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Lilac #867541

Asked May 08, 2024, 10:46 AM EDT

1.)I have several lilac bushes. The last few years my old fashioned white lilacs have not looked healthy by the end of the summer. They have squiggly lines in the leaves and the leaves look slightly yellow to lime greenish instead of deep green like they look at the spring. This year the plumes of white flowers were no larger than the length of the palm of my hand. 2.)This year my lavender lilac had whole plumes of flowers drop off. I probably found 25-30 plumes laying around the circumference of the bush. I found a small black hairy looking worm (1/8"long) at the base of some of the plumes still on the tree....I'm not sure if this is a culprit or not.

Barry County Michigan

Expert Response

Hello

1-From your description you might have lilac leafminer. Please compare what you see with int information here-

https://ag.umass.edu/landscape/publications-resources/insect-mite-guide/gracillaria-syringella-formerly-caloptilia-syringella

Smaller flowers could be an indication of poor soil, less sun exposure, lake of water or other stress to the plant like extensive feeding by insects. Are the shrubs being over-shaded by trees that have grown over the years around the shrubs? Do they get watered during the summer drought?

Lilac care is described here- https://yardandgarden.extension.iastate.edu/how-to/growing-lilacs-home-garden

Get the soil tested and fertilize according to the recommendations-

https://www.canr.msu.edu/news/soil-testing-returns-through-msu-extension

2- The picture is very blurry and has nothing in it to show the comparative size of the caterpillar( a coin or ruler would work). We have had reports of spongy moth hatching out right now and your picture most resembles young spongy moth caterpillars. Here is an article to compare with yours-https://insectlab.russell.wisc.edu/category/caterpillars/

While they most often affect trees, they can feed on shrubs too. As spongy moth caterpillars grow they become lighter in color and the red and blue spots on them become more visible. Here is more on spongy moth management-

https://fyi.extension.wisc.edu/spongymothinwisconsin/

https://cals.cornell.edu/new-york-state-integrated-pest-management/outreach-education/whats-bugging-you/spongy-moth

Thank you for your question! Laura S. Michigan State University Extension Advanced Master Gardener Volunteer You may also contact the toll free MSU Extension lawn and garden hotline at 1-888-678-3464 with your gardening questions or visit www.migarden.msu.edu for Smart Gardening resources. Replied May 08, 2024, 12:45 PM EDT

Thank you for your many links for more information.

1.) I do think leaf miner may be the culprit on my 1st lilac problem. Thank you!

2.) The worm picture I sent did have in the comments box the size of the worm (1/8” long). I don’t see that the spongy moth caterpillar has the ability to deadhead the plumes of fresh lilacs according to the articles you sent.

I do think you are right about the name of the worm (caterpillar image) I sent you. (I now see them everywhere!!)

But, I am still perplexed on my 2nd lilac problem I described concerning the plumes of lilacs that had fallen off the bush.

Any further thoughts?

On May 8, 2024, at 12:45 PM, Ask Extension <<personal data hidden>> wrote:

The Question Asker Replied May 08, 2024, 9:52 PM EDT

Please examine the broken ends where several sections detached to get a sense of any pattern. This can give you a clue as to what caused the damage.
A clean cut at an angle is squirrel or rabbit biting the section off.
A straight across clean break is an insect chewing around the twig.
A ragged or torn end is wind damage or deer biting off the section.
If you can attach clear pictures of a few broken ends and include the flowers we might be able to see something more.
Regards,
Laura

Lilac #867541

Expert Response

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