Model Development to Predict Phenological scale of Table Grapes (cvs. Thompson, Crimson and Superior Seedless and Red Globe) using Growing Degree Days

Phenological models have been made mainly for winegrape cultivars, despite the economic importance of table grapes. The aim of this work was to develop and validate models for predicting phenological scales of table grapes (cvs. Thompson, Crimson and Superior Seedless and Red Globe) grown under semi-arid conditions. Measurements of phenology were carried out weekly from budburst to harvest during four growing seasons (2009-2013). Phenology models were developed using the Mitscherlich monomolecular equation where the dependent and independent variables were the Eichhorn and Lorenz phenological (ELP) scale modified by Coombe and the growing degree days (GDD), respectively. Results indicated that there were strong non-linear correlations between the ELP scale and GDD for the four cultivars with coefficient of determinations (R2) ranging between 0.97-0.99. Also, validation indicated that the models were able to predict ELP scale with a root mean square (RMSE) and mean absolute error (MAE) ranging between 2.1-2.4 and 1.35-1.69, respectively. The prediction variability (expressed in days) was between 4.4-19.4 days, obtaining the best results for the flowering period. This study suggested that the phenological models based on GDD could be useful planning tools for farming, especially from budburst to veraison of table grape cultivars

Classification of wine grape cultivars according to their susceptibility to Botrytis Cinerea : importance of fruit maturity

International audienceBotrytis cinerea causes one of the most serious diseases in grapevines namely Botrytis Bunch Rot (BBR). A classification of different grapevine cultivars (cvs.) according to their susceptibility to B. cinerea is an essential management indicator in Integrated Pest Management. Although such classifications are available, they are based mostly on professional experience rather than experimental results. The main aim of this study was to compare and classify the susceptibility of different winegrape cvs to B. cinerea and its relation to fruit maturity within two contrasting climatic and cropping conditions. Between 2011 and 2015, three field trials were carried out in Chile and France, including 13 common cvs. Both, incidence and severity of the disease were evaluated at harvest and indices of susceptibility (SI) and maturity (FMat) were calculated on a per-site basis. The significant differences in disease incidence and severity observed among cvs. led to a similar susceptibility classification in both countries. Cabernet Sauvignon, Cabernet Franc, Grenache Noir and Petit Verdot were the most resistant cvs., whereas Gewürztraminer and Sauvignon Blanc were the most susceptible ones. Moreover, an exponential and positive relationship was established between SI and maturity. The cultivar classification according to the susceptibility to B. cinerea was similar in both countries, despite the contrasting climatic conditions and cropping practices. These findings might be of interest for choosing cultivars more resistant to B. cinerea in order to reduce the number of specific anti-Botrytis fungicide applications

Performance of a decision rule for integrated control of powdery mildew in grapevine in the central region of Chile

The dominant strategy followed by vine-growers in Chile to control powdery mildew (Erysiphe necator) involves schedule phytosanitary applications resulting between 9 to 18 fungicide sprays depending on the grape cultivar and the geographical area, mainly with sulphur applications. This large application of chemicals generates many environmental and human health risks To solve this, the present study aimed at evaluating the effectiveness of a Phytosanitary Decision Rule (PDR) proposed by French pathologists to rationalize fungicide applications against powdery mildew in grapevine. The PDR was evaluating in two irrigated vine fields, one of cultivar Cabernet sauvignon (CS, 1.56 ha) and another of Chardonnay (CH, 1.66 ha), in the Mediterranean climatic conditions of Talca Region, Chile. The experiment was carried out between 2009 and 2013. For the two experimental fields, two strategies to control powdery mildew were distributed in a randomized block design with four replicates: i) “Optimized traditional management” (OPT), which consisted in periodic applications (mainly sulphur), but with no more than nine treatments per season, ii) Application of a PDR based on field observations but with no more than four treatments per season. Untreated vines were left in each block to assess disease pressure at each studied season. Finally, a survey was conducted to know the practices of crop protection of traditional vine-growers (TVG) in the area, who carry out a “zero risk” strategy without limiting the number of phytosanitary applications. At veraison stage, clusters were observed to assess disease severity. The results show that powdery mildew control based on a PDR was as effective as schedule applications used by the OPT at experimental station for both vine fields. In the OPT and PDR treatments disease severity was lower than 5 %, which was considered as a threshold value for avoid in gloss of wine quality. For both cultivars disease severity was lower than that observed in untreated vines (close to 10% and 40 % for CS and CH, respectively). In the OPT treatment 7 to 9 applications per season independent of cultivar were made, whereas in the PDR treatment only 2-4 application were carried out. The differences are even greater when comparing the PDR with the TVG strategy in which, independent of the season and the cultivar, performed an average of 14 fungicide applications. Finally in the OPT and PDR treatments the cost per season was similar and fluctuated between US $322 and 415 per hectare independent of the cultivar. This value is 60$ 322 et 415 par hectare, valeur qui est 60% inférieure au coût de la stratégie “risque zéro” de viticulteurs

Performance of a decision rule for integrated control of powdery mildew in grapevine in the central region of Chile

