Q.My creeping Jenny was beautiful but now all the leaves have holes as if something is eating them.
The plants are well established and have done well for 3 or 4 years.
It was probably the larval form of some sort of sawfly. They can quickly decimate the host plant. Here is some info from the Univ of IL:The sawfly larvae are whitish to pale green with light tan heads and obvious black eyes. Fully grown larvae are a little over one inch long. Although sawfly larvae look similar to caterpillars, they have more than five pairs of prolegs. Not being true caterpillars, they are not controlled with Btk. Spraying the foliage with carbaryl, Sevin, or a labeled pyrethroid will provide control. Do not spray the blossoms to avoid killing bees and other pollinators.
https://www.gardeningknowhow.com/ornamental/groundcover/creeping-jenny/creeping-jenny-ground-cover.htm