Nymphal Feeding Research Articles

Effects of succession crops and soil tillage on suppressing the syndrome 'basses richesses' vector Pentastiridius leporinus in sugar beet.

Pentastiridius leporinus (Hemiptera: Cixiidae) is the most important vector of syndrome 'basses richesses' (SBR), a new disease that leads to severe economic losses in sugar beet. In this study, different soil tillage methods (ploughing and cultivator) and crops (winter wheat, spring wheat, maize and bare soil) following SBR-infested sugar beet were tested as potential management options in field trials. In the laboratory, the survival and development of first and third instar nymphs on wheat and maize was studied to further assess their suitability as host plants. In five out of seven field sites, reduced soil tillage had no effect on adult planthopper emergence compared to ploughing. In two sites, reduced tillage resulted in higher emergence rates. In nearly all field sites, up to 98.9% fewer emerging adults were detected in bare soil and maize, when compared to winter wheat. Under laboratory conditions, the lowest survival rate was found in first instar nymphs feeding on maize seedlings (4.2%), while 66.7% survived on wheat, over a period of 300 days. In contrast, 73.3% and 70% of third instar nymphs survived on wheat and maize over a period of 150 days. Soil tillage had little effect against Pentastiridius leporinus. Maize is a poor host for first instars but a suitable resource for third instar nymphs, the stage which encounters maize under field conditions. Hence, reductions in planthopper emergence in the field were likely caused by starvation due to the long host-free period between sugar beet harvest and the sowing of maize. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Rice brown planthopper, Nilaparvata lugens (Stål) feeding behavior in relation to elevated CO2 and temperature

Feeding behavior of brown planthopper, Nilaparvata lugens (Stål) populations collected from different geographical regions Ludhiana, Nalgonda and West Godavari at three generations 1, 5 and 10 fed on rice plants grown under different CO2 and temperature levels 1) Ambient CO2@ 380±25ppm + ambient temperature (aCO2+aT), 2) Elevated CO2@500±25ppm + ambient temperature (eCO2+aT) and 3) Elevated CO2@500±25ppm + elevated temperature (eCO2+eT) in closed CO2 chambers was studied. Elevated CO2 + elevated temperature increased feeding rate of BPH nymphs while BPH adults showed declined feeding rate. BPH nymphal feeding rate increased with progressive generations while it decreased in BPH adults. Ludhiana adult BPH population showed higher honeydew excretion compared to West Godavari and Nalgonda populations. CO2 + temperature levels at progressive generations have varying effects on adults and nymphs of three BPH populations. Biochemical composition of rice plants grown under different CO2 levels revealed increased rate of soluble sugars, phenols and decreased rate of reducing sugars, soluble proteins, free amino acids, nitrogen, potassium, phosphorous in elevated CO2 + elevated temperature levels compared to ambient conditions. Increased feeding rate of BPH under elevated CO2 levels may be to compensate changes in host plant quality i.e., high soluble sugars and low nitrogen.

Diversity and composition of the bacterial communities associated with the Australian spittlebugs Bathyllus albicinctus and Philagra parva (Hemiptera: Aphrophoridae).

Spittlebugs and froghoppers (Hemiptera: Cercopoidea) are insects feeding on xylem, which potentially can cause significant economic damage worldwide by transmitting plant pathogenic bacteria such as Xylella fastidiosa. Australia and New Zealand are currently free from X. fastidiosa, but they are home to at least 45 native spittlebug species. Among these, the Australian natives Bathyllus albicinctus (Erichson, 1842) and Philagra parva (Donovan, 1805) are particularly widespread and can be found across southern and eastern Australia, with B. albicinctus also in New Zealand. The potential that both species might be capable of vectoring Xylella fastidiosa poses a substantial biosecurity risk if the bacterium were to invade these regions. In this study, we examined 87 spittlebug nymphs collected across 12 different host plant species, in five locations in Victoria, Australia. Our objective was to explore the factors influencing bacterial communities within and between these widespread spittlebug species, considering geographic location, insect phylogenetics, and host plant associations. We employed COI barcoding to assess insect genetic variation and 16S high throughput sequencing (HTS) metabarcoding to analyse bacterial microbiome diversity across various host plants. Our findings revealed minimal genetic divergence among spittlebug individuals in the same species, highlighting conspecificity despite conspicuous morphological divergences. On the other hand, we recorded significant variation in bacterial communities harboured by Bathyllus albicinctus nymphs feeding on different plants, even when these were collected within close proximity to each other. Therefore, host plant association appeared to shape the bacterial communities of spittlebugs more than insect genetic divergence or geographical location. These diverse bacterial communities could potentially facilitate transmission of plant pathogenic bacteria, underscoring the risk of widespread transmission among numerous plant hosts through insect-plant interactions. This study emphasizes the critical need to understand these complex interactions, particularly in the context of biosecurity.

