Grapevine Canopy Research Articles

Which species of Tortricidae leafrollers are key insect pests in South Australian vineyards?

ABSTRACTLight brown apple moth, Epiphyas postvittana (Lepidoptera: Tortricidae) is regarded as the key insect pest in Australian vineyards and it is also an important pest of apples and citrus. E. postvittana is indigenous to Australia and has a wide geographical distribution. Recent observations suggest that leafroller species other than E. postvittana may be causing damage in grapevine canopies. A study of tortricids was undertaken in Adelaide Hills and McLaren Vale vineyards, South Australia. A total of 407 specimens of Tortricidae were collected from grapevine canopies. Molecular techniques were used to identify species. The mean prevalence of E. postvittana per sample was 91.0% in 2014/15 and 96.2% in 2015/16. Larval Acropolitis rudisana, lucerne leafroller, Merophyas divulsana and cotton tipworm, Crocidosema plebejana were also found on the grapevine canopy at much lower densities for the first time. The presence of leafroller species A. rudisana, M. divulsana and C. plebejana on grapevines confirms these species of Tortricidae may also be present in South Australian vineyards. This study confirms that E. postvittana is the most common tortricid pest in Adelaide Hills and McLaren Vale vineyards and also illustrates the utility of molecular methods in determining with confidence the species identity of larval Tortricidae.

3-D Characterization of Vineyards Using a Novel UAV Imagery-Based OBIA Procedure for Precision Viticulture Applications

Precision viticulture has arisen in recent years as a new approach in grape production. It is based on assessing field spatial variability and implementing site-specific management strategies, which can require georeferenced information of the three dimensional (3D) grapevine canopy structure as one of the input data. The 3D structure of vineyard fields can be generated applying photogrammetric techniques to aerial images collected with Unmanned Aerial Vehicles (UAVs), although processing the large amount of crop data embedded in 3D models is currently a bottleneck of this technology. To solve this limitation, a novel and robust object-based image analysis (OBIA) procedure based on Digital Surface Model (DSM) was developed for 3D grapevine characterization. The significance of this work relies on the developed OBIA algorithm which is fully automatic and self-adaptive to different crop-field conditions, classifying grapevines, and row gap (missing vine plants), and computing vine dimensions without any user intervention. The results obtained in three testing fields on two different dates showed high accuracy in the classification of grapevine area and row gaps, as well as minor errors in the estimates of grapevine height. In addition, this algorithm computed the position, projected area, and volume of every grapevine in the field, which increases the potential of this UAV- and OBIA-based technology as a tool for site-specific crop management applications.

A comparison of energy partitioning and evapotranspiration over closed maize and sparse grapevine canopies in northwest China

Energy exchanges and turbulent fluxes were simultaneously measured using eddy covariance technique over closed maize and sparse grapevine canopies during two growth seasons in an arid region of northwest China. Canopy conductance (Gc) and decoupling coefficient (Ω) were calculated to evaluate differences of fluxes and controlling factors over the two types of canopies. Atmosphere over grapevine canopy was drier, higher evaporative demand and aerodynamical transfer than maize canopy because air temperature, vapor pressure deficit and wind speed over grapevine were higher. Seasonal averaged net radiation (Rn) and soil heat flux (G) over maize canopy was higher and lower, respectively, than grapevine, resulting in that averaged available energy (Rn – G) was higher for maize than grapevine canopies, with 125.0 and 85.6 W m−2 in 2009 and 121.9 and 99.5 W m−2 in 2010, respectively. Energy partitioning of available energy to latent heat flux (λET) was higher for maize than grapevine canopies, with seasonal averaged ratio of 79.8% and 75.0% for maize and 62.3% and 59.8% for grapevine for both years, respectively. Seasonal averaged Bowen ratio (β) was lower for maize than grapevine canopies, with 0.26 and 0.72, respectively. Gc for maize canopy was higher than grapevine, varying nearly from 1 to above 30 mm s−1 and from 0 to above 15 mm s−1, respectively. Ω of maize canopy was higher than grapevine, with averaged values of 0.52 and 0.30, respectively, suggesting that there was a stronger coupling between grapevine canopy and the above air. The slope of linear regression between evapotranspiration (ET) and Rn were higher for maize canopy, indicating that maize ET was mostly controlled by Rn. The relationship between the Priestley-Taylor coefficient (α) and Gc fits an exponential increase for both types of crop canopies, suggesting that grapevine ET was more controlled by Gc because most grapevine Gc was lower than the threshold of 15 mm s−1. The slope of linear regression between α and leaf area index (LAI) <2.8 m2 m−2 was higher for maize canopy, indicating that maize ET was more sensitive to LAI below the threshold. These results are important for water management and agricultural sustainable development across similar croplands in arid regions.

