The leaves you sent appear to be older leaves, and it is possible that some of
the yellowing is natural. Occasionally, older leaves will die away as new growth
begins. It is also possible, that some of the off color is due in part to winter
damage, which often begins to show with warmer weather. If the shade is from
deciduous trees, the ivy was more exposed during the winter and some superficial
damage occurred. I can’t tell if the ‘chewed’ areas are insect in origin, or if
the leaves were spotted with either leaf-burn or disease and the tissue is
falling out. Often large areas of tissue that are damaged will dry out and then
fall out, which can look like insect holes. Could the leaves have been burned by
weather (late frosts, ice, etc) or by fertilizer or herbicide damage? Since so
much of the damage is on the edges of the foliage I would suspect a burn. Do
some pruning of your ivy, removing as much of the damaged foliage as possible.
Earlier in the season, I would even recommend simply taking a weed-eater or lawn
mower over it at a high setting to rejuvenate it. Then keep it watered and if
you have not fertilized, do so. Ivy is normally a very resilient plant and
should begin to fill back in.
My wife planted English ivy in a small bed mostly in the shade except for
afternoon filtered sun. It has grown to be thick and beautiful. We have noticed
the last several weeks that there are scattered dead, yellow leaves and some
green leaves that have been chewed on by some mysterious parasite. I am
enclosing a couple of the leaves. Advise us on what to do to restore our
gorgeous ivy to its original health.