Several methods have been proposed to measure the water status of the vine (Acevedo-Opazo et al. 2008). However, these methods generally require significant equipment and specific skills. They are therefore difficult to implement for systematic monitoring over a large area and throughout the season. In order to overcome these constraints, simpler alternative approaches have been proposed (Acevedo-Opazo et al. 2008). Among these, the apex growth index (Payan, 2018) is interesting because it is based on simple observations of the end of the vine branches, the apices. The Institut Français de la Vigne et du Vin (IFV) recommends the use of the apex growth index (iC-Apex), which is simple to calculate and has made it possible to define correspondences with different levels of water stress measured in the vineyard. Although more imprecise than standard methods, the iC-Apex has the advantage of being easily performed by inexperienced operators and without expensive equipment.

However, the iC-Apex method has certain limitations which have restricted its adoption by the industry. It requires operators to observe 50 apices, classify them into three different classes according to their growth and calculate the iC-Apex. These observations are often supplemented by other information such as the time or location of the observation session. Although simple, these different operations can be cumbersome to implement in a production context. In order to solve this problem and to simplify the use of iC-Apex by the wine industry, it has been proposed to develop a mobile application, called "Apex Vigne". The Institut Français de la Vigne et du Vin (IFV) and Montpellier SupAgro, supported by the Occitanie region, are launching this application on June 3, 2019.

The objective of this mobile application is to provide a simple tool for:

1. facilitate the collection of apex observations,
2. automatically calculate the iC-Apex,
3. georeference and time stamp iC-Apex values ​​and
4. centralize observations in a database to facilitate future analysis of these data at different spatial scales. The mobile application was designed to promote the adoption of the iC-Apex method by wine growers, advisers and other stakeholders in the sector.

This mobile application can be used i) at the plot level by the winegrower or his advisor for the management of the vineyard, ii) at the scale of a network of plots to follow experiments or define a collective strategy or iii) to regional scale to monitor the impacts of climate change or identify particularly sensitive areas.

ApeX Vigne can be downloaded for free from the app store. It allows, thanks to a simple counting system, to count the apices and then to calculate a vegetative growth index. The application can be downloaded from: https://play.google.com/store/apps/details?id=ag.GB.apex&hl=fr&gl=US

The application then offers a summary and monitoring of the evolution of apex growth for each plot. Finally, an application module, developed by IFV, offers an interpretation of the water stress level based on the observations made. The information is stored securely. The user can then retrieve them for further analysis or share them with others.

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Author: Léo Pichon

Acknowledgement: Bruno Tisseyre