Electrical Penetration Graph Waveforms Research Articles

Reliable Augmentation and Precise Identification of EPG Waveforms Based on Multi-Criteria DCGAN

The electrical penetration graph (EPG) technique is of great significance in elucidating the mechanisms of virus transmission by piercing-sucking insects and crop resistance to these insects. The traditional method of manually processing EPG signals encounters the drawbacks of inefficiency and subjectivity. This study investigated the data augmentation and automatic identification of various EPG signals, including A, B, C, PD, E1, E2, and G, which correspond to distinct behaviors exhibited by the Asian citrus psyllid. Specifically, a data augmentation method based on an improved deep convolutional generative adversarial network (DCGAN) was proposed to address the challenge of insufficient E1 waveforms. A multi-criteria evaluation framework was constructed, leveraging maximum mean discrepancy (MMD) to evaluate the similarity between the generated and real data, and singular value decomposition (SVD) was incorporated to optimize the training iterations of DCGAN and ensure data diversity. Four models, convolutional neural network (CNN), K-nearest neighbors (KNN), decision tree (DT), and support vector machine (SVM), were established based on DCGAN to classify the EPG waveforms. The results showed that the parameter-optimized DCGAN strategy significantly improved the model accuracies by 5.8%, 6.9%, 7.1%, and 7.9% for DT, SVM, KNN, and CNN, respectively. Notably, DCGAN-CNN effectively addressed the skewed distribution of EPG waveforms, achieving an optimal classification accuracy of 94.13%. The multi-criteria optimized DCGAN-CNN model proposed in this study enables reliable augmentation and precise automatic identification of EPG waveforms, holding significant practical implications for understanding psyllid behavior and controlling citrus huanglongbing.

Identification and Evaluation of Sugarcane Cultivars for Antixenosis Resistance to the Leafhopper Yamatotettix flavovittatus Matsumura (Hemiptera: Cicadellidae).

Understanding the settling preference, feeding behavior, honeydew production, and biophysical factors, such as trichome density, related to Y. flavovittatus leafhopper infestation in sugarcane cultivation is crucial for effective pest management strategies. This study investigated these aspects across nine sugarcane cultivars. Significant variability was observed among cultivars in terms of settling behavior, with KK3 and LK92-11 showing the highest number of settled leafhopper adults. Similarly, honeydew production varied significantly among cultivars, with KK3 and LK92-11 exhibiting the highest production. Employing the electrical penetration graph (EPG) technique provided insights into distinct probing behaviors across cultivars, highlighting correlations between settling preference, honeydew production, and specific EPG waveforms. Principal component analysis (PCA) categorized cultivars into four groups based on settling preference, honeydew production, feeding behavior, and biophysical factors. Strong correlations were found between settling preference, honeydew production, and various EPG waveforms, while negative correlations were observed with the number of silica cells and rows per unit area, indicating their potential role in deterring leafhopper settlement. We concluded that TPJ04-768 and K84-200 are promising for resistance against leafhoppers and, thereby, can be exploited in sugarcane breeding programs with regard to resistance against insects.

Waveforms Eavesdropping Prevention Framework: The Case of Classification of EPG Waveforms of Aphid Utilizing Wavelet Kernel Extreme Learning Machine

