Scale insect infestation

The choisya in my front garden has a serious infestation of scale insects. The plant is about 6 foot tall and I can barely find a leaf or stem without scale insects on them. There is also a lot of sooty mould, and ants which I gather are probably protecting the scale insects. The choisya is starting to show some yellowing leaves, so I guess that's a sign of stress. There are also a few scale insects on the nearby pieris, on the side facing the choisya.

This is only my second year of having a garden, so I don't know how long they've been there. There were definitely scale insects on the choisya last year - I found a lot of their white fuzzy egg coverings when I was cutting it back last summer, but didn't really know what they were.

The choisya is just coming into flower at the moment, so I don't want to start putting insecticides on if they would affect the bees and other pollinating insects. It's also right at the front of the garden, with one side facing the pavement outside, so I'd want to be careful with what I spray on anyway. I'll try to find a way of blocking the ants, but it might be tricky - there are multiple stems and it touches the wall in quite a few places.

Can anyone advise on what I can do to tackle them, or at least reduce them to a number where the plant won't suffer too much?

Thanks
Stephen

 

I am using Neem oil spray on my lemon tree (which produces lovely large edible lemons when it's happy) with good results. It is harmless to flying insects, so the bees are not affected. But I think coats the leaves/stems, making it difficult for the insects to feed. I know it is harmful for fish though. I ordered the neem oil from t'internet, and make up the spray each week when I need it.

 

Thanks - that sounds promising. There's no water nearby, so I don't need to worry about the fish.