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Plant viruses can produce direct and plant-mediated indirect effects on their insect vectors, modifying their life cycle, fitness and behavior. Viruses may benefit from such changes leading to enhanced transmission efficiency and spread. In our study, female adults of Bemisia tabaci were subjected to an acquisition access period of 72 h in Tomato yellow leaf curl virus (TYLCV)-infected and non-infected tomato plants to obtain viruliferous and non-viruliferous whiteflies, respectively. Insects that were exposed to virus-infected plants were checked by PCR to verify their viruliferous status. Results of the Ethovision video tracking bioassays indicated that TYLCV induced an arrestant behavior of B. tabaci, as viruliferous whitefly adults remained motionless for more time and moved slower than non-viruliferous whiteflies after their first contact with eggplant leaf discs. In fact, Electrical Penetration Graphs showed that TYLCV-viruliferous B. tabaci fed more often from phloem sieve elements and made a larger number of phloem contacts (increased number of E1, E2 and sustained E2 per insect, p<0.05) in eggplants than non-viruliferous whiteflies. Furthermore, the duration of the salivation phase in phloem sieve elements (E1) preceding sustained sap ingestion was longer in viruliferous than in non-viruliferous whiteflies (p<0.05). This particular probing behavior is known to significantly enhance the inoculation efficiency of TYLCV by B. tabaci. Our results show evidence that TYLCV directly manipulates the settling, probing and feeding behavior of its vector B. tabaci in a way that enhances virus transmission efficiency and spread. Furthermore, TYLCV-B. tabaci interactions are mutually beneficial to both the virus and its vector because B. tabaci feeds more efficiently after acquisition of TYLCV. This outcome has clear implications in the epidemiology and management of the TYLCV-B. tabaci complex.

Interactions between plants and herbivores are key drivers of evolution and ecosystem complexity. We investigated the role of plant labile carbohydrates and nitrogen on wheat-aphid relations in a 2 2 factorial combining [CO 2 ] and nitrogen supply. We measured life history traits (assay 1) and feeding behaviour (assay 2) of bird-cherry oat aphid ( Rhopalosiphum padi L.) and English grain aphid ( Sitobion avenae F.) forced to feed on single leaf laminae, and reproduction of R. padi in a setting where insects moved freely along the plant (assay 3). Experimental setting impacted aphid traits. Where aphids were constrained to single leaf, high nitrogen reduced their fitness and discouraged phloem feeding. Where aphids could move throughout the plant, high nitrogen enhanced their reproduction. Aphid responses to the interaction between nitrogen and [CO 2 ] varied with experimental setting. The number of R. padi adults varied tenfold with plant growing conditions and correlated negatively with molar concentration of sugars in stem (assay 3). This finding has two implications. First, the common interpretation that high nitrogen favours insect fitness because protein-rich animal bodies have to build from nitrogen-poor plant food needs expanding to account for the conspicuous association between low nitrogen and high concentration of labile carbohydrates in plant, which can cause osmotic stress in aphids. Second, the function of labile carbohydrates buffering grain growth needs expanding to account for the osmotic role of carbohydrates in plant resistance to aphids.

The recent emergence of Xylella fastidiosa in Europe is a major threat to agriculture, including olive, almond and grape. Philaenus spumarius is the predominant vector of X. fastidiosa in Europe. Understanding vector movement is critical for developing effective control measures against bacterial spread. In this study, our goal was to set up a flight-mill protocol to assess P. spumarius flight potential and to analyse how different variables may affect its flight behaviour. We found that P. spumarius was able to fly ≈ 500 m in 30 min with a maximum single flight of 5.5 km in 5.4 h. Based on the observations, the flight potential of the females was higher in spring and autumn than in summer, and that of the males was highest in autumn. Moreover, we found that P. spumarius had a higher flight potential during the morning and the night than during the afternoon. Our results revealed that P. spumarius is likely to disperse much further than the established sizes of the infected and buffer zones designated by the EU. This knowledge on the flight potential of P. spumarius will be critical for improving management actions against P. spumarius and the spread of X. fastidiosa in Europe.

