A perspective on insect-microbe holobionts facing thermal fluctuations in a climate-change context.

Temperature influences the ecology and evolution of insects and their symbionts by impacting each partner independently and their interactions, considering the holobiont as a primary unit of selection. There are sound data about the responses of these partnerships to constant temperatures and sporadic thermal stress (mostly heat shock). However, the current understanding of the thermal ecology of insect-microbe holobionts remains patchy because the complex thermal fluctuations (at different spatial and temporal scales) experienced by these organisms in nature have often been overlooked experimentally. This may drastically constrain our ability to predict the fate of mutualistic interactions under climate change, which will alter both mean temperatures and thermal variability. Here, we tackle down these issues by focusing on the effects of temperature fluctuations on the evolutionary ecology of insect-microbe holobionts. We propose potentially worth-investigating research avenues to (i) evaluate the relevance of theoretical concepts used to predict the biological impacts of temperature fluctuations when applied to holobionts; (ii) acknowledge the plastic (behavioural thermoregulation, physiological acclimation) and genetic responses (evolution) expressed by holobionts in fluctuating thermal environments; and (iii) explore the potential impacts of previously unconsidered patterns of temperature fluctuations on the outcomes and the dynamic of these insect-microbe associations.

Cascading effects of caffeine intake by primary consumers to the upper trophic level.

Secondary metabolites are central to understanding the evolution of plant-animal interactions. Direct effects on phytophagous animals are well-known, but how secondary consumers adjust their behavioural and physiological responses to the herbivore's diet remains more scarcely explored for some metabolites. Caffeine is a neuroactive compound that affects both the behaviour and physiology of several animal species, from humans to insects. It is an alkaloid present in nectar, leaves and even sap of numerous species of plants where it plays a role in chemical defences against herbivores and pathogens. Caffeine effects have been overlooked in generalist herbivores that are not specialized in coffee or tea plants. Using a host-parasitoid system, we show that caffeine intake at a relatively low dose affects longevity and fecundity of the primary consumer, but also indirectly of the secondary one, suggesting that this alkaloid and/or its effects can be transmitted through trophic levels and persist in the food chain. Parasitism success was lowered by ≈16% on hosts fed with caffeine, and parasitoids of the next generation that have developed in hosts fed on caffeine showed a reduced longevity, but no differences in mass and size were found. This study helps at better understanding how plant secondary metabolites, such as caffeine involved in plant-animal interactions, could affect primary consumers, could have knock-on effects on upper trophic levels over generations, and could modify interspecific interactions in multitrophic systems.

Thermal tolerance of the rosy apple aphid Dysaphis plantaginea and its parasitoids: Effect of low temperatures on some fitness activities of Aphidius matricariae.

Understanding the thermal tolerance of insect herbivores and their natural enemies is crucial for biological control programs. The rosy apple aphid Dysaphis plantaginea is one of the most problematic pests of apple orchards, causing economic losses of up to 30% due to damage to fruits. Dysaphis plantaginea is highly adapted to low temperature, enabling it to appear early in the season. This study aimed at evaluating the critical thermal minimum of D. plantaginea and of two parasitoid species: Aphidius matricariae and Ephedrus cerasicola. For the generalist parasitoid A. matricariae we also evaluated the fitness traits of flight, walking, and oviposition, at four temperatures: 20, 15, 10 and 8 °C. We found that both males and females did not fly at the two lowest temperatures. Walking, parasitism rate and sex ratio (proportion of female progeny) were reduced at 8 °C. In addition, the parasitism rate was significantly lower at 8 and 10 °C compared to 15 and 20 °C. The progeny emerging from the oviposition experiment at 8 °C were significantly larger compared with other temperatures, possibly attributed to longer development time. The fact that the parasitoids were unable to fly at 8 and 10 °C, in combination with a more male-biased sex ratio, could reduce their efficiency at low temperature, even though they may still be able to walk and parasitize aphids.

Effect of developmental temperatures on Aphidius colemani host-foraging behavior at high temperature.

