Beekeepers around me in Maryland use diatomaceous earth (DE) instead of oil in the pan under the screen bottom board and find that it dessicates SHB larvae and beetles without being the mess that oil can be. They also place DE in on the ground around the hives under landscape cloth/carpet with gravel on top to prevent larvae from pupating. 

I keep my bees on a roof and haven't had an issue with SHB, but I think that is because the larvae cannot reach the ground. When I used screen bottom boards with the insert, I would find SHB larvae in the hive debris which is why I switched to solid bottom boards. 

Debbie 

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