Elevated CO 2 (eCO 2 ) modifies plant primary and secondary metabolism that subsequently impacts herbivore insect performance due to changes in its nutritional requirements. This laboratory study evaluated interactions between Aphis gossypii Glover (Hemiptera: Aphididae) and melon ( Cucumis melo L., Cucurbitaceae), previously acclimated two or six weeks to different CO 2 levels, eCO 2 (700 ppm) or ambient CO 2 (400 ppm). Under eCO 2 , melon plants decreased nitrogen foliar concentration and increased carbon to nitrogen ratio, independently of acclimation period, significantly reducing the content of some amino acids (alanine, asparagine, glycine, isoleucine, lysine, serine, threonine, and valine) and increasing the carbohydrate (sucrose) content in melon leaves. The dilution in some essential amino acids for aphid nutrition could have aggravated the reduction in A. gossypii population growth reared on melon previously acclimated two weeks to eCO 2 , as well as the loss of aphid body mass from two successive generations of A. gossypii reared under eCO 2 on plants previously acclimated two or six weeks to eCO 2 . The response to eCO 2 of phloem feeders, such as aphids, is actually variable, but this study highlights a negative response of A. gossypii to this climate change driver. Potential implications on control of this pest in a global change scenario are discussed.

The meadow spittlebug Philaenus spumarius plays a key role in the transmission of the bacterium Xylella fastidiosa to olive in Apulia (South Italy). Currently, available data on P. spumarius feeding behavior is limited, and a real-time observation of the different steps involved in stylet insertion, exploratory probes, and ingestion, has never been carried out. Therefore, we performed an EPG-assisted characterization of P. spumarius female feeding behavior on olive, in order to detect and analyze the main EPG waveforms describing their amplitude, frequency, voltage level, and electrical origin of the traces during stylet penetration in plant tissues. Thereafter, each of the main waveforms was correlated with specific biological activities, through video recording and analysis of excretion by adults and excretion/secretion by nymphs. Furthermore, the specific stylet tips position within the plant tissues during each of the waveforms observed was assessed by microcomputer tomography (micro-CT). Additional EPG-recordings were carried out with males of P. spumarius on olive, in order to assess possible sex-related differences. P. spumarius feeding behavior can be described by five main distinct waveforms: C (pathway), Xc (xylem contact/pre-ingestion), Xi (xylem sap ingestion), R (resting), N (interruption within xylem phase). Compared to males, females require shorter time to begin the first probe, and their Xi phase is significantly longer. Furthermore, considering the single waveform events, males on olive exhibit longer np and R compared to females.

The majority of plant viruses depend on Hemipteran vectors for their survival and spread. Effective management of these insect vectors is crucial to minimize the spread of vector-borne diseases, and to reduce crop damage. The aim of the present study was to evaluate the effect of various systemic insecticides on the feeding behavior of Bemisia tabaci and Myzus persicae, as well as their ability to interfere with the transmission of circulative viruses. The obtained results indicated that some systemic insecticides have antifeeding properties that disrupt virus transmission by their insect vectors. We found that some of the tested insecticides significantly reduced phloem contact and sap ingestion by aphids and whiteflies, activities that are closely linked to the transmission of phloem-limited viruses. These systemic insecticides may play an important role in reducing the primary and secondary spread of tomato yellow leaf curl virus (TYLCV) and turnip yellows virus (TuYV), transmitted by B. tabaci and M. persicae, respectively.

Philaenus spumarius is a vector of Xylella fastidiosa , one of the most dangerous plants pathogenic bacteria worldwide. There is currently no control measure against this pathogen. Thus, the development of vector control strategies, like generalist predators, such as spiders, could be essential to limit the spread of this vector-borne pathogen. In this study, a polymerase chain reaction (PCR)-based approach was developed to principally detect DNA of P. spumarius in the spider’s gut. Accordingly, 20 primer pairs, targeting the mitochondrial cytochrome oxidase I (COI) and cytochrome b ( cyt B) genes, were tested for specificity, sensitivity, and efficiency in detecting P. spumarius DNA. Overall, two primer sets, targeting COI gene (COI_Ph71F/COI_Ph941R) and the cyt B gene (cytB_Ph85F/cytB_Ph635R), showed the highest specificity and sensitivity, being able to amplify 870 pb and 550 bp fragments, respectively, with P. spumarius DNA concentrations 100-fold lower than that of the DNA of non-target species. Among these two primer sets, the cytB_Ph85F/cytB_Ph635R was able to detect P. spumarius in the spider Xysticus acerbus , reaching 50% detection success 82 h after feeding. The feasibility of this primer set to detect predation of P. spumarius by spiders was confirmed in the field, where 20% of the collected spiders presented positive amplifications.

