Effects of injudicious use of spirotetramat on Encarsia formosa's ability to control Bemisia tabaci.

The excessive and frequent use of insecticides has led to serious problems with insecticide residues, impacting nontarget organisms such as the parasitoid Encarsia formosa. This study examined the growth, development, and enzyme activity of E. formosa exposed to spirotetramat at LC10, LC30, and LC50. The regression equation for the toxicity of spirotetramat toward E. formosa was Y = 5.25X-11.07. After exposure to spirotetramat, the survival rates of E. formosa sharply decreased, which occurred earlier than those in the control batch. Although the maximum daily parasitism quantity of E. formosa increased and the average parasitism number, enumerated from the 1st to the 5th day, was 53.97 after being exposed to spirotetramat at LC10, the life span of its F1 generation adults was only 8.47 days, which was significantly shorter than that in the control batch. After being exposed to spirotetramat at LC50, the average parasitism number of E. formosa was 63.30, and the developmental time of its F1 generation, enumerated from the 1st to the 5th day after exposure to spirotetramat, was significantly longer than that of the control batch. The activities of mixed function oxidase, acetylcholinesterase, carboxylesterase, and catalase increased significantly, and the rate of increase in enzyme activity was directly proportional to the increase in the concentration of spirotetramat. These results revealed that the parasitic ability of E. formosa decreased after exposure to spirotetramat at LC10, LC30, and LC50. This leads to a change in parasitoid control of pests, revealing the potential environmental threat of insecticide residues to nontarget organisms.

Modulation of response to braconid wasp venom by adipokinetic hormone in Drosophila melanogaster.

The minute wasp Habrobracon hebetor venom (HH venom) is a potent cocktail of toxins that paralyzes the victim's muscles and suppresses humoral and cellular immunity. This study examined the effect of HH venom on specific biochemical, physiological, and ultrastructural characteristics of the thoracic and nervous (CNS) tissues of Drosophila melanogaster under in vitro conditions. Venom treatment modulated the activities of superoxide dismutase (SOD) and catalase (CAT), endogenous Drome-AKH level, and affected the relative viability of the cells. Additionally, it reduced the expression of genes related to the immune system in the CNS, including Keap1, Relish, Nox, Eiger, Gadd45, and Domeless, as well as in the thoracic muscles, except for Nox. Besides, venom treatment led to deteriorative changes in the ultrastructure of muscle cells, particularly affecting the mitochondria. When venom and Drosophila melanogaster-adipokinetic hormone (Drome-AKH) were applied together, the effects of the venom alone were often modulated. The harmful effect of the venom on SOD activity was relatively reduced and the activity returned to a level similar to that of the control. In the CNS, the simultaneous application of venom and hormones abolished the suppression of previously reported immune-related genes (except for Gadd45), whereas in the muscles, this was only true for Eiger. Additionally, Drome-AKH restored cell structure to a level comparable to that of the control and lessened the harmful effects of HH venom on muscle mitochondria. These findings suggest a general body response of D. melanogaster to HH venom and a partial defensive role of Drome-AKH in this process.

Harmonising control: understanding the complex impact of pesticides on parasitoid wasps for enhanced pest management.

The pervasive application of chemical pesticides is globally recognised for its effectiveness and cost-efficiency in controlling pest populations. However, this approach has inadvertently impacted a diverse array of organisms, including humans and beneficial insects, notably those that naturally regulate pest populations. This review synthesises current research on both the direct and indirect effects of pesticides on parasitoid wasps. These wasps are vital for the biological control of herbivorous insect populations through a top-down approach. Here, we examine the complex ways in which pesticides may compromise the parasitoids' life history traits, interfere with their host-seeking behaviour, and modulate the immune responses of the hosts that in turn affect parasitoid success. Gaining a more nuanced understanding of these dynamics is crucial for the development of integrated pest management strategies that aim to reconcile the use of chemical pesticides with biological control approaches, ultimately fostering more sustainable agricultural practices.

