Dear Amy:

Thank you for contacting the El Paso County Master Gardener Help Desk regarding moth pupae in your garden. You are likely seeing army cutworm pupae prior to their emergence as "miller moths." In the caterpillar stage, the cutworm feeds on garden plants and crops; the adult moth feeds on nectar. Colorado State University tests have found pyrethroid insecticides to be most effective for larvae (you can find agricultural-related guidelines in the attached Fact Sheet No. 5.577). Household insecticides poorly control adult "miller moths," but you can find general information on other ways to control them in the second attachment (Fact Sheet No. 5.597). By the time the caterpillars have become pupae, any damage to the garden has already been done, unfortunately.

If we can help you further, please contact us at <personal data hidden>, <personal data hidden>, or via our in-person help desk at 17 N. Spruce Street in Colorado Springs (open Mondays and Wednesdays from 9-12 and 1-4 p. m.) Best wishes, and happy gardening!

Heidi V. 

Colorado Master Gardener Volunteer

Hi Amy,

Thanks for your question about your roses and the holes in their leaves.

There are several pests that might cause this problem, but the most likely is the sawfly larva. There are three types, the curled, the bristly, and the rose slug.

The sawfly is related to wasps and has four life stages: egg, larva, pupa, and adult. Their larvae look like caterpillars, but they are not. They are about 1/16" - 1/2" long and are greenish-yellow in color.

Leaf etching (scraped surfaces) or small holes in rose leaves are symptoms of feeding damage from sawflies. The larvae can chew holes in foliage or scrape off layers from the top and bottom of each leaf leaving whitish windows. While an infestation may not kill a healthy plant, it can weaken it and reduce future bloom quantities if it is heavy enough.

You can control them by:

1.  Handpicking  or knocking them off with a forceful spray

2. Treating with an insecticidal soap. Additionally, insecticides that you can apply to an active infestation of rose slugs include carbaryl (sold under the brand name, Sevin), Neem oil, and pyrethrin. All three kill rose slugs when they come into contact with them. Of the three, Neem oil and pyrethrin are organic, but many gardeners still avoid them because they can harm beneficial insects as well as pests.

3. Checking your plants in early spring for eggs and removing them

Please refer to these fact sheets for additional information:

https://ipm.ucanr.edu/PMG/GARDEN/PLANTS/INVERT/roseslug.html

Why are there holes in my roses? Roseslugs | Good Growing | Illinois Extension | UIUC

Thank you and happy gardening,

Liz B

Colorado Master Gardener



Thank you !

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On Jun 17, 2024, at 1:48 PM, Ask Extension <<personal data hidden>> wrote: