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Six Diseases of Leyland Cypress

Colleen Warfield, Extension Plant Pathologist

 

Cercospora Needle Blight

-Needles and twigs turn yellow > brown > gray
-Lower branches affected first
-Disease spreads outward and upward
-Needles drop from tree
-Tips of infected branches remain green
-Reddish-brown lesions form on 1 yr old twigs
-Olive-brown tufts of spores on blighted tissue
-Older infected trees have thin, brown foliage
Control-
*Prune affected branches from trees
*Daconil, Fore, Heritage, Systhane, Kocide from bud break until new growth matures at 10 day intervals

Kabatina Tip Blight

-Tip dieback on 1 year old growth in early spring
-3-6 in shoots turn yellow brown and then reddish brown
-Small, gray lesions may be observed at base of shoot
-Small, black spore-producing structures at base of shoot
-Infected shoots will remain on tree or drop prematurely
-Wound pathogen unable to infect healthy plant tissue
-Insects, freeze injury or ice damage create entry points

*Prune infected shoots below site of infection
*Thiophanate-methyl, mancozeb, or copper applied in the fall may help reduce infection

Seiridium Canker

-Twig, branch, and stem dieback
-Cankers from on stems, branches, branch axils
-Sunken, dark brown/purple patches on bark
-Numerous, long, thin cankers
-Cankers often associated with resin flow
-Foliage above cankers yellow, reddish brown
-Fruiting bodies appear on bark surface as dots
-Often occurs on trees under stress

*Prune infected twigs and branches
*Prune at least one inch below canker
*Avoid water stress

Botryosphaeria Canker

-Scattered, bright reddish brown twigs/branches
-Cankers on small twigs or branches
-Cankers often centered on twig/branch stubs
-Cankers resemble those caused by Seiridium
-Fruiting bodies produced just beneath bark
-Canker may girdle trunk, but rare
-Often occurs on trees under stress (drought)

*Prune out and destroy affected branches
*Mulch plants yearly
*Provide adequate water during dry periods
*Avoid heavy fertilization

Phytophthora Root Rot

-General yellowing of foliage, some tip dieback
-Primarily infects smaller roots
-Large, established trees rarely affected
-Plants may grow slowly and gradually decline
-More severe when soil drainage is poor
-Woody roots decaying from Phytophthora are firm and brittle (eventually become soft)
-Roots destroyed by excess water are soft

*Avoid planting in areas that are compacted, drain poorly, or are excessively damp
*Chemical control not recommended for landscape
*Excessive mulch may promote root rot

Armillaria Root Rot

-Yellowing or browning of needles with premature drop
-Symptoms occur over entire plant
-Branch dieback in lower crown
-White “fans” of fungal mycelium form between the bark and the wood; visible when bark is removed from tree from the lower trunk
-Black string-like strands can sometimes be found between the bark and wood
-Plants not growing well are most severely affected
-Most prevalent in landscapes established in areas of natural forests or where oaks once stood
-Thrives under warm, moist conditions
-Mature trees may die quickly or slowly

*No cure for severely affected plants
*Remove and destroy severely affected plants ASAP

Alternative Plants-

Dr. Bob Lyons, formerly of the J.C. Raulston Arboretum at NCSU suggests the following plant material as an alternative to Leyland Cypress.

Thuja 'Green Giant' and cultivars of Cryptomeria japonica


Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical.

For assistance, contact your county North Carolina Cooperative Extension Service agent.

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Published by North Carolina Cooperative Extension Service

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Web page last reviewed January, 2007 by the web person