Pest management facing warming and chemical stresses: Multi-stress effects on the biological agent Trichogramma oleae.

Global change is affecting plant-insect interactions in agroecosystems and can have dramatic consequences on yields when causing non-targeted pest outbreaks and threatening the use of pest natural enemies for biocontrol. The vineyard agroecosystem is an interesting system to study multi-stress conditions: on the one hand, agricultural intensification comes with high inputs of copper-based fungicides and, on the other hand, temperatures are rising due to climate change. We investigated interactive and bottom-up effects of both temperature increase and copper-based fungicides exposure on the important Lepidopteran vineyard pest Lobesia botrana and its natural enemy, the oophagous parasitoid Trichogramma oleae. We exposed L. botrana larvae to three increasing copper sulfate concentrations under two fluctuating thermal regimes, one current and one future. Eggs produced by L. botrana were then exposed to T. oleae. Our results showed that the survival of L. botrana, was only reduced by the highest copper sulfate concentration and improved under the warmer regime. The development time of L. botrana was strongly reduced by the warmer regime but increased with increasing copper sulfate concentrations, whereas pupal mass was reduced by both thermal regime and copper sulfate. T. oleae F1 emergence rate was reduced and their development time increased by combined effects of the warmer regime and increasing copper sulfate concentrations. Size, longevity and fecundity of T. oleae F1 decreased with high copper sulfate concentrations. These effects on the moth pest and its natural enemy are probably the result of trade-offs between the survival and the development of L. botrana facing multi-stress conditions and implicate potential consequences for future biological pest control. Our study supplies valuable data on how the interaction between pests and biological control agents is affected by multi-stress conditions.

Impacts of the cyromazine emergence inhibition procedure of Bactrocera dorsalis on Fopius arisanus: implications for the biological control of diptera pest.

BACKGROUND: Fopius arisanus (Sonan) is an important egg-pupal endoparasitic wasp of Bactrocera dorsalis (Hendel). As traditional method of sorting nonparasitic B. dorsalis from parasitic wasps is labor-intensive, requires specific equipment and poses the risk of spreading fertile hosts, the development of a more convenient, economical and safe sorting procedure is important. RESULTS: The optimal cyromazine emergence inhibition procedure (CEIP) involved facilitating the pupation of B. dorsalis mature larvae (Bdml) in 3 mg kg-1 cyromazine sand substrate (CSS) for 48 h. When the Bdml that had been exposed to F. arisanus during the egg stage were treated with 3-7 mg kg-1 CSS for 48 h, no negative effects on the emergence parameters of parasitoids were observed. Treatment with 3-4 mg kg-1 CSS had insignificant effects on the biological and behavioral parameters of F. arisanus. However, treatment with 5-6 mg kg-1 CSS adversely affected the fecundity and antennating activity of the wasps; specifically, 6 mg kg-1 CSS negatively affected the lifespan and flight ability of wasps. Fortunately, no transgenerational effects on these parameters were observed in the progeny. Regarding the nutrient reserves of both sexes of F. arisanus, significant dose-dependent effects were observed. Moreover, 5-6 mg kg-1 CSS significantly reduced the protein and carbohydrate content in F. arisanus; in particular, 6 mg kg-1 CSS notably reduced the lipid content. CONCLUSION: CEIP provides a more flexible, economical and safe mass-release program for F. arisanus. In addition, it has profound implications for the biological control of other dipteran pests. © 2024 Society of Chemical Industry.

Short- and long-term effects of commercial formulations of imidacloprid, spirotetramat, and mixtures of these active ingredients on pupae of Diaeretiella rapae (Hymenoptera: Braconidae) and its progeny.

