Some type of insect damage on my limelight hydrangea - Ask Extension
Hello,
I noticed a few days ago that I have some damage to my limelight hydrangea. I first noticed several branch tips had been chewed most of the wa...
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Some type of insect damage on my limelight hydrangea #869138
Asked May 19, 2024, 5:14 PM EDT
Hello,
I noticed a few days ago that I have some damage to my limelight hydrangea. I first noticed several branch tips had been chewed most of the way through so that they were dangling, with the leaves at the end turned brown. I can’t see any other damage to these branches, such as evidence of boring. Maybe it’s there but very small and I’m not seeing it.
Then I noticed some lower leaves have a substance that looks sort of like powdered sugar on them. I read online that this can mean there are cane borers. I looked closer and actually saw an adult insect going in and out of a dead hollow branch. It was moving fast so I couldn’t tell much about its features other than that it’s black, narrow/oblong, and small, maybe 5mm in length.
My google searches don’t seem to add up with these two symptoms. Do I maybe have two separate issues going on? I can’t find anything at all online about partially chewed off branch tips.
The hydrangea is about 15 years old, maybe 8-9 feet tall, otherwise pretty healthy. I’ve never had any pest problems with it before. I pruned it in mid-March this year, which I usually do every couple of years, never seal the cuts.
Thanks for your help!
Clark CountyOhio
Expert Response
From the photos provided, it is difficult to determine for sure the cause of the brown leaves and the white substance on the leaves. I have some guesses on what problems may be.
Cerospora Leaf Spot is a common fungal disease that affects panicle hydrangea to which lime light belongs. It begins as tan spots with reddish-brown halos on the leaves. It is not usually deadly, it weakens the plant and may defoliate it. Treatment consists of removing the diseased foliage and cleaning up thoroughly in the fall.
Scale insects deposit white cottony egg masses. Once the insects hatch, and feeding begins, black sooty mold on the honeydew may be noticed. There is only one generation of insects per year, but it is important to take action to control them because they suck the sap out of the plant and weaken it. The first step is to trim off any infested foliage. If infestation persists, apply horticultural oil.
Below are scientific based websites with hydrangea diseases and general information about hydrangeas.
You are correct in stating that for the most part the plant appears healthy. I suggest pruning out any affected areas and keep an eye on it. May you have many more years of enjoyment from this hydrangea.
