Hortiscope

October 7, 2004

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: We have a hackberry tree that was doing fine until last summer when many leaves turned yellow and fell off. This summer the same thing is happening but far worse. We have heard of a lacebug that can damage these trees. Is this what it is, and if so, what can we do to stop the damage? Can they kill a tree? I have noticed two other hackberry trees in town that have some of the same symptoms. (Ada, Minn.)

A: The lacebug is usually a problem in the eastern part of the country. It affects members of the elm family, which the hackberry is. Hackberry trees are also known to defoliate early for other reasons. Wide fluctuations in moisture are a primary reason. Contact a local Certified International Society of Arboriculture Arborist to come out and diagnose the problem. Since you live in Ada, you might not have one locally, but many will travel some distances for work. Try the yellow pages in Grand Forks if none are listed in Ada, or give Kelly Melquist a call at (701) 729-6899. He’s in Fargo and may be willing to come that far.

Q: I have two ornamental pear trees spaced about 40 feet apart. After flowering, one of the trees continued as normal with the production of lush green leaves. The other tree appears distressed. It has a lot less leaves and the leaves are reddish in color. The only thing I have done differently this year is apply some lime to the lawn in the spring. Could this be the problem? If so, why is the other tree showing no signs of distress? (e-mail reference)

A: I assure you the lime application would not work that fast. Something else is going on. Try to get it diagnosed by local experts before you lose the tree.

Q: I appear to have mildew (or something like it) attacking my alpine currents. Both shrubs are on the east side of the house so they don’t get full sun (one is also partially shaded by a tree). They start the season growing nicely and then about mid June some of the leaves get a white powder on them and die. Any suggestions on what can be done? (Valley City, N.D.)

A: Put down a protective fungicide against downy mildew as the leaves unfold next spring.

Q: My husband and I planted over 20 techny arborvitaes two summers ago. They have been doing just great and gave us the privacy we needed for our backyard and pool area. This past spring we have noticed that the trees have produced mini-like pinecone looking nuggets, which are bronze in color, all over its branches. Some of them dried up and fell off, but most have remained. Could it be they are lacking acid? What can we do if this is not the normal growth process? We have noticed that there is plenty of new growth, despite the problem. We would hate to lose them because it was a very costly project. (e-mail reference)

A: You are worrying needlessly. The fruiting bodies are an indication of the plant’s maturity. Some are more prolific at producing (think hamsters versus pandas) than others. As long as the plants are maintaining their rich green color and new growth, you have nothing to worry about.

Q: Can you provide any clue on the green circular patches that are growing on my red oak? Is it a fungus or anything I have to worry about?

A: It is probably moss or algae growing on the trunk, usually on the north or east side, but not always. It is harmless, so there is nothing to worry about.

Q: I have a purple ash that has a problem with its leaves. They have round bumps on them that look like warts. What should I do for the tree? (e-mail reference)

A: The bumps or warts are likely caused by a gall-forming insect that are only causing cosmetic problems, not lethal ones. There is nothing you can do about it now and it isn’t worth attempting to control it in the future. The pest will likely be effectively controlled by normal predation or differing weather conditions from one spring season to the next.

Q: I’m hoping to get a second opinion on a couple of tree questions. The first tree is in the town of Hettinger. It is a large tree in the front yard and gets watered frequently by the sprinkler system. The tree is losing its needles from the inside out. The inner most needles are brown and have fallen off; others are turning yellow. The new growth doesn’t appear to be affected yet. I believe that it is rhizosphaera needle cast, but I can’t find spores on any of the needles when I look at them under a microscope. Am I missing something? I recommended that the owner treat the tree with Bravo. I also pointed out that the sprinkler is probably making it worse by spreading the spores. The second question is about a younger spruce tree. The new growth looks good, but the tips are turning a reddish brown color. This was first noticed about June 22. We had a hard frost on June 17. Is it possible that the tree could be showing signs of frost damage? (Hettinger, N.D.)

A: You are correct in your assumption about the sprinkler’s impact. The spores would not be showing yet, but would be there in early spring. As for the spruce with the reddish brown tip growth, this could very well be the effects of the frost on June 17. The tree should be fine, just set back a little.

Q: I hope you can shed some light on a problem with a newly seeded lawn. The homeowner says her yard was hydroseeded with Kentucky bluegrass and 10 percent perennial ryegrass on May 15. The perennial ryegrass is up and growing, but there are only a few spots that have Kentucky bluegrass. She has kept the area wet with a sprinkler since it was seeded. At first she turned it on for about three minutes, but now she turns it on for 7 to 10 minutes so the area stays wet. She uses well water (425 ppm sodium, 450 ppm sulfates) and the soil is sandy. The homeowner is curious to know why the Kentucky bluegrass isn’t coming up. (Dickinson, N.D.)