Choice and No-Choice Feeding Assays of Cotton Fleahoppers (Pseudatomoscelis seriatus) on Cotton Expressing the Mpp51Aa2 Protein

In Texas, the cotton fleahopper (Pseudatomoscelis seriatus (Reuter)) is considered a highly economically damaging pest of cotton (Gossypium hirsutum L.). Current control methods rely heavily on foliar chemical insecticides throughout the growing season. Considering the cost of insecticides and the critical timeliness of their application, chemical control methods are often not optimized to reduce potential yield losses. The Mpp51Aa2.834_16 gene in cotton (ThryvOn) has shown effectiveness against thrips and several piercing and sucking mirid insect pests, suggesting it has the potential to mitigate yield losses caused by the cotton fleahopper. Choice and no-choice caged feeding assays were conducted to assess the impact of cotton fleahoppers on ThryvOn cotton square retention under controlled laboratory conditions. In the choice assay, feeding by cotton fleahoppers significantly reduced square retention in the gene-lacking cotton to 46%, while the ThryvOn cotton retained 60% of the squares. In the no-choice assay, cotton fleahopper nymph feeding significantly reduced square retention in the cotton not expressing Mpp51Aa2 to 61%, whereas the ThryvOn cotton was unaffected. Based on the differences in square retention observed in both the choice and no-choice feeding assays, our findings indicate that the Mpp51Aa2 protein influences cotton fleahopper feeding preferences and the susceptibility of cotton plants to damage caused by cotton fleahoppers. Our study offers confirmation of the activity of ThryvOn on cotton fleahoppers observed in the field. The ThryvOn trait’s activity towards cotton fleahoppers is consistent with that found for other mirid pests in cotton.

Four-Chlorophenoxyacetic Acid Treatment Induces the Defense Resistance of Rice to White-Backed Planthopper Sogatella furcifera

Chemical elicitors can increase plant defense against herbivorous insects and pathogens. The use of synthetic chemical elicitors is likely to be an alternative to traditional pesticides for crop pest control. However, only a few synthetic chemicals are reported to protect plants by regulating signaling pathways, increasing the levels of defense metabolites and interfering with insect feeding. Here, we found that the exogenous application of a phenoxycarboxylic compound, 4-chlorophenoxyacetic acid (4-CPA), can induce chemical defenses to protect rice plants from white-backed planthoppers (WBPH, Sogatella furcifera). Four-CPA was rapidly taken up by plant roots and degraded to 4-chlorophenol (4-CP). Four-CPA treatment modulated the activity of peroxidase (POD) and directly induced the deposition of lignin-like polymers using hydrogen peroxide (H2O2) as the electron acceptor. The polymers, which are thought to prevent the planthopper’s stylet from reaching the phloem, were broken down by WBPH nymphs. Meanwhile, 4-CPA increased the levels of flavonoids and phenolamines (PAs). The increased flavonoids and PAs, together with the degradation product of the polymers, avoided nymphal feeding and prolonged the nymphal period for 1 day. These results indicate that 4-CPA has the potential to be used as a chemical elicitor to protect rice from planthoppers. Moreover, these findings also open a pathway for molecule structure design of phenoxycarboxylic compounds as chemical elicitors.

