[Beano]

I have a damson tree and the leaves look a mess and the new growth is covered with both mildew and greenfly. The whole tree has flies, wasps, and ants all over it.
I bought Resolva natural power to spray the leaves. As I started spraying I noticed, doted all over are little ladybirds. So I've stopped spraying because I don't want to kill the ladybirds, the natural predators of greenfly.
My question is, will the ladybirds do the job? Or should I spray anyway and try and avoid the ladybirds?  I really don't  want to kill ladybirds but I want to improve the damson tree's chance of surviving. It's only a few years old.
Anyone out there with advice please.