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Don Kinzler, Published May 18 2012

Hortiscope: Cut diseased branches to control canker

Q: We have a 25- to 30-foot spruce tree that has some dead or dying lower branches. At the point where the limbs connect to the trunk, there is considerable white sap oozing out.

The Bismarck city forester told me it could be cytospora canker and told me to prune the dead limbs. I did prune the dead branches that were accessible. Is there a product that I can apply or any other process to save the tree? It is a fine tree, and we do not wish to lose it. (Bismarck)

A: This does in fact sound like it could be cytospora canker. Control of cytospora canker requires that all the diseased branches be cut back to the nearest living laterals or to the trunk.

The bark should not be injured unnecessarily because the fungus may enter through the wounds. If the branches or trunks of affected trees are wet, spores exude from cankers onto the surface of the bark.

Pruning at this time should be avoided because the pruning tools may spread spores. Because weakened trees are susceptible to this disease, fertilizing to stimulate vigorous growth may help combat the problem.

Fertilizing also may stimulate new growth that may fill in small areas in the tree. However, large dead areas seldom fill back in. Too much or too little water are stresses that can weaken spruce trees. Make sure there is adequate drainage, and water the trees during droughts. There are no fungicides that effectively control this disease.

Q: I planted a blue spruce in a raised bed (about a foot above the lawn and filled with compost). It died about 18 to 24 months later. Thinking I maybe didn’t water it enough during the winter, I replaced it with another similarly sized blue spruce. It appeared to be doing well this winter, but this spring it was dead (it made it about two years).

This winter was relatively wet, so I didn’t attribute its demise to insufficient watering. I mixed the compost with the existing soil, planted the tree at the flare and mulched it well. Water for the tree came from lawn sprinklers.

My neighbor said the previous owner also had trouble getting a tree to grow in the area. However, my gamble oak nearby is happy. I’ve sent off a soil sample to Colorado State University. Any help you can provide is appreciated. (Denver)

A: The compost could be the villain. It may contain herbicides that are slow in breaking down, which would prove toxic to the trees. The CSU soil test most likely will give you a reading on the pH, soluble salts, nitrogen, phosphorous, potash (potassium) and possibly organic matter content, but nothing on the presence of herbicide residue.

The cost of such a test is high because of the more sophisticated equipment needed to make such a determination.

Q: I am preparing to plant eight Black Hills spruce trees. I would like some advice on planting them to give them their best chance for survival. I assume I should plant them similarly to any other tree, which is just above the root ball.

Also, I have used a root feeder with good luck to fertilize my young deciduous trees through the years. What is your recommendation about fertilizing conifers? Are there diseases I should be on the lookout for? What about winter preparation? (Bismarck)

A: Black Hills spruce are very hardy and durable trees suited for windbreak or landscape plantings. In their native habitat at about 5,000 feet in the western mountains of South Dakota, they thrive without any additional fertilization.

Being too generous with watering and fertilization is a second-tier downfall of trees in general. Planting trees too deeply is the first tier. Water them in well and monitor them for water needs. Water the trees appropriately through the summer and don’t worry about winter protection.

They should make it through most of our winters in good shape. However, a lot of people make a burlap open-top screen for the young plantings the first year. That should be sufficient to get the roots established, and the tree can grow on its own from there. They will survive on as little as 10 inches of rain per year. Black Hills spruce trees also have very few insect or disease problems.

Q: I am hoping you can give me some guidance or your opinion on a scenario I have.

I have been in my house for two years now. There are three poplar trees in the backyard that are 40 to 45 feet away from the house. One has been cut halfway down and I’m pretty sure it’s dead because it doesn’t have leaves.

The other two are quite tall. One of the two doesn’t have any leaves on the top section. The other tree has full leaves. There is a downslope behind my house, so the ground level where the trees are is probably at the same height as my foundation footings. I have a few foundation cracks that were there before I moved into the house, so I don’t know how old they are.

Is there any chance the roots of the trees are growing under my foundation? The soil in this area is clay. I plan to do some waterproofing work where the cracks are, so I’ll have the area exposed.

I just wanted to get an idea from your experience if you’ve heard of roots being able to grow under houses and if they could cause damage. (email)

A: Roots are opportunistic, so they will grow where there is a suitable balance of water, air and nutrients. Roots will follow the movement of water through the soil profile.

