o:3103 The effect of application of organic biostimulant “Zlatno inje” on the occurrence of lemon balm septoria leaf spot (Septoria melissae Desmazieres) en Abstract: This study examines the impact of the application of organic biostimulant “Zlatno inje” on the occurrence of lemon balm septoria leaf spot (Septoria melissae Desmazieres). This paper aims to find a possible solution for one of the most important diseases of cultivated lemon balm in our region from the economic point of view. This disease is caused by the fungus S. melissae, which can occur in the production of seedlings, but also on the plants in old plantations. The study was conducted in the experimental field of the Institute for Medicinal Plants Research “Dr Josif Pančić”, which is located in Pančevo, Serbia (44°52’20”N; 20°42’06”E; 74 MASL). The experiments were conducted during the growing season in 2018 on a three-year-old plantation by a randomized block design with four repetitions. The soil type at this location is humogley (black soil). The plot size was 8.4 m2 and the effect of the organic biostimulant “Zlatno inje” was estimated according to a scale of 1 to 5 of the presence of the disease on the lemon balm leaf. The “Citron” variety of the lemon balm was used as the herbal material. The “Zlatno inje” biostimulant was used at rate of of 3 l ha-1, and it was applied in three variants and fourth variant was the control variant without the application the bio-stimulator. Following the evaluation of the plant infection by Septoria, the best results were shown by the third variant, with the least presence of Septoria (the average of 2.1 index points), followed by the second variant on the second place, the first variant on the third place and, on the forth place, the fourth (control) variant (without the use of the bio-stimulant), where there was the highest presence of the examined disease (the average of 4.2 index points). The yield of lemon balm dried leaves was lemon balm, leaf spot, septoris, Septoria melissae, biostimulant 2023-10-23T08:45:56.455Z 44 no 46 Vladimir Filipović 46 Ana Dragumilo 46 Vladan Ugrenović Institute of Soil Science 0000-0001-6642-8235 46 Ivana Simić 46 Slobodan Popović 46 Vera Popović 46 Milan Ugrinović application/pdf 1616968 https://unilib.phaidrabg.rs/o:3103 no yes 1 70 92000004 71A05 Proceedings of the VIII Congress on Plant Protection (November 25-29, 2019, Zlatibor, Serbia). 2019