Seminole Crop E News

Agricultural News for Farmers and Agribusiness in SW Georgia

Leyland Cypress Problems

Posted by romeethredge on December 20, 2013

Leyland Cypress Dilemmaleyl

The Leyland cypress (x Cupressocyparis leylandii) is a beautiful evergreen tree that has become one of the most widely used plants in commercial and residential landscapes as a formal hedge, screen, buffer strip, or wind barrier.  However, because of its relatively shallow root system, and because they are often planted too close together, Leyland cypress is prone to stress. Once the plants become stressed, disease may follow.

 Best management practices minimize stress to the tree; and subsequently a healthier tree. The Leyland cypress is best suited for fertile, well-drained soils.  They will not stand wet soils and will respond to ‘wet feet’ by getting sick or dying.  Mulch is desired after planting, but do not mulch deeper than four inches.

Do not water any more than twice a week even during a drought – once a week would be best.  Water soils to a depth of twelve inches and then let them dry out. Soils need to dry out between watering to protect the roots. Three-quarter to one inch of water per week is recommended.

Do not plant Leyland cypress trees closer than eight feet apart.  This is a common problem in the landscape.  Trees may reach 50 feet in height and 20 – 30 feet in width.  When limbs touch, they cause wounds that can be infected by these diseases.

 Okay, Leyland cypress trees may get infected with both root rot and foliage diseases.  Phytophthora root rot and Annosum root rot are important root diseases.  In the landscape, Phytophthora root rot primarily affects smaller plants; larger, established trees are rarely affected by this disease.

Annosum root rot is uncommon in the landscapes.  Leyland’s at new construction sites are more susceptible to Annosum root rot – especially where pine clearing has taken place.  This is because this disease develops through fungal spores infecting freshly cut pine stumps.  The fungus then grows through the stump and its root system, infecting adjacent Leyland cypress trees through root contact.

No fungicides are recommended for root rot diseases. There is no effective control once the tree is infected.  To avoid Phytophthora root rot, establish Leyland cypress in tilled and well-drained soils. Avoid over-irrigating, especially during establishment.

Leyland cypress can also be infected with foliar diseases such as Seiridium Canker and Botryosphaeria (Bot) Canker.  However, UGA Pathologists consider these diseases as more secondary diseases resulting from other stresses.  Seiridium canker can infect any age and size tree with no cultivars known to have resistance. Fungal spores spread from infected trees by water splashing (rain) and pruning tools. In the landscape, fungicides are seldom used and they provide no control once infection has taken place.

Bot canker symptoms resemble Seiridium canker as yellowing or browning of shoots and branches.  The main trunk may develop cankers that produce ‘ooze’ from the infected area. The only method of control, as suggested for Seiridium canker, is cultural control.  Avoid environmental and cultural stresses that predispose the plants to infection.  Also, remove disease twigs and branches to prevent disease spread.

Note from the beginning of this article, stress is the culprit.  UGA Extension Pathologist, Dr. Elizabeth Little described the myriad of Leyland cypress problems all across the state.  Dr. Little provided one underlying message:  Don’t spray.  UGA does not recommend fungicides (even though some fungicides are labeled) for the diseases of Leyland cypress because of little fungicide effectiveness and the fundamental association of disease to cultural problems.

But wait!   What is one common environmental factor across Georgia this year?  Rain! Leyland cypress typically has problems with drought; however, they can also have problems with wet soil.  Dr. Little agreed that the high number of Leyland cypress issues today are likely a delayed response of the environmental impact of rain this season.

Can we control the environment? Nope.  What should you do if your Leyland cypress gets disease?  First, cut out dead limbs ONLY. Clean your shears periodically.  Second, note cultural practices which induce stress your Leyland cypress trees.  This may be too much mulch, overwatering, or not allowing sufficient canopy space.  If tree limbs touch, remove every other tree to allow for space.  Solving Leyland cypress problems usually come down to cultural practices since there is little else we can do.

Most of this post is from an article by Andrew Sawyer, Thomas County Extension. Information from this article was taken from UGA Publication, “Diseases of Leyland Cypress In The Landscape.”

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One Response to “Leyland Cypress Problems”

  1. That’s awesome. Thanks for putting that up. I need to post more landscape problems too.

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