Relative captures of grape root borer, Vitacea polistiformis (Lepidoptera: Sesiidae) in pheromone traps within vineyards and adjacent woodlands

The grape root borer (GRB), Vitacea polistiformis (Harris), is a significant pest of grapes (Vitis spp.) throughout parts of the eastern United States. Early detection and implementation of management tactics can prevent economic losses and vine death. The establishment of an effective monitoring program requires the deployment of pheromone baited traps in vineyards and native wild grapes. An understanding of the spatial distribution of GRB infestations is critical for the development of sampling plans and for implementing management decisions. Wing traps baited with synthetic GRB sex pheromones (99:1 blend of (E,Z)-2,13-ODDA and Z,Z-3,13-ODDA) were deployed in commercial vineyards and surrounding woodlands in wild grapes to monitor GRB abundance and distribution. In addition, pheromone-baited wing traps were placed at low, medium, and high positions (0.5 m–2 m above the ground) on the grapevine trellis in commercial vineyards to evaluate the effect of trap height on the number of GRB captured. Traps placed in the cultivated vineyard had consistently higher counts of GRB compared with traps along the vineyard edge and in the wild grapes in the woodland. The pheromone-baited traps placed on the highest trellis wire caught more GRB adults than traps placed at the lowest position on the bottom trellis wire. Therefore, we recommend to place traps at approximately 2 m in the upper grapevine canopy early in the season before flight of GRB moth begins in order to aid in the timing and implementation of management tactics.

Normalized difference vegetation index obtained by ground-based remote sensing to characterize vine cycle in Rio Grande do Sul, Brazil

ABSTRACT The normalized difference vegetation index (NDVI) obtained by remote sensing is widely used to monitor annual crops but few studies have investigated its use in perennial fruit crops. The aim of this study was to determine the temporal NDVI profile during grapevine cycle in vineyards established in horizontal training systems. NDVI data were obtained by the ground-based remote sensing Greenseeker in Chardonnay and Cabernet Sauvignon vineyards located in the Serra Gaúcha region, Rio Grande do Sul, Brazil, from September to June in the 2014/2015 and 2015/2016 vegetative seasons. The grapevine canopies were managed in horizontal training systems (T-trellis and Y-trellis). The results indicated that the temporal NDVI values varied during the grapevine cycle (0.33 to 0.85), reflecting the changing in vigor and biomass accumulation that resulted from the phenological stages and management practices. The temporal NDVI profiles were similar to both horizontal training systems. The NDVI values were higher throughout the cycle for Cabernet Sauvignon compared to Chardonnay indicating Cabernet Sauvignon as the cultivar with greater vegetative vigor. The NDVI obtained by ground-based remote sensing is a fast and non-destructive tool to monitor and characterize the canopy in real time, compiling into a single data several parameters related to vine development, like meteorological conditions and management practices that are difficult to be quantified together.

