I tried using 4steel bowls with 1/2" of vegetable oil under the 4 hive stand legs last week, to control ants.
No ants now, but I notice about two dozen bees drowned in the oil of each bowl over the first 7 days, which I did not see mentioned as a possibility. Though the number does not seem to be increasing, I wonder if anyone else experienced this, and if anyone thinks this is/will it be a problem enough that I should discontinue the oil moats?
Jerry, not sure vegetable oil is the preferred method. I have seen advice where people elect to use food grade “mineral” oil. Not sure if vegetable oil smells good to bees and attracts them. I actually use grease and put it around the leg so ants have to cross it - been very successful, some people use Vaseline.
cheers
Jeff
Bees will die in any liquid you place in a moat. I have a few hive stands with moats on each leg and bees die from the rainwater that collects in them.
yep- I accidentally left some dishes near a hive and they filled with rainwater- and then drowned bees. Bees seem to wander all around a hive- and nearby it- so if there is any liquid they can drown in: they will drown in it. Especially so if there is nothing in the liquid (like a stick) that they can use to get themselves out.
Thanks to all of you for your help to a novel beekeeper! It is reassuring to know that such ready hospitality exists here in our virtual community.
Nowhere had I read about drowned bees when I researched the options for keeping sugar ants out of the hive.
In retrospect, I suppose I could have just relied on the stainless steel bowls alone under the stainless steel hive stand legs, but the others had recommended vegetable oil.
If more bees drown, I plan to drain the oil, but that won’t stop rainwater accumulating.
Them bees are hard workers but they sure aren’t the sharpest tools in the shed!
so any suggestions on what to put in around i.e. in the leg stands? I am thinking of making/adding them
I put Mineral Oil in mine. Buy it in the pharmacy - very cheap. 
was thinking of just putting/covering grease on the metal legs, nothing in the cup holder? do you think that would keep ants out?
Probably, especially if you used something heavy like axle grease
Greasing the metal legs will work; however, you may also inadvertently catch a few bees too. Once I had a beehive rack with pipe legs driven into the ground and 1 inch square structural tubing welded to the pipe uprights. I started noticing carpenter ants in the inner covers along with their eggs. They were bringing the eggs there to take advantage of the hive heat. I tied greased rags around the pipe legs thinking that would stop them. Nothing changed…still ants/eggs on the inner covers.
Closer inspection revealed that the ants were coming up the inside of the pipe. When the pipes were driven into the ground, an ant-hollowed tree root or underground ant tunnel was punctured giving them direct access into the pipe. From there it was a straight shot to the beehives. So if your pipe legs offer such an opportunity, pour oil down the pipe or bug killer. That will take care of it. Once I poured oil down the inside of the pipes, the greased rags worked fine.
Diatomaceous earth will also work around the legs but it will tend to wash away during rains. You can also use it inside the pipe.
Ants have memories and they will learn to not go places for a while but the next generation will reexplore and perhaps find the same avenues so some on-going vigilance is needed.
Gary