Normal soil wetness…not too dry nor too wet.
Caterpillar eating foliage of ground cover, creeping jenny
There have been several reports of significant sawfly activity this year, mentioning their fondness for Creeping Jenny.
Sawfly larvae come in a fascinating variety of shapes, colours and sizes – most ranging from 10-40mm in length. Sawfly caterpillars have three true legs at the front, the same number as many other insect larvae, but have more ‘stumpy’ prolegs, five or more, extending down the abdomen.
Insecticidal soap will work on the young larvae, but older ones must be hand picked.
For more information, see this article by the Missouri Botanical Garden, but do understand that the chemical pesticides they recommend cannot be used by homeowners in Ontario.