Grapevine Pest Research Articles

Explainable olive grove and grapevine pest forecasting through machine learning-based classification and regression

Pests significantly impact agricultural productivity, making early detection crucial for maximizing yields. This paper explores the use of machine learning models to predict olive fly and red spider mite infestations in Andalusia. Four datasets on crop phenology, pest populations, and damage levels were used, with models developed using the Python package H2O, which focuses on interpretability through SHAP values and ICE plots. The results showed high precision in predicting pest outbreaks, particularly for the olive fly, with minimal differences between models using feature selection. In the vineyard dataset, the selection of characteristics improved the performance of the model by reducing the MAE and increasing R2. Explainability techniques identified solar radiation and wind direction as key factors in olive fly predictions, while past pest occurrences and wind velocity were influential for red spider mites, providing farmers with actionable insights for timely pest control.

Geographical, Seasonal, and Growth-Related Dynamics of Gut Microbiota in a Grapevine Pest, Apolygus spinolae (Heteroptera: Miridae)

A number of insects are associated with gut symbiotic microorganisms, wherein symbiotic partners play pivotal metabolic roles for each other such as nutrient supplementation, diet degradation, and pesticide detoxification. Despite the ecological and evolutionary importance of gut microbial communities in insects, their diversity and dynamics remain unclear in many species. The green plant bug Apolygus spinolae, a notorious grapevine pest in Japan, damages grape shoots and severely reduces grape berry yield and quality. The plant bug possesses a simple tubular gut housing ~ 104 bacteria. Here, we investigated geographic, seasonal, and growth-related dynamics of gut microbiota by high-throughput sequencing in 82 individuals (11 nymphs and 71 adults) from five locations in Hokkaido, Japan. In plant bugs, gut microbiota changed dynamically depending on region, season, and developmental stage. Among the gut bacteria, Serratia was consistently and abundantly detected and was significantly affected by seasonal changes. In addition, Caballeronia, known as a specific symbiont in some stinkbug species, was abundantly detected, especially in insects collected in late summer despite A. spinolae complete lack of midgut crypts known as symbiotic organ harboring Caballeronia in other stinkbug species. Considering their prevalence among host bug populations, it is possible these gut microorganisms play a pivotal role in the adaptation of the green plant bug to grapevine fields, although further confirmation through rearing experiments is needed.

Entomofauna presente en refugios vegetales en un campo de vid var. Crimson Seedless en Ica-Perú

The use of chemical pesticides to control pests also affects beneficial insects, so it is necessary to implement mechanisms that allow them to be protected and promote their development. In the present investigation, three plant shelters were installed to identify their entomofauna and determine the plant species with the potential to host biological controllers of grapevine pests. The study was carried out in the 2020-21 growing season, with seven plant species to make up three plant shelters (A, B, and C) that were installed on the edges of a vineyard of the Crimson Seedless variety in Ica, Peru. In total, 1,209 insects were reported, in six orders, nine families, and sixteen species; the most abundant were pollinators, followed by phytophagous, predators, and some parasitoids. There were no statistical differences between the shelters in terms of the abundance of parasitoids and pollinators, but there were in predators and phytophagous specifically between shelters A and B with C. Shelters A and B, which included the fennel Foeniculum vulgare Mill., stood out for having a larger population of predators, including Chrysoperla externa (Hagen), the main controller of the “vine mealybug” (Planococcus spp.). The importance of plant shelters was demonstrated and their implementation in vineyards is recommended to promote biological control and contribute to integrated pest management in this crop. Keywords: biodiversity, natural enemies, conservation biological control.

Influence of Vineyard Inter-Row Management on Grapevine Leafhoppers and Their Natural Enemies.

