Grape Leafhopper Research Articles

Haplothrips zagrosi sp. n. (Thysanoptera: Phlaeothripidae), a new predatory thrips of the Grape Leafhopper (Arboridia kermanshah Dlabola) from Iran

The thrip Haplothrips zagrosi sp. n. is described from Iran based on specimens collected on grape leaves infected with Grape Leafhopper (Arboridia kermanshah Dlabola). Diagnostic characters and illustrations for the new species are provided. It is similar to H. flavitibia and distinguishing character states are discussed. http://www.zoobank.org/urn:lsid:zoobank.org:pub:4A571310-FC24-438A-841C-38BC5D386F1

The effectiveness of plant protection products against Lobesia botrana Den. U Schift. in Zakarpattya

Goal. To establish the effectiveness of chemical protection of vineyards against pests, taking into account the peculiarities of their biology, distribution, harmfulness, seasonal dynamics of flight in Zakarpattya Ukraine. Methods. The research was conducted in accordance with the generally accepted methods in entomology and viticulture in 2021—2022 on the basis of Chateau Chizay LLC. The dynamics of the pest’s flight were studied in the field using the pheromone monitoring method using «Atrakon» pheromone traps and synthetic sex pheromones from the company «Csalomon» (Hungary). The research was conducted on Muscat, Chersegui, Sovignon Blanc, Pinot Noir, Cabernet Sovignon, Merlot, Rhine Riesling, and Pino Blan varieties. In 2022, in the vineyards of Chateau Chizay LLC, Zakarpattia Oblast, chemical plant protection agents were tested against grape leaf curl: Karate Zeon 050 CS, SK (liambda-tsyhalotryn, 50 h/l), 0.65 l/ha, Korahen 20, KS (khlorantraniliprol, 200 h/l), 0.15 l/ ha, Mavrik, EV (tau-fliuvalinat, 240 h/l), 0.2 l/ha, Voliam Fleksi 300 SC, KS (tiametoksam, 200 h/l + khlorantraniliprol, 100 h/l), 0.3 l/ha according to generally accepted methods. Results. Prolonged spring cooling in 2022 delayed the start of the flight of the first generation of cluster leafhopper, which began only in the first days of May. The second generation of this pest has been actively developing since the end of June. Grape damage on different varieties ranged from 2.1% on Muscat to 8.0% on Pino Blan. In the control (not treated with insecticides) plots, this indicator averaged 96.1%. The yield in the farm by variety averaged about 8 t/ha and ranged from 7.1 t/ha for the Muscat variety to 9.0 t/ha for the Merlot variety. In the control plot, the yield was low, only 1.4 t/ha. The effectiveness of protective measures on all grape varieties reached 90.5%. Conclusion. It was established that the protracted spring cooling caused the late start of flight of the grape leafhopper, which made adjustments to the calendar of protective measures, especially chemical ones. At the same time, thanks to pheromone monitoring, it was possible to establish the exact date of the start of Lobesia botrana’s flight and specify the timing of the application of chemical insecticides at the most favorable time, which made it possible to achieve an efficiency of more than 90%. Use of plant protection products against Lobesia botrana Den. et Schiff. in vineyards, LLC «Chateau Chizay», Zakarpattia Oblast contributed to the reduction of grape damage up to 94% and the preservation of the harvest up to 6.5 t/ha.

Population fluctuations of grape leafhopper, Arboridia kermanshah (Hemiptera: Cicadellidae), under natural conditions of Kermanshah grapes

Population fluctuations of grape leafhopper, Arboridia kermanshah (Hemiptera: Cicadellidae), under natural conditions of Kermanshah grapes

Grape leaf curl and protection against it in the vineyards of Zakarpattya of Ukraine

