Questions on: Box Elder

Ron Smith, Horticulturist, NDSU Extension Service

Q: The city where I live is expanding a road and letting people take the boxelder trees lining the road. The trees are tall, so they would be expensive to move. Iíve been told that only the female trees with seeds attract boxelder bugs. Do males attract the bugs? Is there a machine large enough to move the trees? Any idea about the percentage of trees that survive a move such as this? (e-mail reference)

A: Why anyone would want boxelder trees is beyond me, but as the saying goes, to each his own. Boxelder bugs do have a preference for female trees, but I've seen a lot of uneducated bugs hanging around male boxelder trees. In fact, Iíve seen boxelder bugs hanging on trees of many species. Boxelder bugs are not the brightest bugs to come out of an incomplete metamorphosis! Trees that size that have been in the same location for a decade or more without any root pruning will be very difficult to remove successfully. Large tree spades rarely are available, except in metro areas where large tree movement is commonplace and planned in advance. In your situation, I would be surprised if 10 percent would survive such a move, and I'm sure it wouldn't be cheap.

Q: What's the best way to get rid of box elder trees on conservation reserve program land? (e-mail reference)

A: Other than ripping out the box elders, allow them to leaf out this spring and then cut them back to the ground. The leafing out will spend the carbohydrate reserves from last fall, so the trees will be too weak to releaf to any great extent. Whatever does pop up again can be nuked with Roundup.

Q: We are about to cut down an old and dying boxelder tree. The big branches that have come down were rotten and falling apart. Can you burn rotten boxelder wood? Is it worth trying to keep some of the less rotten parts of the tree to burn or should we avoid it? (e-mail reference)

A: Go ahead and burn all of the tree, unless you are fussy about what goes into your fireplace or storage rack. I can't think of a reason to avoid it.

Q: An old boxelder has lost some bark on the bottom few feet of the tree. There are small, eighth-inch or so round holes drilled over the lower trunk. The holes are in the barkless portion. A lot of sawdust is on the ground below it. Would sapsuckers do that much harm or could borers be a possibility? (e-mail reference)

A: That is an excellent symptom of borer activity.

Q: Are box elder trees toxic to horses? Thanks for your time. (e-mail reference)

A: Red and swamp maples are listed as having toxic properties, but not box elder. That doesnít mean they are not poisonous, just that there have been no reported cases of any poisonings from this species.

Q: Do you know about a natural herbicide produced by box elder trees? I have noticed bare ground around some box elder trees that canít be caused by a lack of sunlight or something else. I know walnut trees secrete juglone. (e-mail reference)

A: My references donít specify the box elder as having an allelopathic effect on surrounding seedling invasions. The references do state that competition is very common among species to assure their survival, especially where plant growth resources are limited, such as in droughty or dry land areas. Leaves and roots, as you probably know, are the most common source of these inhibitors.

Q: How do you tell a female box elder tree from a male? (e-mail reference)

A: If the tree bears seed, then you know it is a female. Otherwise, you have no way of knowing unless the plant is asexually propagated from a male parent, then all the offspring will be male.

Q: I am a woodturner, and often when turning a piece of box elder, there will be an area of red coloring in the wood. Some have said it is caused by an infestation of some sort. I donít always find an obvious worm hole and often the coloring seems to be brushed through the wood instead of concentrated, like the coloration caused by the ambrosia beetle. (e-mail reference)

A: I would have to guess that it is an infection, possibly benign, that shows up at times and is compartmentalized by the treeís defensive mechanisms.

Q: We have a mature boxelder tree in our yard that looks sick. The leaves have black spots, are smaller in size than past years and dropping from the tree. Any idea what might be wrong? (e-mail reference)

A: It could be any number of fungal diseases. Have an International Society of Arboriculture certified arborist inspect the tree. There might be more than one thing wrong with the tree. It is a good idea to get boxelders inspected on a regular basis as they mature.

Q: We have a very large box elder tree in our yard. The base of the tree has tons of suckers coming out of it. Should I prune them off or will that hurt the tree? (E-mail reference)

A: The proliferation of suckers is usually symptomatic of something going wrong with the tree such as water table change, compaction, borers, drought, disease or some other abiotic damage. If the tree is important to you, you might want to have it checked out by a professional ISA certified arborist. Pruning the suckers out will not hurt the tree, but you should look into why it is suckering so much. This is usually a prelude to the death of the tree in the next year or so.

Q: Is a box elder tree supposed to be outside? A friend gave it to me and said it was a house plant. I have been finding box elder bugs so I assume it is a box elder tree. If it is meant to be outside, will I still have the bugs indoors? Will these bugs hurt our home in any way? If it can be an indoor tree, how do I get rid of the bugs? (E-mail reference)

A: Just when I think I have heard it all, then someone tells me that a boxelder tree is a houseplant. I suppose anything is possible, but I would get it out of the house, and if possible, way out in your yard. Keep it away from anything the tree can damage when it drops branches or collapses in 20-30 years. Boxelder bugs are harmless, but annoying critters. I assume you live somewhere where winter weather is starting to close in, and typical of the insect, it is seeking shelter from the cold. They are pests, but not harmful to one's home.

Q: I recently moved into a house that is surrounded by box elder trees. One of them, the oldest and largest, appears to have died suddenly. This happened in the spring of this year. This particular tree is very large, probably 60- to 70-feet tall. The person who lived here before me supposedly sprayed the tree for box elder bugs but I don't know what he used. Roundup was used on nearby box elder stumps to prevent suckers from sprouting. (E-mail reference)

A: The sudden death of a tree seldom occurs. When it does, it is often the result of a lightening strike. More often, the tree is in a state of decline that goes unnoticed by the homeowner, and when it is visibly dead, the cause was something either biological that has been going on for some time, or an abiotic event such as a water table change, construction damage, or spray drift from a potent herbicide. If you haven't done so already, get the tree removed ASAP. Large, dead box elders are not something you want to keep around as souvenirs. Unlike us, they don't get better with age. They usually have problems with internal rot, etc. One of many good reasons they are used in shelterbelt plantings and not around residences.

Q: A client has boxelder trees and lots of boxelder bugs. Any ideas she can use to get rid of the bugs? (Linton, N.D.)

A: Boxelder trees attract boxelder bugs. There are two ways I know of to rid the area of them: remove the trees (not likely!) and spray with Malathion, Asana or Warrior.

Q: Is there a way to control sprouts from box elder trees? Last spring, I cut down a bunch of small box elders with trunks 3 to 4 inches in diameter. By fall I had a nice crop of new shoots coming up from the stumps. (e-mail)

A: If what is coming up are seedlings and not attached to the mother tree then an application of Roundup will take them out. If they are attached via the root system to the main tree, then some damage to that tree could be expected.

At one time, there were sprout inhibitors on the market, but the manufacturers did not re-register under new EPA, rules and the products had to be taken off the market.

Q: We have an 80-year-old box elder tree that has a large crack in it. We cut away the damaged wood, but we are wondering if there is something we can paint on the trunk to preserve the rest of the tree? (Tappen, N.D.)

A: Basically, you don't need to do a thing to the cut surface. If the tree is healthy, the wound will heal naturally; if the tree is unhealthy, there is nothing you can spray on it that will facilitate healing.

I suggest you have the tree checked by a forester for internal soundness. Although the photo shows sound wood where the cut was made, the old box elder is close to the end of its typical lifespan and may have some internal rot that is not evident from the outside. Such a condition could pose a danger to your family.

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