Inter-row management in vineyards can influence the abundance of grapevine pests and their natural enemies. In 2013-2015, in a vineyard in northeastern Italy, the influence of two vineyard inter-row management strategies (i.e., alternate mowing, AM, and periodical tillage, PT) on the population dynamics of grapevine leafhoppers Hebata vitis and Zygina rhamni and their natural enemies, the mymarid Anagrus atomus and spiders (Araneae), and other hymenopteran parasitoids, were studied with different survey approaches. The infestations of both leafhoppers were lower in AM than PT due to the reduced leafhopper oviposition and higher nymph mortality in AM. This occurred although leafhopper egg parasitization by A. atomus was greater in PT than AM according to a density-dependent relationship with the leafhopper egg amount. Hymenopteran parasitoids other than A. atomus were the most abundant in AM, probably due to the higher availability of nectar and pollen than in PM. The significantly higher population densities of hunting spiders in AM than PT can be associated with the higher predation of leafhopper nymphs. Therefore, the study demonstrated that the alternate mowing of vineyard inter-rows enhances the abundance of natural enemies, such as spiders and hymenopteran parasitoids, and can contribute to grapevine leafhopper pest control.

Effects of germicidal ultraviolet-C light on grape mealybug (Pseudococcus maritimus)

Germicidal ultraviolet-C light (UV–C) has been used to effectively suppress grapevine powdery mildew (Erysiphe necator). However, effects on arthropod pests that would be simultaneously exposed to UV-C during applications directed at E. necator, are poorly understood. The grape mealybug (Pseudococcus maritimus) is one such grapevine pest. We exposed mated P. maritimus adult females in a lab study to UV-C light doses of 100, 200, 500 and 1000 J/m2. UV-C was applied during darkness and was followed by an additional 4 h dark period post-treatment to enhance possible suppressive effects of UV-C. Positive (2% horticultural oil) and negative (untreated) controls were included. Adult female P. maritimus oviposition was observed two weeks after treatment, and hatching of eggs was enumerated four weeks after treatment. UV-C treatment of mated adult females, regardless of dose, did not prevent oviposition or reduce ovisac viability. In a separate lab experiment, first instar P. maritimus nymphs were similarly exposed to UV-C doses of 200 and 1000 J/m2 with and without a 4hr dark period. UV-C treatments were compared to the same positive and negative controls. Nymph mortality was assessed at 24 and 48 h after UV-C treatment. Increasing doses of UV-C treatments, followed by a dark period, had a small, but significant impact on nymph mortality relative to the untreated control. Further studies on the potential sublethal effects (e.g., fecundity or longevity) of single or multiple exposures or increased UV-C doses upon juvenile stages of P. maritimus are warranted, as longer-term and multigenerational effects of UV-C have been observed in other arthropod systems.

Efficiency of Bacillus thuringiensis bioinsecticide in grapevine protection

The problem of contamination of agricultural products with toxic substances is an urgent problem in production. One of the most chemically treated crop is vineyards. Multiple treatments during one growing season have led to the fact that grape plantings have become an accumulator of unsafe chemical plant protection products. Moreover, grapes are consumed fresh. Accordingly, the selection of environmentally friendly pesticides and the replacement of chemicals with biological ones has become a priority for producers of this crop. Our research was devoted to evaluation of bioinsecticide based on entomopathogenic bacteria B. thuringiensis in the system of protecting grapes from pests. Such studies are of great interest and, according to the literature, 90 % of registered insecticides are based on Bacillus thuringiensis . Microorganisms isolated from nature as plant protection agents, when reintroduced into natural conditions, preserve beneficial species in biocenoses. At the same time, they are selective and, while affecting certain harmful objects, do not cause harm to humans and the environment. The purpose of this work was to study the effect of the bioinsecticide Biometch Insecto, WP on grapevine pests: European grape worm ( Lobesia botrana Den. Schiff.) and leafy form of phylloxera ( Viteus vitifolii Fitch.). Biometch Insecto, WP is based on strains of Bacillus thuringiensis var. kurstaki HG207 and Beauveria bassiana HG208. The effect of entomopathogens was compared with the effect of insecticide Bioslip, BW, L, the active ingredient of which is Beauveria bassiana . The results of the research revealed high biological effectiveness (90100 %) of Biometch Insecto, WP in protecting grapevines from pests when applied during the period of mass hatching of European grape worm caterpillars and emergence of phylloxera larvae from galls.