Goal. To clarify the features of biology, seasonal dynamics of flight, distribution, damage and protection of grapes from grape leafhopper Lobesia botrana Den. U Shift in Transcarpathia of Ukraine.
 Methods. Field. The research was conducted during 2018—2020 on the basis of Chizay LLC. The dynamics of the pest’s flight was studied by the method of pheromone monitoring using «Atrakon» pheromone traps and synthetic sex pheromones of the company «Csalomon» (Hungary). In order to detect damage to grapes by grape leafroller, the population of inflorescences by caterpillars of the first generation and bunches of the second generation was recorded. The records were made on two grape varieties — Merlot and Cabernet Sauvignon. In 2018—2020, Aktara 25 w.g. preparations were used against grape leaf curl in the vineyards under the conditions of Chizay LLC, Zakarpattia region. (thiamethoxam, 250 g/kg) and Mavrik EV (tau-fluvalinate, 240 g/l) according to generally accepted methods.
 Results. In connection with global warming, the phenology of the pest has changed somewhat. Based on this, the system of protective measures against cluster leaf curl must be adapted to today’s weather conditions. As a result of three-year observations, the changes that occurred in the flight dynamics of the grape leafhopper were recorded, in particular, the periods of mass reproduction of Lobesia botrana were determined depending on hydrothermal conditions, and the timing of protective measures was adjusted.
 Conclusions. The development and spread of cluster leaf curling was analyzed. In 2018 and 2019, the peak flight of the first generation of the cluster leafhopper was stable without sharp outbreaks of the spread of the pest — 155—161 copies/trap. In 2020, the development of the first generation of the leaf twister began sharply. During the mass flight period, 321 specimens/trap were recorded. In 2018, on the contrary, the second generation of leafhoppers developed rapidly — up to 313 butterflies per trap, this was facilitated by weather conditions. Such outbreaks of the number of grape leafhoppers led to significant damage to grapes and affected the yield. Damage to grapes at the initial stage of development and spread of the pest was: Merlot variety — 16—18%, Cabernet Sauvignon variety — 19—23%. In the control area, damage reached 30%. The effectiveness of chemical protection was 86.3—88.7%.

The role of volatile organic compounds in the interactions between leafhopper Arbordiahussaini (Hemiptera: Cicadellidae) and grapevine leaves

The leafhopper Arbordiahussaini can seriously destroy grapevines and is susceptible to the infestation of leafhopper. Volatile organic compounds (VOCs) released from uninfested and infested Kamali grape leaves were identified in this study. VOCs released from leaves were collected by the HS-SPME technique and analyzed by GC-MS. The results indicated that the infested leaves produce 19 VOCs; some VOCs were absent in uninfested because of the grape leafhopper infestation. VOCs were different between uninfested and infested leaves. The Olfactometer results showed leafhoppers preferred uninfested and infested leaves compared to filtered air treatment. Moreover, A. hussaini preferred infested leaves compared to uninfested ones. Our findings imply that these variations in VOCs are a crucial mediator in insect-plant interactions and may be employed in future research to pinpoint the primary substances that might be used as a lure for tracking and managing A. hussaini.

Phytosanitary assessment of the state of populations of the Japanese grape leafhopper (Arboridia kakogawana Mats.) in grape agrocenoses of the Northern Black Sea region of Ukraine

