for integrated pest management (IPM) to reduce pesticide use while preserving crop productivity and profitability. Using selective pesticides, putatively designed to act on pests while minimising impacts on off-target organisms, is one such option - yet evidence of whether these chemicals control pests without adversely affecting natural enemies and other beneficial species (henceforth beneficials) remains scarce. At present, the selection of pesticides compatible with IPM often considers a single (or a limited number of) widely distributed beneficial species, without considering undesired effects on co-occurring beneficials. In this study, we conducted standardised laboratory bioassays to assess the acute toxicity effects of 20 chemicals on 15 beneficial species at multiple exposure timepoints, with the specific aims to: (1) identify common and diverging patterns in acute toxicity responses of tested beneficials; (2) determine if the effect of pesticides on beetles, wasps and mites is consistent across species within these groups; and (3) assess the impact of mortality assessment timepoints on International Organisation for Biological Control (IOBC) toxicity classifications. Our work demonstrates that in most cases, chemical toxicities cannot be generalised across a range of beneficial insects and mites providing biological control, a finding that was found even when comparing impacts among closely related species of beetles, wasps and mites. Additionally, we show that toxicity impacts increase with exposure length, pointing to limitations of IOBC protocols. This work challenges the notion that chemical toxicities can be adequately tested on a limited number of 'representative' species; instead, it highlights the need for careful consideration and testing on a range of regionally and seasonally relevant beneficial species.

Do primary and secondary host plants affect aphid- parasitoid interactions in fruit orchards?

The aim of this study was to investigate how the primary (PHP) and secondary host plants (SHP) in the fruit orchards affect the interactions of aphids and their parasitoids in northwest Turkey during spring and summer 2020 and 2021. In total, 67 tritrophic aphid-parasitoid-host plant interactions, including new association records for Europe and Turkey, were obtained from 16 parasitoid species from the subfamily Aphidiinae (Hymenoptera: Braconidae) reared from 25 aphid species (Hemiptera: Aphididae) on 22 PHP and SHP in the fruit orchards. Also, we evaluated the effect of the PHP and SHP on the parasitoids, aphids and their interactions. We revealed that the species richness and the values of the biodiversity indices of the parasitoids and aphids were significantly higher on the SHP than the PHP. Similarly, the aphid-parasitoid interactions on the SHP showed greater diversity than the PHP. The results of this study clearly show that the interactions of parasitoids and aphids in the fruit orchards were more diverse on the SHP compared to the PHP.

Is what you see what you get? The relationship between field observed and laboratory observed aphid parasitism rates in canola fields

BACKGROUND

Estimating parasitoid abundance in the field can be difficult, even more so when attempting to quantify parasitism rates and the ecosystem service of biological control that parasitoids can provide. To understand how 'field observed' parasitism rates (in-field mummy counts) of the green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) translate to 'laboratory observed' parasitism rates (laboratory-reared parasitoid counts), field work was undertaken in Australian canola fields, over the winter growing season.

RESULTS

Overall, laboratory observed parasitism was on average 2.4 times higher than field observed parasitism, with rates an average of four-fold higher in fields from South Australia. Total field observed and laboratory observed parasitism rates (OPRs) of M. persicae varied considerably across regions, but less so among fields within regions. As crop growth stage progressed, the incidence of field observed mummies increased. The incidence of total parasitoids reared also increased with crop growth stage, averaging 3.4% during flowering and reaching 14.4% during podding/senescing. Although there was a greater diversity of reared parasitoid species at later crop growth stages, the laboratory OPR was unaffected by parasitoid species. Diaeretiella rapae was the most commonly reared parasitoid, increasing in absolute abundance with crop growth stage.

CONCLUSION

These findings indicate that field mummy counts alone do not provide a clear representation of parasitism within canola fields. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Early Season Community of Flower-Visiting Arthropods in a High-Altitude Alpine Environment

In mountain ecosystems, climate change can cause spatiotemporal shifts, impacting the composition of communities and altering fundamental biotic interactions, such as those involving flower-visiting arthropods. On of the main problems in assessing the effects of climate change on arthropods in these environments is the lack of baseline data. In particular, the arthropod communities on early flowering high-altitude plants are poorly investigated, although the early season is a critical moment for possible mismatches. In this study, we characterised the flower-visiting arthropod community on the early flowering high-altitude Alpine plant, Androsace brevis (Primulaceae). In addition, we tested the effect of abiotic factors (temperature and wind speed) and other variables (time, i.e., hour of the day, and number of flowers per plant) on the occurrence, abundance, and diversity of this community. A. brevis is a vulnerable endemic species growing in the Central Alps above 2000 m asl and flowering for a very short period immediately after snowmelt, thus representing a possible focal plant for arthropods in this particular moment of the season. Diptera and Hymenoptera were the main flower visitors, and three major features of the community emerged: an evident predominance of anthomyiid flies among Diptera, a rare presence of bees, and a relevant share of parasitoid wasps. Temperature and time (hour of the day), but not wind speed and number of flowers per plant, affected the flower visitors' activity. Our study contributes to (1) defining the composition of high-altitude Alpine flower-visiting arthropod communities in the early season, (2) establishing how these communities are affected by environmental variables, and (3) setting the stage for future evaluation of climate change effects on flower-visiting arthropods in high-altitude environments in the early season.