The Influence of Groves on Aboveground Arthropod Diversity and Evolution in a Vineyard in Southern Romania

This paper investigates the biodiversity of adult arthropods in two grapevine plantations influenced by two adjacent groves over a three-year period (2020–2022) in the viticultural center of Stefănești Argeș, located in southern Romania. The study holds significant implications for introducing parasitoid/predatory insect species into vineyards to control grapevine pests. A total of 164 arthropod species were identified, including 27 beneficial species. Additionally, two moth species, Lobesia botrana and Sparganothis pilleriana, were identified. L. botrana was consistently observed throughout the study, while S. pilleriana was only observed in 2022. The research reveals that the location with the highest number of identified species was in a grove near a black field, with 103 species. Other areas with notable species diversity included a vineyard maintained as a black field (89 species), a grove near permanent natural grassland (88 species), and a vineyard with intervals between rows of grapevines maintained as natural permanent grassland (81 species). Introducing beneficial organisms, such as the predator Crysoperla carnea, is recommended to control grapevine moths in this ecosystem.

Planococcus ficus (Hemiptera: Pseudococcidae) movement and demography: methods for generating cohorts for laboratory studies.

Planococcus ficus (Signoret) is a worldwide pest of grapevine. Mealybugs overwinter under bark and move into the grape canopy as the season progresses. Because crawlers are more active than later stages, mealybug movement behavior is likely to be stage specific. To quantify P. ficus demography and movement behavior, a series of laboratory experiments were conducted. First, P. ficus populations were monitored on grapevine seedlings to describe survival, change in size, timing of male pupation, and timing of oviposition over a 6-wk period. Subsequently, cohorts of mealybugs were generated by infesting grapevines with crawlers and holding infested grapevines for a specified duration of 0 (crawlers), 1, 2, 3, or 4 wk. Crawlers (0-wk) were more likely to move upwards and towards a light source, than all other age cohorts tested. Further, mealybugs from 4-wk-old cohorts were more likely to move downward than all other age cohorts tested. Results suggest that crawlers are more likely to move to the top of grapevines by moving upwards and orienting towards either the sun or the moon than all other age cohorts tested, whereas older gravid females are more likely to move downward. Passive movement of mealybugs on farm machinery or animals requires surviving a host free period. To quantify risk of passive movement, establishment rates and effects of starvation on each age cohort were quantified. Larger and older mealybugs were more likely to establish on grapevines than smaller and younger mealybugs. Further, mealybug longevity in absence of food was greater for older cohorts compared to younger cohorts. Crawlers survived an average of 2 days without food, whereas females from 4-wk-old cohorts survived for an average of 11 days without food. Further, 70% of starved females from 4-wk-old cohorts deposited fertile eggs. In the absence of food, some mealybugs from cohorts aged 2-, 3-, and 4-wk formed pupa with viable males emerging. Adult males from starved nymphs lived for an average of 3 days post-emergence. Results provide methods for producing cohorts of mealybugs of predictable size and stage and provides insight into P. ficus demography and movement behavior.

