Rose sawfly

Hi Squirrel nuts, I do sympathise with your predicament. We live in 'insect paradise' here....most of them of the stinging/biting variety. Unfortunately, sawflies do seem more resistant than most to chemical and bacterial control. This is a long shot, but would old-fashioned fly papers or yellow sticky traps help by physically trapping the flies before they lay eggs? At least it would reduce numbers quite dramatically, if ordinary flies and whitefly are anything to go by. Perhaps too late this year, but combined with the neem-oil suggestion, something to put in place early next year? I do hope that you find a solution!