By Trevbarb
United Kingdom 
My question is regarding a fruiting sweet apple tree espalier type growing on a fence. This tree has developed what we believe in 'woolly aphid' as it has the remains of sticky grey wool, and also on the new stems small green swollen areas which are smooth. The tree has not had any fruit on it this year. It has been pruned regularly and has a good 15 year old trunk. The growth that is above the fence level does not appear to have any swollen areas on the stems. Any suggestions would help. Thanks in anticipation
Trevor & Barbara Course
14 Oct, 2014
Answers
Is the branches growing above your fence new (green) growth? Wooly aphids usually attack the bark on the tree that is thinner and easier to get through.
Once you have got an infestation of wooly aphid, the winter frost can cause the swellings to split. This could create further problems as they might open up and allow fungal diseases such as apple canker to get into the resulting wound.
I would use a insecticide specifically formulated for apples, i.e. edible fruit. The problem that you have is that these formulations are usually applied in spring or summer. I think that there are sprays or washes that you can use in the winter, but wooly aphid is hard to get rid of in the winter months because they burrow deep into the wood.
14 Oct, 2014
the green swellings sound like scale insect and when they females dies the young emerge from her body leaving a woolly fluff behind. so scrape at the green swellings and see if they come off. if they do then scale would be y suggestion. a good systemic insecticide formulated for crops would be my remedy.
15 Oct, 2014
Could you add a photo please?
14 Oct, 2014