Brown or russet spot

Brown spot or russet spot (or spotting) may be visible on the white ribs of lettuce head. Brown spots can have various causes. It can be symptoms of a storage under too high CO2 conditions. A failure in fresh-air ventilation during storage may allow CO2 accumulation, which will induce the russet spot symptoms. Storage in a room with ethylene also induces russet spot symptoms. Overmature heads will develop russet spot more easily.