ABSTRACT Since all information depends solely on the training data, machine learning algorithms typically do not employ external knowledge or other experiences during the learning process. Methods for machine learning have been rigorously tested against novel varieties of highly technical “black box” or “white box” adversarial attacks. By employing attacks, attackers can change systems to serve a harmful end goal. When authorized implementers and eavesdroppers are geographically close together, it is difficult to perform secure beamforming in waveform applications, for instance, leading to erroneous beam forms and, as a result, disastrous beam leakages. As a result, the first move in a prospective black-box offense will be based on the waveform features of a learning signal. By including a non-orthogonality concept into the physical layer signal waveform, the Waveforms Eavesdropping Prevention Framework (WEPF) proposed in this work aims to boost machine learning security to address these difficulties. The implementation scenario is based on a waveforms scenario used to categorize the Electrical Penetration Graph (EPG) for insects, a crucial tool for researching the feeding conduct of piercing-sucking insects and the transition mechanism between viruses and insects. An attribute vector with six dimensions, consisting of low-frequency wavelet energy (LFWE) in the second and third layers of the Wavelet Kernel Extreme Learning Machine, fractal box dimension (FBD), the Hurst exponent (HE), and spectral centroid (SC) in the first two layers of the HHT, was used to test the proposed framework. Two adversarial scenarios were explored. However, the suggested architecture secures all waveform signals, demonstrating the method’s effectiveness in lowering the risk of eavesdropping or tampering with the waveforms used in advanced machine-learning methods.

Host assessment and feeding behaviour of adult female Glycaspis brimblecombei on preferred and non‐preferred eucalypts

AbstractInsect herbivores assess plants by integrating responses elicited by a variety of external and internal cues and signals mediated by physical and chemical traits. We investigated host assessment behaviours of adult females of the Eucalyptus‐feeding psyllid, Glycaspis brimblecombei Moore (Hemiptera: Aphalaridae), on 10 species and subspecies (comprising preferred and non‐preferred hosts) using video recordings, electrical penetration graph (EPG) technology, and histological examination of tissues surrounding secondary veins. Our video recordings indicated that the shortest first searching time (mean 7.5 s) occurred on preferred hosts. Females placed on novel (non‐preferred) hosts jumped off leaves in <10 s. We found that host acceptance occurred surprisingly rapidly after stylet penetration, e.g., between 7 and 11 s on preferred eucalypts, suggesting a strong role for gustatory cues. Our histological studies provided no evidence of physical barriers to phloem access. Females produced eight EPG waveforms, as observed for other psyllids and aphids, but the durations of PG (xylem activity) and PE2 (phloem ingestion), in particular, were unlike those recorded for any other hemipteran. On preferred hosts, phloem ingestion represented 21.5% (mean duration 4 h 18 min) of individual feeding bouts, whereas on non‐preferred hosts, there was almost no ingestion from phloem. Xylem ingestion on non‐preferred hosts represented 20.1% (mean duration 4 h 1 min) of feeding bouts, presumably to imbibe water. Thus, contrary to widespread belief, female G. brimblecombei did not feed exclusively from phloem even on preferred hosts, but also regularly ingested from the xylem. This is surprising considering that nymphs construct lerps consisting of approximately 16% sugars, and suggests that adults feed from phloem for shorter periods than offspring. Rapid assessment of hosts could also mean that positive stimuli induced by sugars are opposed by negative gustatory stimuli experienced in non‐vascular tissues. The most likely source of such stimuli are water‐soluble polyphenolic compounds that are widespread in cell vacuoles.

Real-Time Feeding Behavior Monitoring by Electrical Penetration Graph Rapidly Reveals Host Plant Susceptibility to Crapemyrtle Bark Scale (Hemiptera: Eriococcidae).