Trioza erytreae is one natural psyllid vector of Candidatus liberibacter, the causal agent of the citrus greening disease (HLB). Since its introduction in 2014 into the Iberian Peninsula, T. erytreae was able to spread continuously toward southern coastal regions of Portugal and northern coastal regions of the Cantabric sea in Spain. Identifying key areas of potential colonization by the psyllid vector is crucial to anticipate derived problems of establishing the disease. This work aimed to find potential areas that could be colonized by T. erytreae throughout the Iberian Peninsula using 1 km spatial data resolution, a physical barrier, long-distance dispersal events (LDEs), and 30 years of simulation. The bioclimatic suitability of Citrus spp. was used as a surrogate of its spatial distribution and a measure of habitat invasibility. Two localities, one in Portugal and one in Spain, were considered as initial points of the spread of T. erytreae . Four spread scenarios were initially simulated, corresponding to very low, low, medium, and high spread. An altitude of 400 m was included in the model as a physical barrier, and cells up to 500 km apart were allowed to be colonized due to LDEs. In this work, three key risk areas were identified, the citrus-growing areas of Setúbal (Portugal) and Huelva (Spain), and the potential corridors that may connect Guipúzcoa, where T. erytreae is already present, with the Ebro valley (Spain). Future modeling and simulation studies should include biological constraints such as the effect of parasitoids on the population of T. erytreae (e.g., Tamarixia dryi ) and other barriers or corridors.

Huanglonbing (HLB) is the most serious disease of citrus in the world, associated with three non-cultivable phloem-restricted bacteria Liberibacter asiaticus ( Las), L. africanus ( Laf) and L. americanus ( Lam). Las is transmitted by the Asian citrus psyllid , and has spread to several countries. The African psyllid , the vector of Laf occurs in Africa and neighbouring islands. Only two major citrus-growing regions - Australia/New Zealand and the Mediterranean Basin - are still HLB-free in the world. However, has recently been introduced into continental Europe (Portugal and Spain) and has become a potential threat to citrus production. The transmission of Las by had been postulated but never tested. To evaluate the risk of transmitting Las, comparative transmissions of Las by and were assessed. Transmission tests were performed on excised leaves and seedlings of with different inoculation access periods (in series) for both insect species. Quantifications of bacterial titers were made in excised leaves, seedlings three and six months after inoculation and on individual insects. Our results showed that was able to efficiently acquire Las. Furthermore, carried significantly higher bacterial titers than , and was able to efficiently transmit the bacteria to seedlings at a similar rate that highlighting the high risk of spread of the most aggressive variant of HLB ( Las) by in Europe. Thus, extreme precautions to prevent any entry of Las into Europe should be adopted.

Assessing the potential of spread of an introduced crop pest in a new country is crucial to anticipating its effects on crop production and deriving phytosanitary management toward reducing potential negative effects. Citrus production represents a key agricultural activity throughout the Mediterranean basin. The African citrus psyllid Trioza erytreae (del Guercio, 1918) (Hemiptera: Triozidae) is a natural vector of Candidatusliberibacter spp., the causal agent of the harmful disease huanglongbing (HLB) or “citrus greening disease”. In continental Europe, T. erytreae was detected for the first time in northwestern Spain in 2014. Pest risk analysis (PRA) approaches, such as modeling, consider both time and space components to predict the potential distribution of pests in a given region. In this work, we aim to parameterize a model able to predict the expected spread of T. erytreae in the Iberian Peninsula using three types of PRA models. The kernel model with two hypothetical entry points accurately predicted the distribution of T. erytreae with respect to latitude. This model should be further refined and validated to support decision-makers in the adoption of timely and successful management and regulatory measures against the spread of T. erytreae to other citrus-producing areas in Europe.