Exploring entomopathogenic nematodes for the management of Lobesia botrana (Lepidoptera: Tortricidae) in vineyards: Fine-tuning of application, target area, and timing

Lobesia botrana (Lepidoptera: Tortricidae) is a crucial grapevine pest worldwide. Expanding the available biocontrol agents can provide new management strategies compatible with organic viticulture. Entomopathogenic nematode (EPN) potential as a biocontrol agent was demonstrated against various developmental stages of L. botrana. For its field application, we hypothesised that by selecting the best combination of EPN-adjuvant and identifying the best area/timing for their application, we will secure their effective implementation against L. botrana. The aim of this study was to determine the best ecological scenarios for their use against L. botrana. We investigate three EPN species naturally occurring in Riojan vineyards: Steinernema feltiae, S. carpocapsae, and Heterorhabditis bacteriophora. We evaluated (i) EPN viability, infectivity, and adherence on leaves combined with adjuvants (Multi-Us, Maximix, Dash HC, Nu-Film-17, and Adrex), (ii) EPN biocontrol against L. botrana larva on leaves and grapes and damage reduction, and (iii) EPN efficacy against L. botrana at 22°, 15°, and 10 °C. Overall, all the adjuvants were compatible with the EPN, except Adrex with Heterorhabditis bacteriophora. Compared with the no application, EPNs (steinernematids) alone or with Maximix increased L.botrana L3 mortality on grapes and leaves, thereby reducing the damage. Pupal mortality caused by steinernematids EPN (alone or with Maximix) decreased with temperature, from ∼60% at 22 °C to <30% at 10 °C. Overall, steinernematids EPN (alone or with Maximix) applied against L. botrana on leaves, grapes, or trunks reduced the damage and increased insect mortality. This study suggests the best-case scenario for the application of EPNs is at sunset during late spring/early autumn at mid-temperatures (22 °C-15 °C). Further field validation is necessary for their full implementation.

Consistent benefits of fungicide reduction on arthropod predators and predation rates in viticulture: a five-year experiment

For reliable pest suppression, benefits of habitat management for natural enemies of agricultural pests need to be consistent over time. Unfortunately, most research projects allow only for one or two years of data collection. Here, we present a five-year study on effects of fungicide reduction and altered plant architecture on arthropod abundances and natural pest control in an experimental vineyard. The vineyard rows were divided into eight groups, half of which were trained in vertical shoot position (“trellis system”) and the other half as semi-minimal pruned hedge (“minimal pruning”). Every row was divided in three sections receiving three different plant protection intensities, respectively, with fungicides certified for organic viticulture. In each year we sampled arthropods from the grapevine canopy by standardized leaf collection and beat-sheet sampling, and exposed baits of a major grapevine pest (Lobesia botrana) to assess natural pest control. Arthropods, in particular predators, benefited from reduced fungicide sprayings and in turn promoted natural pest control. In contrast, effects of minimal pruning were less strong, and restricted to the leaf mesofauna, earwigs and leafhoppers. Across the five study years with their variable weather conditions, we conclude that the advantages of reduced fungicide sprayings in fungus-resistant varieties are consistent over time.

Assessing the risk of invasion by a vineyard moth pest guild

Biological invasions are most effectively managed when identified in their early stages, which often hinges on robust surveillance programs. The recent invasion of the European grapevine moth (Lobesia botrana) in California suggests that viticultural areas in the western United States may face severe economic consequences from this and other Tortricid and Pyralid moth species if they were to establish. To gain insights into the risk these grapevine pests pose, we used occurrence records for L. botrana and four other moths native to Europe or the eastern United States and selected environmental variables to predict the extent of climatically suitable areas and potential pest co-occurrence along the West Coast of the United States. A suite of models was generated using MaxEnt with species-specific tuning of model settings. Overall, the results confirmed high suitability for L. botrana to establish across much of the study region, driven largely by high monthly variability in precipitation and low elevation. Two species were predicted to have intermediate suitability to establish over the study region (i.e., grape tortrix moth, Argyrotaenia ljungiana; grape berry moth, Paralobesia viteana), while two others had low suitability (i.e., European grape berry moth, Eupoecilia ambiguella; Christmas berry webworm, Cryptoblabes gnidiella). The highest predicted potential for co-occurrence was between L. botrana and P. viteana, accounting for 19% of the total viticulture area, followed by L. botrana and A. ljungiana for 11% of the study area. These results may help with the optimization of surveillance efforts by indicating which species or areas should be prioritized for the deployment of invasive pest detection programs with pheromone traps. Indeed, given the apparent potential for co-occurrence of multiple moth pests in certain areas, our results may inform where single or multi-lure traps should be deployed as a more cost-efficient monitoring tool.

