Thin canopy could be result of sooty canker

Q: What could be causing my tree to be so ragged looking and leafless? My neighbors' trees, which appear to be the same type, look fine and looked this way the past four or five years. Theirs are full, mine are ugly! The tree in the rock mulch was in a lawn until last year. What kind of trees are these? I think they are ash. They are beautiful every fall when they turn dark red.

A: They may in fact be Chinese pistache, a tree with a similar appearance in form and leaf to ash when green. As I look at the pictures you sent me, there are three trees: one in front of your house, one between you and your neighbor to the right and one in front of your neighbor to the left.

Your neighbors' trees are doing just fine but your tree has a canopy that appears to be thinning. Your ugly tree, as you say, is in a nice-looking lawn while your neighbor's nice-looking tree is full and in rock mulch.

These trees are still relatively young trees, probably about 15 years old judging from their height. It also appears that this thinning problem happened fairly recently since they are all about the same height. I am guessing that your tree was in good shape except for this year or maybe one or two years back.

One problem that will cause a thinning of the canopy of some trees is a disease called sooty canker. This disease results in a sooty deposit under the bark . The outer bark of small and large limbs peels away leaving this sooty deposit that rubs off on your fingers when you touch it, just like soot in a chimney.

Frequently, but not always, it appears a couple of years after a for-hire tree trimmer has come in and done some pruning with infected equipment. They need to disinfect equipment between each job, at least, and it is mandatory after trimming or removing a tree infested with disease.

A second problem that can cause canopy thinning is nematodes infesting the roots. I have seen that on some trees in Las Vegas over the years, frequently on mulberry. This causes growth to slow considerably, leaf drop and usually smaller leaves to develop, sometimes accompanied by leaf scorch.

Since these symptoms usually accompany root knot nematodes, it can be determined by digging up some small roots in the soil near the tree and looking for swellings, or knots . Usually more fertilizer and water can cause the tree to grow nearly normal, outcompeting the nematodes for nutrients.

If you want to pursue this further, I would examine some of the smaller limbs that are dropping leaves and appear sickly, and look for orange lesions on them or soot under the bark. Secondly, I would dig into the soil and inspect smaller roots for these knots I wrote about.

If you find the soot, you will need to prune back the tree, removing all infected limbs. Make sure you use disinfected pruning equipment (I use alcohol) and disinfect between each limb that is removed. If you discover knots in the roots, fertilize the tree more often and try to give it deeper waterings.

Q: I live in Boulder City. We just noticed that one of our pine trees looks like it might have a problem. The bark is much darker in the lower trunk, there are some holes in the trunk and one of the small lower limbs looks dead. I'm attaching three pictures. I hope you can suggest what might be wrong and how we can treat it.

A: I don't have a picture of the entire tree so I am guessing the rest of the tree looks full, lush and dark green except for this problem area.

The holes in the trunk are most likely from a bird in the woodpecker family, most likely a sapsucker. The sapsucker will grasp the side of the trunk and punch holes into the trunk to feed on sap.

Pine is a favorite tree for feeding by some sapsuckers. We have some extensive damage from these birds done on some of our almonds and apples in the University of Nevada Cooperative Extension Master Gardener Orchard in North Las Vegas. I have attached a picture of damage to one of our trees for your comparison.

Recurrent sapsucker damage may be prevented in susceptible trees by wrapping damaged areas with a loose, coarse material such as burlap. Once the feeding period has passed, the burlap should be removed from the plant.

I believe sapsuckers are migratory in Nevada so feeding usually occurs during sap flow in the spring around February or March.

Q: I recently moved into a house with two large, 50-foot pine trees in the front yard that were only being watered with lawn sprinklers. I would like to make sure they are getting the proper amount of water as there are a lot of small dead branches, especially in the lower parts of the tree. How should I convert my sprinkler system to make sure they are getting enough water and what schedule should I use? I am not concerned about the lawn as I will be removing most of it and covering it with rock.

A: They actually require a lot of water simply because of their size. It is very possible the pine tree could be consuming more water than the lawn if both were by themselves. They may be getting most of it from neighbors since their roots can extend to a distance of two to three times their height, so figure at least a 100-300 foot spread (diameter) on the roots. They do not go into areas where there is no water and roots thrive best where there are low spots in a yard or where water accumulates.

Since they are watered with a lawn sprinkler their roots are most likely fairly shallow, unless you are in an area that is part of our shallow aquifer that runs through the middle of town and ends up in the Las Vegas wash.

This could be a tough call for you -- converting the roots of a very established tree to more local irrigations . You can encourage roots by severing some of them at the edge of the canopy and then increasing your watering closer to the trunk. This transition should be done gradually and preferably in the fall.

Start flooding the area near the trunk once a week to encourage new root growth near the trunk and as you begin to cut back on lawn watering. You would deep water like this maybe once or twice a week right now, increasing the frequency as it gets hotter. As temperatures climb, you may have to deep water twice a week.

There is going to be a period of shock with the tree as it tries to adjust its older roots system from one that was receiving water from a lawn to one where the roots are regenerating and water is applied only in a few locations. It also will help if you plant other landscape plants with a similar water requirement, such as other woody plants, under the tree.

You will have to keep an eye on the tree. This can be tricky but the key is to make sure there are days with no water between the days you are watering deeply.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at morrisr@unce.unr.edu.