Apple caterpillars

[Speed Gardener]

Morning All,
I took a look at my apple cordons last night to look for pests. Last year, something was eating the leaves and making a right mess of the new shoots but by the time I had come back from working abroad, the damage had been done. I noticed that some of the leaves had been eaten but some of them were glued together as well. Closer inspection revealed small caterpillars/grubs knitting leaves together to form cocoons. They range from about 5mm up to 10mm and are green, white or dark grey. Anybody got any ideas as to this infestation? I went over the trees with a fine tooth comb and squashed the little blighters but I don't know how long the onslaught will continue. Maybe I've broken the life cycle...

[FB.]

If the damage is no more than 1/4 of the leaf area, the plants will be fine and I would not intervene.

Damaged leaves attract birds who know that damaged leaves means a supply of tasty grubs to eat!

If the caterpillars bother you, it should be straightforward to pick them off. You shouldn't need to spray.
Be aware that if you use sprays, birds may eat the poisoned/dying caterpillars.