Determination of the economic threshold of damage of red root pigweed (Amaranthus retroflexuxs L.) in green bean (Phaseolus vulgaris L.) field

In order to determine the economic threshold of damage of red root pigweed (RP) in green bean, a two years experiment was conducted in agricultural research station of Islamic Azad University of Tabriz, Iran, based on a randomized complete block design with three replications. The treatments were RP interference times at, 4, 6, 8, 0 weeks after green bean emergence until late growth season (GBE); full season interference (FSI) and control weed free plot. Data were analyzed with Mstatc software and Duncan's test was used for mean comparison. Results showed that the above ground biomass and yield of green bean in control plot was similar to treatment of weed interference at 0 weeks after GBE. Yield loss in FSI was 67.6% in comporison to control. RP emergence at density of 8 plants-m- of row at early 6 and 8 weeks of green bean growth stage to later, was caused. 5% and 6.% yield loss, respectively, in comparison to control. With attention to 0% maximum permissible yield loss in green bean, RP must be controlled, if it was emerged within a period of 6 weeks of early green bean growth stage and economic threshold of damage of RP at studied density level was determined until 6 weeks of early green bean growth stage.