Questions on: Elm

Ron Smith, Horticulturist, NDSU Extension Service

Q: I am hoping you could share some of your knowledge about Manchurian elms. This spring I noticed that many of the elms had a heavy seed set with minimal leafing out. Is this a characteristic of the elms? Is this a sign that the tree is dealing with other issues? We have many Manchurian elm plantations in our park system that were established in the early '60s. They are high maintenance because of all the pruning and spraying to control cankerworms. What is the expected longevity of Manchurian elms under irrigated and nonirrigated conditions? We spray with Btk (Dipel and Foray 48B) as a control for cankerworm. Considering the high public use in these areas, is this the most effective, efficient and safe control measure for cankerworms? Thank you for your time and anticipated response. (e-mail reference)

A: Elms can live for more than 100 years in their natural environment. Generally, cut that length of time in half or more if the trees are in a landscaped environment, depending on the conditions. Manchurian elms have no log of longevity that I can find in any of my references, but the fact that the trees are showing heavy seed set and little vegetative growth is a very ominous sign of the end being near. If you can, you might try to collect a specimen branch showing exactly what you described to me and send it to the land-grant university diagnostic lab in your state for analysis. The materials you are using are about the best and safest on the market. You might check with the people taking care of the turfgrass areas in the park to find out what is being used for weed control. If the product contains Trimec, that could be a contributing cause for the decline. If they never have core aerated the turfgrass, it might be good to have that done because the trees would benefit as well.

Q: I have a lacebark elm that is oozing on the northwest side of the tree. I had the same problem with a tree a few years ago. On that tree, the top started dying about June and by September, the tree was gone. An arborist told me the problem wasn't borers. The arborist said it was a bacteria and advised me to fertilize the tree and water it well. The tree survived, but it is doing the same thing this spring. I also treated the tree with a systemic insecticide for borers (just in case). Although it dries up for a couple of days, the oozing comes back. Any ideas on how I can save this tree? (e-mail reference)

A: If the problem is a bacterial infection as the arborist suggests, there is very little that can be done other than what was recommended. The idea behind this is to compartmentalize the infection and keep it from spreading. It sometimes works, but not with any dependability.

Q: I have a few American elm that have leaves coated with sap and tiny aphids under the leaves. I don't know what Dutch elm disease looks like and there is no forester around to help. The sap coated the leaves of my flowers under the canopy of the tree. (Benedict, N.D.)

A: Leaf-feeding insects, such as you describe, can cause a mess under the canopy of the tree. The insects also are not doing the tree any good. I suggest you try to locate a relatively new product on the market known as Bayer Advanced Tree and Shrub Insect Control. It is applied around the base of the tree and absorbed systemically to kill the insects as they feed. It has a reported effectiveness of 12 months. Be sure to follow label directions or the results will not be satisfactory.

Q: Is it true that lacebark elm trees will grow 4 to 6 feet every year? Another tree I considered was an autumn blaze maple, which is a cross between a red and silver maple. Ultimately, I decided on the lacebark elm. I agree with you that the lacebark is gorgeous! (e-mail reference)

A: I enjoy seeing people make good tree choices. The lacebark elm is an excellent choice!

Q: We have an expanding wet spot at the base of our elm tree. It is below a seam or crack in the tree that appears to go toward the center of the tree, right where the roots go into the ground. It never seems to dry up and grass won’t grow in it. It doesn’t have an offensive smell, but it has us worried. It is in our parkway and some people believe it may be the water line for the house that has sprung a slight leak, but I don’t know exactly where the line runs. I found another tree a few blocks away with the same problem, but the water line is not close to the tree. Any ideas? (e-mail reference)

A: The only thing that is not usual about this is the lack of an offensive odor. Everything else fits. Perhaps the feeding fungi, bacteria and insects haven’t found it yet!

Q: We had elm trees on our berm, but they got Dutch elm disease three or four years ago. We had them cut down and the stumps ground down. Now I have a tough time growing grass and have lots of mushrooms. How do I get rid of the mushrooms? I planted grass seed and put burlap down to get the grass to grow. I’ve got the grass coming through the burlap, but still have trouble with mushrooms. (Jamestown, N.D.)

A: The mushrooms are a response to the decaying wood and roots left in the soil. They are harmless and will die down when the weather dries up a little. The grass should grow despite the mushrooms. The only way to get rid of the mushrooms is to excavate all wood-containing soil from the site.

Q: I would like to know if Manchurian elms have an estimated life span and if they are subject to Dutch elm disease?

A: What you are calling the Manchurian elm is also known as the Siberian elm (Ulmus pumila). So far this species has proven to be resistant to Dutch elm disease. It has enough other problems such as elm leaf beetle and other maladies. I guess the Dutch elm pathogen is exhibiting mercy on this poor cousin to the American elm.

