Hickory tree pest - Ask Extension
Good morning,
I'm in Eaton rapids, Michigan and have noticed the hickory trees on my property we're dropping a lot of leaves in the past few weeks. ...
Knowledgebase
Hickory tree pest #871997
Asked June 07, 2024, 8:16 AM EDT
Good morning,
I'm in Eaton rapids, Michigan and have noticed the hickory trees on my property we're dropping a lot of leaves in the past few weeks. On closer inspection of the leaves, I noticed on the stem of each a small Mass that looks like a miniature burl. I have cracked one of the brawls open and there is a small grub inside. Looking at a tree, I can see that a significant portion of the leaves still on the tree have the past or blight on them. I've never noticed this before and was wondering if you could provide any information on what this might be and if there's anything I can do. I'm attaching several pictures.
Eaton County Michigan
Expert Response
Hello,
This appears to be hickory leaf stem gall aphid. This pest does not usually cause serious damage to mature trees, even though the leaf drop can be alarming to tree owners. If these trees are young, this might be more worrisome. In that case, I would recommend consulting an arborist to assess whether treatment is recommended or not. We always recommend consulting an ISA-certified arborist. Find one here:
https://www.treesaregood.org/findanarborist
It can be hard to determine the correct timing for treatment so that the aphids will be hit by the insecticide. (Once the galls are black the aphids have already left.)
In either case, I would make sure the trees are getting adequate water all summer to reduce stress. Clean up any fallen leaves and galls and bag and dispose of them. Some eggs may remain over winter in the old galls and in crevices of the bark. A spray of insecticidal soap in the spring just before the buds swell can help reduce the number of pests. Sometimes immature galls can be pruned out in the spring, as well. If the tree is large, spraying may need to be done by an arborist. In cases of very heavy infestation, a pesticide such as malathion might be necessary.
Here is more information about this pest.
https://ag.umass.edu/landscape/publications-resources/insect-mite-guide/phylloxera-caryaecaulis
I hope this is helpful.
Thank you for contacting Ask Extension
Ruth
This appears to be hickory leaf stem gall aphid. This pest does not usually cause serious damage to mature trees, even though the leaf drop can be alarming to tree owners. If these trees are young, this might be more worrisome. In that case, I would recommend consulting an arborist to assess whether treatment is recommended or not. We always recommend consulting an ISA-certified arborist. Find one here:
https://www.treesaregood.org/findanarborist
It can be hard to determine the correct timing for treatment so that the aphids will be hit by the insecticide. (Once the galls are black the aphids have already left.)
In either case, I would make sure the trees are getting adequate water all summer to reduce stress. Clean up any fallen leaves and galls and bag and dispose of them. Some eggs may remain over winter in the old galls and in crevices of the bark. A spray of insecticidal soap in the spring just before the buds swell can help reduce the number of pests. Sometimes immature galls can be pruned out in the spring, as well. If the tree is large, spraying may need to be done by an arborist. In cases of very heavy infestation, a pesticide such as malathion might be necessary.
Here is more information about this pest.
https://ag.umass.edu/landscape/publications-resources/insect-mite-guide/phylloxera-caryaecaulis
I hope this is helpful.
Thank you for contacting Ask Extension
Ruth
