Weed management plays a major role in the production and economic benefits derived by agricultural industry worldwide. The monitoring of weed pressure, economic threshold, yield loss and environmental impact is critical for sustainable agriculture. Currently research is being carried out relating to weed mapping at field scale and the development of machine vision controlled equipment. Remote sensing and aerial imaging techniques utilised for site-specific weed management have limitations due to the accuracy of satellite imagery, its cost and timing. The advent of optoelectronic sensing and enhanced computing has provided a demand for the development of the real-time assessment and management of weeds in fields. The available technologies that can be used for developing a ground-sensor based system to assist in determination of weed pressure and economise on the application of herbicide under field conditions are reviewed. These technologies include image-based identification and spectroscopic methods for weed identification and threshold determination. The various methods studied and the concepts pursued by various researchers are discussed in the paper.