1. Andreason, S.A., Prabhaker, N., Castle, S.J., Ganjisaffer, F., Haviland, D.R., Stone-Smith, B., Perring, T.M. (2018). Reduced susceptibility of Homalodisca vitripennis (Hemiptera: Cicadellidae) to commonly applied insecticides. Journal of Economic Entomology 111(5):2340-2348. https://doi.org/10.1093/jee/toy192.

The glassy-winged sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae) is a vector for the bacterium Xylella fastidiosa, which causes Pierce’s disease in grapevines. Infected grapevines exhibit chlorosis, scorching, and eventual death; there is no current effective treatment for Pierce’s disease, so preventing its transmission by insects is critical for vineyard health. In wine-producing regions of California, H. vitripennis abundance was reduced by concerted management efforts beginning in 2001, but increased densities of this species in Kern County, CA in 2012-15 suggest that insecticide resistance may have developed in some populations. This study assessed the susceptibility of H. vitripennis to commonly applied neonicotinoids (imidacloprid, thiamethoxam, acetamiprid) and pyrethroids (bifenthrin, fenpropathrin). Sites for H. vitripennis sampling were selected based on GIS analyses of geo-referenced trap count, pesticide treatment, and land-cover classification data. ArcGIS was used to identify sampling locations in organic citrus orchards that had high trap counts of H. vitripennis earlier in the year and were either within 0.5 mi of imidacloprid application sites, or more than 1.5 mi from imidacloprid application sites to assess effects of field exposure on the concentration of imidacloprid needed to kill half the insects in a treatment group (LC₅₀). Bioassay results indicated that LC₅₀ values increased between July and October, particularly in insects collected from a site where imidacloprid was applied nearby, which saw a 29-fold increase throughout the season. However, the 3.5-fold mean increase in LC₅₀ for imidacloprid across years and sampling sites was not significant when compared to earlier estimates. Significant decreases from 2001-2003 baselines in H. vitiripennis susceptibility to bifenthrin and acetamiprid were detected, supporting the conclusion that resistance to some pesticides is increasing in Kern County. This study provides an example of how GIS can be used to plan sample collection, in addition to its applications in spatial analyses and modeling described elsewhere in this bibliography.

2. Cieniewicz, E.J. (2019). Ecology of grapevine red blotch disease. [Doctoral dissertation, Cornell University]. eCommons. https://doi.org/10.7298/f9vg-7s85.

The grapevine red blotch virus (GRBV; Genus: Grablovirus; Family Geminiviridae) causes leaf-reddening and reduces grape quality and yield, while increasing ripening time. Transmission can result from introduction of infected plant materials to vineyards or from feeding by insects that carry the disease, such as the alfalfa leafhopper (Spissistilus festinus). This dissertation reports five years of monitoring data for grapevine red blotch and identifies additional insect vectors for the disease: the leafhoppers Colladonus reductus and Osbornellus borealis and Melanoliarus planthoppers (Hemiptera: Cixiidae). QGIS was used to produce distribution maps of grapevines in California and New York from United States Department of Agriculture county-level datasets. Free-living (non-cultivated) grapevine samples obtained from these states were tested for GRBV by assaying DNA samples amplified by polymerase chain reactions (PCR), and infection incidences were added to grapevine distribution maps. GRBV was detected in about 20% of sample from California and was not detected in New York. Many of the GRBV-positive samples came from plants that did not exhibit symptoms at time of collection, highlighting the challenge of detecting and managing this disease. The resulting map of grapevine red blotch rates in California indicated that infections in free-living grapevines were associated with greater acreage of planted grapes within a county, supporting prior spatiotemporal modeling work that demonstrated increased likelihood infection in vines nearby infected vines. PCR tests were also used to evaluate the prevalence of GRBV in middle-row cover crops and insects collected from vineyards. No plant species other than grapevines were identified as potential GRBV reservoirs. Larger populations of S. festinus were associated with faster spread of GRBV, but because this species does not frequently colonize grapevines, the author recommends removing sources of infected plant material rather than focusing on the control of potential insect vectors to limit the spread of GRBV in vineyards.

3. del-Campo-Sanchez, A., Ballesteros, R., Hernandez-Lopez, D., Ortega, J.F., Moreno, M.A. (2019). Quantifying the effect of Jacobiasca lybica pest on vineyards with UAVs by combining geometric and computer vision techniques. PLoS ONE 14(4). https://doi.org/10.1371/journal.pone.0215521.