Canopy Separation Did Not Improve Dry-on-Vine Raisin Yield or Quality from Selma Pete Grapevines on Open Gable Trellises

Summary Goals: Dry-on-vine (DOV) raisin growers with open gable trellises can use selective cane-pruning and shoot positioning to separate grapevine canopies into distinct fruiting and renewal zones. This practice is thought to improve canopy structure and microenvironment, increasing raisin yield and quality. However, these assumptions have not yet been confirmed by research. Therefore, an experiment was conducted in which Selma Pete grapevines ( Vitis vinifera ) on open-gable trellises were subjected to one of three canopy separation treatments: non-separated; center-divided, where renewal shoots were gathered in the trellis center and supported by a foliage catch wire; or within-row alternate-bearing (WRAB), where selective pruning left canes and spurs on opposite cordons. The effects of canopy separation treatments on canopy structure, microenvironment and raisin yield, and quality were followed for three years. Key Findings: The WRAB canopy separation method generally reduced the number of leaf layers and increased the proportion of leaves on the canopy exterior in renewal shoot zones. In spring, renewal shoots in WRAB canopies had more direct sun exposure than renewal shoots in other canopy types, but light levels in WRAB canopies diminished thereafter, becoming similar to those in other canopies. Despite effects on canopy structure and microenvironment, no canopy separation method tested affected raisin yield or quality consistently. Impact and Significance: The WRAB canopy separation method affected canopy structure and microenvironment, but insufficiently to increase the yield or quality of DOV raisins on an open gable trellis. Moreover, the selective pruning required to establish WRAB canopies may reduce yield in the season following establishment, and possibly have negative effects on the fruiting zone microclimate, hindering fruit ripening or drying.

Transcriptional Responses to Pre-flowering Leaf Defoliation in Grapevine Berry from Different Growing Sites, Years, and Genotypes.

Leaf removal is a grapevine canopy management technique widely used to modify the source–sink balance and/or microclimate around berry clusters to optimize fruit composition. In general, the removal of basal leaves before flowering reduces fruit set, hence achieving looser clusters, and improves grape composition since yield is generally curtailed more than proportionally to leaf area itself. Albeit responses to this practice seem quite consistent, overall vine performance is affected by genotype, environmental conditions, and severity of treatment. The physiological responses of grape varieties to defoliation practices have been widely investigated, and just recently a whole genome transcriptomic approach was exploited showing an extensive transcriptome rearrangement in berries defoliated before flowering. Nevertheless, the extent to which these transcriptomic reactions could be manifested by different genotypes and growing environments is entirely unexplored. To highlight general responses to defoliation vs. different locations, we analyzed the transcriptome of cv. Sangiovese berries sampled at four development stages from pre-flowering defoliated vines in two different geographical areas of Italy. We obtained and validated five markers of the early defoliation treatment in Sangiovese, an ATP-binding cassette transporter, an auxin response factor, a cinnamyl alcohol dehydrogenase, a flavonoid 3-O-glucosyltransferase and an indole-3-acetate beta-glucosyltransferase. Candidate molecular markers were also obtained in another three grapevine genotypes (Nero d’Avola, Ortrugo, and Ciliegiolo), subjected to the same level of selective pre-flowering defoliation (PFD) over two consecutive years in their different areas of cultivation. The flavonol synthase was identified as a marker in the pre-veraison phase, the jasmonate methyltransferase during the transition phase and the abscisic acid receptor PYL4 in the ripening phase. The characterization of transcriptome changes in Sangiovese berry after PFD highlights, on one hand, the stronger effect of environment than treatment on the whole berry transcriptome rearrangement during development and, on the other, expands existing knowledge of the main molecular and biochemical modifications occurring in defoliated vines. Moreover, the identification of candidate genes associated with PFD in different genotypes and environments provides new insights into the applicability and repeatability of this crop practice, as well as its possible agricultural and qualitative outcomes across genetic and environmental variability.

The Effect of Partial Defoliation, Leaf Position and Developmental Stage of the Vine on Leaf Chlorophyll Concentration in Relation to the Photosynthetic Activity and Light Intensity in the Canopy of Vitis vinif era L. cv. Cabernet Sauvignon

The effect of partial defoliation and leaf position on leaf chlorophyll concentration in relation to the photosynthetic activity and light intensity in the canopy of Vitis vinifera L. cv. Cabernet Sauvignon was investigated at berry set, pea size, veraison and ripeness stages. The leaves of the severely defoliated vines appeared to contain the highest chlorophyll concentration. In general, chlorophyll a decreased as the leaves were situated progressively deeper into the canopy. No consistent relationship between chlorophyll concentration, light intensity and photosynthetic activity could be found for the different leaf positions. However, to obtain leaves that photosynthesize optimally, the amount and time of leaf removal in the grapevine canopy must be carefully planned.

