April 2012. A problem on a few lettuce plants in Cambodia. Description of the problem is not clear, but the image seems to show that a few of the younger leaves have become discoloured.
A member said that the only time that he had seen such symptoms was when there was heavy metal contamination on the leaves and asked if there had been any gasoline dripping from an engine. It was asked if the crops had been sprayed with any chemicals.
The answer was "no", so the problem went unidentified.