1 INTRODUCTION Weed management has been primarily focused on selective herbicides since the inception of herbicides. But, the indiscriminate and increasing trend in herbicides use is a primary concern in present agriculture. Excess consumption of herbicides can be reduced by making rational decisions on weed management (Das et al. 2010). Making appropriate decision on the use of herbicides requires development of weed management decision models (Coble and Mortensen 1992). The development of weed management decision models is possible by through determining the ET of weeds, which assesses whether a treatment against weeds is necessary and economical (Cousens et al . 1986, Cousens 1987, Wilkerson et al . 2002). The ET concept is the principal guideline of pest/weed management that largely avoids eradication of pest(s) to regulate their populations at economically optimum levels (Coble and Mortensen 1992, Wilkerson et al. 2002, Das et al. 2014a). The ET for weed control or the “break-even point” is the level of weed infestation at which the cost of weed control operations is equal to the benefits obtained as a result of controlling the weeds (Cousens 1987, Hazra et al. 2011). Thus, the ET is primarily a binary decision-making concept (‘control’ or ‘not control’) that justifies adoption of control measures (Auld et al. 1987) or decides the weed density at which weed control becomes economically worthwhile (Cousens et al. 1988). The ET concept was first introduced by Stern et al. (1959) and was defined as “the density at which control measures should be adopted to prevent an increasing pest population from reaching the economic injury level (EIL).” The EIL represents “the lowest population density of pests that can cause economic damage to crops.” Stern et al . (1959) opined that the ET should be lower than the EIL, which provides sufficient time for the control measures to take action before the population reaches EIL. Initially, entomologists adopted ET in the early 1970s (Stern 1973, Wilkerson et al. 2002). Weed scientists adopted this later as the decision-making tool/ process for weed management. Coble and Mortensen (1992) and Thornton and Fawcett (1993) reported that this concept was the basis of majority of weed management decision models available to farmers. The ET-based weed management may lead Indian Journal of Weed Science 53(1): 1–13, 2021 Print ISSN 0253-8040 Online ISSN 0974-8164 The economic threshold (ET) is one of the major decision-making frameworks for rationalizing herbicides use for better weed management while reducing environmental impacts. The ET is the density of weeds at which the cost of control equals the benefits obtained under particular weed control measure adopted. The ET rejects complete eradication of weeds, but advocates regulating weed populations at economically optimum levels. Control measure is adopted only when weed competition goes beyond a certain limit, thus, it uses certain damage levels for making cost-efficient weed management decisions. Several decision-making models on ET are available with high to low degree of precision. Despite potentials, the adoption of ET models as the major criterion for cost-effective herbicide use has been low. Limitations are building up of seed bank by residual weeds, complexity in estimating ET density, patchy weed distribution, and limited validity in cropping systems with multiple weed species. Yet, the ET-based decision has great potential in designing weed management under single weed dominance in crops. Information on weeds population dynamics in cropping system, biology, ecology and spatial heterogeneity would make determination of ET more precise and reliable, and managing weeds using integrated approach more successful. DOI: 10.5958/0974-8164.2021.00001.0 Type of article: Review article Received : 26 December 2020 Revised : 10 February 2021 Accepted : 12 February 2021 Key words Decision support system Economic threshold Herbicide Hyperbolic regression model Weed management Article information ABSTRACT Economic threshold concept for weed management in crops: Usefulness and limitation T.K. Das, Suman Sen*, Rishi Raj, Sonaka Ghosh, Biswaranjan Behera and Arkaprava Roy Division of Agronomy, ICAR – Indian Agricultural Research Institute, New Delhi 110 012, India *Email: sumansen.agri@gmail.com