Knowledgebase
Leyland cypress #768520
Asked August 22, 2021, 9:38 AM EDT
Baltimore County Maryland
Expert Response
We looked at the photos. We cannot say for sure what is going on. We do not have enough information such as how you care for them, watering, what are the site conditions, etc.
It is possible you may be dealing with an insect issue, possibly a type of weevil. For example, the white pine weevil - larvae bores into the leader causing it to stunt, flag and die. We recommend that you prune out and split the terminals and look for hollow stems, frass (insect poop), larvae, etc. If you see this, all you can do is let one of the other branches take over as a leader. No chemical control is recommended. https://extension.psu.edu/white-pine-weevil
Also, in general there are several possible insect (bagworms) https://extension.umd.edu/resource/bagworms-trees-and-shrubs and disease issues (seridium canker) https://extension.umd.edu/resource/seiridium-and-botryosphaeria-canker-leyland-cypress that can impact Leyland Cypress when stressed due to poor site conditions, drought, poorly drained soils, winter injury, etc. The best recommendation is to keep the trees well-watered during dry periods. Keep mulch no thicker than several inches deep and away from the base of the trunk. Avoid over-fertilization. Leyland cypresses grow best in full sun with plenty of air circulation and appreciate moisture during dry periods.
Here is our blog on leyland cypress https://marylandgrows.umd.edu/2018/04/11/why-is-leyland-cypress-turning-brown-winter-took-its-toll/
In the future you may want to consider a mixed screen so you do not lost the stand to an insect or disease issue.
Marian
Dear Ty, here's the response to your question:
We looked at the photos. We cannot say for sure what is going on. We do not have enough information such as how you care for them, watering, what are the site conditions, etc.
It is possible you may be dealing with an insect issue, possibly a type of weevil. For example, the white pine weevil - larvae bores into the leader causing it to stunt, flag and die. We recommend that you prune out and split the terminals and look for hollow stems, frass (insect poop), larvae, etc. If you see this, all you can do is let one of the other branches take over as a leader. No chemical control is recommended. https://extension.psu.edu/white-pine-weevil
Also, in general there are several possible insect (bagworms) https://extension.umd.edu/resource/bagworms-trees-and-shrubs and disease issues (seridium canker) https://extension.umd.edu/resource/seiridium-and-botryosphaeria-canker-leyland-cypress that can impact Leyland Cypress when stressed due to poor site conditions, drought, poorly drained soils, winter injury, etc. The best recommendation is to keep the trees well-watered during dry periods. Keep mulch no thicker than several inches deep and away from the base of the trunk. Avoid over-fertilization. Leyland cypresses grow best in full sun with plenty of air circulation and appreciate moisture during dry periods.
Here is our blog on leyland cypress https://marylandgrows.umd.edu/2018/04/11/why-is-leyland-cypress-turning-brown-winter-took-its-toll/
In the future you may want to consider a mixed screen so you do not lost the stand to an insect or disease issue.
Marian
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Split the leaders and check for possible insect damage.
Marian