Peptidomics as a Tool to Assess the Cleavage of Wine Haze Proteins by Peptidases from Drosophila suzukii Larvae

Thermolabile grape berry proteins such as thaumatin-like proteins (TLPs) and chitinases (CHIs) promote haze formation in bottled wines if not properly fined. As a natural grapevine pest, the spotted-wing fly Drosophila suzukii is a promising source of peptidases that break down grape berry proteins because the larvae develop and feed inside mature berries. Therefore, we produced recombinant TLP and CHI as model thermolabile wine haze proteins and applied a peptidomics strategy to investigate whether D. suzukii larval peptidases were able to digest them under acidic conditions (pH 3.5), which are typically found in winemaking practices. The activity of the novel peptidases was confirmed by mass spectrometry, and cleavage sites within the wine haze proteins were visualized in 3D protein models. The combination of recombinant haze proteins and peptidomics provides a valuable screening tool to identify optimal peptidases suitable for clarification processes in the winemaking industry.

Preliminary investigations of the main Flavescence dor&amp;eacute;e vector Scaphoideus titanus and its first record in Kosovo

Scaphoideus titanus Ball is a major pest of grapevine in Europe, being the main vector of Flavescence dor&amp;eacute;e phytoplasma (FDp). The North American grapevine leafhopper was identified in neighboring countries, however, the FDp vector was not recorded and there is no available data on its presence in Kosovo. In 2021, initial investigations were conducted and field surveys were carried out in the region of Rahovec in order to evaluate the presence of S. titanus in Kosovarian vineyards. The survey was established in seventeen vineyards in different locations and grapevine varieties. In the middle of June, in each vineyard chosen for investigation were settled yellow sticky traps for surveying and sampling of leafhoppers. All plantations were subjected to fungicide treatment and no insecticide treatment was applied for S. titanus. The captures on the yellow sticky traps indicated that the North American grapevine leafhopper was present in Kosovo. Its population was different in investigated vineyards. Of the seventeen vineyards monitored, in twelve of them was captured the FDp vector, two sticky traps were damaged, and in three vineyards was not captured any specimen of Scaphoideus titanus. An average, of two up to forty-nine specimens of S. titanus per trap were collected over the surveyed period from the beginning of June until the end of September 2021. These results show only the distribution of S. titanus in the surveyed area. Furthermore, the presence of the North American grapevine leafhopper in Kosovo is an alert for urgent phytosanitary control of the quarantine phytoplasma Flavescence dor&amp;eacute;e (FD).

Evaluation of Alfalfa Fields and Pastures as Sources of Spissistilus festinus (Hemiptera: Membracidae): Quantification of Reproductive and Nutritional Parameters.

The threecornered alfalfa hopper (Spissistilus festinus) is a pest of grapevine, with damage caused by transmission of grapevine red blotch virus. Because grapevine is not a preferred host of the threecornered alfalfa hopper, abundance in vineyards depends on proximity to source habitats and presence of preferred hosts in vineyard understories. The potential for alfalfa fields and pastures in the Central Valley of California to serve as sources of threecornered alfalfa hopper was evaluated by quantifying parameters associated with threecornered alfalfa hopper reproductive and nutritional status. Laboratory studies determined that the threecornered alfalfa hopper is synovigenic, emerging as an adult prior to initiation of oogenesis and that females have multiple rounds of egg production. Alfalfa fields, irrigated pastures, and vineyards were sampled monthly. Adults were observed year-round in alfalfa fields and pastures, with populations peaking in fall. Gravid females were observed from February through November. While rare, adult threecornered alfalfa hoppers were collected from 2 of 4 sampled vineyards. In spring, adults were observed in samples collected from vineyard ground cover. In fall, adults were observed in samples collected from vineyard ground cover and foliage samples. Samples collected from pastures and vineyards were male biased, whereas equal numbers of males and females were observed in alfalfa fields. Adults collected from alfalfa fields were larger, heavier, and had greater estimated energetic reserves than adults collected from pastures. Adults collected from vineyards were of above average size and had relatively high estimated energetic reserves. Results suggest that alfalfa fields are more likely to serve as sources of threecornered alfalfa hoppers than irrigated pastures and that differences in male and female behavior may affect rates of pathogen transmission.