Q: I recently cut down my elm tree because of a disease. I have a fireplace and am wondering if I can burn the wood or should I wait a year or two to let any potential eggs die? (Fargo, N.D.)

A: No problem burning it but you should do it as soon as possible.

Q: Is it possible that elm tree sap, when mixed with water, can spoil and cause an awful stink? I returned home after two days to notice an awful smell coming from the curb. I noticed some standing water along the curb. It wasn’t very much but it extended down the block. At first I thought someone dumped their RV waste because the smell sort of resembled it. The next day I went out with a garden hose and leaf blower to push the waste (note: the water had a white scum on it) to the sewer drain at the end of the block. A neighbor's friend stopped by and said it was sap causing the stink. The sap this year was heavy. I've only been in this home for two years so I'm a rookie when it comes to these things. I called my dad and he thought perhaps a sewer line broke but there's no water coming up and the grass along the curb is bone dry. Any thoughts? (Moorhead, Minn.)

A: Sap doesn't necessarily need water to stink. If you look carefully up into the canopy, you might see a canker where "bleeding" sap could be coming from to form a puddle of the stinky stuff. That is the result of some internal rot. The stinky stuff is called "slime flux."

You might want to contact an International Society of Arboriculture certified arborist to see if something can be done to re route the stinky stuff or remove the cankered branch. The usual summertime sap drippings coming from mature trees is usually the result of aphids feeding on the foliage and the sap passing through their bodies as "honeydew" that get all over sidewalks, cars and streets. During dry periods that normally occur this time of year, the tree leaves bleeding sap through microscopic openings on the leaf edges exacerbate the problem. Try and avoid parking your car under such trees as it damages the finish.

Q: An individual came into the office with a forestry question that I thought you might be able to answer. Last fall he cut up a bunch of American elm trees for firewood. He heard from someone that in order to stop the spread of disease he should strip the bark off of any leftover logs that he would not be burning. This would evidently kill any beetle eggs that might be under the bark. He was wondering if this was true and if he should do this. (McClusky, N.D.)

A: Absolutely and it should be done ASAP. Ideally it should have been done before April 1.

Q: What would you recommend for killing suckers from a elm tree? We’ve removed most of the tree except for about three feet. There are trees on both sides that we would like to keep. Also what would be your general guidelines for watering trees this fall? Specifically, is there any special concerns considering the severe drought we are still in here? (Hettinger, N.D.)

A: Try to get a hold of a material called Sucker-StopperRTU which is sold by a California company. It is a form of NAA, a growth regulator, that apparently works in some situations. It’s worth a try. They have a phone number listed on their label as: (559) 499-2100. It is made by Monterey chemical for Lawn and Garden Products. Inc. in Fresno, CA. Water the trees! They should not be allowed to go into the winter dry. Hydrated plants always have a better chance of surviving than those that are not.

Q: A lady asked me to look at her trees. They are Siberian (Chinese) elm approximately 25- 30 feet tall, with some age of course. Two of them leafed out nice. Now one has lost about half or more of its leaves and one is starting to lose. The third one about 30 feet away is fine. (New Town, N.D.)

A: Siberian elms are racked with disease problems. In fact, it is more unusual to find one that is healthy! The homeowner will have to live with the malady that is attacking the trees or simply remove them to replace with something else. Spraying does little good, and the tree seldom completely dies, usually "surviving" with a branch or two still alive. If she wants to, have her get the healthy tree sprayed with a fungicide for protection by a local arborist. Chinese elms and Siberian elms are not the same; the Siberian elm is hardy in our area and is Ulmus pumula; the Chinese elm is not hardy and is a beautiful, disease-resistant tree with attractive characteristics I could lapse into poetry about. It is Ulmus parvifolia . It is also knows as the Lacebark elm. The principle attribute of the Siberian elm is that it is useful genetically for breeding in Dutch elm disease resistance. If we could grow the Chinese elm in North Dakota, everybody would love it and want to have one.

Q: A few years ago I had to have our American elm tree removed because of disease and the stump was ground out. The year after, and every year since, mushrooms come up around the base of the former tree, in increasing numbers and in a widening circle. Is there any kind of herbicide I can spray on them to kill them without doing damage to the lawn? And how about some kind of sporicide to take care of the released spores so they won't sprout? Or is this just something I have to live with? (Hatton, N.D.)

A: Live with it, unless you want to do a lot of digging. Sorry! It should pass in a few more years when everything is broken down.