Simple SummaryCrapemyrtle bark scale (CMBS; Acanthococcus lagerstroemiae), an invasive polyphagous sap feeder in the United States, has spread across 16 U.S. states in less than two decades, posing potential risks to the Green Industry. Confirming the host range is crucial for effective pest management of invasive insects. However, host range confirmation relying on greenhouse or field trials is often inefficient and time-consuming. In this study, we used the electrical penetration graph (EPG) to monitor the stylet penetration of CMBS in plant tissue in real-time. An R programming-based application was developed to better characterize the insect EPG waveforms recorded by EPG. By analyzing EPG-based EPG parameters, we demonstrated that CMBS has difficulty accessing the phloem tissue (salivation and ingestion) of a resistant plant compared to a susceptible plant. Importantly, we hereby present CMBS typical feeding behaviors on susceptible and non-susceptible plants comparatively, which provides direct evidence for revealing unknown hosts rapidly.Host range confirmation of invasive hemipterans relies on the evaluation of plant susceptibility though greenhouse or field trials, which are inefficient and time-consuming. When the green industry faces the fast-spreading threat of invasive pests such as crapemyrtle bark scale (Acanthococcus lagerstroemiae), it is imperative to timely identify potential host plants and evaluate plant resistance/susceptibility to pest infestation. In this study, we developed an alternative technology to complement the conventional host confirmation methods. We used electrical penetration graph (EPG) based technology to monitor the A. lagerstroemiae stylet-tip position when it was probing in different plant tissues in real-time. The frequency and relative amplitude of insect EPG waveforms were extracted by an R programming-based software written to generate eleven EPG parameters for comparative analysis between plant species. The results demonstrated that the occurrences of phloem phase and xylem phase offered conclusive evidence for host plant evaluation. Furthermore, parameters including the percentage of insects capable of accessing phloem tissue, time duration spent on initiating phloem phase and ingesting phloem sap, provided insight into why host plant susceptibility differs among similar plant species. In summary, this study developed a novel real-time diagnostic tool for quick A. lagerstroemiae host confirmation, which laid the essential foundation for effective pest management.

Simplified and rapid staining of leafhopper salivary sheaths in plant tissues for electrical penetration graph waveform correlations

Herbivorous insects in the order Hemiptera use piercing-sucking mouthparts to utilize plant sap. Among them salivary sheath feeders penetrate into the plant by their flexible stylets to reach vascular elements. Manoeuvering stylets in plant tissues is aided by the creation of salivary sheaths, which solidify from proteinous gelling saliva and remain as lasting artefacts in the plant tissues. Studying their structure reveals hidden details of the feeding behaviour and the transmission of pathogens in case of vector insects. One important aspect of studying salivary sheaths is that it can be used to confirm the biological function of electropenetrography (EPG) waveform patterns. Previously, complex and vaguely documented histological methods have been used to observe salivary sheath structure. Building on existing methodologies, we report a simplified histological procedure where each step was optimized to offer a rapid process that does not require special equipment, can be applied to many samples, has good success rate and a low cost of errors in terms of time and materials. We describe the procedure, using a Psammotettix alienus – barley model system, in three steps. (i) Clarification of entire plant parts and pre-staining salivary sheaths with aqueous fuchsin. This step allows to identify salivary sheath starting points on the surface. (ii) Knowing salivary sheath location, using hand sectioning, produce a single c. 60 μm section that contains the entire salivary sheath. (iii) Counterstain the section with methylene green and, after further clarification, study under light microscope in a glycerol - ethanol embedding solution, without fixed mounting.

Comparative Analysis of Stylet Penetration Behaviors of Eriosoma lanigerum (Hemiptera: Aphididae) on Main Apple Cultivars in China

The preference and behavioral mechanism of the feeding behavior of the woolly apple aphid, Eriosoma lanigerum (Hausmann), on Chinese apple cultivars was investigated using the electrical penetration graph (EPG) technique. Feeding of adult aphids was assessed for the four main cultivars of apple in China (Red Fuji, Ralls Genet, Starkrimson, and Jonagold) over an 8-h monitoring period, what that of fourth-instar nymphs was assessed for 8 h on Jonagold only. EPG waveforms representing the details of probing behaviors, parameters were measured for analysis. We found that at the nonphloem phase, the total duration of the nonpenetration (np) waveform and the total duration of the stylet pathway phase (the 'C wave') on Ralls Genet and Starkrimson were significantly longer than on Red Fuji. In addition, the phloem-feeding phase, the total duration of 'release of saliva into the phloem', (the E1 waveform) was significantly longer on Ralls Genet and Jonagold than on Red Fuji. The total duration of the 'ingestion from sieve cells' phase (the E2 waveform) on Red Fuji, meanwhile, was significantly longer than on Ralls Genet or Starkrimson. At the same time, when combined with EPG parameters, Red Fuji was found to have no obvious resistance to woolly apple aphid and to be a susceptible cultivar. This experiment also recorded the feeding waveform of fourth-instar aphid nymphs. Based on the phloem and nonphloem parameters recorded in this study, it was inferred that adult aphids are more likely than nymphs to feed on apple trees.

