we have siberian elms on our university park lot. - Ask Extension
we do not see any beetles but the leaves are definitely chewed. how do we protect our treesthank youcathy
Knowledgebase
we have siberian elms on our university park lot. #156272
Asked October 08, 2013, 6:49 PM EDT
we do not see any beetles but the leaves are definitely chewed. how do we protect our trees
thank you
cathy
thank you
cathy
Denver County Colorado
Expert Response
Hello Cathy,
Well, coincidentally, I happen to work in the University Park neighborhood and on my office property there are 2 Siberian Elm trees. This summer they both were heavily infested with the Elm Leaf Beetle. The trees were covered with this beetle and most of the leaves were skeletonized. A number of elm trees in UP neighborhood were likewise infested with this insect, and I would suspect that this is also the culprit that was chewing the leaves of your trees.
It is important to determine what insect you are dealing with in order to treat the problem. Next spring as your trees are leafing out keep a close eye on them. Look for evidence of insect activity on the leaves and trunk. If you see any insect eggs, insect larvae on the leaves or flying insects in the area of the trees, try to capture some samples. The adult Elm Leaf Beetle is green with black markings.
Below I have included links to some information on Elm trees and the Elm Leaf Beetle. If you have trouble identifying the insect, it would be easy for you to bring a sample to the Denver Extension office located at 888 East Iliff Ave. on the northeast corner of Harvard Park. They will be able to positively identify it.
If you are dealing with the Elm Leaf Beetle, there are systemic insecticides with Imidacloprid available at garden centers and big box stores. You would probably want a trunk drench for this. When you go to purchase the product you will need to measure the circumference of your tree trunks at 3 feet from ground level. Add up the total circumferences so you will know how much to purchase. Follow the directions very carefully for application. Some of these tree drenches are effective for one year from the date of application.
http://www.ext.colostate.edu/ptlk/1746.html
http://www.ext.colostate.edu/pubs/insect/05521.html
Well, coincidentally, I happen to work in the University Park neighborhood and on my office property there are 2 Siberian Elm trees. This summer they both were heavily infested with the Elm Leaf Beetle. The trees were covered with this beetle and most of the leaves were skeletonized. A number of elm trees in UP neighborhood were likewise infested with this insect, and I would suspect that this is also the culprit that was chewing the leaves of your trees.
It is important to determine what insect you are dealing with in order to treat the problem. Next spring as your trees are leafing out keep a close eye on them. Look for evidence of insect activity on the leaves and trunk. If you see any insect eggs, insect larvae on the leaves or flying insects in the area of the trees, try to capture some samples. The adult Elm Leaf Beetle is green with black markings.
Below I have included links to some information on Elm trees and the Elm Leaf Beetle. If you have trouble identifying the insect, it would be easy for you to bring a sample to the Denver Extension office located at 888 East Iliff Ave. on the northeast corner of Harvard Park. They will be able to positively identify it.
If you are dealing with the Elm Leaf Beetle, there are systemic insecticides with Imidacloprid available at garden centers and big box stores. You would probably want a trunk drench for this. When you go to purchase the product you will need to measure the circumference of your tree trunks at 3 feet from ground level. Add up the total circumferences so you will know how much to purchase. Follow the directions very carefully for application. Some of these tree drenches are effective for one year from the date of application.
http://www.ext.colostate.edu/ptlk/1746.html
http://www.ext.colostate.edu/pubs/insect/05521.html
1) Have the beetles gone for this year (so there's no sense looking for them until the trees leaf out next spring)?
2) Are the beetles already adults when trees leaf out (so they would be green with black markings as you mentioned)? If not, what do they look like at the time of leaf out (remembering that the UPCC newsletter article mentioned yellow and black insects in June)?
2) Are the beetles already adults when trees leaf out (so they would be green with black markings as you mentioned)? If not, what do they look like at the time of leaf out (remembering that the UPCC newsletter article mentioned yellow and black insects in June)?
Hi Cathy,
The adult beetles are probably still around but they would not be doing damage at this time and they would be difficult to find. They are overwintering under debris and in cracks in sidewalks and other protected areas. Look for them to emerge in late winter or early spring.
Last summer I saw eggs, larvae and adult beetles on the trunk of the trees (all at the same time) here at my office. I found quite a few in the crevices of the tree bark. Our trees are so tall that I was unable to see the leaves close up. If you are able to get to the branches and leaves of your trees next spring, look on the undersides of the leaves for eggs and larvae. The adults will be flying around the trees or crawling on the trunk and surrounding areas. You may even have some in your house or on your screens.
There are some good pictures of all 3 stages of the Elm Leaf Beetle in the first link I sent you. They should be easy to identify. If you have something different from the pictures on that fact sheet, the Denver Extension office would be able to help you. Also, if you are able to take a digital picture of the insect and attach it to an email, we may be able to help you through Ask an Expert.
The adult beetles are probably still around but they would not be doing damage at this time and they would be difficult to find. They are overwintering under debris and in cracks in sidewalks and other protected areas. Look for them to emerge in late winter or early spring.
Last summer I saw eggs, larvae and adult beetles on the trunk of the trees (all at the same time) here at my office. I found quite a few in the crevices of the tree bark. Our trees are so tall that I was unable to see the leaves close up. If you are able to get to the branches and leaves of your trees next spring, look on the undersides of the leaves for eggs and larvae. The adults will be flying around the trees or crawling on the trunk and surrounding areas. You may even have some in your house or on your screens.
There are some good pictures of all 3 stages of the Elm Leaf Beetle in the first link I sent you. They should be easy to identify. If you have something different from the pictures on that fact sheet, the Denver Extension office would be able to help you. Also, if you are able to take a digital picture of the insect and attach it to an email, we may be able to help you through Ask an Expert.
