Black shrubs

Was out in the garden today and I noticed a couple of shrubs were covered in what looks like black soot. I tried to hose it off but no luck. It will rub off by hand but washing wont remove it.
I presume it is some sort of disease, if so what? and what should i treat it with?
I have put some photos on but they are not very clear but hope fully they will help.
Thanks

 

Hi

Looks like sooty mould to me , probably from last year does tend to dry on doubt if alive now normaly the winter kills it off , caused normaly by aphids/greenfly poo , which the sooty mould (feeds on) loves as you can see it can be washed off as in each leaf a cloth some warm water if you realy want to , other shrubs like camelias have a scale insect and the same happens with that with the poo they produce as well

you have to treat the cause so keep a eye out for insects late spring


Hope this is useful

Spruce

 

Might be worth giving it a spray with bug killer in the spring then. Can you recommend any types that are worth a try?
Thanks for the reply

 

If you use insecticide, you'll kill the aphids, but you'll also kill the things that eat the aphids that are lurking in the bushes waiting for their dinner to arrive. The aphids population can regenerate faster than most of their natural predators. In other words, once you resort to the sprayer, expect to be using it routinely.

Greenfly are easy enough to hunt. They tend to congregate under young leaves and hide inside newly opening buds. They are feebly things, with a needle like feeding thing that they stick into the plant to suck the juices. A blast with the hose will knock many greenfly off, and even those that aren't washed off will be injured by the force of water and unable to attack the plant.

Some people use soapy water to rinse the plants. Some say the aphids don't like the taste, others say it stops them being able to grip onto the plant, and still others say it masks the scent of the plant from the aphids. Most are agreed that however it works, it reduces the severity of greenfly infestations.