Detection of winter tick, Dermacentor albipictus, infestations using near infrared reflectance spectroscopy of bovine feces

The objective of this study was to determine whether artificial infestations of D. albipictus could be detected in cattle using near infrared reflectance spectroscopy of bovine feces (fNIRS) and if detection capability was sensitive to size of tick infestation and phase of on-host stage-specific tick development. Fecal samples were collected daily from six non-infested then later tick-infested Bos taurus yearling heifers who each served as their own control. Cattle with D. albipictus infestations arising from as few as 1000 larvae were identified by fecal chemistry changes using fNIRS technology. In two separate trials, three animal pairs were infested with one of three treatment levels (low: ∼ 1000, medium: ∼ 4000, and high: ∼ 8000) of D. albipictus larvae in a repeated measures experimental design. Trial 1 consisted of tick naïve cattle while Trial 2 consisted of prior tick exposed cattle. Date of drop and daily sum of engorged female ticks were tabulated to characterize each infestation. Cluster, common factor, principal component and MANOVA analyses were used to define and assess fecal spectra changes associated with experimental stages of infestation. Cluster analyses found significant differences in fecal samples for heifer pairs in each treatment level group (low, medium, and high) in Trial 1 and then in Trial 2 from two pre-infestation control periods (outside and inside), three stages of tick development (larval feeding, nymphal feeding, adult feeding), and post-tick recovery periods. Five shifts in fecal chemistry of non-infested and tick-infested periods were identified by six clusters of NIRS fecal spectra measured between 576 and 1126 nm. The PCA’s resulted in 97.56% and 97.77% for Trials 1 and 2 respectively of the total variation in the 1050 frequencies being explained by the first three principal components (P1, P2, P3). Results from the MANOVA and the Wilk’s Lambda test for both trials showed highly significant evidence (p-values < 0.0001) of a difference in the means of the three principal components across the six Stages. There was significant evidence in Trial 1 (p-values = 0.0067) and Trial 2 (p-values < 0.0001) of a difference between the means of the three principal components across the three levels of tick infestation. These significant pair-wise comparisons reflect developmental phases of tick attachment and blood-feeding that define periods of increasing, peak and declining stress identified in five fecal chemistry shifts defined by six fecal spectral clusters.

Technique to deliver dsRNA in Bemisia tabaci nymphs and its validation through silencing of juvenile hormone esterase gene

AbstractRNA interference (RNAi) is a technique employed to investigate the functions of various genes in whitefly and other insects. The effectiveness of the RNAi technique depends upon the delivery of dsRNA into the insects and it has been achieved through microinjection, oral feeding, egg soaking, transfection, topical application, spraying with nanoparticles, leaf‐mediated dsRNA feeding or plant‐mediated/ transgenic plants. In Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), most of the studies on RNAi were conducted on the adult through either injection or oral feeding. There is a need to develop a system to deliver dsRNA in whitefly nymphs because the first instar nymphs after hatching find a suitable place on the leaf and feed on the same place till adult emergence. So, we evaluated nine different techniques using different sponges, tubes, and, Petri plates for feeding nymphs. The detached leaf survived for maximum number of days (8.25 days) with minimum nymphal mortality (12.01%) in the Whitefly Nymphal Feeding System‐1 (WNFS‐1) treatment; therefore, WNFS‐1 was selected for the delivery of dsRNA to B. tabaci nymphs. In WNFS‐1, blue food dye was used to confirm that nymphs were being fed, and the results were evidenced by blue‐coloured bodies. The juvenile hormone esterase (jhe) gene was silenced in order to successfully deliver dsRNA to nymphs using WNFS‐1 and resulting in much higher nymphal mortality (68.36%). Therefore, WNFS‐1 is a reliable method of delivering dsRNA for the purpose of silencing the genes in the nymphal stages of whiteflies. The WNFS system may also be used extensively to evaluate any chemistry (insecticides, hormones, biopesticides, etc.) in nymphs of whitefly.

Nymph development and adult feeding on, and damage to, immature siliquae of canola by different species of stink bugs.