BACKGROUND: Compatibility studies of insecticides and natural enemies usually focus on short-term lethal effects, without considering the long-term sublethal effects (including progeny). Even less-explored are the effects of commercial insecticides formulated with more than one active product. Short- and long-term lethal and sublethal effects were studied for the first time on the progeny of commercial formulations of spirotetramat, imidacloprid and a commercial mixture of these active ingredients on pupae of Diaeretiella rapae (M'ntosh) (Hymenoptera: Braconidae), an endoparasitoid of aphids considered to be a potential biological control agent. Insecticides were exposed topically on aphid mummies in which the parasitoid was in the pupal stage. RESULTS: Imidacloprid reduced adult emergence by more than 30% and prolonged intra-host development time with respect to control from half the maximum recommended field dose (MFRD). Spirotetramat and commercial mixture only showed significant effects on these endpoints at doses above the MFRD. The tested formulations did not affect adult longevity, sex ratio, and percentage of parasitism in the exposed generation. At low concentrations the active ingredients in the commercial mixture behave synergistically, whereas at medium and high concentrations they behave antagonistically. Considering the 10% lethal dose (LD10), imidacloprid showed the highest hazard coefficient, whereas the commercial mixture was more hazardous when considering the LD50 and LD90. The commercial mixture and imidacloprid induced higher adult emergence and altered the sex ratio in the progeny. CONCLUSIONS: The following order of toxicity on D. rapae can be established: imidacloprid > commercial mixture > spirotetramat. Joint use of this species with imidacloprid and commercial mixture should be avoided in integrated pest management programs. © 2024 Society of Chemical Industry.

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.

Effect of sublethal concentrations of the bioinsecticide spinosyn treatment of Trichoplusia ni eggs on the caterpillar and its parasitoid, Trichogramma brassicae.

BACKGROUND: Integrated Pest Management (IPM) seeks to combine multiple management strategies for optimal pest control. One method that is successfully employed in IPM is the use of beneficial organisms. However, in severe circumstances when pest insects exceed threshold limits, insecticides may still need to be implemented. Thus, understanding the effects of insecticides on biocontrol agents, such as parasitoid wasps, is paramount to ensure sustainable agroecosystems. Sublethal effects of the bioinsecticide spinosyn, a mixture of the bacterial Saccharopolyspora spinosa (Mertz and Yao) fermentation products spinosyn A and D, on eggs of Trichoplusia ni (Hübner), a cruciferous crop pest, and its egg parasitoid Trichogramma brassicae (Bezdenko) was investigated. RESULTS: The LC50 for spinosyn A and D (dissolved in ethanol) on T. ni eggs is 54 ng mL-1. Transcriptomics on caterpillars (1st and 3rd instars) that hatched from eggs treated with sublethal concentrations of spinosyn identified the upregulation of several genes encoding proteins that may be involved in insecticide resistance including detoxification enzymes, such as cytochrome P450s, glutathione S-transferases and esterases. Sublethal T. ni egg treatments did not affect parasitoid emergence, however, there was a marked increase in the size of T. brassicae hind tibia and wings that emerged from spinosyn-treated eggs. CONCLUSIONS: For the caterpillar, treatment of eggs with sublethal concentrations of spinosyn may induce insecticide resistance mechanisms. For the parasitoids, their increased size when reared in spinosyn-treated eggs suggests that the emerged wasps may have higher performance. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of thiamethoxam on physiological and molecular responses to potato plant (Solanum tuberosum), green peach aphid (Myzus persicae), and parasitoid (Aphidius gifuensis).