If I understand your question correctly, it appears that you have nothing to worry about concerning roots. However, be on the lookout for poplars this size and age because of the threat of limbs dropping off.

If you do get your foundation waterproofed this summer, it will set your mind at ease for any future root-penetration problems.

Q: I have a question about our lilac bushes. We have lived in our house for almost four years and have four giant lilac bushes lining our backyard. We get a ton of beautiful flowers every year. This year, I have noticed that we only have a few blooms and the branches are looking sickly. I’m wondering if there is anything we can do to save them.

Also, I should mention that my husband keeps compost under the bushes. The compost is everything from grass trimmings to dead squirrels. Also, the tree located near the bushes has been dying slowing. Maybe this might have something to do with my lilacs not doing well. Please help. (email)

A: I would say that your assumption is absolutely correct. A common mistake many make is that shrubs or trees are so well-established that they won’t mind a little extra stuff dumped under or around them.

The best move to save these plants and others affected by this action is to get everything cleared out and back to the original grade. After that, give them a shot of water-soluble fertilizer in the hope that this combination of treatment will do the trick.

Q: We have a compass cherry tree that has a saplike substance in the crotch of several branches. If I cut out the branches, there wouldn’t be much of the tree left.

The tree is about 10 years old and has done well through the years. (Jamestown, N.D.)

A: It could be canker development if it is where you say the oozing is located.

If that is the case, the tree isn’t long for this world. Unfortunately, there is no treatment for the problem. If you can, please take some good-quality photos of what you are concerned about and send them to me or Kasia Kinzer, our NDSU plant diagnostician. Between the two of us, we could give you a little more definitive answer.

Borers also are known to be a problem, but the treatment for those pests is something that has the potential to be successful.

Q: I had a tree-moving company transplant a very nice-looking spruce tree taken from a shelter belt. I have moved 30 trees from that location before. The transplant went well, and I did exactly what I was told to do.

I watered the base of the spruce until the crack around the root ball was filled with water. Then I chopped the crack to seal up the root ball. A week later, I watered around the base of the tree for 45 minutes at a low stream.

Two weeks after the transplant, the tree is changing from a nice green to a lighter shade of green. Should I turn my head to it or is there something I’m missing? How should I water it?

What would have you done from the point of transplant? (email)

A: Removing trees from shelter belts to be planted into the landscape is a risky operation because a large part of the root system that is responsible for water and nutrient uptake is left behind.

Your tree mover gave you good advice. He or she just didn’t go quite far enough concerning the roots that were left behind.

I cannot claim that it will work, but try giving your tree a foliar feeding of Miracle-Gro. If anything will bring the color back, that will.

Q: We just cut down an evergreen tree. It is my understanding that I have to treat the soil before I can get grass to grow in that area. Is this true, and what do I have to do? (West Fargo)

A: Nothing needs to be done to the soil as long as it isn’t full of wood chips or sawdust. Scratch the surface of the soil, sprinkle some seed and integrate it with the top half-inch of soil. If you give the seeds some water, they should grow.

To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or email ronald.smith@ndsu.edu.

Q: I live in a town that does not allow yard fences to be used on corner lots.

Unfortunately, I have two young children who play in our backyard. I would like to create a privacy and safety barrier for them. We have a number of arborvitaes planted along the sidewalk, but they’re quite old and weren’t taken care of by the previous owners. I also let a number of heavy snowfalls damage them beyond repair. I’m going to have them removed and replant 17 arborvitaes in their place. My landscaper has suggested nigra arborvitae, but the owner of a local garden center told me that nigra have multiple shoots from the trunk and will splay apart when it snows. He suggested green giants instead because they have a single trunk. I also happen to like the look of the emerald but assume I would need to plant them closer together and would need to increase the number of trees I need to buy. I have promised that I will take good care of them. Do you have any advice on which variety would be best for our family? (New Jersey)

A: Based on appearance, there is no doubt that the emerald green arborvitae is the better of the two selections. However, you will have to plant more of them to get the safety screen you want. The nigra would spread 5 feet or more. In some instances, you will get a 10-foot spread. Because you sound fastidious about wanting to take care of them, you could tie up the spreading branches with cloth or burlap going into the winter or control the spread with selective, intelligent pruning. From the economics of purchase numbers, the nigra wins. From superior looks, the decision usually goes to the emerald greens.

The choice is yours, but I don’t think you’d go wrong with either one. Just like many professions, opinions will vary among experts.