Studies were conducted in the laboratory and in the greenhouse with the objective of evaluating nymph development, adult body weight gain, and damage of different species of pentatomids feeding on fruit (hereafter referred to as siliqua) of canola, Brassica napus (L.) var. oleifera. Nymphs of Nezara viridula (L.) were able to reach adulthood feeding on siliquae (93.3% survivorship), while nymphs feeding on siliquae that had their seeds removed showed arrested development, only reaching the 4th instar and did not complete development to adulthood. Adults of N. viridula gained body weight feeding on canola siliquae, particularly during the first two weeks of adult life, dropping weight thereafter. Adults of another species of pentatomid, Diceraeus furcatus (F.), also gained body weight, while adults of Euschistus heros (F.) lost weight. N. viridula adults caused significantly greater damage to seeds (shrunken and with rotten aspect) within siliqua and to the siliqua walls (whitish spots with lesions in the form of starbursts, called rosettes) compared to D. furcatus and to E. heros. The amount of damaged seeds caused by N. viridula adults during the first week of adult life was greater (ca. 60%) compared to those of older females 32days of age (27%). Damage symptons caused by the feeding activity on siliqua walls (commonly known as rosettes) reached up to 10% of the total area with similar injury rates for N. viridula adults of different ages. The majority of N. viridula (70%) caused rosette, while only 20% of E. heros and 5% of D. furcatus produced similar damage.

Sand lizards (Lacerta agilis) decrease nymphal infection prevalence for tick‐borne pathogens Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum in a coastal dune ecosystem

Abstract Understanding which factors determine tick‐borne disease hazard can contribute to effective disease control. In Europe, the hazard of the pathogens Borrelia burgdorferi s.l. and Anaplasma phagocytophilum is determined by local tick densities (mainly Ixodes ricinus) and the reservoir competence of the host species community. Sand lizards (Lacerta agilis) are common hosts for larvae and nymphs of I. ricinus and non‐competent reservoirs for both pathogens. Consequently, high relative abundance of L. agilis is hypothesized to be associated with lower infection prevalence in nymphs. Here, we aimed to test whether this effectively occurs in natural settings. We sampled different habitat types within a heterogenous dune landscape at the Dutch coast and estimated (1) L. agilis densities, (2) host community competence, (3) the density and infection prevalence of questing I. ricinus ticks and (4) the number and infection prevalence of ticks feeding on L. agilis. Captured L. agilis had high tick burdens and contributed substantially to feeding I. ricinus larvae in their natural habitat. B. burgdorferi s.l. and A. phagocytophilum were virtually absent from feeding larvae and nymphs. The nymphal infection prevalence of both pathogens in questing ticks was lower in habitat types where L. agilis was more abundant. Hence, L. agilis strongly reduced community competence. The density of questing nymphs was higher in habitat types with denser vegetation and also varied more between habitat types than infection prevalence. As a result, nymphal density had a stronger effect on the density of infected ticks than did nymphal infection prevalence. Synthesis and applications. Coastal dune habitats favourable for L. agilis have lower densities of questing nymphs and a lower human infection hazard. These results might be applicable to similar ecosystems where L. agilis is present. From a public health perspective, this underlines the importance of preserving early successional habitat, as encroaching shrubs are associated with higher tick‐borne disease hazard, and vegetation removal might be a solution to reduce hazard in coastal dunes. The high degree of spatial heterogeneity in the abundance of tick‐borne pathogens also poses opportunities to manage recreational activities to limit human exposure to tick‐borne diseases.

