When looking for low-maintenance trees and shrubs to act as wind barriers or hedges, many homeowners turn to evergreens, specifically the Leyland cypress. However, those once green branches may begin to mysteriously die off — leaving homeowners feeling blue about less curbside appeal.

Mahfuz Rahman, a plant pathology specialist with the West Virginia University Extension Service, offered some insight as to why homeowners are seeing this happening.

“The popularity of Leyland cypress has increased over the past decade due to its rapid growth properties, resistance to pests and usefulness as a functional landscape item,” said Rahman. “However, the shallow root system makes it susceptible to stress through desiccation, which in turn may predispose the tree to infection.”

Desiccation is a condition of extreme dryness within the tree. The phenomenon can be caused in winter by prolonged sub-freezing temperatures, which makes it hard for trees to absorb water lost through transpiration, especially on sunny and windy days.

Below average temperatures over the last two winters is the main reason that many homeowners in the area are seeing their evergreens fall prey to opportunistic diseases according to Rahman, especially those that find desiccated branches a perfect place to call “home.”

One such disease that has been particularly troublesome is seiridium, or cypress, canker.

Indicators of the fungal infection include branches that start to turn yellow to reddish-brown in the middle of normal, green branches. Closer examination should reveal slightly sunken, reddish cankers with resin exuding profusely several feet down on the infected branch, closer to the trunk.

The fungal infection spreads primarily by releasing spores during rainy weather and allowing the rainwater to splash and carry them to other branches. Infection on multiple branches throughout the tree or on the main trunk can kill the entire tree.

The only known cure for seiridium canker is eradication of the infection source — currently, no fungicidal treatments exist. The fungus survives in infected bark tissue, and Rahman recommends pruning the infected branch three to four inches below the infected area.

“While pruning, it’s vital to sterilize the blades between each and every cut with a 10 percent bleach or a 70 percent alcohol solution,” said Rahman. “The disease is a living organism that can spread by contact, so every effort must be made to minimize its spread as you remove infected areas.”

Rahman also advises destroying the infected branches as soon as possible by burning to completely eradicate spores that may still be living and infectious.

“While Leyland cypress is the major target of seiridium fungus, not all winter-desiccated trees get infected and plants affected solely by desiccation may grow back,” said Rahman. “However, in the unfortunate event when the tree dies from desiccation and a critical infection, it’s best to remove and dispose of those trees and replace them with something a bit hardier, such as ‘emerald green arborvitae’ or ‘Cryptomeria cypress’ which are less susceptible to seiridium canker.”

For homeowners looking to preserve their current evergreens, Rahman has some simple suggestions.

“Of course, the most practical way to prevent problems is to make sure you do everything in your power to make sure the tree isn’t stressed,” said Rahman. “While the weather is uncontrollable, ensuring that trees aren’t planted too close together and the surrounding soil is well-mulched, fertilized and irrigated during long periods of drought aids in a healthier tree in all seasons.”

Rahman also advised that additional protection from winter desiccation can come from providing irrigation in the fall and covering smaller trees with burlap.

For more information on caring for the trees in your yard or identifying problems, contact your local office of the WVU Extension Service.



CONTACT: Cassie Thomas, WVU Extension Service
304-293-8735, Cassie.Thomas@mail.wvu.edu
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