Temperatures experienced by insects during their adult life often differ from developmental temperatures. Yet, developmental thermal acclimation can play an important role in shaping physiological, morphological, and behavioral traits at the adult stage. We explored how three rearing temperatures (10, 20, and 28 °C) affected host-foraging behaviors and associated traits under warm conditions in the parasitoid Aphidius colemani, a key model in behavioral ecology and an important natural enemy of aphids. Developmental time was longer at lower temperatures, resulting in bigger emerging parasitoids, with higher egg-loads. Parasitism rates, emergence rates, and parasitoid survival (once placed at high temperature) were the highest for parasitoids developed at 20 °C. When exposed to 28 °C, the expression of all behavioral items (time spent walking searching for hosts, number of antennal and ovipositor contacts with hosts) was higher for parasitoids reared at 20 °C, followed by those reared at 10 °C, then those reared at 28 °C. Finally, we showed that parasitoid residence time on aphid patches was determined by both developmental temperatures and the number of host encounter without oviposition, representative of the resource quality. We revealed that developing at 28 °C did not lead to increased adult performance at this temperature, probably because of complex interactions and trade-offs between developmental costs at high temperature and optimal foraging behaviors (e.g., parasitoid size and host-handling capacities). Our results strengthen the idea that thermal developmental plasticity may play an important role in insect behavioral responses to varying temperatures, and is important to consider in the context of climate change.

Banana Tree Infected with Banana Bunchy Top Virus Attracts Pentalonia nigronervosa Aphids Through Increased Volatile Organic Compounds Emission.

Banana plants are affected by various viral diseases, among which the most devastating is the "bunchy top", caused by the Banana bunchy top virus (BBTV) and transmitted by the aphid Pentalonia nigronervosa Coquerel. The effect of BBTV on attraction mechanisms of dessert and plantain banana plants on the vector remains far from elucidated. For that, attractiveness tests were carried out using a two columns olfactometer for apterous aphids, and a flight cage experiment for alate aphids. Volatile Organic Compounds (VOCs) emitted by either healthy or BBTV-infected banana plants were identified using a dynamic extraction system and gas-chromatography mass-spectrometry (GC-MS) analysis. Behavioral results revealed a stronger attraction of aphids towards infected banana plants (independently from the variety), and towards the plantain variety (independently from the infection status). GC-MS results revealed that infected banana plants produced VOCs of the same mixture as healthy banana plants but in much higher quantities. In addition, VOCs produced by dessert and plantain banana plants were different in nature, and plantains produced higher quantities than dessert banana trees. This work opens interesting opportunities for biological control of P. nigronervosa, for example by luring away the aphid from banana plants through manipulation of olfactory cues.

Impact of the COVID-19 pandemic on apple orchards in Europe.

CONTEXT: The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has affected global agricultural chains and intensified the issue of food insecurity worldwide. OBJECTIVE: We propose a short retrospective of the reported effects of the COVID-19 pandemic from its beginning in March 2020 in Europe, on orchard management and harvest, sales and agricultural chains, monitoring and research in orchards, and we expose some of the solutions undertaken to tackle down these issues. RESULTS AND CONCLUSION: In Europe, the fruit and vegetable sector has been affected by the pandemic in terms of production, distribution, and disturbance in market performance. Concerning apple, the most harvested and exported fruit in Europe, national governments, European institutions, the industry and producers have undertaken actions to ensure production and supply demand. Yet, stakeholders have faced several difficulties and additional costs for growth and harvest, sales, but also monitoring and research. However, European Union demand for fresh apples has increased during the pandemic. In addition, apple harvest has started a couple of months after the end of the first lockdown in most countries, and European apple orchards are usually in more flexible smallholder or family farms. Finally, the fruit itself has relatively long shelf-life comparatively to other fruits. For these main reasons, we argue that the apple sector might be more resilient than other fruit sectors or other cultures, despite the negative effects of seasonal workforce shortage and unstable market. The apple sector may suffer more from side-effects such as increasing labor, distribution, and packaging costs, than from actual stock and production issues. SIGNIFICANCE: The pandemic could be an opportunity to reconsider production modes and to innovate for the future of food production in different crop systems in Europe, including apple orchards.

