Can these suckers kill the whole plant or will they just de-leaf?

Hi,
Just figured I have these after 4 years of lovely green bushes. The 80 bushes have heaps of these under the leaves and a few on top and all leaves starting to droop. How long would it take to kill a single tree? Is there any way to get rid of these with non-pesticide products - I have heard washing-up liquid works???. I have about 180 feet of these bushes.

Your help would be most appreciated.

Thanks.

John.