Ramanayaka, R. J. M. D. K.Prematilake, K. G.2022-02-182022-02-1820159789550481088http://www.erepo.lib.uwu.ac.lk/bitstream/handle/123456789/8385/66-TEA-Investigating%20the%20Causes%20for%20Poor%20Control%20of%20Erigeron%20sumatrensis%20.pdf?sequence=1&isAllowed=yErigeron sumatrensis (Alawangupillu) could be considered as a hard-to-kill weed in tea plantations because it has become totally resistant to Paraquat (Marambe et al, 2002) and from the recent past, there are claims that this weed shows a poor control also by Glyphosate (Prematilake, 2010). Recent investigations under upcountry conditions have shown that such poor control of weed is attributed to the dosages of Glyphosate applied and age or growth phase of weeds under up country conditions (Prematilake and Nawaratne, 2010 ; Prematilake and Darshani, 2011) . Hence, this study was aimed to determine the degree of control of E. sumatrensis weed at its different stages of growth by different dosages of Glyphosate under the conditions of Uva region. Materials and Methods Plants of E. sumatrensis at five different growth phases, having 3-5, 6-8, 9-11, 12-14 and more than 15 leaves per plant, were collated from Ury Estate, Passara (30 plants from each of the five growth phases) and planted them on a raised bed, randomly at a spacing of 50 x 50 cm. Plants were left on beds for 2 weeks period to establish. Plants of each of the five growth phases were treated with two dosages of Glyphosate (3ml/Land 5ml/L) at two weeks after planting. An untreated control was also maintained. A drenching application of Glyphosate was given to each plant during morning time using a hand sprayer. The experimental design was Complete Randomized Design with two factor factorial with 2 replications.Visual injury symptoms in the weed (chlorosis of leaves, wilting of leaves, drying and scorching of leaves and leaf fall) were observed and scored at 7, 14 and 21days after application (DAA). The degree of damage on leaves and whole plant was taken in to account in scoring using a scale (0 to 9).The viable plants were counted and the dry weight of above ground part and roots were measured at 21 DAA. Results and Discussion All visual symptoms such as chlorosis, wilting, scorching and drying of leaves and leaf fall were occurred at a higher intensity with Glyphosate at 5ml/L (2.75 L/ha) than the Glyphosate at 3 ml/L (1.65L/ha). Chlorosis of leaves and wilting of leaves were most prominent at seven DAA and scorching and drying of leaves and leaf fall prominent at 14 DAA.enAgricultureExport AgricultureTea IndustrialsTea TechnologyweedChemicalOther