Yesterday I was helping a friend go through his hive and noticed several worker bees that had a yellow spot on their thorax, much like you would want to mark a queen. These honeybees originated from a feral swarm and the yellow spots were not noticed until yesterday. I found this thread from a few years ago:
http://forum.beemaster.com/index.php/topic,17082.0.html (http://forum.beemaster.com/index.php/topic,17082.0.html)
The yellow spots I found look very similar to the pictures posted on that thread. The discussion seemed to indicate that it was pollen from a certain flower. I just wanted to make sure the hive is not diseased. Currently it is queenless and I am working on introducing a queen, but don't want to do that if there is a problem....
Any ideas?
I have never heard of a disease that causes a yellow spot as a symptoms.
I have never heard of a disease causing yellow spots either.
My helper and I were on a job site one day taking a break and honey bees were coming and going to a pop can, I took my paint marker (use it to mark steel pipe with) to show him how the bees would leave and then return to the same spot. Maybe you are seeing something like that. If pollen is on them a few squirts from a spray bottle will wash that off.
Catch one of them with a spot and see if you can knock or wipe the yellow spot off to see if it is pollen.
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Plant Linaria vulgaris makes yeollow spot on bee's back when bee open may times flowers.