Effect of Fungicide Protection of Sugar Beet Leaves (Beta vulgaris L.): Results of Many Years Experiments

Abstract

The rosette is the above-ground morphological part of sugar beet in the first year of its ontogenesis. The size and health of the leaves determine photosynthesis and the production of sugars and their redistribution throughout the plant and thus the yields and quality of individual organs. One means of protecting leaves is to apply fungicides. Their efficacy and effects of use depend on, among other things, the active ingredient and number of sprayings, as well as environmental conditions. The aim of the 11-year study was to evaluate the effect that the foliar application of fungicides in sugar beet cultivation had on leaf infestation and damage, the Leaf Area Index (LAI), leaf yield, and a plant foliage index (FI) expressed as the ratio of leaf mass to root mass. In field experiments, six treatments were compared: a control without fungicides; three sprayings with triazoles, benzimidazoles, and strobilurins as the active ingredients; and a single application of tebuconazole, epoxiconazole, strobilurin, and an epoxiconazole + thiophanate-methyl mixture. The efficacy and effects of the fungicide protection depended on its method of application and environmental conditions. Applying fungicides weakened the positive correlation of sugar beet leaf infestation and leaf damage to the sum of precipitation relative to the unprotected plants. In ten of the eleven years of the study, fungicide protection significantly increased leaf yields of plants and decreased their FI. In only three years did three sprayings increase leaf yield more than single sprayings, and, in six years, at least one of the active ingredients or the epoxiconazole + thiophanate-methyl mixture was as effective as triple sprayings. It is therefore warranted to permanently monitor the condition of plants and to select the fungicide application method depending on conditions.