Thing thing about bees and horses not getting on is 5% truth and 95% hysteria. I have a bridle path running alongside land on which I built my honey farm, and had to deal with such objections at the planning stage. Apparently I was being irresponsible and would cause regular injury and distress to horses and their riders...
The big problem with horses mixing with bees (speaking as a non horse person) is that they kick when threatened. If they stray too close to an unfenced hive and get stung, their kick response might just knock the hive over and multiply their problems a thousand fold. Cattle, on the other hand, just run away. The idea that bees act aggressively to horse sweat is often mentioned but without any evidence to back it up.
It sounds like the siting of the hive complies with the BBKA's published (to members) guidance; you have a 10' hedge between the hive and the stable block, and indeed the stable block wall acts as a further barrier. There is a free information leaflet on the BBKA site entitled "
Bees and neighbours" which gives their recommendations for dealing sympathetically with concerned neighbours. Further screening so that your bees are not visible from the adjacent land, and so that flying bees are raised above (horse) head hight, would be wise.
The "senior beekeeper" line is probably a bluff - I don't know of many beekeepers who would be so damning. The advice to ask your local bee inspector to appraise the situation is a good one.
There are many beekeepers who keep bees and horses in the same field, as some here have said. The horses do quickly learn that white suits mean a trip to the far side of the field! One particularly useful testimony I had was from the chairman of a BKA on the other side of the county, who was a beekeeper, horse owner, and vet, and who saw no problem in what I was proposing.
I spoke to the British Horse Society, in particular their 'Rights of Way' and 'Welfare' officers. The latter told me he could recall no reported incidents in recent years of bees causing harm to horses; indeed he offered the view that horse flies would be a greater and much more frequent irritation than the odd passing bee. He knew of no such case of a stung horse bolting and causing either itself or its rider injury, which is another scare story often thrown into the mix.
Molasses is not an attractive feed for bees; dark sugars and the like are toxic to them anyway. Indeed there have been studies conducted into the use of molasses as a honeybee repellant, e.g.
here.
So all in all, there's not much for the farmer to go on. Do you have legal cover on your house insurance? Should cover a few solicitor's letters if necessary. Make sure you join a local BKA and you will get 3rd party liability insurance to cover the unlikely event that any claim for injury is made.
Finally, if you wake up one morning and find that the bees have been killed, DEFRA operates a department called the
Wildlife Incident Unit, who would be very interested and who will fine landowners or spray contractors in cases of mis-applied pesticides. The farmer knows that you have bees there - document your conversations/correspondence! - so is obliged to give you 48 hours notice if he intends to spray insecticide near those hives; it is up to you whether you close or move the bees for the duration of the spraying but it is certainly not a notice to move them permanently.
Chin up!