Liz and I spent a week in Southern California taking samples for the National Honey Bee Disease Survey. We came across purple brood – something I had never seen before. The larvae had a bright purple hue to them along their gut line. It was quite pretty.
After some research, it seems that the most likely cause for purple brood is nectar from the plant Cyrilla racemiflora (common names are southern leatherwood or summer titi). It is poisonous to the brood, so beekeepers either have to move their colonies away or take the loss. Only one colony of the eight we sampled had it, so hopefully the other colonies were finding different nectar sources.
The range for this plant is supposed to be in the southeast, but we saw effects in the southwest. My guess is there was a plant nursery nearby growing the plants for sale or a house that was especially found of using that plant for landscaping. It was really neat to see, but unfortunate for the beekeeper.