Estimating biophysical and geometrical parameters of grapevine canopies ('Sangiovese') by an unmanned aerial vehicle (UAV) and VIS-NIR cameras

Three zones of different vine vigour were identified in a mature vineyard (Vitis vinifera 'Sangiovese') to test the potential of the Visible-Near Infrared (VIS-NIR) spectral information acquired from an unmanned aerial vehicles (UAV) in estimating the leaf area index (LAI), leaf chlorophyll, pruning weight, canopy height and canopy volume of grapevines. A significant linear correlation between the normalized differential vegetation index (NDVI) and LAI or between NDVI and leaf chlorophyll was found at day of the year (DOY) 162 and 190, whereas in August the relationship between NDVI and leaf chlorophyll was less evident. The canopy volume of low-vigour (LV) vines was 35 and 45 % of the high-vigour (HV) and medium-vigour (MV) ones, respectively. The pruning weight was linearly correlated with NDVI values of each vigour cohort. A good correlation between the measured canopy volume and UAV-estimated one as well as between measured and estimated canopy height was found. Our results indicated that the combined use of VIS-NIR cameras and UAV is a rapid and reliable technique to determine canopy structure and LAI of grapevine.

Determining Grapevine Canopy Effects on Effective Rainfall in Vineyards

Rainfall interception was determined for six trellis systems in a vineyard at Stellenbosch. Measurements made directly under the canopy and in the centre of the work row were compared to rainfall measured outside the vineyard. Rainfall was measured over two growing seasons from October until March. There was no difference between rainfall in the centre of the work rows and rainfall outside the vineyard. Due to the effect of seasonal increases in leaf area on rainfall that penetrated through the canopy, rainfall interception was estimated from rainfall measured outside the vineyard, as well as day of season when it occurred by means of multiple linear regressions. Since canopy orientation also influenced the amount of water that reached the soil surface, two regression equations were developed that explained 96% and 89% of the variation in the amount of water that reached the soil surface under slanting and vertical canopies, respectively. On average 86 % and 80 % of the rainfall landed under slanting and vertical canopies, respectively. Based on the assumption that rainfall on the uncovered fraction of the work row was similar to the rainfall measured outside the vineyard, the calculated weighted mean rainfall over the total area did not differ drastically from actual rainfall. This indicated that canopy effects on rainfall interception in vineyards were relatively small.

Rapid measurement of the three-dimensional distribution of leaf orientation and the leaf angle probability density function using terrestrial LiDAR scanning

At the plant or stand level, leaf orientation is often highly anisotropic and heterogeneous, yet most analyses neglect such complexity. In many cases, this is due to the difficulty in measuring the spatial variation of the leaf angle distribution function. There is a critical need for a technique that can rapidly measure the leaf angle distribution function at any point in space and time. A new method was developed and tested that uses terrestrial LiDAR scanning data to rapidly measure the three-dimensional distribution of leaf orientation for an arbitrary volume of leaves. The method triangulates laser-leaf intersection points recorded by the LiDAR scan, which allows for easy calculation of normal vectors. As a byproduct, the triangulation also yields continuous surfaces that reconstruct individual leaves. In order to produce a probability density function for leaf orientation from triangle normal vectors, it is critical that the proper weighting be applied to each triangle. Otherwise, results will heavily bias toward normal vectors pointed toward the the LiDAR scanner. The method was validated using artificially generated LiDAR data where the exact leaf angle distributions were known, and in the field for an isolated tree and a grapevine canopy by comparing LiDAR-generated distribution functions to manual measurements. The artificial test cases demonstrated the consistency of the method, and quantitatively showed that errors in the predicted leaf angle distribution functions decreased as scan resolution was increased or as the density of leaves was increased. The isolated tree field validation showed qualitatively similar trends between manual and LiDAR measurements of distribution functions. Manual measurements of leaf orientation in the vineyard were shown to have large errors due to high leaf curvature, which illustrated the benefits of the more detailed LiDAR measurement method.

