Early stages: Yponomeuta plumbella

The feeding signs of the very young larvae are quite evident on Spindle right now.  Look for obviously wilted young shoots as the wilting is caused by the young larvae feeding from within the stems.  Closer investigation will reveal tiny holes where the larva has entered the shoot and if you take great care in opening the shoot, the larva can be found, although at such a small size, it really is a needle in a haystack job.