New Insights into the Nature of Symbiotic Associations in Aphids: Infection Process, Biological Effects, and Transmission Mode of Cultivable Serratia symbiotica Bacteria.

Symbiotic microorganisms are widespread in nature and can play a major role in the ecology and evolution of animals. The aphid-Serratia symbiotica bacterium interaction provides a valuable model to study the mechanisms behind these symbiotic associations. The recent discovery of cultivable S. symbiotica strains with a free-living lifestyle allowed us to simulate their environmental acquisition by aphids to examine the mechanisms involved in this infection pathway. Here, after oral ingestion, we analyzed the infection dynamics of cultivable S. symbiotica during the host's lifetime using quantitative PCR and fluorescence techniques and determined the immediate fitness consequences of these bacteria on their new host. We further examined the transmission behavior and phylogenetic position of cultivable strains. Our study revealed that cultivable S. symbiotica bacteria are predisposed to establish a symbiotic association with a new aphid host, settling in its gut. We show that cultivable S. symbiotica bacteria colonize the entire aphid digestive tract following infection, after which the bacteria multiply exponentially during aphid development. Our results further reveal that gut colonization by the bacteria induces a fitness cost to their hosts. Nevertheless, it appeared that the bacteria also offer an immediate protection against parasitoids. Interestingly, cultivable S. symbiotica strains seem to be extracellularly transmitted, possibly through the honeydew, while S. symbiotica is generally considered a maternally transmitted bacterium living within the aphid body cavity and bringing some benefits to its hosts, despite its costs. These findings provide new insights into the nature of symbiosis in aphids and the mechanisms underpinning these interactions.IMPORTANCES. symbiotica is one of the most common symbionts among aphid populations and includes a wide variety of strains whose degree of interdependence on the host may vary considerably. S. symbiotica strains with a free-living capacity have recently been isolated from aphids. By using these strains, we established artificial associations by simulating new bacterial acquisitions involved in aphid gut infections to decipher their infection processes and biological effects on their new hosts. Our results showed the early stages involved in this route of infection. So far, S. symbiotica has been considered a maternally transmitted aphid endosymbiont. Nevertheless, we show that our cultivable S. symbiotica strains occupy and replicate in the aphid gut and seem to be transmitted over generations through an environmental transmission mechanism. Moreover, cultivable S. symbiotica bacteria are both parasites and mutualists given the context, as are many aphid endosymbionts. Our findings give new perception of the associations involved in bacterial mutualism in aphids.

Evidence for Gut-Associated Serratia symbiotica in Wild Aphids and Ants Provides New Perspectives on the Evolution of Bacterial Mutualism in Insects.

Many insects engage in symbiotic associations with diverse assemblages of bacterial symbionts that can deeply impact on their ecology and evolution. The intraspecific variation of symbionts remains poorly assessed while phenotypic effects and transmission behaviors, which are key processes for the persistence and evolution of symbioses, may differ widely depending on the symbiont strains. Serratia symbiotica is one of the most frequent symbiont species in aphids and a valuable model to assess this intraspecific variation since it includes both facultative and obligate symbiotic strains. Despite evidence that some facultative S. symbiotica strains exhibit a free-living capacity, the presence of these strains in wild aphid populations, as well as in insects with which they maintain regular contact, has never been demonstrated. Here, we examined the prevalence, diversity, and tissue tropism of S. symbiotica in wild aphids and associated ants. We found a high occurrence of S. symbiotica infection in ant populations, especially when having tended infected aphid colonies. We also found that the S. symbiotica diversity includes strains found located within the gut of aphids and ants. In the latter, this tissue tropism was found restricted to the proventriculus. Altogether, these findings highlight the extraordinary diversity and versatility of an insect symbiont and suggest the existence of novel routes for symbiont acquisition in insects.

Bottom-up regulation of a tritrophic system by Beet yellows virus infection: consequences for aphid-parasitoid foraging behaviour and development.