Influence of grapevine canopy trimming and maturity variability within fruit population on the sensory properties of Pinot noir wine

The effects of differences in Pinot noir fruit maturity on the sensory properties, overall complexity and typicality of 'Marlborough Pinot noir' wines was studied over two seasons. Trimming canopies to 100 (TT), 60 (MT), or 30 (ST) cm above the fruiting cordon produced fruit with high, moderate and low soluble solids at harvest respectively. To investigate the variability of fruit populations (i.e. homogeneous v. heterogeneous soluble solids concentrations) on wine sensory properties, each treatment was harvested on the same date and fermented both separately and after blending fruit to ratios of 10:80:10 and 30:40:30 of low, moderate, and high maturities respectively. Additional wines were created after fermentation by blending wines made from each trim treatment to the same ratio as used for the pre-fermentation fruit population blends. Moderate and high fruit maturities provided wines with similar sensory properties, complexity and typicality as 'Marlborough Pinot noir'. Low 'Pinot noir' fruit maturity resulted in less fruity, spicy, full-bodied characters, more green/vegetal, and overall less complex wines compared with moderate and high fruit maturity wines. Composite wines made by blending, post-fermentation, wines produced from low, moderate and high maturity fruit did not differ from the wines made from similar blends of fruit. Indeed, the four composite wines made from blending fruit or wines had organoleptic properties comparable to those of the wine made with a homogeneous fruit population of moderate maturity with the same mean soluble solids concentrations. We conclude that 'Pinot noir' wines made using fruit with a wide range of maturities do not have different sensory properties from those made with fruit with a narrow range of maturities, providing the mean soluble solids concentrations of the fruit populations are similar.

Application of the Kinect sensor for three dimensional characterization of vine canopy

Monitoring grapevine canopy size and evolution during time is of great interest for the management of the vineyard. An interesting and cost effective solution for 3D characterization is provided by the Kinect sensor. To assess its practical applicability, field experiments were carried out on two different grapevines varieties (Glera and Merlot) for a three months period. The results from 3D digital imaging were compared with those achieved by direct hand-made measurements. Estimated volume was then effectively correlated to the number of leaves and to the leaf area index. The experiments demonstrated how a low cost 3D sensor can be applied for fast and repeatable reconstruction of vine vegetation, opening up for new potential improvements in variable rate application or pruning

Application of sprinkler cooling within the bunch zone during ripening of Cabernet Sauvignon berries to reduce the impact of high temperature

Background and Aim High temperature stress has been linked to detrimental effects on berry composition during ripening. This study aimed to assess the impact of an evaporative cooling system located inside the grapevine canopy to mitigate extreme temperature effects on grape berry composition during ripening. Methods and Results During three seasons (2012 to 2015), an intra-canopy sprinkler system at the bunch zone was tested on Cabernet Sauvignon vines. The system cyclically sprayed (20 s/10 min) for an air temperature above 38°C, cooling the air inside the canopy by 3 to 5°C. This is in agreement with an air cooling simulation model. The relative humidity in the canopy also increased in the sprinkler-cooled canopy. No differences were detected in TSS, although sugar per berry was significantly higher in treated vines because of increased berry mass. There was a tendency for higher anthocyanins and phenolic substances per berry in cooled berries measured from two seasons and higher concentration of anthocyanins in wine from cooled fruit measured only in one season. We define indices that can be used to assess the efficiency of sprinkler cooling and to demonstrate the high efficiency of intra-canopy sprinklers compared to other systems. Conclusion Despite cooling operating only over a small duration of the ripening period, the increased berry mass indicates that high temperature, even for a short period, has a profound effect on berry growth. Other berry compositional properties and wine, however, were not impacted. Significance of Study This research demonstrates the potential of an efficient intra-canopy sprinkler system to reduce heat stress during ripening.