Goal. To clarify the species composition of the order Cicada (Hemiptera: Cicadinea (Auchenorrhyncha)) and their distribution in the grape agrocenoses of the Northern Black Sea Coast of Ukraine. Investigate the peculiarities of the seasonal dynamics of the Japanese grape cicada (Arboridia kakogawana Mats.) and identify the varieties that are most susceptible to damage by this leafhopper.
 Methods. Phytosanitary monitoring of leafhopper distribution in grape agrocenoses, the results of which determined the species composition of cicadas, the number of populations and the nature of plant population. The study of seasonal dynamics and determination of the flight peaks of the imago of the Japanese grape leafhopper was carried out with the help of yellow glue traps.
 Results. The data of the increase of species composition and expansion of the range of the order Cicadinea in agrocenoses of vineyards in the conditions of the Northern Black Sea zone of Ukraine are presented. The most significant changes were noted in invasive species of leafhoppers. The reasons are the process of adapting the development of cicadas to the conditions of grape ecosystems in the region. The dynamics of the number of Japanese grape leafhopper (Arboridia kakogawana Mats.) is given and the periods of its maximum abundance in industrial vineyards are traced. The number of generations of A. kakogawana was determined and the varieties that are most susceptible to damage by this cicada are indicated.
 Conclusions. According to the results of the research, 12 species of leafhoppers from different ecological and trophic groups belonging to 5 families were identified. It was noted that among the studied leafhoppers, the most common is the invasive species of the Japanese grape leafhopper, which ranges from 28.7 to 46.5% of the total number of populated bushes. It is noted that in the conditions of the Northern Black Sea leafhopper develops in three generations. Adults are caught from early June to mid-October. During this time, 3 peaks of leafhopper are recorded — the first — in mid-July, the second — in the first decade of August and the third peak — in early September. The development cycle of one generation is about 35—40 days. Migration to wintering grounds begins in mid-September. It was found that all surveyed grape varieties were inhabited by Japanese grape leafhopper, but it was analyzed that the number of populations in the varieties is different. Varieties with medium or more intense leaf pubescence were more intensively populated, such as Cabernet Sauvignon, Sukholimansky White, Odesa Souvenir, Chardonnay, Odessa Black, Rkatsiteli and Muscat Tairovsky. The smallest number of leafhoppers was found on varieties without pubescence or with weak pubescence of leaves on the underside, it is Arcadia, Flora, Riddle, Raisin Tairovsky, Kardishah and others.

Does grape leafhopper Arbordia hussaini (Hemiptera: Cicadellidae) effect on chlorophyll content of grape leaves?

The leafhopper Arbordia hussaini is a phloem feeding pest of the grape leaves causing a drop in chlorophyll levels in the grape leaves, which decreases photosynthesis and causes drying of the leaves depend on the population density of insects and found in various grape varieties growing around the world. The direct effects of A. hussaini on biomass dynamics, particularly the chlorophyll content of grapevine leaves, are investigated in this study. the high population of A. hussaini were 19.33 insect adult per grape leave in the first of September, while the low density of A. hussaini was 0.11 insect adult per grape leave at the end of December that trapped in blue sticky trap. The high density of leafhopper was recorded on the variety of Kamali followed by the variety of Halawani and Faranci. Chemical analysis of the chlorophyll content between the uninfested and infested grape leaves with the grape leafhopper showed decreasing of chlorophyll content and has been given 19.03 and 15.11 mg/L of the Halawani variety for the uninfested and infested leaves, respectively. Whereas, th mean of chlorophyll content of uninfested and infested leaves was 24.63 and 18.85 mg/L for Faranci variety, respectively. Moreover, the comparession of chlorophyll content between uninfested and infested Kamali leaf variety was 23.69 and 12.30 mg/L, respectively. Finally, depending on the degree of the attack, the grapevine response to A. hussaini infestation that affects on grape leaves and photosynthesis. This research shows that leafhopper feeding on tree sap has a significant direct impact on the chlorophyll content of grape leaves.

Pest categorisation of Arboridia kakogawana.

The EFSA Panel on Plant Health performed a pest categorisation of the Japanese grape leafhopper, Arboridia kakogawana (Matsumura, 1932) (Hemiptera: Cicadellidae), for the EU territory. This species is not included in the EU Commission Implementing Regulation 2019/2072. Adults of A. kakogawana overwinter in broad‐leaved and mixed forests and move to vineyards in the spring where there may be up to four generations, before adults move back to forests during late summer–early autumn to overwinter, possibly under diapause. A. kakogawana has a restricted host range (Vitis spp. and Parthenocissus quinquefolia). It is native to Eastern Asia, from where it moved westwards reaching southern Russia in 1999, and subsequently Ukraine, Romania, Bulgaria and Serbia in 2020. A. kakogawana develops on the abaxial side of the leaves causing chlorotic spots that reduce grape quality. Plants for planting of Vitis L. are banned from entering the EU except from Switzerland, where A. kakogawana is not known to occur. Therefore, this can be considered as a closed entry pathway. However, other plants for planting including the host P. quinquefolia and many broad‐leaved trees where overwintering takes place, as well as isolated bark and wood with bark provide potential pathways which are partly regulated but remain open. There are no EU records of interception. Additional introductions and further spread of A. kakogawana into/within the EU, coupled with the ample availability of grapevines and the climatic conditions would most probably allow successful establishment in most EU member states. Should this happen, economic impact in table and wine grapes is anticipated. A. kakogawana satisfies all the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest (UQP).