Effects of plants on herbivores can cascade up the food web and modulate the abundance of higher trophic levels. In agro-ecosystems, plant viruses can affect the interactions between crops, crop pests, and natural enemies. Little is known, however, about the effects of viruses on higher trophic levels, including parasitoids and their ability for pest regulation. We tested the hypothesis that a plant virus affects parasitoid foraging behaviour through cascading effects on higher trophic levels. We predicted that the semi-persistent Beet yellows virus (BYV) would influence plant (Beta vulgaris) quality, as well as aphid host (Aphis fabae) quality for a parasitoid Lysiphlebus fabarum. We determined amino acid and sugar content in healthy and infected plants (first trophic level), lipid content and body size of aphids (second trophic level) fed on both plants, as well as foraging behaviour and body size of parasitoids (third trophic level) that developed on aphids fed on both plants. Our results showed that virus infection increased sugars and decreased total amino acid content in B. vulgaris. We further observed an increase in aphid size without modification in host aphid quality (i.e., lipid content), and a slight effect on parasitoid behaviour through an increased number of antennal contacts with host aphids. Although the BYV virus clearly affected the first two trophic levels, it did not affect development or emergence of parasitoids. As the parasitoid L. fabarum does not seem to be affected by the virus, we discuss the possibility of using it for the development of targeted biological control against aphids.

Composition and Structure of Thripidae Populations in Crops of Three Geographical Regions in Colombia.

The composition and structure of thrips populations were determined in agroecosystems of 10 crops in the Andean, Caribbean, and Orinoquia regions of Colombia. From 18,183 identified specimens, 81 species belonging to 20 genera and three families were found. The Andean region was the most diverse with 60 species (n = 11,360, Chao 1 = 70.5, H' = 1.986), followed by the Caribbean region with 42 (n = 5,960, Chao 1 = 57.6, H' = 2.256) and the Orinoquia with 24 (n = 863, Chao 1 = 31; H' = 2.301). The crop with the richest fauna was avocado (Persea americana) Mill. with 40 species (n = 4,047, Chao 1 = 55.17, H' = 1.302), followed by coffee (Coffea arabica) L. with 26 (n = 1,395, Chao 1 = 33; H' = 1.026), cassava (Manihot esculenta) Crantz. with 25 (n = 1,050, Chao 1 = 29.67, H' = 1.635), citrus (Citrus spp.) with 22 (n= 836, Chao 1 = 25.75, H' = 1.748), corn (Zea mays) L. with 22 (n = 1,647, Chao 1 = 24.5, H' = 1.365), mango (Mangifera indica) L. with 17 (n = 1,144, Chao 1 = 18.5, H' = 1.303), blackberry (Rubus glaucus) Bentham. with 11 (n = 545, Chao 1 = 16, H' = 0.886), banana (Musa spp.) with 9 species (n = 1,798, Chao 1 = 9, H' = 0.208), cotton (Gossypium hirsutum) L. with 8 (n = 5,621, Chao 1 = 11, H' = 0.913), and rubber tree (Hevea brasiliensis) Müll.Arg. with 4 species (n = 90, Chao 1 = 4, H' = 0.594). Differences were found in the distribution of the species in the altitudinal gradients and in the biogeographical regions. Frankliniella gardeniae Moulton, was the most abundant species, with the highest presence in crops, the greatest geographic and altitudinal distribution.

Impact of differences in nutritional quality of wingless and winged aphids on parasitoid fitness.

Winged aphids are described as hosts of lesser quality for parasitoids because a part of their resources is used to produce wings and associated muscles during their development. Host lipid content is particularly important for parasitoid larvae as they lack lipogenesis and therefore rely entirely on the host for this resource. The goal of this study was to determine to what extent winged and wingless aphids differ from a nutritional point of view and whether these differences impact parasitoid fitness, notably the lipid content. We analysed the energetic budget (proteins, lipids and carbohydrates) of aphids of different ages (third instars, fourth instars and adults) according to the morph (winged or wingless). We also compared fitness indicators for parasitoids emerging from winged and wingless aphids (third and fourth instars). We found that in third instars, parasitoids are able to inhibit wing development whereas this is not the case in fourth instars. Both winged instars allow the production of heavier and fattier parasitoids. The presence of wings in aphids seems to have little effect on the fitness of emerging parasitoids and did not modify female choice for oviposition. Finally, we demonstrate that Aphidius colemani, used as a biological control agent, is able to parasitize wingless as well as winged Myzus persicae, at least in the juvenile stages. If the parasitism occurs in third instars, the parasitoid will prevent the aphid from flying, which could in turn reduce virus transmission.