Precision agriculture strategies seek to reduce pesticide use by obtaining spatial and temporal information about variability in agricultural systems and targeting application of products to areas where they are most needed. Remote sensing techniques are frequently used in precision agriculture, but the spatial resolution provided by satellite imagery may not be sufficient to capture information about crop health. Unmanned aerial vehicles (UAVs) and ground sensors can obtain data with higher spatial and temporal resolutions. This paper outlines methods of representing grape vines and soil in 3D based on radiometric and tri-dimensional data collected by UAV-mounted RGB cameras. The planned UAV flight was fitted to variations in vineyard terrain with a digital elevation model from the National Geographic Institute of Spain to maintain a constant height about the ground. Once aerial images were obtained, the photogrammetry software Agisoft Photoscan was used to generate 3D point clouds from them; the Classify Ground Points tool in this software was used to differentiate between vegetation and ground surfaces. Feeding damage by the leafhopper Jacobiasca lybica (Hemiptera: Cicadellidae) was estimated from the vineyard orthoimages using the software Leaf Area Index Calculation, which employs Artificial Neural Networks that, following calibration by the user, can create a raster in which pixels are assigned to different classes of vegetation health based on RGB values. Because J. lybica feeding reduces plant photosynthetic output and can cause leaf reddening, red and brown discoloration were considered to indicate infestation. The accuracy with which vines were classified as affected or unaffected was assessed by sampling for pests within 97 randomly selected 10 m x 10 m areas within the study area. The authors compared the accuracy of infestation estimates generated from both 2D and 3D products and found that the combined geometric and computer vision classification system that utilized 3D products was more accurate in distinguishing vegetation from ground surfaces and infested from healthy vegetation. The similarities in reflective characteristics of infested vegetation and soil were identified as a potential source of error in this study.

4. EFSA (European Food Safety Authority). (2021). Pest survey card on Xylella fastidiosa. EFSA. https://arcg.is/09m4r1.

This supporting publication from the European Food Safety Authority employs Esri story maps to communicate information about the biology, transmission, and distribution of the bacterium Xylella fastidiosa (which causes Pierce’s disease in grapes and other plant infections) within the European Union. Although it does not directly outline how GIS techniques can be applied to the analysis and management of X. fastidiosa and its insect vectors, it includes several examples of informative maps produced in ArcGIS and illustrates how these figures can be used in outreach efforts. The story map format can easily integrate ArcGIS maps and could be used to communicate survey or modeling results to a public or non-technical audience.

5. Guenser, J., Bourgade, E., Vergnes, M., Dufourcq, T., Mary, S. (2018). Assessment of biodiversity and agronomic parameters in two agroforestry vineyards. E3S Web of Conferences 50.
https://doi.org/10.1051/e3sconf/20185001013.

Agro-ecology is an approach to agriculture that attempts to maintain and benefit from ecosystem services by mitigating the declines in biodiversity and habitat heterogeneity driven by conventional agricultural practices. Combining tree cover with crops and livestock (referred to as agroforestry) is one component of agro-ecology that attempts to increase biodiversity on land used for food production. However, effects of landscape diversification on food production, including risk of pest outbreaks, must be determined in order for agroforestry practices to be adopted more widely. This study evaluates vine vigor and arthropod diversity in organic agroforestry vineyards in southwestern France, with a focus on the vineyard pest Empoasca vitis (Hemiptera: Cicadellidae). Normalized Difference Vegetative Index (NDVI) values were calculated using the ground-based GreenSeeker LED sensor to estimate vine vigor. Geo-references yellow sticky traps and pitfall traps were deployed to monitor E. vitis abundance and diversity of other vine-associated and ground-dwelling arthropods. ArcGIS was used to determine distances between sampling points and trees. Proximity to trees was not found to affect vine vigor or E. vitis abundance and had variable effects on foliar and ground-level arthropod diversity depending on the site and year. The authors were unable to identify general effects of tree cover on arthropod biodiversity or pest abundances from this study, perhaps due to other landscape factors like presence of ground cover that could have driven patterns in arthropod distribution and community structure.

6. Gutierrez, A.P., Ponti, L., Hoddle, M., Almeida, R.P.P., Irvin, N.A. (2011). Geographic distribution and relative abundance of the invasive glassy-winged sharpshooter: effects of temperature and egg parasitoids. Environmental Entomology 40(4): 755-769.  https://doi.org/10.1603/EN10174.