BACKGROUND: To improve integrated pest management (IPM) performance it is essential to assess pesticide side effects on host plants, insect pests, and natural enemies. The green peach aphid (Myzus persicae Sulzer) is a major insect pest that attacks various crops. Aphidius gifuensis is an essential natural enemy of M. persicae that has been applied effectively in controlling M. persicae. Thiamethoxam is a neonicotinoid pesticide widely used against insect pests. RESULTS: The current study showed the effect of thiamethoxam against Solanum tuberosum, M. persicae, and A. gefiuensis and the physiological and molecular response of the plants, aphids, and parasitoids after thiamethoxam application. Thiamethoxam affected the physical parameters of S. tuberosum and generated a variety of sublethal effects on M. persicae and A. gefiuensis, including nymph development time, adult longevity, and fertility. Our results showed that different thiamethoxam concentrations [0.1, 0.5, and 0.9 µm active ingredient (a.i.)/L] on different time durations (2, 6, and 10 days) increased the antioxidant enzyme activities SOD, POD, and CAT of S. tuberosum, M. persicae, and A. gefiuensis significantly compared with the control. Our results also showed that different thiamethoxam concentrations (0.1, 0.5, and 0.9 µm a.i./L) on different time durations (2, 6, and 10 days) increased the expression of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), acetylcholinesterase (AChE), carboxylesterase (CarE) and glutathione-S-transferase (GST) genes of S. tuberosum, M. persicae, and A. gefiuensis compared with the control. CONCLUSION: Our findings reveal that using thiamethoxam at suitable concentrations and time durations for host plants and natural enemies may enhance natural control through the conservation of natural enemies by overcoming any fitness disadvantages. © 2024 Society of Chemical Industry.

Effects of juvenile hormone in fertility and fertility-signaling in workers of the common wasp Vespula vulgaris.

In the highly eusocial wasp, Vespula vulgaris, queens produce honest signals to alert their subordinate workers of their fertility status, and therefore they are reproductively suppressed and help in the colony. The honesty of the queen signals is likely maintained due to hormonal regulation, which affects fertility and fertility cue expression. Here, we tested if hormonal pleiotropy could support the hypothesis that juvenile hormone controls fertility and fertility signaling in workers. In addition, we aimed to check oocyte size as a proxy of fertility. To do that, we treated V. vulgaris workers with synthetic versions of juvenile hormone (JH) analogue and a JH inhibitor, methoprene and precocene, respectively. We dissected the treated females to check ovary activation and analyzed their chemical profile. Our results showed that juvenile hormone has an influence on the abundance of fertility linked compounds produced by workers, and it also showed to increase oocyte size in workers. Our results corroborate the hypothesis that juvenile hormone controls fertility and fertility signaling in workers, whereby workers are unable to reproduce without alerting other colony members of their fertility. This provides supports the hypothesis that hormonal pleiotropy contributes to keeping the queen fertility signals honest.

Evaluation of Sensitivity to Phoxim and Cypermethrin in an Endoparasitoid, Meteorus pulchricornis (Wesmael) (Hymenoptera: Braconidae), and Its Parasitization Efficiency Under Insecticide Stress.

Insecticides can have consequences for beneficial arthropods. Insect parasitoids can contact insecticides through direct exposure spray droplets or residues on crop foliage. Here, we focus on better understand the response of Meteorus pulchricornis (Wesmael), a parasitoid wasp of lepidopteran pests, and its detoxification mechanisms on stress caused by phoxim and cypermethrin. Hence, we determined the dose-mortality curves and estimating the sublethal concentrations (LC30 and LC50). Then, we applied the sublethal concentrations against adult parasitoids to assess its survival, parasitism efficacy, and also developmental and morphometric parameters of their offspring. Simultaneously, we check the activities of glutathione S-transferase (GST), acetylcholinesterase (AChE), and peroxidase (POD) after sublethal exposure of both insecticides, which has measured until 48 h after treatment. Overall, phoxim and cypermethrin exhibited acute lethal activity toward the parasitoid with LC50 values 4.608 and 8.570 mg/liter, respectively. Also, we detect that LC30 was able to trigger the enzymatic activity of GST, AChE, and POD, suggesting a potential detoxification mechanism. However, even when subjected to sublethal exposure, our results indicate strong negatives effects, in particular for phoxim, which has affected the parasitism efficacy and also the developmental and morphometric parameters of M. pulchricornis offspring. Therefore, it can be concluded that both phoxim and cypermethrin have negative impacts on M. pulchricornis and we suggest cautioning their use and the need for semifield and field assessments to confirm such an impact.

