I have quite a few Hostas in my yard located under a tree canopy; they grow very well but at the end of the summer they always seem to get holes in the leafs. I thought it might be slugs so I’ve put bait out, but it doesn’t seem to matter. I’m having the same issue with my Hydrangea.
Thank you for contacting the Toronto Master Gardeners with your question concerning your hostas.
It is most likely slugs or earwigs that are feasting on your hosta leaves. Both slugs and earwigs are nighttime feeders. Earwigs will hide under the soil or in between the axil of leaves. Putting out slug bait is a start; however it will never eliminate the entire population.
We have numerous archived posts concerning slugs and earwigs. One of our archived posts titled Leaf Eater? gives information on how to treat both pests.
In the case of your Hydrangeas it could be earwigs or Japanese beetles eating your leaves. Have you noticed any shiny copper coloured beetles on your leaves or flowers? As with the slugs and earwigs we offer lots of information concerning Japanese Beetles.
Just enter the term Japanese Beetle into the Search Box on the main page of our website: www.torontomastergardeners.ca and press the magnifying glass. Up will come a few pages of articles on this very problem.
The following information is from two of our archived posts:
“We have been hearing a lot from gardeners about this problem , and if it is of any comfort, many others are having the same issues. Here is a reply that was posted from our website a short time ago on the same topic, I hope it is of some help.
“This is a common question posted at this time of year. The Ontario Ministry of Agriculture and Food has a website at the bottom of which there is a lists of plants that are most susceptible to damage by this insect. To control Japanese beetles you can either control the adult or the larvae. the best method (although still time consuming but strangely satisfying) is to go out in the early morning or in the late evening when they are not as likely to fly around and simply knock them into a small bucket/jar of water (add a few drops of soap) where they drown. You will need to begin this process at the end of June or the beginning of July and continue until sometime in early August. After that, the next method of control is to go after the larva. Nematodes are best applied in August and are watered into the affected area. They attack the larva of Japanese beetle, June bugs and European chafer all of which racoons and skunks like to dig up the lawn in search of. When applying nematodes it is important to keep them refrigerated until you are ready to apply them. Ideally they should be applied on an overcast morning or evening. If the lawn is dry it should be irrigated first with about ½ to 1 inch of water. You should prepare and use the entire pack and water (while agitating) them into the soil. You might need to irrigate the lawn again to “wash” the nematodes into the soil. You can also reference our other responses to this problem at Roses and Grey Grubs in the Lawn”
“When Japanese beetles discover your garden they seem to do so in great numbers, as you have experienced. Experts say that the best method for control is to hand pick them in the early morning or late evening when they are less likely to be flying, and simply knock them into a pail of soapy water, where they will drown. Another option, similar to what you are suggesting, is to use what is called row cover cloth to drape plants, making sure that the edges are secured at the base of the plant, to prevent the beetles from landing. Gardeners and nurseries use this cloth to cover fruit trees or prized roses. It is an air permeable fabric that is closely woven so that insects cannot penetrate it. Row cover cloth is available in rolls from gardening specialty stores . Other fabrics that you could consider are tulle or mosquito netting. A covering that is breathable would be preferable to plastic, but covering in clear plastic overnight and removing in the morning would likely not harm your containers in the short term. We should see the end of these beetles in mid-August, when they mate, lay their eggs and gradually die off.
I know it is little consolation, but there are many gardeners in Southern Ontario who share your frustration with this pest. Here is a fact sheet from the Ontario Government that lists plants that are more and less susceptible to the Japanese beetle: https://www.omafra.gov.on.ca/english/crops/facts/92-105.htm”