Influence of Vineyard Vegetational Borders on Western Grape Leafhopper (Erythroneura elegantula Osborn), its Egg Parasitoids (Anagrus spp.) and Generalist Insect Predators

Studies have shown that vegetational diversity in or around cropping systems can enhance naturalenemy abundance, although the impact on herbivores is less certain. We studied the influence of vineyardvegetational borders on density of the western grape leafhopper, Erythroneura elegantula, its majorparasitoids, Anagrus spp., and two generalist predators, Orius spp. and Leptothrips mali. Two studyvineyards had planted, perennial flowering hedgerows, one bordered a natural riparian zone, and onehad a sparse border of native trees. From April to September 2007, we counted leafhopper nymphs andadults of Anagrus spp., Orius spp. and L. mali within 10 m of the border, and at additional 20 m intervalsup to 90 m. At two sites with a diverse border, leafhopper density was stable nearest the border; at otherdistances leafhopper density decreased between the first and second generations. This effect was notseen at the sparse border site. Anagrus spp. density was enhanced at one site with a diverse border, butonly late season. There was no border effect on the generalist insect predators, by site or early vs. lateseason. Regression analysis showed a positive relationship between leafhopper and Anagrus spp. density,suggesting that the parasitoids were responding to higher leafhopper density. We conclude that, dependingon the nature of the border vegetation, there can be an effect on leafhopper nymphal density, but in thisstudy there is no evidence that it was due to natural enemies.

Grape Production Critical Review in the World

Grape Production Critical Review in the World

Biology, Ecology, and Management of Eastern Grape Leafhopper (Hemiptera: Cicadellidae), a Key Pest of Vineyards in North America

AbstractEastern grape leafhopper, Erythroneura comes (Say), is a key pest of grapes (Vitales: Vitaceae) in the central and northeastern United States and eastern Canada. This native insect uses its piercing-sucking mouthparts to puncture the mesophyll cells of leaves and suck out the contents, thereby reducing the quality and quantity of fruit. Eastern grape leafhopper has been reported as a vineyard pest for nearly 200 yr and is one of several Erythroneura spp. that feed on grapes in North America. Overwintered adults become active in early spring and may feed on grasses, weeds, and other plants before feeding on grapevines. Although eastern grape leafhopper has an extensive host range, it is only known to oviposit on wild and cultivated grapes. This multivoltine species can outbreak periodically, which has generated much research into improved monitoring and integrated pest management strategies employed throughout its native range. In this review, we describe the biology, life history, population dynamics, and phenology of eastern grape leafhopper and provide a historical account of monitoring and management strategies for this important vineyard pest.

First record of the Japanese grape leafhopper Arboridia kakogawana (Matsumura, 1932) (Hemiptera: Cicadellidae) from Romania