The Colomerus vitis (Eriophyidae) identity crisis: genetic evidence of highly diverged groups not associated with plant symptoms

The worldwide grapevine pest, Colomerus vitis (Trombidiformes: Eriophyidae), comprises three strains recognised by different plant symptoms: bud, erineum, and leaf curl strains. It has been hypothesised that these may represent different cryptic species, each causing a specific symptom.

Effect of vibrational mating disruption on flight activity and oviposition to control the grapevine pest, Scaphoideustitanus

The increasing demand for safe and sustainably produced food is leading to the development of strategies of pest control alternative to chemicals. One innovative method is Vibrational Mating Disruption (VMD) to disrupt insect communication in plants. VMD was proven effective in preventing mating of the grapevine pest Scaphoideus titanus, vector of flavescence dorée. However, the stress induced by VMD on the target species has the potential to influence other crucial aspects of the insect biology and ethology. Therefore, the goal of this study was to understand side effects of VMD on the flight activity and oviposition of S. titanus. The results of our experiments conducted in the greenhouse showed that in the presence of a receptive female, males fly more if exposed to vibrations than in the silent control but not differently from singles males in silence. Surprisingly, we found that also females subjected to VMD fly more than in the silence. Regarding oviposition, we found that mated females exposed to vibrations and single females (unmated) laid significantly fewer eggs than mated females in silence. In conclusion, this study shows the potential of VMD to interfere, besides with mating, with other important biological aspects of the pest species.

EPPO Datasheet: Naupactus xanthographus

EPPO Datasheet: <i>Naupactus xanthographus</i>

Ozone treatments to induce systemic-acquired resistance in leaves of potted vines: molecular responses and NIR evaluation for identifying effective dose and exposition duration

The European Community has recently imposed considerable restrictions on the use of pesticides, with the establishment of a regulatory framework for the sustainable use of agro-chemicals. However, in the viticulture sector, the intensive use of chemical pesticides, as well as sulfur and copper, is often required. Recently, ozone has been proposed as a possible environmentally friendly tool for controlling the development of pests on vines. However, little is known about the parameters linked to the practical application of ozone for controlling grapevine pests and how it triggers plant defence mechanisms. The main aim of this preliminary study was to determine the concentration of ozone and exposure duration in a treatment for stimulating the expression of systemic acquired resistance (SAR)-related genes, without inducing toxic effects and affecting vine health. In the first trial, three different combinations of ozone concentration and duration of treatment were tested on potted grapevines: i) gaseous ozone at 300 ppb for 12 hours, ii) gaseous ozone at 100 ppb for 6 hours, and iii) gaseous ozone at 100 ppb for 3 hours. Based on the results of the first trial, the potted vines were treated with just 100 ppb for 3 hours in a second trial. Leaves at different developmental stages were sampled. The expression level of systemic acquired resistance-related genes was analysed 12 hours and 7 days after each treatment. Furthermore, physiological parameters and NIR spectra were analysed. Ozone induced a transient up-regulation (limited to 12 hours after the treatments) of chitinases, β-1,3-glucanase and glutathione-S-transferase. On the other hand, pathogen-related (PR) genes showed a more persistent over-expression. The ozone treatment selectively affected the stomatal conductance depending on the different ozone concentrations. Detected NIR spectra revealed significant structural changes in ozone-treated plants, especially in leaves exposed to higher concentrations of ozone. These results suggest that ozone is able to transiently stimulate the expression of some resistance-related genes even at low and non-toxic doses for the vine leaves.

