Ivashchenko O. Biological features of weeds and perfection of protection of sugar beet stands

The thesis deals with a new direction in solving an important scientific problem which consists in establishing biological features of the major species of weeds in agrophytocenosis and regularities of the formation of productivity of sugar beet, depending on technological practices of weed control under conditions of the central forest-steppe zone of Ukraine. The leading factor which determines the degree of weed infestation of stands is PAR energy coming to the soil surface; under conditions of reduction of lighting degree by 97.3 % of full light provision, the number of weeds amounts only to 4.8 % of the maximum. The most sensitive to decrease of the degree of intensity of energetic provision appeared to be the species Amaranthus retroflexus L., Chenopodium album L., Solanum nigrum L. A new system of protection of sugar beet stands from weeds which is grounded on the basis of their long-term shading allows to reduce herbicide expenditure twice and more. In the species Gallinsoga parviflora Cav., Chenopolium album L., under conditions of application on the stands of genetically modified sugar beet hybrids of the Round-Up-herbicide at the rates of 1.0; 0.5; 0.25; 0.125 l/ha, among the plants which successfully survived and gave progeny, there were found resistant mutants with hypoaneuploid, hexaploid and pentaploid state of genome.Productivity of sugar beet stands with the use of the new system of crop protection from weeds amounted to 103.3-104.8 %. Profitability of its use of herbicides exceeded the traditional systems by 14.9-19.2 %.