>If a colony has foulbrood and the bees visit the open feeder the 
spores could infest the water and be transported to other hives.

I doubt foulbrood spore concentration on bee bodies is high enough to 
transfer into the feed for other bees to carry back to their hives in 
sufficient concentration to cause an outbreak of foulbrood.  There 
should be no spores in the feed unless you mix in honey from 
foulbrood colonies.  

What could potentially happen though is this: after the open feed is 
exhausted, greedy bees scatter looking for weak colonies to rob.  If 
such colonies are weak due to a loss of brood to foulbrood, their 
contaminated honey will end up in the robbers' hives.

Foulbrood spores are very numerous in the honey and wax of colonies 
with clinical symptoms of foulbrood.  Some say though that you can 
take the bees [alone] from an infected colony, hold them in a box for 
3 days [so they digest the honey with spores in their stomachs], 
shake them into new equipment and not get foulbrood symptoms.  
Winston published that bee stomachs filter out most spores [, pollens 
and other particles] in the honey in about an hour.

I don't recommend this approach since the official NY state policy is 
to burn colonies with clinical symptoms.  A lot of beekeepers 
inappropriately try to contain foulbrood with terramycin only to 
preserve and spread foulbrood.

No, I don't believe opening feeding spreads disease but I know it 
results in a disproportionate distribution of the feed.  Just like 
with nectar gathering, the strongest colonies will gather the lion 
share of the open feed.  If the strong colonies have ample stores to 
start, they will plug up the entire nest as well.  The needy colonies 
are not helped by this unless you later redistribute frames with 
stores.  In-hive feeding, and only as needed, is the way to go.

Waldemar
Long Island, NY

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