Barley yellow dwarf virus Can Be Inoculated During Brief Intracellular Punctures in Phloem Cells Before the Sieve Element Continuous Salivation Phase.

The distinguished intracellular stylet puncture called phloem-pd (potential drop [pd]) produced by Myzus persicae has been associated with the transmission of the semipersistently transmitted, phloem-limited Beet yellows virus (BYV, Closterovirus). However, the production of intracellular punctures in phloem cells (phloem-pd) by other aphid species and their role in the transmission of persistently transmitted, phloem-limited viruses are still unknown. Previous studies revealed that inoculation of the persistently transmitted, phloem-limited Barley yellow dwarf virus (BYDV, Luteovirus) is associated mainly with the sieve element continuous salivation phase (E1 waveform). However, the role of brief intracellular punctures that occur before the E1 phase in the inoculation of BYDV by aphids is unknown. We aimed to investigate whether the bird cherry-oat aphid Rhopalosiphum padi (Hemiptera: Aphididae) produced a stereotypical phloem-pd and to study its role in the inoculation of BYDV. The feeding behavior of viruliferous R. padi individuals in barley (Hordeum vulgare) was monitored via the electrical penetration graph (EPG) technique. The feeding process was artificially terminated after the observation of specific EPG waveforms: standard-pds, phloem-pd, and E1. Analysis of the EPG recordings revealed the production of a phloem-pd pattern by R. padi, in addition to a short, distinct E1-like pattern (short-E1), both resulting in successful inoculation of BYDV. Also, the transmission efficiency of BYDV was directly proportional to the time spent by aphids in intracellular salivation in phloem cells. Finally, we discussed the main differences between the inoculation process of semipersistent and persistently transmitted phloem-limited viruses by aphids.

An analysis of the feeding behavior of three stages ofToxoptera citricidabyDCelectrical penetration graph waveforms

AbstractWith the purpose of studying the feeding behavior of the brown citrus aphid pest,Toxoptera citricida(Kirkaldy) (Hemiptera: Aphididae), we compared stylet probing behaviors of third and fourth instars and adults onCitrus unshiuMarc (Rutaceae) seedlings using the electrical penetration graph (EPG) technique.EPGwaveforms exhibited the full suite of stylet behaviors – stylet pathway, intracellular stylet puncture, phloem salivation (E1), sieve ingestion (E2), and xylem sap ingestion activities, plus the non‐penetration (Np) waveform. Before the phloem phase, the number of probes was significantly higher for third‐instar nymphs than for adults. Overall duration of Np events by adults was significantly lower than the duration of third and fourth instars. The number of short probes of the fourth instars was significantly higher than that of the adults. In the phloem phase, adults made more frequent and longer E1 events than the third and fourth instars. Third instars made more frequent but shorter E2 events, whereas adults made fewer but longer events. These results showed adults gained nutrients by increasing feeding time during phloem ingestion. Thus, the probability of phloem‐associated virus acquisition and transmission ofT. citricidawas higher in adults than in nymphs.

Acizzia solanicola (Hemiptera: Psyllidae) probing behaviour on two Solanum spp. and implications for possible pathogen spread.

