Beetles doing a number on willow

Question: Our willow in the front yard is getting overwhelmed by beetle larvae feeding on it. Like they are all over. I cut many of them off by sheering the willow and for a few days I have been picking off adults and looking for larvae and finding lots. Looking this up it looks exactly like the cottonwood beetle: https://extension.okstate.edu/programs/digital-diagnostics/insects-and-arthropods/willow-leaf-beetle-chrysomela-knabi-cottonwood-leaf-beetle-chrysomela-scripta/

Don’t like killing bugs but nothing is eating these larvae and I think they could kill the tree. 

I wonder if leaving the leaves like I do for wildlife is making this situation worse? 

Any recommendations? I assume pulling adults off is helpful to keep the population down?    

 Don’t have any photos of the larvae  as it’s mostly adults and I took off many many larvae when I trimmed it back. It was really just smothered with them.

responder: An Ask Extension Expert Replied June 12, 2023, 4:00 PM EDT
response: Hello, Thank you for reaching out regarding your cottonwood leaf beetles. There is some information available about management of this pest, but a lot of it is for poplar plantations, which would have more need to tightly control the pest due to it being a commercial crop.   In general, trees can handle some defoliation of the canopy without much harm to the tree, but if it becomes too extensive it can be problematic.  How large is your tree? There are some pesticides that can be used, however spraying full size trees is pretty challenging. If the damage isn't too extensive, you can keep removing the pests. I would also focus on removing any groups of eggs that you see, since that will reduce the population. There will be a second generation of the pest, so keep that in mind that additional feeding will be happening later in the summer. I am putting a link to a publication below which has management techniques. They have a recommendation to spray a biological product called Bt var. tenebrionis when the larvae are small. This is a pretty safe option if you would prefer not to use broad spectrum insecticides.  http://cues.cfans.umn.edu/old/Web/100CottonwoodLeafBeetle.pdf  The adults overwinter in cracks in the tree bark or in clumps of grass. It is possible the leaves could help shelter them. Have you had this issue before? How old is your tree?  Thank you for using Ask Extension!

responder: The Question Asker Replied June 12, 2023, 5:04 PM EDT
response: Thank you! I thought about BT and also soap and water was recommended for eggs. I can check into it. I dont' like to use chemicals. The tree was here when we moved in about 10 years ago (we're renting). It's possible that since I leave the leaves more than maybe the maintenance person did in the past (he worked her until like 3 or so years ago) that they overwintered better. They have been a problem only for last two years and it looks pretty bad- and potentially one section of the tree is dead, not sure from what but it seems like they are pretty intense. You can't tell in photo as I have been clearing larvae and beetles as well as foliage for about a week. I also cleared a bunch of pupae from the base of tree that hadn't hatched yet. Perhaps I just need to: clear the leaves from around this tree in fall/winter- spray soap or bt in early spring and mid June/early July and monitor. If there are some but it's not terrible I can leave them, it was just really crazy with the larvae everywhere. I left them alone last year and the tree survived but I think if this keeps happening and they continue to proliferate it may kill the tree. It doesn't seem like an old growth tree or anything, it's not a baby but it's not super old as far as I can tell, though it's been trimmed back each year so it may be a bit stunted, not sure how it would be in the wild.thanks for your help,AlexaOn Mon, Jun 12, 2023 at 1:00 PM Ask Extension <<personal data hidden>> wrote:

responder: An Ask Extension Expert Replied June 12, 2023, 6:22 PM EDT
response: Hi Alexa, Thank you for the extra information, it sounds like you have things well in hand. Bt or potentially insecticidal soap applications would be helpful if they are practical for the size of the tree. Be sure to follow all the instructions on the label.   If the tree has dead sections and keeps getting insect infestations, perhaps your landlord might consider planting a different tree that doesn't have pest issues and taking this one out.  Thank you for using Ask Extension