The alleopathic effects of common associated weeds, on germi‌nation, growth, yield and,quality of sugar beet plant was detected. Aqueous leachated of weed roots reduced markedly germination %, germination rate, plumule and radicle lengths and fresh and dry weights of sugar beet seedling. Radicle elongation was more sensitive than plumule whereas fresh and dry weights were the most sensitive traits with respect to the harmful allelopathic activity. Plant height, number and area of sugar beet leaves of diameter, size, fresh and dry weights RGR of roots were significantly reduced by residues of decayed weed roots. Reduction was more pronounced with bermuda-grass (Cynodon dactylon (L) Pers:), canarygrass (Phalaris minor Retz) and wild beet (Beta maritima L.) and at the 1st assessment (105 days) than late one (180 days). Reduction by the rest of weeds can be arranged as follows: lambsquarters (Chenopodium morale L.), bindweed (Convolvulus arvensis L.) and dock weed (Rumex dentatus L.) Juice quality (T.5.5%, sucrose % and N, P and Na concentrations) of sugar beet roots were not statistically influenced by allelochemicals liberated from decayed weed roots irrespective to the slight reduction in values of such traits under allelopathic condition. Results confirmed the phenomenon of allelopathy and its marked sharing in weed-crop interaction. The highest dangerous weeds in weed interference trial were imposed also the strengther allelopathic impact on growth and productivity of sugar beet plant.