Evaluation of onion protection against diseases

Abstract The destruction of pathogenic microflora on vegetable plantations improves the phytosanitary condition of cenoses, and quality control of disease pathogens allows onion plants to realise their varietal yield potential. The aim of the experiment was to compare the effectiveness of synthetic preparations for phytosanitary control of peronosporosis, alternariosis and fusariosis pathogens: Ridomil Gold MZ 68 WG and Quadris 250 SC, as well as to consider the biological preparation Phytocide as an alternative to chemical protection. During the experiment, the dynamics of the leaf surface area was determined by the method of cutting and subsequent weighing, the height of onion plants was determined by measuring with a ruler, and the incidence of plant diseases was determined according to the methodology for recording diseases of vegetable and melon crops. The results of studies on the protective effect of fungicides were analysed. Spraying the plots with a mixture of Ridomil Gold MZ 68 WG 2.0 kg/ ha (three times at 10-day intervals) + Quadris 250 SC 0.4 l/ha (twice at 10-day intervals) allowed onion plants to grow taller than the control plants – by 4.5 cm – and to exceed the control plants in terms of leaf area dynamics by 37.4-59.6%. Treatment with this mixture contributed to the best control of onion disease pathogens and ensured the formation of bulb yield on average over two years of research at the level of 55.7 t/ha with a marketability index of 85.3%. Treatment of the plots with a biofungicide also provided high-quality protection against diseases, high biometric indicators in plants and a significant increase in onion yield. The highest marketability of bulbs – 85.5% – was observed in the variant with the application of the biological preparation Phytocide, which exceeded the control by 8.7%. The biological fungicide was slightly inferior to synthetic preparations in terms of protecting onions from pathogens, but the slight lag in yield was offset by higher marketability of the product. The analysis of the obtained results provides practical guidance for vegetable growers on how to effectively protect onion plants from diseases using various preparations or their combinations