Leaf damage

Leaf damage

Observation - Leaf damage - UK and Ireland. Description: Something is eating the leafs of my Morning Glory which is entwined around the clothes line pole. It is also spreading to nearby plants such as Dicentra and Osteospurnum (but not the thicker leaves of a rhododendron. No bugs or insects are visible to th

Something is eating the leafs of my Morning Glory which is entwined around the clothes line pole. It is also spreading to nearby plants such as Dicentra and Osteospurnum (but not the thicker leaves of a rhododendron. No bugs or insects are visible to the naked eye and a spraying with a greenfly/general pesticide is ineffective. Could anyone please identify the culprit and suggest a course of action? Thanks