Accessing the Hidden Microbial Diversity of Aphids: an Illustration of How Culture-Dependent Methods Can Be Used to Decipher the Insect Microbiota.

Microorganism communities that live inside insects can play critical roles in host development, nutrition, immunity, physiology, and behavior. Over the past decade, high-throughput sequencing reveals the extraordinary microbial diversity associated with various insect species and provides information independent of our ability to culture these microbes. However, their cultivation in the laboratory remains crucial for a deep understanding of their physiology and the roles they play in host insects. Aphids are insects that received specific attention because of their ability to form symbiotic associations with a wide range of endosymbionts that are considered as the core microbiome of these sap-feeding insects. But, if the functional diversity of obligate and facultative endosymbionts has been extensively studied in aphids, the diversity of gut symbionts and other associated microorganisms received limited consideration. Herein, we present a culture-dependent method that allowed us to successfully isolate microorganisms from several aphid species. The isolated microorganisms were assigned to 24 bacterial genera from the Actinobacteria, Firmicutes, and Proteobacteria phyla and three fungal genera from the Ascomycota and Basidiomycota phyla. In our study, we succeeded in isolating already described bacteria found associated to aphids (e.g., the facultative symbiont Serratia symbiotica), as well as microorganisms that have never been described in aphids before. By unraveling a microbial community that so far has been ignored, our study expands our current knowledge on the microbial diversity associated with aphids and illustrates how fast and simple culture-dependent approaches can be applied to insects in order to capture their diverse microbiota members.

Seasonal Terpene Variation in Needles of Pinus radiata (Pinales: Pinaceae) Trees Attacked by Tomicus piniperda (Coleoptera: Scolytinae) and the Effect of Limonene on Beetle Aggregation.

Concentrations of four monoterpenes were determined in needles of Pinus radiata (D.Don) (Pinales: Pinaceae) trees that were attacked or nonattacked by Tomicus piniperda (L.) (Coleoptera: Scolytinae). Compounds were identified and quantified by gas chromatography-mass spectrometry. The mean ambient temperature was obtained using climate-recording data loggers. The effect of limonene on field aggregation was also evaluated at three limonene release rates using Lindgren attractant-baited traps and trap logs. Attacked trees produced less α-pinene in March, July, and November than nonattacked trees, less ß-pinene in July and November, and less limonene from May to November. Limonene reduced the attraction of T. piniperda to attractant-baited traps and trap logs. Results were linked to better responses to high temperatures, with respect to terpene contents, by the nonattacked trees after the spring attack.

Impact of living with kin/non-kin on the life history traits of Tetranychus urticae (Acari: Tetranychidae).

In many vertebrates and invertebrates, living in a group may influence the life history traits, physiology and behaviour of its individual members, whereas genetic relatedness affects social interactions among individuals in a group. The two-spotted spider mite Tetranychus urticae is characterised by a communal organization, in which silk production plays a key role. A silken web protects the colony against biotic and abiotic agents such as predators, competitors, humidity, wind, rain and acaricides. To evaluate the potential costs and benefits of being associated with genetically distant vs genetically close individuals in T. urticae, we assessed various fitness indicators (faecal pellet production, fecundity, death rate) in pure and mixed groups of two distinct populations of T. urticae: a red-form population from Tunisia and a green-form population from Belgium. If genetic origin had no influence, the values of fitness indicators in mixed groups composed of green and red individuals, would be intermediate between those of the pure green-form and red-form groups. Our results show that in a mixed group, faecal pellet production and death rate were statistically similar to the values obtained in the pure group of green-form individuals. Therefore, our study suggests that strain recognition ability may occur in T. urticae and that the genetic background of an individual may have a great impact on several of its life history traits.