For ectotherms such as insects, weather and climate may strongly affect the phenology, abundance, distribution, and dynamics of local and regional populations. Weather-driven effects on population dynamics can be represented using physiologically based demographic models (PBDMs), which can also incorporate trophic interactions between plants, insect herbivores, and natural enemies. This paper uses a PBDM approach to model invasion dynamics of the glassy-winged sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae), a vector for Pierce’s disease in grape, that was introduced to California from the southeastern United States. The authors explore the dynamics of grapevine, H. vitripennis, and egg parasitoids (Gonatocerus ashemeadi and G. triguttatus, Hymenoptera: Mymaridae) populations in California under 2 C and 3 C climate warming scenarios. Model results were mapped using inverse distance weighting interpolation in Geographic Resources Analysis Support System (GRASS) GIS. Predicted H. vitripennis distribution without parasitoids largely conformed to the species’ observed range. Adding G. ashemeadi to the model reduced H. vitripennis densities but did not alter its spatial distribution; including G. triguttatus slightly reduced host range. G. triguttatus had a smaller predicted range and density than G. ashemeadi, due to its lower tolerance for temperature extremes. Increasing average daily temperatures increased abundance of H. vitripennis and extended its northern range, but control by parasitoids was predicted to be similarly effective under 2-3 C warming scenarios as without warming. PBDMs could be developed for other leafhopper pests in California and elsewhere, allowing for hypothetical population dynamics to be represented under different climate and biocontrol conditions.

7. Kelly, M. California Department of Food and Agriculture. (2004). Spatial database creation and maintenance for Pierce’s disease and the glassy winged sharpshooter in California. https://www.researchgate.net/publication/242594231_SPATIAL_DATABASE_CREATION_AND_MAINTENANCE_FOR_PIERCE’S_DISEASE_AND_GLASSY-WINGED_SHARPSHOOTER_IN_CALIFORNIA_Project_Leader.

In order for field-collected data (such as records of the extent of plant diseases and distribution of insect vectors) to be combined with geo-referenced landcover, climate, and hydrology data for spatial analyses, these datasets must be shared in an appropriate format that is compatible with Geographic Information Systems. This report outlines a plan to establish and maintain a web-based GIS database of the location of Pierce’s Disease (PD) and trap counts of the glassy-winged sharpshooter Homalodisca vitripennis (Hemiptera: Cicadellidae) throughout California. The University of California’s Disease Grant Program and California Department of Food and Agriculture’s (CDFA) Pierce’s Disease and Glassy-winged Sharpshooter Board are identified as sources of funding for the project, which was to be developed by the Kelly lab at UC Berkley. The California Department of Food and Agriculture and University of California are identified as potential organizations to manage the GIS database so that stakeholders, policymakers, and scientists would be able to access data obtained through systematic monitoring programs. Making results of statewide tracking programs available online would support management of the economically damaging grapevine infection and leafhopper that transmits it by facilitating epidemiological modeling and data-based control efforts. The author suggests that increasing accessibility of spatial data about PD/H. vitripennis distribution and providing online tools for reporting H. vitripennis sightings would allow researchers to develop novel hypotheses about the distribution, transmission, and management of Pierce’s disease.

8. Lessio, F., Mondino, E.B., Alma, A. (2011). Spatial patterns of Scaphoideus titanus (Hemiptera: Cicadellidae): a geostatistical and neural network approach. Integrated Journal of Pest Management 57(3): 205-216. https://doi.org/10.1080/09670874.2011.566642.

Scaphoideus titanus (Hemiptera: Cicadellidae) is a leafhopper that feeds on grapevines (Vitis spp.) and acts as a vector for the phytoplasma disease flavescence dorée, which is a concern for commercial grape growers. S. titanus is native to North America but has since been introduced to Europe. This paper presents a Multi Layer Perceptron (MLP) Artificial Neural Network (ANN) model that predicts the population density of S. titanus based on environmental parameters. Lessio et al. estimated distribution of S. titanus in NW Italy by deploying 230 sticky traps with geo-referenced (WGS 84 reference system) satellite positioning receivers in woodlands and in vineyards under different pest management regimens. The spatial correlations among S. titanus captures were analyzed using the GIS and spatial modeling freeware SADA (Spatial Analysis and Decision Assistance). Using geostatistical techniques, the authors identified moderate spatial correlations among nearby (70-210 m) adult captures, supporting prior observations of aggregation behavior in this species. Inputs for the ANN model relating to terrain characteristics (elevation, slope, patch shape, etc.) were calculated from a digital elevation model and from land-use vector maps and aerial imagery using ArcGIS. Sensitivity analyses of model results indicated that the type of pest management practice and local habitat diversity had the greatest effects on leafhopper population density. Lessio et al. argue that distance indices and geostatistics may not produce accurate spatial interpolation of S. titanus distribution due to the limited dispersal ability of this species and the mandatory chemical control program instituted in the study area. They instead suggest the use of ANN modeling to predict habitat vulnerabilities.