Susceptibility of different developmental stages of Trichogramma parasitoids to insecticides commonly used in the Mediterranean olive agroecosystem.

Insecticide application and augmentative parasitoid releases are often considered incompatible. However, pesticide applications and parasitoid releases can be integrated into a pest management scheme if there is careful time scheduling of these interventions. In this study, we assessed the influence of commonly used insecticides (chlorpyrifos-methyl, deltamethrin, pyriproxyfen, thiamethoxam) in olive agroecosystems to two currently present Trichogramma parasitoids in the Mediterranean basin. Exposure to insecticides in relation to parasitoid's development was also tested. Both, insecticide type and application time influenced parasitism and the emergence rates of the two parasitoid species. Chlorpyrifos-methyl had the strongest impact on parasitoids resulting in low numbers of emerged adults followed by deltamethrin. The two parasitoids also exhibited different levels of susceptibility to the insecticides used. Potential integration of insecticides to integrated pest management using Trichogramma parasitoids is discussed.

Altered feeding behavior and immune competence in paper wasps: A case of parasite manipulation?

Paper wasps (Polistes dominula), parasitized by the strepsipteran Xenos vesparum, are castrated and desert the colony to gather on plants where the parasite mates and releases primary larvae, thus completing its lifecycle. One of these plants is the trumpet creeper Campsis radicans: in a previous study the majority of all wasps collected from this plant were parasitized and focused their foraging activity on C. radicans buds. The unexpected prevalence and unusual feeding strategy prompted us to investigate the influence of this plant on wasp behavior and physiology through a multidisciplinary approach. First, in a series of laboratory bioassays, we observed that parasitized wasps spent more time than non-parasitized ones on fresh C. radicans buds, rich of extra-floral nectaries (EFNs), while the same wasps ignored treated buds that lacked nectar drops. Then, we described the structure and ultra-structure of EFNs secreting cells, compatible with the synthesis of phenolic compounds. Subsequently, we analysed extracts from different bud tissues by HPLC-DAD-MS and found that verbascoside was the most abundant bioactive molecule in those tissues rich in EFNs. Finally, we tested the immune-stimulant properties of verbascoside, as the biochemical nature of this compound indicates it might function as an antibacterial and antioxidant. We measured bacterial clearance in wasps, as a proxy for overall immune competence, and observed that it was enhanced after administration of verbascoside-even more so if the wasp was parasitized. We hypothesize that the parasite manipulates wasp behavior to preferentially feed on C. radicans EFNs, since the bioactive properties of verbascoside likely increase host survival and thus the parasite own fitness.

Reproduction and signals regulating worker policing under identical hormonal control in social wasps.

In social Hymenoptera, fertility and fertility signalling are often under identical hormonal control, and it has been suggested that such hormonal pleiotropies can help to maintain signal honesty. In the common wasp Vespula vulgaris, for example, fertile queens have much higher juvenile hormone (JH) titers than workers, and JH also controls the production of chemical fertility cues present on the females' cuticle. To regulate reproductive division of labour, queens use these fertility cues in two distinct ways: as queen pheromones that directly suppress the workers' reproduction as well as to mark queen eggs and enable the workers to recognize and police eggs laid by other workers. Here, we investigated the hormonal pleiotropy hypothesis by testing if experimental treatment with the JH analogue methoprene could enable the workers to lay eggs that evade policing. In support of this hypothesis, we find that methoprene-treated workers laid more eggs, and that the chemical profiles of their eggs were more queen-like, thereby causing fewer of their eggs to be policed compared to in the control. Overall, our results identify JH as a key regulator of both reproduction and the production of egg marking pheromones that mediate policing behaviour in eusocial wasps.

Peppermint essential oil inhibits Drosophila suzukii emergence but reduces Pachycrepoideus vindemmiae parasitism rates.

