Elm Tree

Asked April 20, 2016, 9:35 AM EDT

This past fall (2015) I planted a 12' tall, 2.5" caliper Ulmas Americana. It was purchased from a reputable nursery within 25 miles of my house. It had some damage from Leaf Beetles when I planted. Does that mean there are Leaf Beetle larva in the soil of the root ball I planted and will they emerge this summer? Should I treat the soil before that happens??? Thanks!

Macoupin County Illinois

4 Responses

The first question I need to ask is, has this tree's damage been positively identified as elm leaf beetle feeding? Who identified it for you?

Here is an article from the Univ. of California on Elm Leaf Beetle: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7403.html . It discusses the life cycle of the pest, and has pictures showing the stages of development. According to this article, the larvae do NOT overwinter in the soil, so at this time, there's no need to treat the soil. Adults overwinter in cracks in the bark; a young tree may not have sufficient cracks or rough bark for overwintering of adults, so you may not have any of the insects. Keep an eye open right now for eggs being laid on the leaves; if you don't see that, you don't have to worry about Elm Leaf Beetle.

Now...if the feeding was caused by any other beetle, I cannot answer your question until I know which critter caused the damage. I would suggest observing your tree carefully once per week and look for the first signs of damage or infestation. Take photos of what you see, and send them to us here at eXtension for examination.

The person at the tree farm identified the damage as being from leaf beetles when I made the purchase. The tree is young and still has very smooth bark. I'll keep an eye on the leaves for eggs. If I see anything suspicious I'll send photos. Thank you very much for the Elm Leaf Beetle link and for answering my question!

Hello Larry, and thanks again for addressing my question. I have attached a couple of pictures of the leaf damage I'm seeing already. I realize it's early Spring and bugs eat leaves, but I'd like to know if you can identify the culprit and if it's something that should concern me. The third picture is the only bug I've seen, but it appears to be in the ladybug family and to my knowledge this is a good thing. I think they are predators that eat other bugs, but I may be wrong. If what I've sent tells you anything please advise. Thank you, Doug Baugh

This does not appear to be the standard feeding damage for elm leaf beetle. That type of damage is not quite so uniform. It starts off more as a rasping damage as the tiny larvae scrape off layers of the leaves. Eventually they eat small holes between the veins. As they mature, the holes become larger, encompassing most of the tissue between the veins...what your pictures show. Since I don't see the other types of damage, I am not sure it's truly ELB.

Certain sawfly larvae might do this type of damage. Sawfly larvae look like caterpillars, but they're not; they're technically a maggot, because the adult is a fly. Right now, I'm seeing a different type of sawfly larvae on roses (locally called a "rose slug").

Some insecticide options for sawfly control:

  • acephate (Orthene)
  • bifenthrin
  • carbaryl (Sevin
  • insecticidal soap (M-Pede)
  • malathion (Malathion)
  • permethrin
Be sure to read and follow all label directions before buying and using any pesticide.