9. Lessio, F., Tota, F., Alma, A. (2014). Tracking the dispersion of Scaphoideus titanus Ball (Hemiptera: Cicadellidae) from wild to cultivated grapevine: Use of a novel mark-capture technique. Bulletin of Entomological Research 104(4): 432-443. doi:10.1017/S0007485314000030.

Scaphoideus titanus (Hemiptera: Cicadellidae) is a specialist grapevine herbivore and vector of grape diseases that is invasive throughout much of Europe. Tracking the movement of this insect within vineyards using traditional mark-release-recapture techniques can be difficult, as the number of marked insects that is released is generally too small (proportionate to the total field population) to allow for sufficient rates of recapture, and common markers can alter S. titanus flight behavior. In this study, albumin and casein, derived from egg and milk respectively, were applied to wild grapevines and used as immunomarkers to track dispersion of S. titanus from application sites to geo-referenced sticky traps within the vineyard. Captured insects were tested for marker proteins, and the proportion of marked insects was used to model dispersal of S. titanus from natural vegetation to the vineyard interior. Albumin proved to be a more reliable marker protein and was more frequently identified in captured insects. Captures were most likely to be marked within 20-30 m of wild grapevines, although some long-range dispersal (320 m) was observed. Likely pathways for S. titanus dispersal were interpolated in ArcGIS using Inverse Distance Weighting (IDW) and Kernel interpolation with barrier (KB) models. Both methods of interpolation identified clusters of marked adults at vineyard edges, especially when vineyard rows were oriented parallel to vegetation. Based on RMSE values, KB, which permitted modeling of insect movement within and through non-grapevine habitat, produced more accurate maps than with IDW, which assumes movement along line-of-site distances between sample points.

10. Lessio, F., Picciau, L., Gonella, E., Mandrioli, M., Tota, F., Alma, A. (2016). The mosaic leafhopper Orientus ishidae: host plants, spatial distribution, infectivity, and transmission of 16SrV phytoplasmas to vines. Bulletin of Insectology 69(2): 277-289.

Scaphoideus titanus (Hemiptera: Cicadellidae) is known as the main insect vector of the vine diseases flavescence dorée. However, the 16SrV-C and -D phytoplasmas associated with the disease have been identified in other insects such as Orientus ishidae (Hemiptera: Cicadellidae), which may also play a role in transmission. This paper investigates the potential for O. ishidae to act as a vector for flavescence dorée, as well as the spatial ecology of this species in vineyards in the Piedmont region of Italy. Sticky traps were placed in vineyards and among nearby trees/shrubs, which were presumed hosts for O. ishidae. Maps of O. ishidae distribution were spatially interpolated from capture results by Ordinary Kriging and by Inverse Distance Weighting in ArcGIS. Both methods produced similar magnitudes of error and bias based on RMSE and ME values. Captures were clustered around edges of vineyards and were most abundant near ornamental plants and fruit trees, with little dispersal into vineyard interiors. The authors tested transmission of FD-phytoplasmas by rearing O. ishidae on infected plants, transferring them to uninfected plants in lab, and, after a feeding period of 21-60 days, PCR testing both insects and hosts for phytoplasmas. FD-phytoplasmas were detected in about 20% of experimental insects and were transmitted to 2 of 18 grapevines; no transmission was documented from O. ishidae to other plant hosts (broad bean, hazelnut). Whole mount fluorescent in situ hybridization analyses found high levels of FD-phytoplasmas in the salivary glands of O. ishidae used in transmission experiments. Field-collected adults were also found to carry FD-phytoplasmas at rates of 7.04-12.82%, which conforms to previously observed rates from other regions of Europe. This study confirms that O. ishidae can act as a vector for flavescence dorée in grapevines under laboratory conditions but does not suggest that this species is a frequent transmitter in field due to its limited movement within vineyards and low vectoring efficiency.

11. Pilkington, L.J., Lewis, M., Jeske, D., Hoddle, M.S. (2014). Calculation and thematic mapping of demographic parameters for Homalodisca vitripennis (Hemiptera: Cicadellidae) in California. Annals of the Entomological Society of America 107(2): 424-434.  https://doi.org/10.1603/AN13144.