Preference of Pentalonia nigronervosa for infected banana plants tends to reverse after Banana bunchy top virus acquisition.

Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae) is the vector of the Banana Bunchy Top Virus (BBTV), the most serious viral disease of banana (Musa spp.) in the world. Before acquiring the virus, the vector is more attracted to infected banana plants in response to the increased emissions of volatile organic compounds (VOCs). Here, we test the hypothesis that BBTV acquisition directly modifies the preference of P. nigronervosa for infected banana plants, and that the change in preference results from the alteration of the organs linked to the VOC detection or to the behaviour of the vector. We found that the preference of P. nigronervosa for infected banana plants reverses after virus acquisition in dessert banana, while it remains similar between healthy and infected banana plants before and after the acquisition of BBTV. At the same time, aphids reared on infected bananas had smaller forewing areas and hind tibia length than aphids reared on healthy bananas, although the number of secondary rhinaria on the antennae was lower on dessert banana-reared aphids than plantain-reared aphids, this was not affected by the infection status of the aphid. These results support the "vector manipulation hypothesis-VMH" of pathogens to promote their spread. They have implications for the BBTV management.

PacBio Hi-Fi genome assembly of Sipha maydis, a model for the study of multipartite mutualism in insects.

Dependence on multiple nutritional endosymbionts has evolved repeatedly in insects feeding on unbalanced diets. However, reference genomes for species hosting multi-symbiotic nutritional systems are lacking, even though they are essential for deciphering the processes governing cooperative life between insects and anatomically integrated symbionts. The cereal aphid Sipha maydis is a promising model for addressing these issues, as it has evolved a nutritional dependence on two bacterial endosymbionts that complement each other. In this study, we used PacBio High fidelity (HiFi) long-read sequencing to generate a highly contiguous genome assembly of S. maydis with a length of 410 Mb, 3,570 contigs with a contig N50 length of 187 kb, and BUSCO completeness of 95.5%. We identified 117 Mb of repetitive sequences, accounting for 29% of the genome assembly, and predicted 24,453 protein-coding genes, of which 2,541 were predicted enzymes included in an integrated metabolic network with the two aphid-associated endosymbionts. These resources provide valuable genetic and metabolic information for understanding the evolution and functioning of multi-symbiotic systems in insects.

Still standing: The heat protection delivered by a facultative symbiont to its aphid host is resilient to repeated thermal stress.

Insects have evolved diverse strategies to resist extreme high temperatures (EHT). The adaptive value of such strategies has to be evaluated when organisms experience multiple EHT events during their lifetime, as predicted in a changing climate. This is particularly the case for associations with facultative microbial partners involved in insect heat tolerance, the resilience of which to repeated heat stress has never been studied. We compared two artificial lines of the pea aphid (Acyrthosiphon pisum) differing by the absence or presence of the heat-protective facultative bacterium Serratia symbiotica. We exposed insect nymphs to a varying number of EHT events (between 0 and 3), and recorded fitness parameters. Except survival traits, fitness estimates were affected by the interaction between aphid infection status (absence/presence of S. symbiotica) and thermal treatment (number of heat shocks applied). Costs of bacterial infection were detected in the absence of thermal stress: symbiont-hosting aphids incurred longer development, decreased fecundity and body size. However, symbiotic infection turned neutral, and even beneficial for some traits (development and body size), as the number of heat shocks increased, and compared to the aposymbiotic strain. Conversely, symbiotic infection mediated aphid response to heat shock(s): fitness decreased only in the uninfected group. These findings suggest that (i) the facultative symbiont may alternatively act as a pathogen, commensal or mutualist depending on thermal environment, and (ii) the heat protection it delivered to its host persists under frequent EHT. We discuss eco-evolutionary implications and the role of potentially confounding factors (stage-specific effects, genetic polymorphism displayed by the obligate symbiont).

Deciphering the functional diversity of the gut microbiota of the black soldier fly (Hermetia illucens): recent advances and future challenges.

