Canker and Dieback Diseases of Leyland Cypress

Alabama A&M and Auburn Universities Canker and Dieback

ANR-1160 Diseases of Leyland Cypress

ithin the last decade, cypress in California. Within 20 Leyland cypress has years, a dieback and canker disease been widely used in caused by the fungus Seridium cardina- residential and com- le devastated stands of this tree in mercialW landscapes across Alabama the hot and dry Central Valley of not only as a specimen tree, screen, California. During the same time or hedge, but also as a Christmas frame, native stands of this tree tree. Popularity of this tree, which is along the cooler and wetter a hybrid of the Monterey cypress California central coast suffered little (Cupressus macrocarpa) and the Nootka if any disease-related damage. In the falsecypress (Chamaecyparis nootkaten- mid-80s, Seridium canker was re- Figure 1. Yellowed foliage on branch sis), is due in large part to its graceful ported on Leyland cypress in of Leyland cypress damaged by columnar to pyramidal shape, its at- Seridium canker. (Photo courtesy of L. California. Since then, this disease Barnes, Texas A&M University.) tractive dark green foliage, and its has emerged across the Southeast as rapid growth rate. Mature Leyland a common and damaging disease in cypress may reach a height of 70 landscape plantings and on gray, discolored areas on the bark. feet or more. In its native England, Christmas tree plantations. As was Resin often oozes from cracks on Leyland cypress reportedly has suf- the case with Monterey cypress, dis- the surface of the cankers and flows fered from relatively few damaging ease development on Leyland cy- down the diseased branches or tree diseases. However, in recent years, press has been closely tied with hot, trunk. Fruiting bodies of the causal several threats to the health and dry summer weather. Two other spe- fungus S. cardinale appear on the can- beauty of Leyland cypress have cies of Seridium, S. unicornie and S. cu- ker face as small black dots about emerg ed in Alabama landscapes and pressi, are also known to cause canker the diameter of pencil lead. on Christmas tree plantations. diseases in juniper and cypress, but Leyland cypress is best adapted their importance is unknown. Disease Cycle to fertile, moist, well- drained soils. The causal fungus S. cardinale Unfortunately, this tree is often Symptoms overseasons in the landscape and planted on poorly drained sites The most noticeable symptom nursery in cankers on diseased where it is not well adapted. In addi- of Seridium canker is yellowing or Leyland cypress. Other native and tion, Leyland cypress, which is rela- browning of the foliage on one or introduced evergreens may also be a tively shallow-rooted, may be weak- more top or lateral branches (Figure source of this fungus. When the ened when exposed to prolonged 1). This discoloration may appear at bark surface is moist, masses of periods of drought during Alabama’s any time of the year but is most like- spores of S. cardinale ooze from blistering-hot summers. Finally, poor ly to be seen in the spring. Disease fruiting bodies called acervuli. The planting and maintenance practices development often continues until a spores are spread to healthy foliage as well as extremely close plant spac- considerable portion of the tree is and branches of adjacent Leyland ing further increase plantARCHIVE stress and killed. cypress by splashing water and con- the risk of fungal-incited canker and taminated pruning tools. The disease dieback diseases, including Seridium The causal fungus often invades Leyland cypress and other hosts can also be easily spread to new lo- canker and Botryosphaeria, or Bot, cations on diseased liners, cuttings, canker. through wounds on the twigs and branch bases. Girdling cankers form and container-grown plants. Insects on the twigs, the scaffold branches, may also be involved in dispersing Seridium Canker and the main trunk, and then the fo- this pathogen. Warm and wet condi- Seridium canker was first de- liage dies. Lens-shaped cankers on tions favor infection. Pathogen activ- scribed in the mid-20s on Monterey the twigs and branches appear as ity ceases during hot, dry weather.