The glassy-winged sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae), is a vector of the bacterium Xylella fastidiosa that causes Pierce’s disease in grapes, as well as other plant diseases. H. vitripennis was introduced to California from the southeastern United States and is now a management concern for viticulturists. This study measured demographic parameters (time for eggs to hatch and nymphs to pass through each stage of development, daily survivorship rates, adult fecundity, etc.) of H. vitripennis at different temperatures under laboratory conditions to develop predictive maps of H. vitripennis reproductive success throughout California. The authors estimated the temperature minima, maxima, and optima for development at each life stage. GIS mapping was used to calculate the estimated number of H. vitripennis generations and population growth rates in different areas of California based on daily minimum and maximum temperature values. Data from California Irrigation Information System and Western Regional Climate Center weather stations were used as model inputs. When mapped, the known distribution of H. vitripennis (primarily in southern California) coincided with the areas that supported a higher growth rate and allowed more generations to be produced annually in the temperature-dependent models. There were some discrepancies between the number of annual generations predicted by modeling and the observed number of H. vitripennis generations under field conditions, which may have resulted from failure to include other biologically relevant parameters like day length that can affect insect activity. Models of hypothetical populations throughout the state predicted fewer annual generations and lower population growth rates in northern California, including in important wine-producing countries such as Napa, Sonoma, and Fresno, suggesting lower susceptibility to invasion for cooler areas of the state.

12. Ponti, L., Gutierrez, A.P., Boggia, A., Neteler, M. (2018). Analysis of grape production in the face of climate change. Climate 6(2). https://doi.org/10.3390/cli6020020.

Climate change threatens agricultural production in Mediterranean climates, including culturally and economically important crops like grapes, olives, and wheat. This study applies PBDMs and GIS to the bioeconomics of grape production under a +1.8 C (A1B) warming scenario in the Euro-Mediterranean region. One of the main demographic processes of interest was changes to crop-pest dynamics between grape and the grapevine moth, Lobesia botrana (Lepidoptera: Tortricidae), that could result from warming. The authors used historical weather records, the PROTHEUS regional atmosphere-earth climate model, and grape distribution and yield datasets to model weather-driven grape/L. botrana dynamics. PBDM results were geospatially analyzed and mapped in GRASS GIS. Model results predict decreases in grape yield in Mediterranean countries and in northern France, increase in yield in Germany and Hungary, and net zero or variable effects in most other European countries. Infestations by L. botrana are expected to increase throughout much of the study area, although they are predicted to decrease in some countries (Morocco, Algeria, Portugal, Egypt) where grape yields are also expected to decline. A similar modeling approach could be applied to represent dynamics of other grape pests, including leafhoppers, or to predict effects of multiple pest species. Field-level models could also be developed to inform management decisions, given site-specific parameter estimates. Unlike some of the population models used by other sources in this bibliography, this paper explicitly considers changes to grape yield, rather than focusing on pest population dynamics.

13. Raffini, F., Bertorelle, G., Biello, R., D’Urso, G., Russo, D., Bosso, L. (2020). From nucleotides to satellite imagery: approaches to identify and manage the invasive pathogen Xylella fastidiosa and its insect vectors in Europe. Sustainability 12(11). https://doi.org/10.3390/su12114508.

The gram-negative bacterium Xylella fastidiosa causes serious plant disease, such as olive quick decline syndrome in olive trees and Pierce’s disease in grapes, that currently have no effective treatment. This pathogen was introduced from North and South America to Europe around 2013. Its vectors include many xylem-feeding true bugs (Hemipterans): leafhoppers and sharpshooters (Cicadellidae), spittlebugs (Cercopoidea), and cicadas (Cicadidae), among other families. This paper combines genetic and ecological studies on X. fastidiosa to present a multidisciplinary review of the biology, transmission, and management of this bacterium. GIS tools are highlighted for their contributions to our understanding of the spatial ecology of X. fastidiosa and its vectors. For example, field surveys have been integrated with GIS data to track the movement of the polyphageous spittlebug Philaenus spumarius within habitats, and GIS analyses of land-cover have identified features (herbaceous and shrub plants near orchards) associated with outbreaks of diseases vectored by P. spumarius. Remote sensing data and spatially explicit models can also be analyzed and processed to produce maps of X. fastidiosa range and invasion risk using GIS technology. To incorporate genetic approaches, spatial ecology studies can address the genetic diversity of X. fastidiosa, such as by analyzing how regional temperature affects the distribution of its strains and modeling potential future ranges under different climate change scenarios. The authors note that GIS, remote sensing, and spatially explicit models have, thus far, only been used to a limited extent to explore the spatial ecology of X. fastidiosa and its insect vectors because low resolution of data and limited access to GIS databases present barriers to research.   

