Hazel, I won't be checking in on the new bee colony until the weekend to see if the queen is laying eggs yet, but they seem to still be there, so that's a good sign. The weather has been yucky, they should be happy.
Yes pesticides are a major problem with the bee's and other insects. For the past several years many farmers and such have been using a type called Neonicotinoids (Bayer is a major manufacturer). These are neuro active pesticides that don't seem to harm larger mammals, but are extremely detrimental to insects. They block many of the receptors in the insects brains and then the insects (like bee's) can't find their way back to their hives. As bee keepers we are faced with constant stress on the hives through outside pesticides that we can't control, plus the issues with mites and diseases. There's a fine line with trying to treat the bee's for many of these issues, but through all the treating they are becoming resistant to the treatments and then dying more frequently because we can't control the issues - much like humans with all our drug resistant viruses.
I personally try to take a more natural approach to my bee's. I don't over treat them, very rarely actually. Swarms also are a natural part of bee's life cycle where they create new hives, that said, most people don't really appreciate a swarm of bee's in their back yard, so we try not to have the bee's swarm. Unfortunately sometimes bee's will just be bee's and we can't stop what they put into process.
All that said, when the bee's swarm they are very gentle as they are not protecting their hive or honey. I make hubby suit up because he is allergic to stings, but professional bee keepers won't even both to put on protective gear when collecting a swarm they are so docile.