University of Maryland Extension

Seiridium and Botryosphaeria canker of Leylands - Trees

close up of a canker on branch of Leyland
Botryosphaeria canker on branch of Leyland cypress

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.

sap on infected Leyland cypress branch
Close-up of Seiridium canker

Botryosphaeria canker on trunk
Botryosphaeria canker on Leyland

evidence of canker inside of branch
Cutaway of canker

Brown tips on Leyland cypress
Flagging on branches of Leyland cypress due to Seiridium canker
Photo: Jennifer Olson, Oklahoma St. Un.,

Seiridium canker on Leyland

Seiridium canker on tips Leyland cypress branch
Photo: Dave Clement, HGIC,

Management Strategies 

Both of these fungi cause disease when trees are stressed especially by drought. Watering and mulching will help retain soil moisture during dry periods. Prune out any diseased branches at least several inches below any visible cankers or dead wood. Avoid over fertilization. No fungicides are effective for these diseases.

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