Critical period for weed control in Stevia rebaudiana (Bert.) Bertoni

Knowledge on the critical period to conduct specific crop-weed interference is an important component for the development of an effective integrated weed management approach. The present experiment was carried out in a glass house at the Rice Research Centre, MARDI Serdang. Weeds were allowed to compete with the Stevia plants at different growth periods (after the Stevia plants were transplanted), before being removed manually. Full term weedy and weed-free treatments were included as controls for comparison. It was observed that the yield of Stevia decreased with increasing duration of weed competition. Based on the predicted Logistic equation and Gompertz response curve, the critical period for controlling weeds in Stevia was found to be as early as the first week after transplanting until the end of the third week. During this phase, the weeds have to be controlled in order to prevent losses that could exceed the economic threshold.