Q: We are retired farmers near Aberdeen, SD. Our shelterbelts are quite old maybe 30 to 40 years. Many "residents" there are the old Chinese and Siberian elms that have long since lost favor, but they were the "tree-of-the-hour" when we planted them, as they grew fast and provided much shade, beauty, and wind protection for us all. This winter and spring a weird phenomenon has taken place. Of those that have survived, and in some new growth, many of the tops, perhaps10 to 15 feet, have been completely stripped of all bark all the way around the branch. This spring when these old trees leaf out, we will have most of them showing dead tops, if the whole tree doesn't die. Can you shed some light on what has happened to these old trees? (Aberdeen, S.D.)

A: About the only thing we can be certain of is that the trees will be dead from that point up! It is likely a cause of borer damage along with a canker disease of some kind that girdles the trees.

If you get a chance, you might want to try talking with your local NRCS people to see if they can help you with tree replacement in your shelter belt. I assure you, the Siberian elm will not be a replacement!

Q: We had an old American elm that died from Dutch Elm and maybe some other diseases. We have an offspring of that elm. Can it catch any diseases from the roots of the old tree even though it’s dead? (E-mail reference)

A: There is every possibility, but I think it is worth the risk.

Q: In May 2000 I planted a ‘Cathedral’ elm. Its leaves this year are pale yellow-green. I fertilized this June, but the leaves have only darkened slightly. Now within the last week they have developed light yellow to almost white spots on virtually all the leaves. Should I fertilize again? Also, can you recommend a reliable purple-leafed plum that produces sweet fruit and doesn’t get over 20 feet tall or so? I’d like to use it as an ornamental in our front yard; it would be on the northeast side of the house. (Fargo, N.D.)

A: I do not recommend fertilizing again this year. I would like a leaf sample so our Plant Diagnostic Lab can evaluate it for a disease problem. The ‘Newport’ is an attractive ornamental plum that tops out at 20 feet in southern Minnesota. It should stay under that in North Dakota. Purple leaf sandcherry has purple foliage, bears purplish fruit in August and gets to about 8 feet tall. In my opinion the ‘Princess Kay’ is the most beautiful plum around. The flowers are double and very fragrant.

Q: This coming spring I need to replace four American elm trees in our yard. What do you recommend as replacement trees? (Rogers, N.D.)
A: I recommend polyculture rather than one species of tree. For example, you could plant an Amur or Tatarion maple in your front yard, a Japanese tree lilac or serviceberry in the back, and either laurel willows, Manchurian ash or Ohio buckeye along the street.

Q: I have three 2-year-old volunteer American elm trees that I would like to see continue growing. Does Dutch elm disease affect these trees too? (Montrose, S.D.)

A: Yes, they will likely be vulnerable to Dutch elm disease as well.

Q: I have lost a substantial number of elm trees from my property due to disease. I like the elm because it grows fairly fast, doesn't rot and rarely falls in storms. I have heard of a disease resistant hybrid that grows fast but will not be affected by Dutch elm disease. Is there such a tree, and where can I find it? What other trees would you suggest that are fast shade and look nice?
(Fergus Falls, Minn.)

A: You are correct in describing all the characteristics of the American elm. Look for three cultivars that appear infrequently on the market: Sapporo Autumn Gold, Regal, and Pioneer.

All three have Dutch elm disease resistance. If you should come across Accolade or Jacan, these two are also Dutch elm disease resistant and have beautiful form. If you love the American elm, it is a lot like falling in love with a redhead—others are nice, but only one will do!

Q. I am having to replace my ash tree and have been looking for a replacement. In the Gurney catalog I find something called "Hybrid Elm." It is supposed to be fast growing, up to 10 feet per year. I am wondering if this hybrid is suitable for North Dakota. I wonder if this may be the Chinese elm strain that grew fast and died off about three years later. I am enclosing the clipping from the catalog.

As I mentioned the last time I wrote you, I am a little long in the tooth so I want shade reasonably soon for my screen house! I just turned 86! If you don't think the hybrid is OK, perhaps you have a suggestion. I read your column faithfully. (LaMoure, N.D.)

A. While they don't give botanical names for their nursery stock (which irritates me), I would assume they are ethical enough to truly be selling a hybrid elm--likely a cross between Siberian and American elm. I would say go for it. This elm should grow fairly fast and provide you shade for the many birthdays you have to look forward to. Enjoy.

Q: One of my American elm trees has curled up leaves and small, red nodules on several branches. On another tree the curled up leaves have small green, bumps
inside. Are either of these treatable or will they hurt the trees? (Herreid, S.D.)

A: They are no cause for alarm. These are insect caused galls that do mostly cosmetic damage to the tree. Nature has already laid out the course, so all
you can do is observe!

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