Willow leaf beetles. - Ask Extension
My curly willow is infested with willow leaf beetles. It is about 25 feet tall and difficult to treat. I am considering cutting the tree down as it ...
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Willow leaf beetles. #873066
Asked June 14, 2024, 7:45 AM EDT
My curly willow is infested with willow leaf beetles. It is about 25 feet tall and difficult to treat. I am considering cutting the tree down as it gets worse every year and my plants around the tree are also getting ruined. One concern is if we take the tree down will the beetles go dormant in the ground and still be a problem for other plants and trees?
Macomb County Michigan
Expert Response
Hi Jo,
It appears that the reason willow leaf beetles are so hard to control is that their eggs overwinter in the soil, and hatch occurs of the period of a week to 10 days. So, it's hard to kill the larvae without daily checks on vegetation you can reach.
https://www.pubs.ext.vt.edu/ENTO/ENTO-139/ENTO-139.html
Removing the tree may be best. The beetles are known to attack relatives of willow, including cottonwood and poplar (aspen trees).
It looks like the beetles are on the hosta, but may not be eating it? You can treat the hosta with neem oil, which will repel (not kill) the insects. Neem is best when applied in the evening as it can discolor the leaves if applied while the plant is in direct sunlight. You may also use the other products listed in the article at the link above to control the pest on other plants.
When using any kind of pesticide, always read and follow label directions.
Thank you,
-Julie
It appears that the reason willow leaf beetles are so hard to control is that their eggs overwinter in the soil, and hatch occurs of the period of a week to 10 days. So, it's hard to kill the larvae without daily checks on vegetation you can reach.
https://www.pubs.ext.vt.edu/ENTO/ENTO-139/ENTO-139.html
Removing the tree may be best. The beetles are known to attack relatives of willow, including cottonwood and poplar (aspen trees).
It looks like the beetles are on the hosta, but may not be eating it? You can treat the hosta with neem oil, which will repel (not kill) the insects. Neem is best when applied in the evening as it can discolor the leaves if applied while the plant is in direct sunlight. You may also use the other products listed in the article at the link above to control the pest on other plants.
When using any kind of pesticide, always read and follow label directions.
Thank you,
-Julie
Hello Julie,
Thank you for the information. I have tried lady bugs but either they can’t keep up with the beetles or they went for treats elsewhere. It’s impossible to treat the leaves of the tree as it is over 25 feet tall.
Do you have any thoughts or advice on using a chemical on the ground when they go dormant? Chemical treatment is a last resort for me, but this problem is way out of control. I think we will take the tree down but I also want to make sure they do not come back and find another source of food, so I also want to treat the ground. I’m having trouble finding a product specifically for willow leaf beetles. Any direction in my search would be helpful.
Thank you again for your time!
Jo
Hi Jo,
There is a systemic insecticide that you can use to kill the pests - and it will also kill all other insects, including pollinators that visit the flowers in the spring. The insecticide is imidacloprid, and it is available at local box stores. Be sure to read and follow all label directions if you choose to use the chemical.
Electronic page 179 of the publication at the link below lists all insecticide options. Some only kill on contact, which requires full treatment of the tree; others are systemic.
https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/456/456-018/ENTO-567.pdf
I'm sorry you are dealing with this. Please let me know if I can provide further information.
Thank you,
-Julie
There is a systemic insecticide that you can use to kill the pests - and it will also kill all other insects, including pollinators that visit the flowers in the spring. The insecticide is imidacloprid, and it is available at local box stores. Be sure to read and follow all label directions if you choose to use the chemical.
Electronic page 179 of the publication at the link below lists all insecticide options. Some only kill on contact, which requires full treatment of the tree; others are systemic.
https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/456/456-018/ENTO-567.pdf
I'm sorry you are dealing with this. Please let me know if I can provide further information.
Thank you,
-Julie
Thank you Julie. This looks like a lot of good info. I am concerned for my dogs and the pollinators- which we have designed our gardens to support. I have plenty of reading to do before making a decision. Thanks again!
Jo
