The development of phytosanitary monitoring methods – creating of a schematic scale for as-sessing the development of Alternariosis on grape leaves

Abstract

To ensure consistent good quality grape yields it is necessary to minimize losses associated with affection of grape plants by various dis-eases. One of the main conditions to ensure the effective control of phyto-pathogens is a timely monitoring, revealing and assessing of harmful or-ganisms development intensity. In modern research, in order to improve the accuracy and reliability of quantitative characteristics of disease devel-opment intensity, as well as comparability of the results obtained, it is pro-posed to use a “set of standard diagrams” or a “schematic scale” - a set of illustrations depicting an increasing percentage of damage to the surface of one or another plant organ. To date, similar "sets of standard diagrams" were proposed for such grape diseases as mildew, anthracnose and grape leave rust. The article presents the results of creating a new "schematic scale" for assessing the development intensity of grape Alternariosis as a disease with the recorded increasing importance at a recent time of climate change. The scale was developed using colored and black–and-white pho-tographs of grape leaves affected by Alternariosis to varying degrees to de-termine the real intensity of the disease in digital form. Scale levels were established in accordance with minimum and maximum values of damage degree. Validation was carried out by two groups of assessors with differ-ent experience in accounting. The determination coefficient (R2) of regres-sion line and the absolute error variance demonstrated an increase in accu-racy, repeatability and reproducibility of estimates using the developed “schematic scale”. Using of the developed scale made it possible to in-crease the accuracy of quantitative assessment of intensity of Alternariosis damage to grape leaves.