Bioconversion using insects is a promising strategy to convert organic waste (catering leftovers, harvest waste, food processing byproducts, etc.) into biomass that can be used for multiple applications, turned into high added-value products, and address environmental, societal and economic concerns. Due to its ability to feed on a tremendous variety of organic wastes, the black soldier fly (Hermetia illucens) has recently emerged as a promising insect for bioconversion of organic wastes on an industrial scale. A growing number of studies have highlighted the pivotal role of the gut microbiota in the performance and health of this insect species. This review aims to provide a critical overview of current knowledge regarding the functional diversity of the gut microbiota of H. illucens, highlighting its importance for bioconversion, food safety and the development of new biotechnological tools. After providing an overview of the different strategies that have been used to outline the microbial communities of H. illucens, we discuss the diversity of these gut microbes and the beneficial services they can provide to their insect host. Emphasis is placed on technical strategies and aspects of host biology that require special attention in the near future of research. We also argue that the singular digestive capabilities and complex gut microbiota of H. illucens make this insect species a valuable model for addressing fundamental questions regarding the interactions that insects have evolved with microorganisms. By proposing new avenues of research, this review aims to stimulate research on the microbiota of a promising insect to address the challenges of bioconversion, but also fundamental questions regarding bacterial symbiosis in insects.

The aphid Pentalonia nigronervosa (Hemiptera: Aphididae) takes advantage from the quality change in banana plant associated with Banana bunchy top virus infection.

Viral diseases can change plant metabolism, with potential impacts on the quality of the plant's food supply for insect pests, including virus vectors. The banana aphid, Pentalonia nigronervosa Coquerel, is the vector of the Banana bunchy top virus (BBTV), the causal agent of Banana bunchy top disease (BBTD), the most devastating viral disease of bananas in the world. The effect of BBTV on the life-history traits and population dynamics of P. nigronervosa remains poorly understood. We therefore studied the survival rate, longevity, daily fecundity per aphid, tibia length, population growth, and winged morph production of a P. nigronervosa clone grown on healthy or infected, dessert, or plantain banana plants. We found that daily fecundity was higher on infected banana than on healthy banana plants (plantain and dessert), and on plantain than on dessert banana plants (healthy and infected). Survival and longevity were lower on infected dessert bananas than on other types of bananas. In addition, virus infection resulted in a decrease in aphid hind tibia length on both plant genotypes. The survival and fecundity table revealed that the aphid net reproduction rate (Ro) was highest on plantains (especially infected plantain), and the intrinsic growth rate (r) was highest on infected plants. Finally, the increase of aphids and alate production was faster first on infected plantain, then on healthy plantain, and lower on dessert banana (infected and uninfected). Our results reinforce the idea of indirect and plant genotype-dependent manipulation of P. nigronervosa by the BBTV.

Essential Oil Trunk Injection Into Orchard Trees: Consequences on the Performance and Preference of Hemipteran Pests.

Apples and pears are among the most widely cultivated fruit species in the world. Pesticides are commonly applied using ground sprayers in conventional orchards; however, most of it will not reach the target plant, increasing the contamination of nontarget organisms such as natural predators, pollinators, and decomposers. Trunk injection is an alternative method of pesticide application that could reduce risks to beneficials and workers. Essential oils represent a 'green' alternative to pesticides due to their reported insecticidal, antimicrobial, antiviral, nematicidal, and antifungal properties. The aim of this study was, therefore, to evaluate the impact that the injection of a cinnamon essential oil solution into the trunk of apple and pear trees could have on their respective pests, Dysaphis plantaginea and Cacopsylla pyri, respectively. The feeding behavior (preference), the life history traits (performance), and the timing of this effect were measured. The injection of an essential oil emulsion in trees impacted hemipteran host-plant colonization, as for both species a modification of their preference and of their performance was observed. The feeding behavior of D. plantaginea was altered as a significantly lower proportion of aphids ingested phloem sap on injected trees, suggesting that the aphids starved to death. On the contrary, the feeding behavior of the psyllids was little changed compared to the control condition, implying that the observed mortality was due to intoxication. The results presented here could theoretically be used to control these two orchard hemipteran pests, although the effectiveness in real conditions still has to be demonstrated.