Small Brown Planthopper Nymph Infestation Regulates Plant Defenses by Affecting Secondary Metabolite Biosynthesis in Rice

The small brown planthopper (SBPH, Laodelphax striatellus) is one of the most destructive insect pests in rice (Oryza sativa), which is the world's major grain crop. The dynamic changes in the rice transcriptome and metabolome in response to planthopper female adult feeding and oviposition have been reported. However, the effects of nymph feeding remain unclear. In this study, we found that pre-infestation with SBPH nymphs increased the susceptibility of rice plants to SBPH infestation. We used a combination of broadly targeted metabolomic and transcriptomic studies to investigate the rice metabolites altered by SBPH feeding. We observed that SBPH feeding induced significant changes in 92 metabolites, including 56 defense-related secondary metabolites (34 flavonoids, 17 alkaloids, and 5 phenolic acids). Notably, there were more downregulated metabolites than upregulated metabolites. Additionally, nymph feeding significantly increased the accumulation of seven phenolamines and three phenolic acids but decreased the levels of most flavonoids. In SBPH-infested groups, 29 differentially accumulated flavonoids were downregulated, and this effect was more pronounced with infestation time. The findings of this study indicate that SBPH nymph feeding suppresses flavonoid biosynthesis in rice, resulting in increased susceptibility to SBPH infestation.

First record of mayfly Povilla (Languidipes) taprobanes Hubbard from Karnataka

Mayflies are important as macroinvertebrates of aquatic ecosystems and are reliable bioindicators of water quality. Most mayfly nymphs feed by scraping algae from underwater rocks or by extracting food particles in the littoral and benthic zones of the water bodies. The mayfly Povilla (Languidipes) taprobanes originally described from Sri Lanka was observed in plastic lined ponds in coastal Karnataka. Not only, this is the first report of the species from Karnataka, but the unique case making behaviour of this species is also described for the first time. Additionally, the species was found damaging plastic tarpaulins of 750 gsm thickness used as lining for water storage in the tank by chewing. This chewing behaviour was responsible for damage of plastic sheets leading to water leakage. The possible loss caused and a need of alternate strategies to store water is discussed.

A comparison of horizontal and transovarial transmission efficiency of Borrelia miyamotoi by Ixodes scapularis

Borrelia miyamotoi is a relapsing fever spirochete carried by Ixodes spp. ticks throughout the northern hemisphere. The pathogen is acquired either transovarially (vertically) or horizontally through blood-feeding and passed transtadially across life stages. Despite these complementary modes of transmission, infection prevalence of ticks with B. miyamotoi is typically low (<5%) in natural settings and the relative contributions of the two transmission modes have not been studied extensively. Horizontal transmission of B. miyamotoi (strain CT13–2396 or wild type strain) was initiated using infected Ixodes scapularis larvae or nymphs to expose rodents, which included both the immunocompetent CD-1 laboratory mouse (Mus musculus) and a natural reservoir host, the white-footed mouse (Peromyscus. leucopus), to simulate natural enzootic transmission. Transovarial transmission was evaluated using I. scapularis exposed to B. miyamotoi as either larvae or nymphs feeding on immunocompromised SCID mice (M. musculus) and subsequently fed as females on New Zealand white rabbits. Larvae from infected females were qPCR-tested individually to assess transovarial transmission rates. Tissue tropism of B. miyamotoi in infected ticks was demonstrated using in situ hybridization. Between 1 and 12% of ticks were positive (post-molt) for B. miyamotoi after feeding on groups of CD-1 mice or P. leucopus with evidence of infection, indicating that horizontal transmission was inefficient, regardless of whether infected larvae or nymphs were used to challenge the mice. Transovarial transmission occurred in 7 of 10 egg clutches from infected females. Filial infection prevalence in larvae ranged from 3 to 100% (median 71%). Both larval infection prevalence and spirochete load were highly correlated with maternal spirochete load. Spirochetes were disseminated throughout the tissues of all three stages of unfed ticks, including the salivary glands and female ovarian tissue. The results indicate that while multiple transmission routes contribute to enzootic maintenance of B. miyamotoi, transovarial transmission is likely to be the primary source of infected ticks and therefore risk assessment and tick control strategies should target adult female ticks.

