Abstract: A crop spraying system adapted for attachment to an implement frame pulled by a traction vehicle employs a spray nozzle for each crop row in combination with a photo detector arrangement for sensing the presence of weeds or other unwanted plants extending above the crop height. Following detection of a weed in a crop row, a controller momentarily turns on a spray nozzle covering that row after a selected time interval depending upon traction vehicle speed and detector-spray nozzle spacing for applying a herbicide to the detected weed. Operating in the near infrared (IR) band, the crop spraying system allows for selected spraying of oversized, unwanted plants in the crop row in reducing herbicide usage, and thus cost, and minimizing the environmental impact of such chemicals. One embodiment employs an IR beam bending reflector arrangement to detect not only weeds extending above the crop height, but also weeds extending laterally beyond the crop row into the inter-row space.