The most promising keyword here would be chlorosis to me. The dye is added by men and is an one-off event. Can't be a plant, for sure. That would not have any

The most promising keyword here would be chlorosis to me. The dye is added by men and is an one-off event. Can't be a plant, for sure. That would not have any sense Could be a treatment or colored sugar, but then the beekeeper would know about it. As is against their interests to have blue honey they would stop doing it. Can't be copper sulfate sprayed in the crops. The bees would die. Could be somebody trolling, but then the beekeeper would suspect it So this left us with the blueberry fields, that are a synonym of chlorosis, that explains the aluminium UPDATE: See also the Bregma's explanation above