K wrote:

Over the last few days I've found several dead or sluggish bumblebees,
in my garden and in my father's about 1/4 mile away.

I noticed several too on a hot Saturday afternoon. They were just
sitting perfectly normally on top of various large leaves. Looked
perfectly fine excapt that they fell off rather than flew away.

We haven't sprayed anything, but I suppose it's likely that at least one
of our neighbours have.

Peter