Spotted Wing Drosophila (Drosophila suzukii; Matsumura) is an invasive fruit fly with the ability to oviposit in a broad range of agriculturally valuable fruits. Volatile organic compounds (VOCs) produced by botanical oils may reduce D. suzukii's attraction to hosts and decrease survival, but it is unknown whether their efficacy varies across D. suzukii life stages or affects the survival and success of higher trophic levels. Through a series of laboratory bioassays, we evaluated the effects of peppermint (Mentha arvensis L.) oil produced VOCs on D. suzukii survival and the survival of and parasitism rates by a pupal parasitoid wasp, Pachycrepoideus vindemmiae (Rondani). First, we determined whether fumigation with peppermint oil VOCs at the pupal stage reduced adult emergence, and whether this depended on environmental conditions (i.e. soil moisture). Second, we evaluated whether fumigation with peppermint oil VOCs reduced or enhanced parasitism by the pupal parasitoid and whether this depended on the timing of peppermint oil VOC exposure (i.e. before, during, or after parasitoid access). Fumigation with VOCs of 4.5 mg of peppermint oil reduced D. suzukii emergence under moist soil conditions but dry soil had a similar effect on reducing adult emergence as peppermint oil presence. Peppermint oil VOC fumigation was toxic to adult P. vindemmiae, but developing P. vindemmiae were unaffected by peppermint oil VOC fumigation. Using peppermint essential oil as a fumigant may reduce D. suzukii emergence from the pupal stage. However, this could negatively impact P. vindemmiae dependent on the timing of application.

Superparasitism by a parasitoid wasp: The absence of sublethal effects from the neonicotinoid insecticide imidacloprid enlightens the specificity of the cholinergic pathway involved.

Imidacloprid is an insecticide that is used globally and is suspected to be at least partly responsible for the decrease in the number of pollinator insects. The effects of an LC20 of imidacloprid on the parasitic behavior of the parasitoid wasp Leptopilina boulardi were investigated. Two genetically identical L. boulardi strains were used for the experiments. The strains differed in that one was infected by LbFvirus and the other was not. LbFvirus is a virus that induces an increase in the superparasitism behavior of the wasp. Results of two previous works have shown that the organophosphorus insecticide chlorpyrifos induces an increase in the superparasitism rate of L. boulardi through its specific action on cholinergic nervous pathways. Imidacloprid targets receptors implicated in cholinergic nervous pathways and thus it was expected that imidacloprid would also increase the superparasitism rate of L. boulardi. However, the results of the present experiment demonstrate that imidacloprid does not interfere with the parasitic behavior of L. boulardi and does not increase the rate of superparasitization. It can then be concluded that the major target of imidacloprid, namely type 1 α-bungarotoxin resistant nicotinic acetylcholine receptors (nAChR1), which imidacloprid is an agonist of, and the minor target, type D α-bungarotoxin sensitive nicotinic acetylcholine receptors (nAChRD), which imidacloprid is an antagonist of, are not involved in the superparasitism behavior by L. boulardi. Therefore, the superparasitism behavior of the parasitoid wasp is controlled by cholinergic pathways that do not involve nAChR1 or nAChRD subtype receptors. These findings may enable a better understanding of the mechanisms by which the LbFvirus acts, and contribute to a better evaluation of the potential environmental impact of imidacloprid use.

Kairomones from Euschistus heros egg masses and their potential use for Telenomus podisi parasitism improvement.

Telenomus podisi Ashmead (Hymenoptera: Scelionidae) is the most important egg parasitoid of Euschistus heros (Fabricius) (Hemiptera: Pentatomidae), and its successful parasitism is related to their searching ability to find suitable hosts under a complex chemical environment using host-reliable cues. Thus, the objective of this study was to elucidate chemical substances on the external layer of E. heros eggs and report its potential kairomonal activity on T. podisi. We tested female wasps in olfactometer system to synthetic compounds obtained from a chemical identification of E. heros egg masses. The synthetic blend was also evaluated in parasitism tests under laboratory and semi-field conditions. We identified 31 substances from egg surface extracts, including monoterpenes, aldehydes and alkanes. Among those compounds, a synthetic solution including camphene, ß-pinene, limonene and benzaldehyde-induced chemotaxic behaviour on the wasps and increased the parasitism on E. heros eggs, either in laboratory or semi-field test, suggesting its potential use to T. podisi manipulation and parasitism improvement.