Chironji (Buchanania lanzan Spreng.): a new host for Idiocerinae leafhopper Busoniomimus mudigerensis (Viraktamath) Hemiptera: Cicadellidae from India

Idiocerinae leafhoppers are serious pests of economically important fruit crops like mango. Buchanania lanzan Spreng., commonly known as chironji is an underutilized potential dry fruit tree well known for its edible kernels with almond aroma. The Idiocerinae leafhopper species Busoniomimus mudigerensis (Viraktamath) was found to be feeding and damaging the Buchanania lanzan trees in Jhansi, Uttar Pradesh, India. Continuous feeding of nymphs and adults on the tender shoots and leaves resulted in characteristic white speckles on the upper surface of the leaf, downward leaf curling, withering, and drying of tender shoots. Excessive honeydew secretion by nymphs and adults also favored the growth of sooty mold on leaf surfaces were observed under field conditions. Also, the leafhopper genus and species were documented as a new record from North India (Jhansi: Uttar Pradesh) in the present study. Which was earlier restricted only to southern Indian state Karnataka. Taxonomic descriptions for a female are given in this study which is unknown from the original descriptions and the male characters are redescribed with photographic illustrations.

Plasticity in the timing of detachment of an Eurasian-African songbird tick, Ixodes frontalis

In non-permanent parasites, host detachment should take place in an environment that ensures the continuation of their life cycle. Timing of detachment - in combination with the host's space use - affects dispersal and transmission success of the parasites and of the pathogens they vector. Before reaching the adult reproductive stage, ticks need to go through multiple immature developmental stages (larva and nymph), each feeding on host blood. In between the feeding bouts, they often remain in the off-host environment for considerable periods of time. With this study, we aimed to obtain more insight in Ixodes frontalis’ off-host habitat use by comparing its detachment pattern in different life stages with that of two habitat-specialized ticks also found on birds: the endophilic tree-hole tick (Ixodes arboricola) and the exophilic sheep tick (Ixodes ricinus), the latter living in humid understory vegetation of forests. For this, we artificially infested hole-roosting (great tits, Parus major) and open-roosting (blackbirds, Turdus merula) birds with ticks under laboratory conditions, and recorded whether detachment occurred during the day or the night. We hypothesize that nocturnal detachment improves off-host mating opportunities and host localization, whereas diurnal detachment optimizes tick dispersal. Ixodes frontalis nymphs detached during the night, especially when feeding on blackbirds. This behaviour was very similar to that of I. arboricola (larva and nymph) feeding on great tits. In contrast, I. frontalis larvae detached during the day, especially when feeding on great tits, which resembles that of I. ricinus’ feeding behaviour (larva and nymph). Ixodes frontalis left the host within seven days, immediately after completion of the blood meal. This is similar to both developmental stages of I. ricinus but contrasts with the very long (up to 20 days) feeding duration in I. arboricola. Thus I. frontalis shows strong plasticity, switching from dispersal-centered (larvae) to host-centered (nymphs) detachment behaviour. Findings are discussed with regard to the ticks’ habitat use, dispersal, life history and host specificity.

Bovine fecal chemistry changes with progression of Southern Cattle Tick, Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) infestation

