A field image is formed using a tristimulus color model and used to detect target plants or entities on a field. Through the use of a luminance parameter floor, hue and saturation selection steps, feature recognition, a sizing floor and an aspect ratio ceiling, a very fast way is devised to recognize a target plant without need for consulting plant attribute databases, or to analyze spectral or other specialized data for comparison with known attributes. This allows a low calculational processing load and use of simple hardware such as a single board computer to handle machine vision in real time. Treatment steps can include a spray event, a light treatment, and a thermal/mechanical trauma.