Side effects of chlorantraniliprole, phosalone and spinosad on the egg parasitoid, Trichogramma brassicae.

The combined use of chemicals and biological control is not always a successful strategy owing to the potential side effects on biocontrol agents. Lethal and sublethal effects of three commonly used insecticides were assessed on adult and immature stages of the egg parasitoid Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae). Recommended field concentrations of chlorantraniliprole, phosalone and spinosad caused mortality on preimaginal stages by 24, 87, and 98%, respectively. Lethal effects on parasitoid adults exposed to the insecticide dry residues were estimated as median lethal concentrations (LC50) that were 13.28, 0.25, and 0.03 µg a.i. ml-1 for chlorantraniliprole, phosalone, and spinosad, respectively. The effect of a low lethal concentration (LC30) of the compounds was evaluated on various adult biological traits, such as longevity, fecundity, emergence rate and other life table parameters. All compounds caused detrimental effects on all the estimated demographical indexes. Chlorantraniliprole affected the net reproductive rate, mean generation time and doubling time in comparison to the control; while, phosalone and spinosad adversely affected all assessed parameters. Phosalone and spinosad significantly reduced gross reproductive rate, net reproductive rate, intrinsic rate of increase, finite rate of increase, mean generation time and doubling time and reduced longevity, fecundity, emergence rate related to other biological parameters in comparison with control. The results suggest that all compounds are not fully compatible with the activity of T. brassicae, and that the inclusion of chlorantraniprole, spinosad and phosalone into Integrated Pest Management (IPM) involving this parasitoid has to be avoided. Nevertheless, further studies in open field conditions and on a multiple generation scale are necessary for providing a more definitive conclusion on the IPM suitability of the three tested insectcides.

Metaphycus macadamiae (Hymenoptera: Encyrtidae) - a biological control agent of macadamia felted coccid Acanthococcus ironsidei (Hemiptera: Eriococcidae) in Hawaii.

A new species of encyrtid wasp, Metaphycus macadamiae Polaszek & Noyes sp. n., (Hymenoptera: Encyrtidae: Encyrtinae) is described as a solitary endoparasitoid of the invasive macadamia felted coccid, Acanthococcus ironsidei (Hemiptera: Eriococcidae) in Hawaii. This parasitoid is native to Australia, and the species description is based on material collected from a Macadamia integrifolia Maiden & Betche (Proteaceae) plantation in New South Wales, Australia, the native region of the host tree and insect. It is described here because it is a potential biological control agent against this pest where it has recently invaded Hawaii and South Africa.

Changes in Microbiome Confer Multigenerational Host Resistance after Sub-toxic Pesticide Exposure.

The gut is a first point of contact with ingested xenobiotics, where chemicals are metabolized directly by the host or microbiota. Atrazine is a widely used pesticide, but the role of the microbiome metabolism of this xenobiotic and the impact on host responses is unclear. We exposed successive generations of the wasp Nasonia vitripennis to subtoxic levels of atrazine and observed changes in the structure and function of the gut microbiome that conveyed atrazine resistance. This microbiome-mediated resistance was maternally inherited and increased over successive generations, while also heightening the rate of host genome selection. The rare gut bacteria Serratia marcescens and Pseudomonas protegens contributed to atrazine metabolism. Both of these bacteria contain genes that are linked to atrazine degradation and were sufficient to confer resistance in experimental wasp populations. Thus, pesticide exposure causes functional, inherited changes in the microbiome that should be considered when assessing xenobiotic exposure and as potential countermeasures to toxicity.