One way to thin the herd is to put honey traps out for hornet queens- early on they are doing a lot of work and get hungry.Hornet will attack your fruit yes. They are a freaking plague for plums. We put traps for them, you can home make them, but you need to be careful not to kill bees to. You put olive oil in it (I think ?), the bees don't like it, but hornet are OK with it. I don't remember, you gotta check google![]()
Its important to note though that European Hornets are useful, its the Asian Hornets (smaller, with a black abdomen and gold ring) which are bee killers. Quite often I'll let the former go. Since the latter are now endemic in France hopefully they'll find a niche away from bee killing- I've seen them slice up carrion and they do pollinate as well.