14. Romàn, C., Arnò, J., Planas, S. (2021). Map-based zonal dosage strategy to control yellow spider mite (Eotetranychus carpini) and leafhoppers (Empoasca vitis & Jacobiasca lybica) in vineyards. Crop Protection 147. https://doi.org/10.1016/j.cropro.2021.105690.

In fields where crop vigor varies, pesticide dosage can be reduced in low-vigor zones to reduce total pesticide use. Decision support systems such as DOSA3d may be used to develop pesticide prescription maps when zonal-dosage is applied. This study evaluates the efficacy of map-based zonal dosage in controlling populations of the leafhoppers Empoasca vitis and Jacoviasca lybica (Hemiptera: Cicadellidae) and the mite Eotetranychus carpini (Acari: Tetranychidae), which can damage grape leaves and decrease grape yield. Variability in vine vigor was assessed by calculating plant cell density (PCD, a simple ratio of near-infrared to red band reflectance) indices from multispectral aerial imagery. PCD values were used to assign areas to high or low vigor classes by cluster analysis in ArcGIS. Vigor maps were converted to prescription maps by calculating pesticide application rates based on leaf area indices (LAI), which were estimated from field samples for some trials and by the DOSA3D system in others. Prior to treatment, pest population densities were 77% higher in high vigor zones than in low vigor zones. Pesticide application based on vigor maps reduced pest populations to below the economic damage threshold in zones of both types, and reduced pesticide use by 16.6-23.9%. The efficacy of map-based zonal dosage in controlling leaf pests while decreasing pesticide use/costs was supported by this study. The approach for evaluating vine vigor using remote sensing techniques outlined in this paper could also be used to identify areas within vineyards that are likely to attract insect herbivores, and perhaps to inform the application of non-pesticide treatments in an Integrated Pest Management program.   

15. Sciaretta, A., Trematerra, P. (2014). Geostatistical tools for the study of insect spatial distribution: practical implications in the integrated management of orchard and vineyard pests. Plant Protection Science 50 (2): 97-110. https://doi.org/10.17221/40/2013-PPS.

Although it was historically treated as a problem in experimental design to be minimized and controlled statistically, spatial heterogeneity has increasingly become a topic of interest in agricultural research. Spatial variation in distribution of resources can greatly influence the distribution and dispersal patterns of insect herbivores and their natural enemies, which has important implications for IPM programs. This paper outlines geostatistical approaches to analyzing the distribution of insects within orchard and vineyard agroecosystems, with an emphasis on applications in IPM. The authors note that standard interpolation procedures (namely, ordinary kriging) may need to be adjusted for insect population data, which often consist of count data that includes many zero values; indicator kriging, which is appropriate for binary data, may be preferable. Furthermore, when sampling for geostatistical applications, traditional approaches developed to collect independent measurements and control for non-experimental sources of variation, may not be suitable. Autocorrelation, sources of natural variability, and areas where target species are absent are instead, desired, allowing for less restrictive or more spatially irregular sampling designs. Sciaretta and Trematerra provide examples of geostatistical applications in orchard and vineyard pest management, including modeling the spatial dynamics of the spread of invasive species, identifying hotspots and landscape elements that facilitate pest dispersal, and creating risk assessment maps that can be used to inform trap placement and other monitoring or management actions. The authors promote wider adoption of GIS technology and geostatistical approaches in IPM programs. Many studies cited in this review focus on moths (Lepidoptera; for example, Lymatria dispar, Grapholita funebrana, Cydia pomonella), although one (Nestel and Klein 1995) describes periodic clumped and random patterns of leafhopper distribution in fruit orchards, and the importance of overwintering sites in facilitating colonization of orchards by these insects. The principles and practices described could be applied to geospatial analyses of numerous leafhopper species that are of management concern in vineyards.

16. Thomas, C.S., Skinner, P.W., Fox, A.D., Greer, C.A., Gubler, W.D. (2002). Utilization of GIS/GPS-based information technology in commercial crop decision making in California, Washington, Oregon, Idaho, and Arizona. Journal of Nematology 34(3): 200-206.