www.aces.edu Control ed for the control of Seridium can- Most likely, development of this dis- In residential and commercial ker on Leyland cypress. ease, like that of Seridium canker, is landscapes, proper establishment None of the cultivars or selec- related to a combination of heat and and maintenance are the best de- tions of Leyland cypress that are drought stress or possibly transplant fense against Seridium canker. Since available to the nursery industry are shock. Leyland cypress is a relatively shal- known to be resistant to Seridium low-rooted tree, site preparation and canker. When planted in areas with Symptoms amending with aged or rotted organ- hot, dry summers, Monterey cypress Visually, the symptoms of Bot ic material are critical for maintain- is also highly susceptible to this dis- canker are quite similar to those of ing tree vigor. (See Extension publi- ease. Although eastern red cedar is Seridium canker. Yellowing or cation ANR-410, “Establishing susceptible to Seridium canker, this browning of the foliage on a shoot Woody Ornamentals,” for more in- disease has been responsible for little or branch is usually the first symp- formation about site preparation.) if any damage on this hardy tree in tom seen (Figures 2 and 3). An elon- To minimize competition for water Alabama. Arborvitae, Japanese gated, slightly sunken, girdling can- between the tree and surrounding cedar, Lawson cypress, and Sierra ju- ker can usually be seen at the base lawn grasses, use aged pine bark or niper are resistant to Seridium can- of the dead shoot or branch. The pine straw to mulch an area several ker, and an additional 12 evergreens canker surface may be cracked and feet beyond the lowest limbs. (See have partial disease resistance. darker than the surrounding healthy Extension publication ANR-385, bark. Tissues below the canker face “Mulches for the Landscape,” for Botryosphaeria (Bot) turn brown, and this discoloration more information about tree mulch- Canker often extends several inches above es.) Leyland cypress mature into and below the canker margin. Unlike large trees and therefore must be A second dieback and canker Seridium canker, there is little or no spaced accordingly in the landscape. disease, called Botryosphaeria, or resin flow. For screen or hedge use, plant Bot, canker, has recently emerged as Leyland cypress on a minimum of a damaging disease on Leyland cy- Disease Cycle 15- to 20-foot centers in partial to press in landscapes across the Deep Botryosphaeria dothidea survives in full sun. During prolonged periods South. Bot canker may be a more the bark and in other dead tissues on of hot, dry summer weather, thor- common and destructive disease of host shrubs and trees. Typically, the oughly soak the soil around the base Leyland cypress than Seridium can- black pinhead-sized fruiting bodies of the tree every 5 to 7 days. ker is. The causal fungus, of this fungus (pycnidia) are embed- Crop sanitation is quite useful in Botryosphaeria dothidea, is an aggressive pathogen on a number of woody ded in these tissues. Spores of the preventing disease outbreaks in nurs- causal fungus are spread to adjacent eries, on Christmas tree plantations, shrubs and trees, including azalea, rhododendron, and flowering dog- healthy tissues by splashing water. and, to a lesser extent, in landscapes. Free moisture is needed for spores The immediate removal of cankered wood. This disease is particularly damaging to those suffering from to germinate. Colonization of twigs twigs and branches, along with ad- and branches is largely limited to herence to recommended mainte- drought- and heat-related stress. nance practices, may prevent further disease spread. If the main trunk is damaged, the tree should be re- moved. In nurseries and on Christmas tree plantations, cuttings for propagation must not be collect- ed from diseased Leyland cypress. Also, all diseased liners, containers, and field stock should immediately be destroyed. Containers,ARCHIVE pruning tools, and other equipment should be cleaned before each propagation cycle is started. When pruning or taking cuttings, dip the pruning knife or shears in alcohol or germicidal soap. No fungicides are recommend- Figure 2. Discolored bark on limb of Leyland cypress damaged by Bot canker

2 Alabama Cooperative Extension System the foliage. Immediately prune discolored or wilted branches back to the green wood. No fungicides are recommended for the control of Bot canker on Leyland cypress.

Sources Dreistadt, S.H., et al. 1994. Pests Figure 3. Bot canker: limb dieback in of Landscape Trees and Shrubs: An landscape planting of Leyland cypress Integrated Pest Management Guide. UC Publication 3359. trees damaged by extreme heat or Sinclair, W.A., H.H. Lyon, and cold alone or in combination with W.T. Johnson. 1987. Diseases of Trees drought stress. and Shrubs. Cornell University Press, Ithaca and London. Control Stress-related diseases such as Bot canker can be avoided if proper establishment and maintenance practices are followed. To minimize the impact of transplant shock, new plantings of Leyland cypress should be established in the fall. Till an area three to four times the diameter of the original root ball, adjust soil fertility and pH according to the results of a soil fertility test, and amend the soil as needed with well-rotted pine bark or sawdust. Always set Leyland cypress so that the root ball sits at or just above the soil level. On poorly drained soils or sites prone to flood- ing, plant this tree on a raised bed. (See Extension publication ANR- 410, “Establishing Woody Ornamentals,” for more planting tips.) Mulch around Leyland cypress with fresh pine straw, rotted sawdust, or pine bark to hold moisture in the soil. (See Extension publication ANR- 385, “Mulches for the Landscape.”) Avoid mechanical inju- ry to the tree trunk, and keep com- peting lawn grasses away. During prolonged periods of hot, dry weather, water establishedARCHIVE Leyland cypress every 5 to 7 days. Water newly established trees as needed to prevent wilting and discoloration of

Canker and Dieback Diseases of Leyland Cypress 3 ARCHIVE Austin Hagan, Extension Plant Pathologist, Professor, Entomology and Plant Pathology, Auburn University For more information, call your county Extension office. Look in your telephone directory under your county’s name to find the number. Published by the Alabama Cooperative Extension System (Alabama A&M University and Auburn University), an equal opportunity educator and employer.