Here is a strange one:
My parents have a garden in Brooklyn NY, and in late summer, they seem to have a problem with house flies gathering around their plants to make a place for themselves to die. I think that they are being affected by some sort of parasitic fungus, but I am not sure which one. The problem has become a nuisance recently as the flies are now making their death beds in the Hydrangea - which my mother likes to dry out and use to decorate the house. I think that the problem may be associated with our rear neighbor's fig tree, as it seems that the problem has spread from that region to the rest of the garden.

Any ideas on how to get rid of these parasite ridden flies and prevent them from coming back? I have some pics attached.