Sizing the Knowledge Gap in Taxonomy: The Last Dozen Years of Aphidiinae Research

Simple Summary

Taxonomy is a biological discipline with the task to identify, name, and describe organisms, and as such, it provides necessary data for all other biological disciplines. The biodiversity crisis through which we are living draws attention to the crucial role of taxonomy in biology today. At the same time, the scientific community, as well as society in general, has become more aware of the difficulties associated with taxonomy, such as gaps in taxonomic knowledge, a lack of taxonomic infrastructure, and an insufficient number of taxonomic experts (“taxonomic impediment”). With this study, we tried to size this knowledge gap by analyzing the taxonomical studies on Aphidiinae (Hymenoptera: Braconidae) conducted from 2010 to 2021. Aphidiinae are endoparasitoids of aphids; a single specimen completes its development inside the living aphid host, which are used in biological control programs. Here, we summarize the knowledge gathered over the last dozen years and discuss it in a general context.

Abstract

Taxonomic impediment is one of the main roadblocks to managing the current biodiversity crisis. Insect taxonomy is the biggest contributor to the taxonomic impediment, both in terms of the knowledge gap and the lack of experts. With this study, we tried to size the knowledge gap by analyzing taxonomical studies on the subfamily Aphidiinae (Hymenoptera: Braconidae) conducted from 2010 to 2021. All available taxonomic knowledge gathered in this period is critically summarized: newly described species, detection of alien species, published identification keys, etc. All findings are discussed relative to the current state of general taxonomy. Future prospects for taxonomy are also discussed.

Interspecific competition among aphid parasitoids: molecular approaches reveal preferential exploitation of parasitized hosts

When a guild of species exploit the same limited resources, interspecific competition induces the exclusion of inferior competitors, in which case, interspecific recognition mechanisms are needed. Here, we address resource partitioning and interspecific competition among three main solitary parasitoid species attacking the same host resource, the aphid Sitobion avenae in wheat fields. Optimal host acceptance models predict that parasitoid species should prefer attacking unparasitized hosts when they are available in order to maximize their fitness, as already parasitized hosts are less valuable for laying eggs, especially for inferior competitors. Therefore, we expected the level of competition (multiparasitism) in the field to increase at low host density. By using a combination of taxonomical (determination) and molecular (PCR-based) approaches, we assessed the species of all parasitoid adults and immature stages within aphid hosts. Our results demonstrate that, early in the season, the multiparasitism rates were low, whereas they were high in the mid-late season, corresponding to an aphid density decrease over time. Moreover, parasitoid species could not have been exploiting host resources randomly and the better competitor, Aphidius ervi, seemed to be foraging preferentially on hosts already parasitized by the inferior competitor A. rhopalosiphi, even when unparasitized hosts were still available. This could be due to differences in their host detection capability, as species with a narrow host range may be better at detecting their hosts in comparison with species with a greater host range, such as A. ervi, with a greater host range within the guild. Our study suggests differences in the host exploitation of two prevalent parasitoid species through the main period of aphid colonization, which still allowed the coexistence of a third inferior competitor (A. rhopalosiphi) within the assemblage, in spite of some negative interactions (multiparasitism) and redundancies.

Phylogenetic relationships and subgeneric classification of European Ephedrus species (Hymenoptera, Braconidae, Aphidiinae)

In this study two molecular markers were used to establish taxonomic status and phylogenetic relationships of Ephedrus subgenera and species distributed in Europe. Fifteen of the nineteen currently known species have been analysed, representing three subgenera: Breviephedrus Gärdenfors, 1986, Lysephedrus Starý, 1958 and Ephedrus Haliday, 1833. The results of analysis of COI and EF1α molecular markers and morphological studies did not support this classification. Three clades separated by the highest genetic distances reported for the subfamily Aphidiinae on intrageneric level. Ephedrusbrevis is separated from persicae and plagiator species groups with genetic distances of 19.6 % and 16.3 % respectively, while the distance between persicae and plagiator groups was 20.7 %. These results lead to the conclusion that the traditional subgeneric classification of Ephedrus needs revision. Species from persicae species group are raised to subgenus level as Fovephedrus Chen, 1986 and Lysephedrussyn. nov. is assigned as a junior synonym of subgenusEphedrus. Key for identification of Ephedrus subgenera is provided. Ephedrushyadaphidis Kocić & Tomanović sp. nov. is described and several species are confirmed as valid species for the first time. Furthermore, two species are synonymised: E.dysaphidissyn. nov. as a junior synonym of E.cerasicola and E.blattnyisyn. nov. as a junior synonym of E.plagiator.