A: It could be that the seed is being kept too wet or she has seed with poor viability. Most hydroseeding companies will do touch-ups to keep clientele happy. Most also get excellent results using this procedure.

Q: A lady purchased a product at a seed store in Mandan that is supposed to be good for controlling little black bugs (flea beetles?) in her garden. The product is called Diatomaceous Earth, Crawling Insect Killer and is made by Natural Guard. Now she is wondering if this product is okay to use directly on the plants in her garden or if it should just be used on the soil. Can you tell me anything about this product? The bag’s label says nothing about avoiding garden vegetables during application. (Dickinson, N.D.)

A: She can use Diatomaceous Earth anywhere she wants. It is an excellent, mild abrasive on soft-bodied insects. Placing it in the soil around her plants as well as on them, if she can keep it from falling off, will prevent soft-bodied insects from setting up home. She would be controlling the larval stage of the flea beetle as well as any others. It kills by lacerating the soft body tissue and causing death by dehydration.

Q: I just looked at a row of young lilacs with leaves that are turning brown and dying. I know there was a lot of standing water near them for some time, but apparently they were not actually standing in water. I dug up some soil and found it’s still very saturated. I’m suspecting just too much water at the root zone cutting off the oxygen to the roots. I also saw swelled main stems on a few, which may possibly be borer. The lilacs are on the north side of a high fence with large cottonwoods behind the fence, which shades them most of the day. (Cando, N.D.)

A: They could have a double whammy, too much water in the root zone, which led to a borer attack. It’s not the first time this has happened and it won’t be the last!

Q: I’m afraid my rubber plant got too much of a cool draft. The leaves are now turning yellow and falling off. Is there any hope for my plant? (e-mail reference)

A: Yes, but you need to be patient and keep it out of drafts.

Q: I have a split leaf peony plant, and I would like to know when to cut it back after it is done blooming. It blooms on Memorial Day and now has several pods where the blossoms were. Do I leave it until fall or cut it back now? (Rothsay, Minn.)

A: Cut the stems that flowered off back to where they originated.

Q: Last year I received two trees as a gift. We planted one on the west side of our home and one on the east. This spring they both set wonderful leaves, but now all of a sudden the one on the east side has a wilting appearance. The leaves have turned a pale green to light yellow with brown/black spots. Some spots seem to have a light center that looks like an eye. The vines of the leaves are dark green, but some are turning brown. Also, the branches and trunk seem to have a bright orange color where the other tree is still green/brown looking. Is this a problem that is treatable? We also had a large very old red maple that was taken down when we built our home because part of the tree was dead. I am now wondering if there is a problem with the soil. Are these trees adapted to our area? (Hartland, Minn.)

A: The red maple is adapted to most Minnesota conditions; however the situation, as you described, doesn’t sound good for the tree. Something is killing the tree and only an on-site diagnosis can determine what it is. It sounds like a combination of rust fungus, chlorosis and a leaf-spot disease. Since the tree is so young, I would simply remove it and replant in another area. There might be spores from the removed tree still in the soil.

Q: We have a fair share of silver maple trees. I have one nice specimen next to the house. A month ago I noticed a woodpecker on the side of the tree and didn’t think twice about it until a couple of weeks later. This little pest has punched about a dozen holes in the tree and now the tree is bleeding. The sap is running down the tree to the point it’s foaming at the base. How do I stop the tree from bleeding? I am concerned this will destroy one of my nicest trees. I did a close inspection of one of the injuries and it’s deep into the meat of the tree. (e-mail reference)

A: Spread Tanglefoot where the bird is working or wrap it in aluminum foil. Both will discourage the woodpecker from returning. The tree should heal itself without trouble if it is otherwise healthy.

Q: This is the first year I’m growing tomatoes, jalapenos and bell peppers. Do I have to replant every year or will these plants produce every year? (e-mail reference)

A: All the crops you listed are annuals so they need replanting every year because the frost kills them in the fall. The two most common vegetable plants in most gardens that are perennial are rhubarb and asparagus.

Q: The leaves on our hibiscus are covered with some sort of white crystals that give the leaves a grainy feel when you rub your fingers across them. I’m sure they are not white flies because I never see any movement and have looked at them through a magnifying glass. They seem a bit sticky and drop down to make the floor underneath a bit sticky. Is this normal? (e-mail reference)

A: The white crystals could be some of the salts coming out of the ends of the leaves. It could be some kind of insect, but I doubt it from your description. It’s probably not because I’ve not heard of this before nor experienced it myself in growing hibiscus. If the surface can be wiped with a damp cloth, do so to clean up whatever it happens to be.

Do you have a gardening or houseplant question? Write to Hortiscope, Box 5051, NDSU Extension Service, Fargo, ND 58105 or e-mail to Ron Smith at ronsmith@ndsuext.nodak.edu. Note to e-mail correspondents: please identify your location (city and state) for most accurate recommendations.

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Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu

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