The availability of geo-referenced data and geographic information system software, remote-sensing technology, accurate and current weather station data, and advanced crop and pest models have allowed commercial agricultural operations to make data-informed management decisions more rapidly. GPS and GIS software facilitate the distribution and analysis of ground-based measurements at a rate and scale that were not feasible prior to the development of these technologies. This study uses the GIS software Terrior to produce disease risk maps for four fungal diseases in crops such as grape, lettuce, and apple from automated, georeferenced weather station data, and analyzes aerial imagery captured by multispectral sensors in ENVI GIS to predict grape yield in vineyards. The authors evaluated the accuracy of different disease and harvest models in predicting disease-associated weather conditions, harvest dates, and harvest yields for numerous crop systems in the western United States; their objective was to test the capacity of (at time of publication) novel technologies like GIS/GPS, weather satellites, and weather network data to produce useful measurements for growers. More directly relevant to the topic of managing insect pests, insect degree day models were used to inform management decisions in Washington apple orchards for five moth species and one fruit fly (Rhagoletis indifferens, Diptera: Tephritidae). Degree-day models predict insect life cycle events based on minimum and maximum temperature thresholds for phenological changes in specific insects. They are commonly used to time application of insecticides that target particular life stages. Here, degree days were mapped from weather station data, and insecticide treatments were applied based on the predicted times and locations of development events in the target insects. Model accuracy was evaluated based on changes in pest insect capture numbers following treatment. Thomas et al. report that the degree day maps were useful for timing insecticide application and provide an example of a degree day map, but do not give as much quantitative support to this claim as to evaluation of other models described in this report. The kinds of degree-day maps described here could be produced for leafhooper species for which temperature-dependent developmental thresholds have been determined.

17. University of California Cooperative Extension. (2022). Improving control of the Virginia Creeper leafhopper. Virginia Creeper Leafhopper Areawide Project. https://ucanr.edu/sites/vclh/.

The Virginia Creeper leafhopper, Erythroneura ziczac (Hemiptera: Cicadellidae), has been introduced to the North Coast region of California, where it presents a management concern in vineyards due to its relatively fast rate of development, ability to reduce vine productivity by feeding on grape leaves, and potential role in transmitting red blotch disease, a viral grapevine infection. This website, established with funding from the Department of Pesticide Regulation and American Vineyard Foundation, promotes awareness about the biology, impacts, and management of E. ziczac in vineyards in Mendocino and Lake Counties, California, USA. It includes sections on the efforts to identify parasitoids that can effectively controlpopulations, guidelines for IPM strategies, and information about how to identify this species of leafhopper. Annual reports uploaded to the site describe plans to develop a database of georeferenced counts of E. ziczac throughout the region. The Hopland Research and Extension Center GIS and Ecological Mapping Unit is identified as a partner for disseminating monitoring data and developing maps of E. ziczac population densities and parasitism rates. However, according to the Annual Report for the 2016 crop year, only low-resolution hotspot maps could be generated due to the limited number of sites from which count data were obtained. More extensive sampling would be required to produce useful distribution and risk maps. As of the most recent monitoring update in 2018, it is unclear whether the database or regional mapping project has been completed.  

18. Van Helden, M., Pain, G., Pithon, J., Simmonneau, M.A. (2008). Experimenting with landscape management to control pest populations in viticulture. Proceedings of the International Organization for Biological Control, Western Palaearctic Regional Section (IOBC-wprs) working group “Landscape Management for Functional Biodiversity” (3): 117-120. http://www.iobc-wprs.org/pub/bulletins/iobc-wprs_bulletin_2008_34.pdf#page=125.

Addition of non-crop elements to agricultural landscapes, e.g. by planting hedgerows, has been proposed as a landscape management strategy that could limit pest dispersal and benefit natural enemies, contributing to control of pest populations. Hedges and other patches of non-crop vegetation could, conversely, provide alternative hosts for some pests. This study investigated the effects of farmscaping on abundance of vineyard pests including the spongy moth Lobesta botrana (Lepidoptera: Torticidae) and the green leafhopper Empoasca vitis (Hemiptera: Cicadellidae) by monitoring insect populations in a vineyard in the Saumur-Champigny region of France using pheromone-baited traps and correlating captures with local landscape characteristics. Land cover within 250-1,000 m of each trap was classified in ArcGIS from orthorectified aerial photographs. The percentage of land surface planted with vines was positively associated with L. botrana captures and negatively associated with E. vitis captures. The authors suggested that the negative correlation between E. vitis adults and high percentage of vine cover may have resulted from reliance of E. vitis on non-vine vegetation for hibernation sites. Especially in the spring, E. vitis may have been more abundant in plots with nearby winter hosts because they were dispersing from overwintering sites. Van Helden et al. identify potential tradeoffs involved in breaking up vineyard monocultures with hedgerow: some pests (such as L. botrana) may be inhibited by habitat fragmentation and barriers to colonization, while others (like E. vitis) could use the hedgerows themselves as resources.