Soil and Climate Geographic Information System Data-Derived Risk Mapping for Grape Phylloxera in Washington State.

Grape phylloxera (Daktulosphaira vitifoliae, syn. Viteus vitifoliae), a destructive root and foliar pest of grapevines, occurs in almost all viticulture regions worldwide. However, certain regions have remained “phylloxera free.” Until recently, this included Washington state (United States), where this insect is regulated as a quarantine pest by Washington State Department of Agriculture. In 2019, established phylloxera populations were discovered in Washington. Phylloxera is typically managed by using resistant or tolerant rootstocks. In Washington, most wine grapes are grown on their own roots of the susceptible species Vitis vinifera instead of grafted rootstock, and thus, are at high risk of vine death should they become infested with phylloxera. This article reports development of a phylloxera risk map for Washington state using geographical soil texture (sand content) and soil temperature data. Weighted averages of soil texture data (mapping year: 2016, depth: 0–100 cm) were obtained from United States Department of Agriculture-Natural Resource Conservation Service (USDA-NRCS) and soilgrids. Soil temperature data were obtained from over 200 weather stations of Washington State University’s AgWeatherNet network. Threshold-based classifications were performed in Quantum GIS software on the rasterized soil sand content and temperature independently to derive low, moderate, and high-risk areas, with risk defined as site suitability for optimal phylloxera development. The validation identified 22 out of 23 confirmed phylloxera-positive sites as “high risk,” and one site as “moderate risk” when considering soil sand content alone. Soil temperature data alone classified 10 sites as “high risk” and 13 sites as “low risk.” When soil sand content was combined with soil temperature (as a risk modifier), 10 sites were classified as “high risk,” 12 sites as “high-moderate risk” and one site as “moderate-low” risk. Ground-truth comparisons of confirmed positive sites for phylloxera agreed with past research suggesting that soil sand content is the dominant factor influencing phylloxera infestation. Pertinent risk assessment can be an important component for vineyard decision-making, including whether to use rootstocks in vineyard development or replant scenarios. It may also help to focus the initial scouting and identification efforts to sites and may be helpful when tracking and developing solutions for quarantine pests, such as phylloxera.

Silencing of ATP Synthase β Impairs Egg Development in the Leafhopper Scaphoideus titanus, Vector of the Phytoplasma Associated with Grapevine Flavescence Dorée.

Scaphoideus titanus (Hemiptera: Cicadellidae) is the natural vector of Flavescence dorée phytoplasma, a quarantine pest of grapevine with severe impact on European viticulture. RNA interference (RNAi) machinery components are present in S. titanus transcriptome and injection of ATP synthase β dsRNAs into adults caused gene silencing, starting three days post injection (dpi) up to 20 dpi, leading to decrease cognate protein. Silencing of this gene in the closely related leafhopper Euscelidius variegatus previously showed female sterility and lack of mature eggs in ovaries. Here, alteration of developing egg morphology in S. titanus ovaries as well as overexpression of hexamerin transcript (amino acid storage protein) and cathepsin L protein (lysosome proteinase) were observed in dsATP-injected females. To evaluate RNAi-specificity, E. variegatus was used as dsRNA-receiving model-species. Different doses of two sets of dsRNA-constructs targeting distinct portions of ATP synthase β gene of both species induced silencing, lack of egg development, and female sterility in E. variegatus, indicating that off-target effects must be evaluated case by case. The effectiveness of RNAi in S. titanus provides a powerful tool for functional genomics of this non-model species and paves the way toward RNAi-based strategies to limit vector population, despite several technical and regulatory constraints that still need to be overcome to allow open field application.