A new invasive species, the Japanese grape leafhopper, Arboridia kakogawana (Matsumura). is reported for the first time in Romania. Arboridia kakogawana is a serious pest of grapevine (Vitis vinifera L.) in East Asia (South Korea and China) and in Southern Russia (Krasnodar and Rostov regions) and Ukraine. In 2018, very high numbers of A. kakogawana were caught on yellow sticky traps in a vine plot in Romania in Northern Bucharest. Adults were trapped from early June to the middle of November. The dynamics of the adult population were measured using yellow sticky traps, and in 2018 four peaks were observed in the middle of July, in the first 10 days of August, at the beginning of September and in the first 10 days of October. The first overwintering adults appeared from the beginning of June. Foliar symptoms associated with the trophic activity of the leafhopper were observed on grapevine and Virginia creeper (Parthenocissus quinquefolia (L.)). Yellow sticky traps used in prior studies in the Bucharest area were re‐examined and the Japanese leafhopper was discovered on these, which leads to the conclusion that the species has been present at least since 2016 in this area. This is the first report of A. kakogawana in Romania and in the European Union.

Investigations on the Grape Leafhopper Erasmoneura vulnerata in North-Eastern Italy.

The leafhopper Erasmoneura vulnerata (Fitch) (Hemiptera: Cicadellidae) is native of Northern and Central America where it occurs on wild and cultivated grapes as well as on a number of secondary hosts. This species was recorded for the first time in Europe (Italy, Veneto region) in 2004. Since then it has spread over Northern Italy and Slovenia. Studies on the biology of E. vulnerata in America are limited and thus its phenology was investigated on Vitis labrusca L. and Vitis vinifera L. plants under field and semi-field conditions. These observations suggest that E. vulnerata can complete 2–3 generations per year. The development of E. vulnerata from first instar nymphs to adults was studied under controlled conditions (about 23 °C). Developmental times lasted from 16.1 days in July–August to 19.5 days in September, and this variability was probably due to grape cultivar and plant susceptibility. Data were consistent with the number of generations previously reported. Erasmoneura vulnerata was more abundant on vines close to overwintering sites than on those located 100–250 m from these sites and contiguous to commercial vineyards.

Abrupt and gradual temperature changes influence on the climatic suitability of Northwestern Alpine grapevine-growing regions for the invasive grape leafhopper Scaphoideus titanus Ball (Hemiptera, Cicadellidae)

The paper aims to elucidate the influence of abrupt and gradual climate changes on the suitability for colonization of Scaphoideus titanus populations in grapevine-growing areas of the Northwestern Alpine region. This study spans several decades of temperature recordings and is carried out in ten grapevine-growing areas. A time-varying distributed delay with attrition model, linked to a grapevine phenology model, is used to simulate the development of S. titanus populations and produce an annual Climatic Suitability Index (CSI). Area-specific CSI time series were obtained. The Breusch-Godfrey test revealed few significant partial autocorrelations in nine areas and the occurrence of six consecutive - first decreasing and then increasing - partial correlations in one case only. The occurrence of abrupt and gradual changes of the index were studied via multiple least square regression analyses. In general, the climatic suitability of all areas tended to improve through time. However, gradual and abrupt temperature changes were not consistently reflected in gradual and abrupt CSI patterns: abrupt and gradual CSI changes were observed in two areas, abrupt changes were detected in three areas, and exclusively gradual changes in the remaining five. Pest control institutions of the region under study may deal with different scenarios of pest status such as long-time presence and increasing risks, high colonization risks or limited colonization risks for the foreseeable future. Institutions charged with pest control elsewhere are advised to use a mechanistic demographic model to study area-specific infestation patterns and colonization risks because the results obtained here cannot be transferred to other areas without site-specific evaluations.

Landscape diversity and crop vigor outweigh influence of local diversification on biological control of a vineyard pest