19. Weber, E.A., Bettiga, L.J., Johnson, L.F., Battany, M. (2013). Remote sensing for vineyard pest management. In L.J. Bettiga (Ed). Grape Pest Management (3, 55-60). UCANR Publications.

This chapter summarizes basic principles of remote sensing as they relate to vineyard management and describes how remote sensing can be used to identify pest outbreaks and determine other causes of poor vine health. It explains that information about plant health can be deduced from spectral characteristics of vegetation in remote-sensing imagery; for example, lower reflectance of near-infrared (NIR) radiation may indicate stress or disease. Vegetation indices such as NDVI (normalized difference vegetation index), which are calculated from multispectral reflectance values associated with each pixel in an image, can be used to differentiate between vegetation and other surfaces based on the distinctive spectral characteristics of green plants. Because digital imagery captured from satellites or aircrafts is usually geo-registered to ground coordinates, it is readily compatible with GIS software, allowing users to generate maps that can be used in vineyard management decisions. Weber et al. suggest that pest and disease outbreaks tend to cause patterns in weak vine growth, represented by low NDVI values, that are spatially irregular and temporally variable. In contrast, weak growth caused by differences in cultivar or cultivation practices tend to appear as spatially regular blocks, and weak growth caused by gradients in soil characteristics may appear spatially irregular but tends to be more temporally stable than patterns caused by disease. Examples of changes in NDVI induced by nematodes, fungal and bacterial pathogens, and grape phylloxera (Hemiptera: Phylloxeridae) are provided to illustrate typical spatial and temporal patterns of pest outbreaks. The blue-green sharpshooter, Graphocephala atropunctata (Hemiptera: Cicadellidae), is also mentioned as a vector for Pierce’s disease; similar remote-sensing and GIS approaches could perhaps be extended to spatial analyses of other leafhopper-borne vine diseases like flavescence dorée.

20. Wilson, S.H. (2014). Influence of landscape diversity and flowering cover crops on biological control of the Western grape leafhopper (Erythroneura elegantula Osborn) in North Coast vineyards. [Doctoral dissertation, UC Berkley]. California Digital Library. https://escholarship.org/uc/item/59s6g10d.

Monoculture cropping can facilitate pest outbreaks by providing continuous resource patches for pests while removing habitat for natural enemies of unwanted insects. Retention of habitat heterogeneity, either on-farm or at a landscape level, may enhance biological control in agroecosystems by supporting populations of parasitoids and predators. This dissertation assesses how habitat diversity at different scales affects the biological control of Western grape leafhopper, Erythroneura elegantula (Hemiptera: Cicadellidae), which feed on grape leaves and reduce photosynthetic capacity of host plants, by the egg parasitoids Anagrus erythroneurae and A. daanei (Hymenoptera: Mymaridae). Anagrus spp. are thought to be sensitive to removal of natural vegetation that supports their overwintering hosts. The author evaluates effects of landcover diversity, proximity to riparian habitats, and flowering cover crops on E. elegantula abundance and egg production, natural enemy abundance, parasitism rates, and crop vigor in vineyards in Napa and Sonoma counties, California, USA. ArcGIS was used to quantify landscape diversity at study sites based on the US Forest Service CALVEG (Classification and Assessment with Landsat of Visible Ecological Groupings) dataset. E. elegantula were less abundant in more diverse landscapes, but this association did not seem to be driven by parasitism, as parasitoid abundance was not correlated with habitat heterogeneity. Parasitoid density was more strongly associated with E. elegantula density than with landscape-variables, indicating that Anagrus wasps may disperse over relatively long distances in search of hosts. The author suggests that predation during overwintering could reduce E. elegantula populations in vineyards with more surrounding natural habitat, due to the increased abundance of some predators such as Anyphaenidae spiders and the lady beetle Hippodamia convergens (Coleoptera: Coccinellidae) at these sites. Flowering crop cover, which was expected to enhance biological control of E. elegantula by supporting dense populations of natural enemies, did not reduce leafhopper abundance, despite parasitism rates being somewhat higher in plots where groundcover was planted.