Surveillance for cattle fever ticks is an essential activity in the U.S. Cattle Fever Tick Eradication Program which prevents reestablishment of these tick vectors of the pathogens causing bovine babesiosis. Other methods of detecting tick infested cattle could augment current physical inspection of restrained cattle by program inspectors. The objective of this study was to determine whether a single infestation of ∼5000 Rhipicephalus (Boophilus) microplus larvae induced changes in fecal chemistry that were detectable using near-infrared reflectance spectroscopy (NIRS). Fecal samples were collected daily from 6 tick-infested and 6 non-infested Bos taurus yearling heifers. Each infested animal received ticks from one of 6 different strains of laboratory colonies of R. microplus. Date of drop and daily sum of engorged female ticks were tabulated to characterize each infestation. Cluster, common factor, principal component and MANOVA analyses were used to define and assess fecal spectra changes associated with experimental stages of infestation. Cluster analyses found no significant differences in fecal samples from each of the 6 infested heifers. Two shifts in fecal chemistry of infested animals were identified by three clusters of NIRS fecal spectra. The first cluster was comprised of samples from pre-infestation to 9 days after infestation, a period inclusive of larval tick attachment and feeding. The second cluster was comprised of samples from day 10–22 corresponding to the period of nymphal feeding, adult feeding, and early drop of engorged females. A third cluster was comprised of samples from days 23−46 corresponding to the period of engorged female drop and declining tick numbers. A Tukey-Kramer multiple comparison procedure identified significant differences in fecal spectra between five experimental stages of R. microplus infestation for principal component 1 including pre-infestation to nymphal feeding, pre-infestation to adult feeding, larval feeding to adult feeding, nymphal feeding to adult feeding and nymphal feeding to engorged female drop; for principal component 2 including pre-infestation to nymphal feeding, pre-infestation to adult feeding, and pre-infestation to engorged female drop; and for principal component 3 including pre-infestation to drop, and adult feeding to drop. These significant pair-wise comparisons reflect developmental phases of tick attachment and blood-feeding that define periods of increasing, peak and declining stress identified in two fecal chemistry shifts defined by three fecal spectra clusters. Among non-infested animals, two shifts in fecal chemistry were also detected by three fecal-spectra clusters that occurred in synchrony with those of their tick-infested counterparts. There were no significant differences in principal components or MANOVA analyses between infested and non-infested animals and the pattern of significant pair-wise Tukey-Kramer multiple comparisons for non-infested animals were similar to those of infested animals. This unintended confounding effect is attributed to the manner in which all 12 animals were preconditioned as a group, then isolated in randomly assigned blind stalls in a common barn facility for the study, creating the basis for physiological stress resonance among non-infested animals.

Pest categorisation of Bagrada hilaris.

The EFSA Panel on Plant Health performed a pest categorisation of Bagrada hilaris (Hemiptera: Pentatomidae) for the EU territory. B. hilaris, known as the bagrada bug or painted bug, is a polyphagous pest feeding on at least 25 plant families including several economically important brassica crops such as broccoli, cabbage and cauliflower. Other economically important hosts suffering impacts include beans (Fabaceae), wheat and maize (Poaceae). Young plants are particularly vulnerable to adults and nymphs feeding on tender leaves and growing points, which can cause yield losses. B. hilaris occurs in Africa and Asia and has spread to North America (USA and Mexico) and South America (Chile) where there are multiple generations per year. It is not widely distributed in the EU but has been established in Malta and on the Italian island of Pantelleria, south west of Sicily, since the 1970s where it is an economically important pest of capers. The reasons why it has not spread further within southern Europe are unknown. B. hilaris is not a regulated pest in the EU. It could further enter and spread within the EU via the import and movement of host plants or as a hitchhiking species forming aggregations in conveyances and amongst non‐plant traded goods. Host availability and climate suitability suggest that, in addition to Malta and Pantelleria, southern areas of the EU around the Mediterranean would also be suitable for B. hilaris establishment. The introduction of B. hilaris to other Mediterranean areas of the EU would likely cause impacts in a range of crops, particularly brassicas. Measures to prevent entry and spread are available. B. hilaris satisfies all of the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Effects of nymphal density (Bactericera trigonica) and feeding on photosynthetic pigments, proline content and phenolic compounds in carrot plants

Effects of nymphal density (Bactericera trigonica) and feeding on photosynthetic pigments, proline content and phenolic compounds in carrot plants

The Combined Effects of Warming and Body Size on the Stability of Predator-Prey Interactions

Environmental temperature and body size are two prominent drivers of predation. Despite the ample evidence of their independent effects, the combined impact of temperature and predator-prey body size ratio on the strength and stability of trophic interactions is not fully understood. We experimentally tested how water temperature alters the functional response and population stability of dragonfly nymphs (Cordulegaster boltonii) feeding on freshwater amphipods (Gammarus pulex) across a gradient of their body size ratios. Attack coefficients were highest for small predators feeding on small prey at low temperatures, but shifted toward the largest predators feeding on larger prey in warmer environments. Handling time appeared to decrease with increasing predator and prey body size in the cold environment, but increase at higher temperatures. These findings indicate interactive effects of temperature and body size on functional responses. There was also a negative effect of warming on the stability of predator and prey populations, but this was counteracted by a larger predator-prey body size ratio at higher temperatures. Here, a greater Hill exponent reduced feeding at low prey densities when predators were much larger than their prey, enhancing the persistence of both predator and prey populations in the warmer environment. These experimental findings provide new mechanistic insights into the destabilizing effect of warming on trophic interactions and the key role of predator-prey body size ratios in mitigating these effects.