AbstractThe influence of local and landscape habitat diversification on biological control of the Western grape leafhopper (Erythroneura elegantula Osborn) by its key parasitoids Anagrus erythroneurae S. Trjapitzin & Chiappini and Anagrus daanei Triapitsyn was studied in wine grape vineyards. At the landscape scale, Anagrus rely on alternative host species in non‐crop habitats outside of the vineyard to successfully overwinter, while at the local scale vineyard diversification can provide resources, such as shelter and floral nectar, which improve parasitoid performance. In a two‐year experiment, plots with and without flowering cover crops were compared in vineyards representing a gradient of landscape diversity. While the cover crops did attract natural enemies, their populations were unchanged in the crop canopy and there was no difference in parasitism rate, leafhopper density, crop quality, or yield. Vineyards in diverse landscapes had higher early‐season abundance of Anagrus spp., which was linked to increased parasitism and decreased late‐season populations of E. elegantula. Leafhopper densities were also positively associated with crop vigor, regardless of landscape or cover crops. Flowering cover crops did increase abundance of some natural enemy species as well as parasitism rate in vineyard landscapes with intermediate levels of diversity, indicating a local × landscape interaction, although this did not lead to reductions in E. elegantula densities. These findings indicate that, in this agroecosystem, landscape diversity mediates and in many ways outweighs the influence of local diversification and that E. elegantula densities were regulated by a combination of biological control and crop vigor.

Evaluating the Toxicity of Candidate Organic and Conventional Insecticides on Western Grape Leafhopper and Virginia Creeper Leafhopper (Hemiptera: Cicadellidae) under Vineyard and Laboratory Conditions

Abstract The western grape leafhopper (Erythroneura elegantula Osborn) and the Virginia creeper leafhopper (Erythroneura ziczac Walsh) are the two leafhopper pests frequently observed in Washington State vineyards. Organic viticulturists have difficulties controlling these leafhopper pests, and outbreaks can result in economic loss. We vineyard-tested the efficacy of several candidate bioinsecticides and conventional insecticides against the western grape leafhopper and the Virginia creeper leafhopper. This study included the initial testing of several alternative candidate insecticides for leafhopper control. Controlled laboratory bioassays also were completed, and the 50% and 90% lethal concentrations were calculated for the nonsystemic insecticides tested. Of the bioinsecticides tested, pyrethrum (PyganicTM, Valent Bioscience Corporation, Libertyville, IL) was the only product that provided effective control of leafhoppers in both the vineyard and laboratory components of this study. In vineyard effic...

Endophytic Beauveria bassiana in grapevine Vitis vinifera (L.) reduces infestation with piercing-sucking insects

Fungi are important natural pathogens of arthropod pests and are successfully used as biocontrol agents in various crops. In addition to colonizing arthropods, evidence has accumulated that some entomopathogenic fungi like Beauveria bassiana can endophytically colonize a wide array of plant species. However, only limited information is currently available on the endophytic colonization of grapevines with B. bassiana and whether the fungus still maintains its pathogenic habit against insect pests.Greenhouse and field experiments were conducted to optimize endophytic establishment of the entomopathogenic fungus B. bassiana in younger, potted plants and mature grapevine plants in the vineyard. We used two different commercialized B. bassiana strains, applied either as conidial suspensions (ATCC 74040 and GHA) or as a formulated product (Naturalis®, strain ATCC 74040) on grapevine leaves. The potential of endophytic B. bassiana to provide protection against putative target pest insects like the vine mealybug Planococcus ficus was assessed in a bioassay using surface sterilized leaves. Endophytic survival of B. bassiana inside leaf tissues of seven-week-old potted plants was evident for at least 21days after inoculation, irrespective of the inoculum used. Endophytic B. bassiana reduces infestation rate and growth of P. ficus. In the vineyard B. bassiana was detected as an endophyte in mature grapevine plants up to five weeks after last application with significant reduction of infestation with grape leafhopper, Empoasca vitis.

Spatially Targeted Applications of Reduced-Risk Insecticides for Economical Control of Grape Berry Moth, Paralobesia viteana (Lepidoptera: Tortricidae).

