A customer has asked:

I have a sample (see picture) from my Euonymus wall shrub this morning which I’ve been training for over 20 years in his garden. The plant cover 4m (16ft) in length and 2.4m (8ft) high. However, the leaves on one area, around 1m square are covered in these white "things" (cushion scales). It is absolutely infested and some of the leaves are starting to turn yellow and dropping off too.

Chris replies:

Spraying is the only control, either organically with products based on plant oils or extracts (Growing Success Fruit & Veg Bug Killer, Vitax Organic 2 in 1 Pest and Disease Control, Scotts Bug Clear for Fruit & Veg) or fatty acids (Bayer Organic Pest Control, Doff Greenfly and Blackfly Killer, Doff Greenfingers Organic Pest Spray) are contact in action. They have a short persistence and thorough application to the underside of leaves is required. More frequent applications of organic pesticides may be required to deal with the scale nymphs as they hatch.

Systemic insecticides containing thiacloprid (Bayer Provado Ultimate Bug Killer concentrate) or acetamiprid (Scotts Bug Clear Ultra) are absorbed into the foliage and taken in by the young scales as they feed.