Salicylic acid mediated immune response of Citrus sinensis to varying frequencies of herbivory and pathogen inoculation

BackgroundPlant immunity against pathogens and pests is comprised of complex mechanisms orchestrated by signaling pathways regulated by plant hormones [Salicylic acid (SA) and Jasmonic acid (JA)]. Investigations of plant immune response to phytopathogens and phloem-feeders have revealed that SA plays a critical role in reprogramming of the activity and/or localization of transcriptional regulators via post-translational modifications. We explored the contributing effects of herbivory by a phytopathogen vector [Asian citrus psyllid, Diaphorina citri] and pathogen [Candidatus Liberibacter asiaticus (CaLas)] infection on response of sweet orange [Citrus sinensis (L.) Osbeck] using manipulative treatments designed to mimic the types of infestations/infections that citrus growers experience when cultivating citrus in the face of Huanglongbing (HLB) disease.ResultsA one-time (7 days) inoculation access period with CaLas-infected vectors caused SA-associated upregulation of PR-1, stimulating defense response after a long period of infection without herbivory (270 and 360 days). In contrast, while repeated (monthly) ‘pulses’ of 7 day feeding injury by psyllids stimulated immunity in CaLas-infected citrus by increasing SA in leaves initially (up to 120 days), long-term (270 and 360 days) repeated herbivory caused SA to decrease coincident with upregulation of genes associated with SA metabolism (BMST and DMR6). Similarly, transcriptional responses and metabolite (SA and its analytes) accumulation in citrus leaves exposed to a continuously reproducing population of D. citri exhibited a transitory upregulation of genes associated with SA signaling at 120 days and a posterior downregulation after long-term psyllid (adults and nymphs) feeding (270 and 360 days).ConclusionsHerbivory played an important role in regulation of SA accumulation in mature leaves of C. sinensis, whether or not those trees were coincidentally infected with CaLas. Our results indicate that prevention of feeding injury inflicted by D. citri from the tritrophic interaction may allow citrus plants to better cope with the consequences of CaLas infection, highlighting the importance of vector suppression as a component of managing this cosmopolitan disease.

Heritable variation in host quality as measured through an ectoparasite's performance

Obligate parasites need one or more hosts to complete their life cycle. However, hosts might show intraspecific variation in quality with respect to the parasites themselves, thus affecting on‐host and off‐host parasite performance. High heritability in host quality for the parasite may therefore exert long‐lasting selective pressures on the parasite and influence host–parasite coevolution. However, the amount of variation and heritability in host quality are unknown for most parasite species, especially in wild populations of hosts. Both measures were estimated in a wild‐caught birdParus majorthat was experimentally infested by two developmental stages (larva and nymph) of a ectoparasite (the tickIxodes arboricola). We examined variation in host quality through variation in tick performance, namely the on‐host performance (attachment success, feeding time, engorgement weight and feeding success) and the off‐host performance (moulting time, moulting success and overall survival). Herein we also investigated the influence on tick performance of host traits linked with the bird's life history and physiology such as body condition, sex, age and haematocrit. By correlating tick performance variables between larvae and nymphs feeding on the same bird at different times, we found a significant correlation in attachment success, suggesting consistent among‐host variation for this performance measure, but no significant larva‐nymph correlations for the other tick variables. Animal models relating tick performance variables to the host pedigree showed a strong heritable signal for host quality as measured through tick feeding time, and lower but substantial estimates in other performance variables. With regard to the host traits, feeding success and survival of tick larvae were lower on female birds, and nymphal survival was higher on older birds. Larval feeding time was negatively correlated with host haematocrit. This is one of the first studies showing consistent intraspecific variation and heritability of host quality for a multi‐stage ectoparasite.