The grape berry moth, Paralobesia viteana Clemens (Lepidoptera: Tortricidae), is a key economic pest of vineyards in eastern North America, and prevention of fruit infestation is particularly challenging along vineyard borders that are adjacent to wooded areas containing wild grape (Vitis spp.). For three years, infestation and damage in vineyards where reduced-risk insecticides were applied to borders at timings based on a degree day model (Integrated Pest Management program) were compared to that in vineyards where broad-spectrum insecticides were applied across the whole vineyard (Standard program). Infestation at vineyard borders immediately prior to harvest was consistently lower in IPM vineyards than in Standard program vineyards, and in two of the years this was also true at veraison (fruit coloring). Grape berry moth infestation was similar between treatments at vineyard interiors throughout the study, despite no insecticide applications to the interiors of the IPM program vineyards. Populations of two other key vineyard pests, the eastern grape leafhopper, Erythroneura comes (Say) (Hemiptera: Cicadellidae), and Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae), were not significantly different between programs, and natural enemy captures on yellow sticky traps were also similar. The per hectare cost of insecticides applied in the IPM program was consistently lower than for the Standard program, with a significant difference in the third year of this study. We demonstrate how spatially selective applications of reduced-risk insecticides can provide improved control of grape berry moth at lower cost than standard broad-spectrum insecticide-based programs.

Host Plant Associations of Anagrus spp. (Hymenoptera: Mymaridae) and Erythroneura elegantula (Hemiptera: Cicadellidae) in Northern California.

Anagrus erythroneurae S. Trjapitzin & Chiappini and Anagrus daanei Triapitsyn are the key parasitoids of the western grape leafhopper (Erythroneura elegantula Osborn) in northern California vineyards. Erythroneura elegantula overwinters as an adult in reproductive diapause. To successfully overwinter, Anagrus spp. must locate an alternate leafhopper host that overwinters in an egg stage that they can parasitize. These alternate leafhopper hosts are thought to be primarily located in the natural habitats surrounding vineyards. This study identifies the noncrop host plants utilized by Anagrus spp. not only during the overwintering period but throughout the entire year, as well as the leafhopper species associated with these host plants. Over a 2-yr period, Anagrus spp. and leafhoppers were sampled from numerous plants in natural and cultivated habitats surrounding vineyards. Results from this study confirm previously known Anagrus spp. host plants, but also identify new host plant species. Some of the host plants harbored Anagrus spp. year-round while others were utilized only during certain periods of the year. Leafhoppers associated with Anagrus spp. host plants may potentially serve as the alternate host utilized by Anagrus spp. on these plants, but this was not confirmed in the current study. Records of E. elegantula demonstrate their cyclical movement between the vineyard floor (winter), temporary noncrop hosts (spring/fall), and the grape vine canopy (summer).

Spatial Distribution and Sampling Plans for Grapevine Plant Canopy-Inhabiting Scaphoideus titanus (Hemiptera: Cicadellidae) Nymphs.

The paper deals with the study of the spatial distribution and the design of sampling plans for estimating nymph densities of the grape leafhopper Scaphoideus titanus Ball in vine plant canopies. In a reference vineyard sampled for model parameterization, leaf samples were repeatedly taken according to a multistage, stratified, random sampling procedure, and data were subjected to an ANOVA. There were no significant differences in density neither among the strata within the vineyard nor between the two strata with basal and apical leaves. The significant differences between densities on trunk and productive shoots led to the adoption of two-stage (leaves and plants) and three-stage (leaves, shoots, and plants) sampling plans for trunk shoots- and productive shoots-inhabiting individuals, respectively. The mean crowding to mean relationship used to analyze the nymphs spatial distribution revealed aggregated distributions. In both the enumerative and the sequential enumerative sampling plans, the number of leaves of trunk shoots, and of leaves and shoots of productive shoots, was kept constant while the number of plants varied. In additional vineyards data were collected and used to test the applicability of the distribution model and the sampling plans. The tests confirmed the applicability 1) of the mean crowding to mean regression model on the plant and leaf stages for representing trunk shoot-inhabiting distributions, and on the plant, shoot, and leaf stages for productive shoot-inhabiting nymphs, 2) of the enumerative sampling plan, and 3) of the sequential enumerative sampling plan. In general, sequential enumerative sampling was more cost efficient than enumerative sampling.