Piercing-sucking insects are vectors of plant pathogens, and an understanding of their feeding behaviour is crucial for studies on insect population dynamics and pathogen spread. This study examines probing behaviour of the eggplant psyllid, Acizzia solanicola (Hemiptera: Psyllidae), using the electrical penetration graph (EPG) technique, on two widespread and common hosts: eggplant (Solanum melongena) and tobacco bush (S. mauritianum). Six EPG waveforms were observed: waveform NP (non-probing phase), waveform C (pathway phase), G (feeding activities in xylem tissues), D (first contact with phloem tissues), E1 (salivation in the sieve elements) and E2 (ingestion from phloem tissues). Results showed that A. solanicola is predominantly a phloem feeder and time spent in salivation and ingestion phases (E1 and E2) differed between hosts. Feeding was enhanced on eggplant compared to tobacco bush which showed some degree of resistance, as evidenced by shorter periods of phloem ingestion, a higher propensity to return to the pathway phase once in the sieve elements and higher number of salivation events on tobacco bush. We discuss how prolonged phloem feeding could indicate the potential for A. solanicola to become an important pest of eggplant and potential pathogen vector.

Characterization of the electrical penetration graphs of the psyllid Bactericera trigonica on carrots

AbstractThe psyllid Bactericera trigonica Hodkinson (Hemiptera: Triozidae) is a carrot and celery pest recently described as a vector of the plant pathogenic bacterium Candidatus Liberibacter solanacearum (Lso) on Apiaceae. Detailed information on vector stylet penetration activities is essential in the study of Lso transmission. In this study we used the electrical penetration graph (EPG) technique, characterized waveforms produced during the various stylet penetration activities in carrot leaves, and correlated them with stylet tracks and salivary sheath termini on plant tissues as well as with Lso inoculation. In addition, the effect of Lso in B. trigonica on the stylet penetration activities was tested. The EPG waveforms identified were: waveforms C1 and C2 detected in the mesophyll, waveforms D, E1, and E2 near or in the phloem sieve elements, and waveform G in the xylem vessels. A waveform pattern not previously reported for psyllids was the ‘pseudo‐potential drop’ (pseudo‐pd), characterized by sudden voltage dips similar to potential drops. However, the lowered voltage appeared to be inverted when the plant voltage is negative, indicating that it is caused by an increased resistance period and not due to a cell puncture. A direct correlation is shown between the waveform E1 and salivation into phloem sieve elements by B. trigonica as the inoculation of Lso occurred in a period as short as 30 s of E1; Lso transmission occurred in 17 of 35 plants (48%). Stylet activities during waveforms C or D had no consequences on the inoculation of Lso. In conclusion, Lso infection directly affects the probing behaviour of B. trigonica by increasing the total duration of C and D waveforms, but not variables related to phloem salivation (Lso inoculation) or ingestion (Lso acquisition). The reported information here is fundamental for identifying the psyllid vector traits of behaviour associated with transmission of Lso to Apiaceae.

Characterization of Direct Current-Electrical Penetration Graph Waveforms and Correlation With the Probing Behavior of Matsumuratettix hiroglyphicus (Hemiptera: Cicadellidae), the Insect Vector of Sugarcane White Leaf Phytoplasma.

The leafhopper Matsumuratettix hiroglyphicus (Matsumura) (Hemiptera: Cicadellidae) is an important vector of phytoplasma causing white leaf disease in sugarcane. Thus, the aim of our study was to understand and describe the stylet-probing activities of this vector while feeding on sugarcane plants, by using direct current (DC) electrical penetration graph (EPG) monitoring. The EPG signals were classified into six distinct waveforms, according to amplitude, frequency, voltage level, and electrical origin of the observed traces during stylet penetration into the host plant tissues (probing). These six EPG waveforms of probing behavior comprise no stylet penetration (NP); stylet pathway through epidermis, mesophyll, and parenchymal cells (waveform A); contact at the bundle sheath layer (waveform B); salivation into phloem sieve elements (waveform C); phloem sap ingestion (waveform D); and short ingestion time of xylem sap (waveform E). The above waveform patterns were correlated with histological data of salivary sheath termini in plant tissue generated from insect stylet tips. The key findings of this study were that M. hiroglyphicus ingests the phloem sap at a relatively higher rate and for longer duration from any other cell type, suggesting that M. hiroglyphicus is mainly a phloem-feeder. Quantitative comparison of probing behavior revealed that females typically probe more frequently and longer in the phloem than males. Thus, females may acquire and inoculate greater amounts of phytoplasma than males, enhancing the efficiency of phytoplasma transmission and potentially exacerbating disease spreading. Overall, our study provides basic information on the probing behavior and transmission mechanism of M. hiroglyphicus.

