Help identify problem with Buddleja please

My previously healthy, 4 year old Buddleja Buzz plants have both developed a problem with misshapen shrivelled leaves, turning dry and black. Whole stems are affected. Photos attached. Any advice welcome please

 

I think it's a virus, I've seen a lot like that this Spring (fortunately not mine yet). A whole sales area in a GC I visited recently, I'd have been embarrassed to put them up for sale

 

Clear up and burn any fallen leaves. I have no idea what is causing this. I suppose you could try a suitable plant feed. Over my many years of growing I have had plants that are doing badly suddenly recover and do well. Hopefully yours will recover best of luck.

 

If it is the older growth then it could be a virus but I've seen a similar thing caused by aphids in early spring on the new growth.

 

I don't think it's a virus, I think it's more likely to be a fungal problem and related to the excessively wet weather. I have several Buddleja and one has similar symptoms to yours with whole stems dying back, first noticed a couple of months ago when the previously healthy vigorous Buddleja was observed to have a couple of dead/nearly dead branches; the third has now joined the party. I had a similar thing happen to a Buddleja officinalis some years ago, one month flowering and healthy next month virtually dead.
I don't see many aphids on my Buddleja.

 

Mullein (Verbascum) aphid is causing the distortion and yellowing - I can see them in photo #4. Sooty moulds follow due to the sugar content of the aphid excrement and you get die-back. In the short term, try washing off the aphids with water, possibly with a horticultural soap. Don't consider using anything systemic or a contact insecticide. The former will contaminate the nectar and damage pollinators, the latter will kill the predators who'll cure the problem.

The predators - ladybirds, their larvae, hoverfly and lacewing larvae - will soon appear and clear up the aphids.

It's a new pest for Buddleja, and it seems the mullein aphid has evolved and expanded its diet - Buddleja is a close relative of verbascum.

Nigel also has a point - the wet winter has stressed Buddleja, and any plants with weakened roots become more susceptible to all sorts of problems including die-back.

 

Verbascum aphid that's a new one on me; I have found mullein moth caterpillars on buddleja in past years.
I'll keep an eye open for these aphids in the future.

 

Thank you so much, that's very helpful! Horticultural soap ordered today

 

Here they are, vicious little monsters, on the underside of a leaf and destroying one of my precious cuttings.