Digital surface model applied to unmanned aerial vehicle based photogrammetry to assess potential biotic or abiotic effects on grapevine canopies

Abstract: Accurate data acquisition and analysis to obtain crop canopy information are critical steps to understand plant growth dynamics and to assess the potential impacts of biotic or abiotic stresses on plant development. A versatile and easy to use monitoring system will allow researchers and growers to improve the follow-up management strategies within farms once potential problems have been detected. This study reviewed existing remote sensing platforms and relevant information applied to crops and specifically grapevines to equip a simple Unmanned Aerial Vehicle (UAV) using a visible high definition RGB camera. The objective of the proposed Unmanned Aerial System (UAS) was to implement a Digital Surface Model (DSM) in order to obtain accurate information about the affected or missing grapevines that can be attributed to potential biotic or abiotic stress effects. The analysis process started with a three-dimensional (3D) reconstruction from the RGB images collected from grapevines using the UAS and the Structure from Motion (SfM) technique to obtain the DSM applied on a per-plant basis. Then, the DSM was expressed as greyscale images according to the halftone technique to finally extract the information of affected and missing grapevines using computer vision algorithms based on canopy cover measurement and classification. To validate the automated method proposed, each grapevine row was visually inspected within the study area. The inspection was then compared to the digital assessment using the proposed UAS in order to validate calculations of affected and missing grapevines for the whole studied vineyard. Results showed that the percentage of affected and missing grapevines was 9.5% and 7.3%, respectively from the area studied. Therefore, for this specific study, the abiotic stress that affected the experimental vineyard (frost) impacted a total of 16.8 % of plants. This study provided a new method for automatically surveying affected or missing grapevines in the field and an evaluation tool for plant growth conditions, which can be implemented for other uses such as canopy management, irrigation scheduling and other precision agricultural applications. Keywords: remote sensing, canopy cover, viticultural management, frost damage, digital surface model DOI: 10.3965/j.ijabe.20160906.2908 Citation: Su B F, Xue J R, Xie C Y, Fang Y L, Song Y Y, Fuentes S. Digital surface model applied to unmanned aerial vehicle based photogrammetry to assess potential biotic or abiotic effects on grapevine canopies. Int J Agric & Biol Eng, 2016; 9(6): 119－130.

Integrating Geographic Information Systems and hemispherical photography in the assessment of canopy light profiles in a vineyard

The light conditions in a vineyard primarily depend on the latitude of the vineyard and day of the year. Based on these parameters, the exact daily Sun path can be calculated with astronomical functions. However, effective Sun hours also depend on the topography of the territory, both for direct and diffuse radiation, as a result of the presence of hills and mountains on the Sun path (direct radiation) or, in general, reducing the sky fraction (diffuse radiation). A 360° orographic profile can be assessed by topographic survey, by using hemispherical pictures or Geographic Information Systems (GIS) and Digital Elevation Models (DEM). Moreover, row orientation, vine spacing, trellis system and height, leaf area density, exposure side, etc. further affect the light micro-climate within the canopy and, particularly, at bunch level, which may have consequences for the temperature and composition of the berries.In the present work two grapevine row orientations (NS and EW) were used to integrate various tools (Photovoltaic Geographical Information System, Visual Basic functions for the calculation of solar position and radiation, and results from the processing of hemispherical pictures) into an Excel Worksheet, called “SunMask”, that can be used as a new multi-purpose tool to 1) quickly calculate both the astronomic and the topographic sunrise, sunset, and maximum potential day length, 2) evaluate the effect of row orientation and canopy dimensions on the transmittance of the direct solar beam at high temporal resolution and, finally, 3) separate the effect of topographic and canopy masks on the Sun hours under clear-sky conditions.By combining the different tools in SunMask, both the astronomic and topographic (as affected by the surrounding hills and mountains) sunrise, sunset, and maximum potential day length can be quickly and easily calculated for every specific vineyard terroir/location at any date or time in Europe, Africa and Asia. In addition, the software allows the evaluation of the effect of the canopy mask on the transmittance of the direct solar beam. SunMask will be a very important asset to improve information regarding radiation profiles of vineyards at meso- and micro-levels. It will be most valuable in the assessment of terroir suitability for vineyard establishment as well as for viticulture practice choices and the management of grapevine canopies.

