Diagnosing problem Leland Cypress trees

Asked May 25, 2016, 11:35 AM EDT

I have a row of 12 cypress in my back yard that are showing extensive browning of small individual branches. I have had 3 arborist a look at them and had 3 different opinions. The arborist this morning suggested contacting you for a diagnosis. He said it might be the common type of canker. I don't know if someone can come out and look at them or can I bring a sample in? I have questions about pruning them also.

New Castle County Delaware plant disease leyland cypress

9 Responses


Leyland cypress was recommended widely about 20 years ago, as a fast growing, evergreen landscape tree. These trees were good for property lines and privacy screens. What we have found over the past 20 years, is that many times the trees were planted too close together. As the leyland cypress grew, they often grew together and became over-crowded. The crowded growth and maturity of the trees led to lack of air circulation, stress, and increased disease and insect pests. Bagworms are often a problem on leyland cypress. Leyland cypress is also very susceptible to environmental stress, winter injury and wind damage. Leyland cypress does not re-grow a nice shape after pruning. Often we need to recommend that homeowners and landscapers remove every other tree to reduce crowding and stress. Unfortunately, leyland cypress does not re-grow its nice shape after pruning.

There are a couple of plant diseases that affect leyland cypress, caused by opportunistic fungal pathogens. Usually, I recommend that owners try to keep trees in good health and vigor, and try to avoid environmental stresses by planting properly and in good sites (not windy, good drainage, etc), to avoid favoring tree diseases. There is no good control for plant disease such as tip blight except for pruning.

An alternative to leyland cypress is the Green Giant arborvitae, and some other evergreens that may be more adapted to our region such as holly, juniper, or flowering shrubs such as Chionanthus and Weigelia, or ornamental grasses. You may want to consider mixing the tree species down a property line instead of planting all one type. Diversity helps to avoid diseases. You could mix in some blue spruce between leylands for diversity and color.

Than you for contacting Cooperative Extension,


Can I bring a branch in and are you able to test for the Seiridium Canker? Is it necessary to clean pruning shears if you remove dead or crowded branches to avoid spreading disease? If so what to you recommend. I've heard, bleach, alcohol, even Lysol.


Sure, you can bring a branch in. Seiridium canker would show as orange to brown sunken areas on branches, and there would be abundant resin flow on the main branches and trunk. It is not as common as people think, and control is the same, to prune out.
If you prune behind the dead areas, you will not need to clean pruners with this type of dieback. For disease such as fire blight on apple and pear, cleaning pruners is important, and 70% alcohol works well, with wiping dry. Bleach 10%, is just too messy.

My best,

Thank you so much for your help. One last question- where do I bring a branch in to have it looked at?


Sorry for my delay. You can take a sample in to the County Extension office on Wyoming Road in Newark. There is an after hours box there too. Sample submission instructions and the downloadable form can be found at the web site below:


I brought samples of my Leland cypress to the extension today. I also brought sample from my flowering crab apple which suddenly has developed yellowing,spotty leaves and it has spread very quickly. I would like to save this tree but don't know what to treat it for or if it can be saved.

The apple leaves are most likely apple scab, a fungal leaf spot that can also infect the fruit. A fruit tree spray, or fungicide spray may help, but most fungicides are preventative and will not cure existing infections. The weather has made disease more prevalent this season. I'll look for your samples,

Thank you Nancy. I looked up Apple scab and I'm sure that's what my tree has. I keep coming back with more questions☹️. The tree needs to be pruned. Is this disease fatal? Most of the dying leaves are on upper branches . I thought perhaps pruning it and spraying early next spring would hopefully save the tree. Also is this fungus specific to fruit trees? I have 2 Cleveland pears in the backyard about 20 ft away. I've been raking up falling leaves and bagging them. Thanks,

The apple scab fungus affects only apple and crabapple. The key to management is a fungicide spray early in the spring as the leaves are unfurling. Spore infect during wet weather. Fungicides are preventative, will not cure infections. You may need to spray a couple of times, in late April and mid-May. Here is a link to a fact sheet:
The pears are susceptible to other plant diseases. It is a good idea to rake up leaves that fall.