Peony leaf insects

Asked August 4, 2020, 11:47 PM EDT

At this time of year my peony leaves are showing signs of being chewed on. They look like a hole punch has been used around the outer edge of the leaf. I also notice similar damage on lilac leaves. What can I do to prevent this?

Flathead County Montana

3 Responses

That may be damage caused by either leafcutter bees (https://extension.colostate.edu/docs/pubs/insect/05576.pdf) or any of a number of root weevils (https://extension.colostate.edu/docs/pubs/insect/05551.pdf) . Photos would help determine which is more likely but you can review both attached publications for more information.
Chemical control for root weevils is variable with several common products available. Chemical control is not recommended for leafcutter bees as they are important native pollinators. That's why identification of the damage and the cause is so important. There are other non-chemical, cultural controls that you can try and those methods are also discussed in the publications above.
If you need assistance identifying the damage and the cause, you can also take samples in to your local Extension Office in Kalispell. I hope this information is helpful and wish you the best of luck.


My permanent home is in Eagle, CO, but I am now at my summer home in Lakeside, MT. Can I assume that the insects are the same in both places?

Thanks

1st foto- Peony
2nd foto- lilac

That's a pretty fair assumption to make, which is why I like to use materials from Colorado State University Extension. Many of them are just as applicable here in Montana as they are in Colorado.

Looking at the photos, I'm inclined to think root weevils. In that case, you could apply one of the insecticides mentioned in the root weevil publication to the base and lower stems of the plants. This catches the root weevils as they move up into the plant to feed and minimizes non-target exposure to other insects, even though the plants aren't blooming right now.

It's important to remember that the damage you're seeing is caused by the adults and that the larvae can also damage the roots should you choose not to use insecticides of some sort. The literature reports that beneficial nematodes may be available to purchase and add to the soil to prey upon the larvae. Presumably, the link to the fact sheet in the publication may provide more information.
Let me know if you have any other questions.