VitiCanopy: A Free Computer App to Estimate Canopy Vigor and Porosity for Grapevine.

Leaf area index (LAI) and plant area index (PAI) are common and important biophysical parameters used to estimate agronomical variables such as canopy growth, light interception and water requirements of plants and trees. LAI can be either measured directly using destructive methods or indirectly using dedicated and expensive instrumentation, both of which require a high level of know-how to operate equipment, handle data and interpret results. Recently, a novel smartphone and tablet PC application, VitiCanopy, has been developed by a group of researchers from the University of Adelaide and the University of Melbourne, to estimate grapevine canopy size (LAI and PAI), canopy porosity, canopy cover and clumping index. VitiCanopy uses the front in-built camera and GPS capabilities of smartphones and tablet PCs to automatically implement image analysis algorithms on upward-looking digital images of canopies and calculates relevant canopy architecture parameters. Results from the use of VitiCanopy on grapevines correlated well with traditional methods to measure/estimate LAI and PAI. Like other indirect methods, VitiCanopy does not distinguish between leaf and non-leaf material but it was demonstrated that the non-leaf material could be extracted from the results, if needed, to increase accuracy. VitiCanopy is an accurate, user-friendly and free alternative to current techniques used by scientists and viticultural practitioners to assess the dynamics of LAI, PAI and canopy architecture in vineyards, and has the potential to be adapted for use on other plants.

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).

Selective spraying of grapevines for disease control using a modular agricultural robot

Due to their recognised role in causing environmental pressures, the need to reduce production costs and public concerns over the healthfulness of fresh products and food, reducing pesticide use in agriculture is a major objective. In current farming practice, pesticides are typically applied uniformly across fields, despite many pests and diseases exhibiting uneven spatial distributions and evolving around discrete foci. This is the fundamental rationale for implementing the selective targeting of pesticide applications such that pesticides are deposited only where and when they are needed and at the correct dose. This approach is explored using the example of powdery mildew on grape vines controlled by means of a modular agricultural robot developed within the EU-project CROPS. The CROPS manipulator was configured to six degrees of freedom and equipped with a new precision-spraying end-effector with an integrated disease-sensing system based on R-G-NIR multispectral imaging. The robotic system was tested on four different replicates of grapevine canopy plots (5 m in length × 1.8 m in height) prepared in a greenhouse setup by aligning potted plants exhibiting different levels of disease. The results indicate that the robot was able to automatically detect and spray from 85% to 100% of the diseased area within the canopy and to reduce the pesticide use from 65% to 85% when compared to a conventional homogeneous spraying of the canopy. This work, to the best of our knowledge, is the first using a totally automatic selective system for spraying of diseases in specialty crops.

Reduced grapevine canopy size post-flowering "via" mechanical trimming alters ripening and yield of 'Pinot noir'

The degree and time of canopy trimming can alter phenology, rates of increase or decrease in berry components during grape ripening, and may influence yield and its components. The objective of this study was to investigate the extent to which reducing canopy size, by mechanical trimming post-flowering, changed Vitis vinifera L. 'Pinot noir' fruit yield and composition. Vines were mechanically trimmed to three different canopy heights at fruitset: 1000 mm (100 % canopy height), 600 mm (60 % canopy height relative to the control treatment) and 300 mm (30 % canopy height relative to the control treatment). Total soluble solids concentration and content, titratable acidity, pH and fresh berry mass were measured throughout ripening, and yield and leaf area were measured at harvest. Reduced canopy size via trimming to 30 and 60 % of the control treatment height slowed total soluble solids accumulation and in some cases increased titratable acidity and increased pH. The total soluble solids-titratable acidity ratio was therefore reduced throughout ripening by these trimming treatments relative to the full canopy height. Trimming to reduce canopy size had two effects on the source-sink ratio; it reduced the source (canopy) but increased fruit yield, an important sink. Therefore, the time of trimming is an important management consideration because it can delay and slow ripening due to reduced source leaves but could potentially accentuate the delay via increasing yield (sink). This technique may represent a way to offset the acceleration of phenology and grape ripening that has been observed to occur as a result of warmer seasons.