How important is UAVs RTK accuracy for the identification of certain vine diseases?

Abstract

The recent deployment of GNSS-RTK positioning on remotely piloted vehicles has increased real-time positioning accuracy by almost three orders of magnitude. This not only provides a significant geometric improvement but, in practice, makes possible some applications that were simply not possible before. For example, positioning crops with centimetre accuracy makes it possible to distinguish a single plant and to detect or treat that very plant without any possibility of misunderstanding. This is obviously not possible with ‘traditional’ drones that work in ‘point positioning’ with indeterminacies of even tens of metres. In this paper we will illustrate how the possibilities of RTK can be applied to a specific vinepathology. The symptoms of the flavescence dorée and bois noir are grouped into the so-called Grapevine Yellows (GY). These diseases are affecting the viticultural regions worldwide and all varieties and rootstocks seem susceptible but with varying degrees of severity. Typical symptoms include discolouration and necrosis of leaf veins and leaf blades, downward curling of leaves, lack or incomplete lignification of shoots, stunting and necrosis of shoots, abortion of inflorescences and shrivelling of berries. The compulsory control plan for the fight of these diseases includes both the use of insecticides and the eradication of the vines. This latter is part of a monitoring plan of the grapevine yellows that aims to identify outbreaks of the disease and its progression and limit the compulsory phytosanitary control only in the truly affected areas. The identification of the GY is a very time-consuming technical work because each vineyard must be visually inspected plant by plant. This type of monitoring is made even more difficult in the case of steeply sloping vineyards and where the vineyard landscape is fragmented. So, we raised the following question: is it possible to use Unmanned Aerial Vehicles (UAVs or drones) to remotely monitor the vines that are difficult to reach and identify the grapevine yellows? We present here the results of our field tests made in Trentino (IT) with different drone models (prosumer and professional) and with different types of image acquisition sensors (RGB and multi-spectral).