The dominant strategy followed by vine-growers in Chile to control powdery mildew (Erysiphe necator) involves schedule phytosanitary applications resulting between 9 to 18 fungicide sprays depending on the grape cultivar and the geographical area, mainly with sulphur applications. This large application of chemicals generates many environmental and human health risks To solve this, the present study aimed at evaluating the effectiveness of a Phytosanitary Decision Rule (PDR) proposed by French pathologists to rationalize fungicide applications against powdery mildew in grapevine. The PDR was evaluating in two irrigated vine fields, one of cultivar Cabernet sauvignon (CS, 1.56 ha) and another of Chardonnay (CH, 1.66 ha), in the Mediterranean climatic conditions of Talca Region, Chile. The experiment was carried out between 2009 and 2013. For the two experimental fields, two strategies to control powdery mildew were distributed in a randomized block design with four replicates: i) “Optimized traditional management” (OPT), which consisted in periodic applications (mainly sulphur), but with no more than nine treatments per season, ii) Application of a PDR based on field observations but with no more than four treatments per season. Untreated vines were left in each block to assess disease pressure at each studied season. Finally, a survey was conducted to know the practices of crop protection of traditional vine-growers (TVG) in the area, who carry out a “zero risk” strategy without limiting the number of phytosanitary applications. At veraison stage, clusters were observed to assess disease severity. The results show that powdery mildew control based on a PDR was as effective as schedule applications used by the OPT at experimental station for both vine fields. In the OPT and PDR treatments disease severity was lower than 5 %, which was considered as a threshold value for avoid in gloss of wine quality. For both cultivars disease severity was lower than that observed in untreated vines (close to 10% and 40 % for CS and CH, respectively). In the OPT treatment 7 to 9 applications per season independent of cultivar were made, whereas in the PDR treatment only 2-4 application were carried out. The differences are even greater when comparing the PDR with the TVG strategy in which, independent of the season and the cultivar, performed an average of 14 fungicide applications. Finally in the OPT and PDR treatments the cost per season was similar and fluctuated between US $322 and 415 per hectare independent of the cultivar. This value is 60$ 322 et 415 par hectare, valeur qui est 60% inférieure au coût de la stratégie “risque zéro” de viticulteurs

Identification of main factors affecting the within-field spatial variability of grapevine phenology and total soluble solids accumulation: towards the vineyard zoning using auxiliary information

International audienceGrapevine phenology and total soluble solids (TSS) accumulation are important information to plan agricultural operation in the vineyards over the season. The study aims at identifying the main environmental factors and related high spatial auxiliary information that could be used to define within-field zones of phenology and TSS accumulation. An experiment was carried out in the Maule Valley, Chile, considering two representative vineyards with different environmental characteristics: vineyard 1 (cv. Cabernet Sauvignon) which presents differences in elevation and vineyard 2 (cv. Chardonnay) which is considered flat. Within each vineyard, a regular sampling grid was defined to perform measurements: phenology, TSS accumulation, plant water status, vegetative expression, yield, soil physical properties and soil apparent electrical conductivity. Observations were made during four and two years respectively for vineyard 1 and 2. The analysis of the results is based on principal component analysis (PCA) to identify the relationships between variables. Results show that factors affecting the spatial variability of phenology and TSS accumulation are different for each vineyard. For vineyard 1, topography is the main factor that affects the spatial variability both in phenology and TSS accumulation. For vineyard 2, the soil apparent electrical conductivity was the most important factor explaining the spatial variability observed in the phenology, while balance between vegetative expression and fruit load affected the TSS accumulation. These results highlight the possibility to define zones of differentiated management in relation to the phenology and TSS accumulation using auxiliary information easy to acquire or available with high spatial resolution

Evaluation of a decision support strategy for the control of powdery mildew (Erysiphe necator [Schw.] Burr.) in grapevine in the central region of Chile

BACKGROUND: The primary strategy to control powdery mildew in Chileanvineyards involves periodic fungicide spraying, which may lead to many environmentaland human health risks. This study aimed to implement and evaluate the effectivenessand economic feasibility of a novel Decision Support Strategy (DSS) to limit thenumber of treatments against this pathogen. An experiment was conducted between the2010 and 2013 seasons in two irrigated vine fields, one containing a cultivar ofCabernet Sauvignon (CS) and another of Chardonnay (CH).RESULTS: The results showed that the DSS effectively controlled powdery mildew inCS and CH vine fields as evidenced by a disease severity lower than 3%, which waslower than that observed in untreated vines (approximately 10% and 40 % for CS andCH, respectively). The DS strategy required the application of only 2-3 fungicidetreatments per season in key vine phenological stages, and the cost fluctuated betweenUS $ 322 and 415 per hectare, which was 40 to 60 % cheaper than the traditionalstrategy employed by vine growers.CONCLUSION: The Decision Support Strategy evaluated in this trial allows a goodcontrol of powdery mildew for various types of epidemics with an early and lateinitiation

Vigor thresholded NDVI is a key early risk indicator of Botrytis bunch rot in vineyards

Botrytis bunch rot (BBR) is a major disease occurring in vineyards worldwide. Its control is still largely based on the use of synthetic fungicide sprayings at predetermined intervals, which often produces negative residues in grapes and wines that may affect the environment and/or human health. To rationalize BBR management, disease risk indicators were developed and evaluated in a set of field experiments carried out between 2010 and 2019 in France and Chile. Key indicators include early grapevine vegetative growth, i.e. ground-based normalized difference vegetation index (NDVI), and the potential berry susceptibility to Botrytis cinerea, which is driven by tannin content in the skin. Under these contrasting weather and cropping conditions, regression analyses, including weather information, showed a highly significant positive correlation between the early NDVI, measured at berry pea size stage, and BBR incidence or severity at harvest, whereas the opposite was demonstrated for tannin content in the berry skin measured at an early herbaceous fruit stage. The exponential relationship between the final disease severity and the early NDVI allowed us to identify a possible threshold NDVI value, i.e. between 0.5 and 0.6, under which the BBR severity should be lower or close to 5% at harvest (BBR tolerance threshold for wine quality)