Leyland Cypress Pathogens Summer of 2018?

Asked August 2, 2018, 3:46 PM EDT

Have there been an influx of questions regarding Leyland Cypress this year? Specifically Seiridium Canker?

Jackson County Oregon trees and shrubs leyland cypress canker

4 Responses

Both Seiridium and Botryosphaeria are fungi that cause dieback in Leylands planted in the landscape. The first symptoms are yellowing or fading of the foliage on scattered lateral branches that eventually turn a reddish brown color. Small lesions or cankers often appear as dark cracked areas on the bark. Seiridium cankers may develop fruiting bodies that appear as small black dots and will often have resin flow associated with them. Healthy Leylands can also show resin flow so this is not necessarily the only diagnostic symptom. Botryosphaeria cankers develop fruiting bodies just under the bark and typically have little or no resin flow. Botryosphaeria can also develop extensive cankers on the main stem.

Cultural practices are important in disease management. All infected branches should be pruned about 3 to 4 inches below the cankered area and destroyed as soon as symptoms are observed. As an added precaution, disinfect pruning blades after each cut with either 10 percent household bleach or 70 percent alcohol. Since these two canker diseases are often associated with environmental and cultural stresses, plants should be irrigated properly during lengthy drought periods. Field observations suggest that trees grown in shady conditions are more prone to develop these canker diseases. If the plants are irrigated by overhead means, this should be done during the early morning hours. By minimizing overhead water, the level of disease spread can be reduced. In nursery situations, container grown trees should be protected from prolonged periods of subfreezing temperatures, which may create wounds on the stems. Do not take and propagate cuttings from infected plants. If Leyland cypress is to be grown as a screen, be sure to have a minimum of 12 to 15 feet between plants. Currently, fungicides are not effective for controlling this disease.

I have not heard of widespread occurrence of this disease in Oregon. If you believe you have this problem I would recommend that when removing infected trees or branches from infected trees, be sure to dispose of all infected parts. Your other plants and trees should be fine and not affected by the cankers.

Here are some publications you may find useful.

https://extension.umd.edu/hgic/plants/seiridium-and-botryosphaeria-canker-leylands-trees

https://www.uaex.edu/publications/pdf/FSA-7536.pdf

Hope this helps!

I'm pretty sure what I have is Seiridium Canker. The Leylands that I'm talking about were planted in the early '70's. They are "bleeding" pretty bad. These trees are 60+ feet tall.

If you look at the picture the Leyland with the green circle is by far the worst but the others circled in red have between 6 and 8 large stems that show major signs of canker. They all get plenty of irrigation. This all happened at the end of last year with one tree staring to show signs and by this spring there were limbs that had to be removed and jump to present and all of the trees now have it. What gives? I've talked to 3 different Tree cCompanies down here in So. Oregon and they all ahve said they are removing at least 10 Leylands a week. With these signs and also a needle blight.

Please take the time to read the publications I sent. Be careful not to apply too much irrigation or too much fertilizer.

Cultural practices are important in disease management. All infected branches should be pruned about 3 to 4 inches below the cankered area and destroyed as soon as symptoms are observed. As an added precaution, disinfect pruning blades after each cut with either 10 percent household bleach or 70 percent alcohol. Since these two canker diseases are often associated with environmental and cultural stresses, plants should be irrigated properly during lengthy drought periods. Field observations suggest that trees grown in shady conditions are more prone to develop these canker diseases. If the plants are irrigated by overhead means, this should be done during the early morning hours. By minimizing overhead water, the level of disease spread can be reduced. In nursery situations, container grown trees should be protected from prolonged periods of subfreezing temperatures, which may create wounds on the stems. Do not take and propagate cuttings from infected plants. If Leyland cypress is to be grown as a screen, be sure to have a minimum of 12 to 15 feet between plants. Currently, fungicides are not effective for controlling this disease.

Hope his helps!