Monitoring and characterization of DC electrical penetration graph waveforms of tea green leafhopper, Empoasca onukii, on tea plants

AbstractThe tea green leafhopper, Empoasca onukii (Homoptera: Cicadellidae), is a serious pest of “Yabukita”, the most popular tea cultivar in Japan. This study investigated its stylet‐probing behavior with a direct current (DC) electrical penetration graph (EPG) system. The EPG signals were classified into four distinct waveforms according to amplitude, frequency, voltage level and electrical origin. The waveforms were then characterized by fast Fourier transformation. The waveforms were correlated with distinct feeding behaviors: Np, non‐probing, when stylets were not inserted; Eo1, putative pathway and channel‐cutting phase, when stylets were inserted but not ingesting sap; Eo2, putative phloem phase, when the leafhoppers were probably ingesting from phloem; and Eo3, putative non‐phloem phase, when the leafhoppers were probably ingesting from mesophyll. Mean durations of waveforms showed that E. onukii likely ingested plant fluid mainly from phloem and partly from mesophyll. The description of DC EPG waveforms associated with feeding behaviors of this serious pest constitutes a fundamental step toward the understanding of the resistance mechanisms of the host plants against herbivorous insects.

Plant penetration activities by the flatid planthopper Metcalfa pruinosa (Hemiptera: Fulgoroidea): an electrical penetration graph‐histology analysis

AbstractThe citrus flatid planthopper, Metcalfa pruinosa Say (Hemiptera: Flatidae), is a very polyphagous native insect in North America and currently a serious pest in Europe and South Korea. To understand the feeding behaviour of M. pruinosa, stylet penetration behaviour of M. pruinosa was investigated with an electrical penetration graph (EPG) system. This study reports seven EPG waveforms related to M. pruinosa feeding behaviour: np (no stylet penetration), Mp1 (initiation of stylet penetration), Mp2 (stylet movement and salivation), Mp4 (phloem feeding), Mp4‐H (honeydew excretion), Mp5 (xylem feeding) and Mp6 (unknown). To determine respective feeding behaviour related to the Mp4 and Mp5 waveforms, stylets were cut with a laser beam, and the location of the stylet tip within plant tissue was examined. We found plant sap was exuded from the severed stylets only when the Mp4 waveform was observed, suggesting phloem sap ingestion. The stylet tip was located in the xylem region, indicating xylem‐feeding activity, when the Mp5 waveform was observed. The analysis of 24 different EPG parameters suggests that M. pruinosa stylets reached the vascular bundle of a plant within ca. 5 min and spend ca. 70% of the time feeding on xylem and phloem feeding. This is the first study that reports seven distinctive EPG waveforms with respect to the feeding behaviour of M. pruinosa which could help determine host specificity and host plant susceptibility.

EPG를 이용한 담배가루이(Bemisia tabaci)의 섭식행동과 Cyantraniliprole에 대한 섭식변화

Feeding behaviors of the sweet potato whitefly, Bemisia tabaci, and changing of their feeding behaviors were recorded and analyzed with an Electrical Penetration Graph (EPG) analysis against cyantraniliprole. The characteristic patterns of feeding behaviors investigated were as follows; NP (non probing), pathway phase waveform, waveform of feeding xylem. In results, B. tabaci did not almost feeding the phloem. And It was not appeared potential drop during recording time. It was predominantly indicated pathway activity waveform and waveform of xylem feeding. After treatment of cyantraniliprole with recommended concentrations to tomato plants, EPG waveforms were recorded during 3 hours. Cyantraniliprole treatment showed longer time to first feeding xylem than untreated (P=0.043). It was showed shorter duration of first feeding xylem than untreated (P=0.017). And it was showed longer NP (non-probing) time than untreated. Consequently, It was supposed that cyantraniliprole was effect of anti-feeding or avoidance to B. tabaci.

