Real-time spot spraying of weeds implies the use of plant detectors ahead of a sprayer. The range of weed spatial autocorrelation perpendicularly to crop rows is often greater than the space between the corn rows. To assess the possibility of using less than one plant detector scouting each inter-row, a one hectare field was entirely sampled with ground pictures at the appropriate timing for weed spraying. Different ways of disposing the detectors ahead of the sprayer were virtually tested. Scouting one inter-row out of two results in less than 10 % herbicide waste and 0.5 % weed escape. Also, the higher weed escape occurs in scenarios in which the inter-rows that are not compacted by the wheels of the planter or tractor are scouted.