Aphid-AutoEPG software for analysing electrically monitored feeding behaviour of aphids

Aphid-AutoEPG is a new software program, developed to acquire and automatically analyse electrical penetration graph (EPG) signals used for monitoring plant penetration by aphids. Characteristically EPG signals include waveforms that allow one to study the effects of plants on the acquisition and transmission of viruses, plant protection substances on pests and identify the location of resistance in plants to aphids. The success of electrical monitoring arises from the fact that different species of aphids generate similar EPG patterns. But the visual analysis of EPG waveforms in recorded signals is very time consuming, which has greatly hampered the wider application of EPG technology. To overcome this Aphid-AutoEPG software was developed, which has been extensively tested using data files for several different species of aphids, M. persicae, A. frangulae gossypii, M. albifrons, S. avenae, B. brassicae and N. ribis-nigri. The results have also been compared with visual analyses using Stylet+ software. When used in combination with the user friendly correction options Aphid-AutoEPG is not only easy to use but can also result in a considerable saving in terms of time.

Characterization and Correlation of EPG Waveforms of Bactericera Cockerelli (Hemiptera: Triozidae): Variability in Waveform Appearance in Relation to Applied Signal

AbstractThe tomato-potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), was recently shown to be a vector of “Candidatus Liberibacter solanacearum” (Lso), a phloem-limited bacterium that is the putative causal agent of “zebra chip” in potato and unnamed diseases in other solanaceous species. Despite its importance, very little is known about B. cockerelli stylet probing behaviors that control transmission of Lso to its host plants. Herein, we report the first study characterizing the electrical penetration graph waveforms representing stylet penetration behaviors of the B. cockerelli feeding on potato. Waveforms produced by adult B. cockerelli on potato were also correlated using light microscopy of salivary sheath termini in plant tissue after probes were artificially terminated during the identified waveforms. In addition, behavioral activities were inferred based on electrical origins of waveforms as well as similarities in waveform appearances with those of other psyllids, aphids, and whiteflies. Adult B. cockerelli produced six waveform families and four types, which represent the following proposed biological meanings: family A, initial penetration and sheath salivation; family B, penetration of epidermal cells; family C, secretion of most of the salivary sheath and stylet pathway in mesophyll and parenchyma, with two types, C1 and C2, of unknown meaning; family D, initial contact with phloem cells; family E, activities in phloem cells, with two types, El, putative phloem salivation, and E2, phloem sap ingestion; and family G, xylem ingestion. In addition, a previously unreported variant of waveform G was characterized and correlated with applied signal type. Variation in D and G waveform appearances was correlated with polarity, type, and magnitude of applied signal. Results suggest that active phloem sap ingestion during E2 may play a critical role in acquisition of Lso bacterial cells. E1 may be important in inoculation of the bacterium into phloem sieve elements because it may represent salivation into phloem sieve elements. Analysis of B. cockerelli waveforms could lead to faster development of resistant host plant varieties, strengthen integrated pest management strategies by incorporating alternative plant hosts, and maximize the efficiency of pesticides.

Stylet penetration activities linked to the acquisition and inoculation of Candidatus Liberibacter solanacearum by its vector tomato potato psyllid

AbstractThe tomato potato psyllid (TPP), Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), is the main vector of the bacterium Candidatus Liberibacter solanacearum (Lso), a major disease of solanaceous crops. Feeding of TPP is associated with Lso transmission. However, very little is known about the stylet penetration activities linked to acquisition and inoculation of Lso. The electrical penetration graph (EPG)‐DC system was used to monitor stylet penetration activities during acquisition and inoculation of Lso by individual TPP on tomato [Solanum lycopersicum L. (Solanaceae)]. Female TPP from Lso‐free and Lso‐infected colonies were used in acquisition and inoculation tests, respectively. In the acquisition tests, TPP were tested for Lso after EPG recording of their stylet penetration activities on Lso‐infected tomato shoots. In the inoculation tests, samples from the tomato plants on which the stylet penetration of Lso‐infected TPP had been recorded were tested for Lso infection. The relationships between qPCR results and the EPG waveforms (C, G, D, E1, and E2) representing the main stylet penetration activities performed by individual insects in inoculation and acquisition tests were investigated. Results confirmed that a single adult TPP is capable of infecting a plant with Lso. Our data suggest that acquisition of the bacteria occurs during phloem ingestion (E2), and inoculation is likely associated with salivation into the phloem sieve elements (E1). The durations of EPG parameters were not significantly different between Lso‐infected and Lso‐free TPP (later shown by qPCR) in acquisition tests. In inoculation tests, the durations of E1 or E2 recorded from TPP on Lso‐infected and Lso‐free plants that were later shown by qPCR were not significantly different. However, C was shorter on Lso‐infected plants than on Lso‐free plants, where TPP performed phloem activities. The minimum plant access period required for Lso transmission by a single TPP was estimated to be ca. 2 h, with an acquisition threshold of about 36 min.

EPG-Calc: a PHP-based script to calculate electrical penetration graph (EPG) parameters

Electrical penetration graph (EPG) technique is a powerful tool to investigate the hidden feeding behavior of piercing–sucking insects allowing to link recorded EPG waveforms to stylet penetration and complex behaviors related to feeding activities occurring within plant tissue. Calculating the numerous EPG parameters necessary to unravel the complex insect–plant interactions is very time consuming, and few tools have been developed to automate it. EPG-Calc is a rich internet application intended to fill this gap, providing a fast and user-friendly web-based interface that uses analysis files from dedicated software (STYLET+) or database-compatible CSV text files containing waveform codes and cumulative time as input, and produces output files in database-compatible CSV text or Microsoft Excel® XLS format that are directly usable by different statistical analysis softwares. EPG-Calc greatly reduces the time needed for EPG parameters calculation and allows to calculate more than 100 different parameters based on standardized definitions and calculus methods in such a way that avoid confusion between all kinds of definitions and calculations by individual authors.

Probing behavior of Empoasca vitis (Homoptera: Cicadellidae) on resistant and susceptible cultivars of tea plants.

Feeding activities of the tea green leafhopper, Empoasca vitis (Gothe) (Homoptera: Cicadellidae), on resistant and susceptible cultivars of tea plants (Camellia sinensis L.) were recorded and analyzed using the direct current electrical penetration graph (EPG) system. Six distinct EPG waveforms characterizing the feeding behavior of the tea green leafhopper, categorized as waveforms A, C, E, S, F, and R, were obtained during the investigation. Duration of passive ingestion, possibly of phloem (E), was the longest among all the probing waveforms on susceptible cultivars, whereas durations of the salivation (S) waveform and stylet work waveform (F) became longer on resistant cultivars. The durations of waveforms S and F on the resistant cultivar Jiandecha were slightly longer than those on the less resistant cultivar Yunguidaye , and both were significantly longer than those on the susceptible cultivars Hangzhoudaye and Zhushan-1 . Waveform E was shorter on the resistant cultivar Jiandecha than on the less resistant cultivars Yunguidaye and was significantly shorter than on the susceptible cultivars ( Hangzhoudaye and Zhushan-1 ). It is suggested that E, S, and F are the important waveforms related to leafhopper feeding behavior and tea plant resistance. Based on the results, the resistance levels of tea cultivars against the tea leafhopper can be evaluated quickly by direct current EPG.