EPLP-038 02/18

Diseases of Italian Cypress and Related Species in Texas

Sheila McBride, Extension Program Specialist Kevin Ong, Associate Professor and Extension Pathologist David Appel, Professor, Plant Pathology and Microbiology*

Many distinctive trees in the family Cupres- the inner bark of trees, saceae are popular choices for Texas landscapes: bald causing dead lesions cypress (Taxodium spp.), (Juniperus spp.), (cankers) on branches arborvitae (Thuja spp.), and cypress ( spp.). and trunks. The patho- Most popular among the cypresses are Italian gen enters a tree via cypress (C. sempervirens), Arizona cypress (C. arizon- a wound through the ica), and Leyland cypress (x Cupressocyparis leylandii). bark. Freeze damage, Their unique pyramid and column-like shapes make hail, insect feeding, them attractive for hedges and windbreaks or as indi- mower damage, prun- vidual, well-placed landscape specimens. With fertile, ing cuts, weed-eater moist, but well-drained soils and full sunlight, these damage, wind damage, drought-hardy trees will provide beauty and contrast to and other sources of the landscape for decades. However, with their increas- wounds all help to ing use in recent years, several diseases have emerged increase the likelihood that limit their lifespan in Texas landscapes. of infection. Fig. 2. Dead and necrotic Symptoms Diseases branches on Italian cypress. The first symp- Source: Sheila McBride Cankers toms are isolated, dead Seiridium canker branches (Fig. 2). As Cause the disease progresses, Seiridium canker is more of these “flags” one of the most com- occur throughout the mon cankers in Texas, tree because of usually on the increas- spores dispersed during ingly popular Italian wet, rainy, and windy cypress, but also on conditions. Distinct, and arborvitae. sunken, necrotic (dead) The pathogen is a fun- lesions can occur along with the dead gus—either Seiridium Fig. 1. Microscopic view of branches, sometimes unicorne or S. cardinal Seiridium sp. spores/conidia. (Fig. 1)—that infects Source: Sheila McBride with gummy, resinous Fig. 3. Italian cypress trunk exudates leaking out of with resinous exudate. *All of the Texas A&M University System the surface (Fig. 3). As Source: Sheila McBride

1 the cankered areas continue to spread from a branch Microscopic examination of diseased tissues to identify into the trunk, they may eventually girdle and kill the typical fungal fruiting bodies and spores may be entire portions of the upper crown. If conditions are necessary to distinguish the two different pathogens. conducive to disease development, the entire tree can Management die over 3 to 5 years. There are no chemical controls for bot canker; prun- Management ing and sanitation are the only measures available for Cypresses are drought-tolerant and grow best on minimizing disease progress. well-drained soils. Clayey, poorly drained soils are par- ticularly damaging to them and will predispose them to Foliar problems infection. But, any environmental conditions that stress Cercospora blight the tree can make it unable to resist infection. Choose Cause other trees to plant on sites unsuitable for growing Cercospora needle blight, caused by the fungus cypresses. Passalora sequoia (formerly Cercospora sequoia) is a Prevent infections by planting trees on proper soil problem on Arizona cypress, arborvitae, and other types, watering judiciously during periods of drought, cypresses. Eastern redcedar (J. virginiana) is resistant to and avoiding wounds. Use remedial pruning on dying Cercospora blight. and dead branches to delay disease progress and destroy or discard all pruned materials. Between prun- Symptoms ing different trees or making cuts within diseased trees, The symptoms clean the pruning tools with a solution of 10 percent begin in mid-to-late household bleach. There are no direct chemical controls summer in the older for seiridium canker. scale needles located on the branches closest to Botryosphaeria canker (Bot canker) the main trunk. These Cause leaves turn dull green The fungus Botryosphaeria stevensii causes botryos- and brown and fall off phaeria canker. In addition to Italian cypress, it occurs during the following on eastern redcedar and other junipers. In many months. Defoliation respects, bot canker is similar to seiridium canker. proceeds for a few years Wounds in trees increase the incidence and severity of from the inner part of Fig. 5. Cercospora needle bot canker, and, unlike seiridium canker, bot canker the branches to the tip blight, Passalora sequoia on disease may occur on vigorously growing trees. until the branch dies. oriental arborvitae. Infected trees develop Source: Florida Division of Plant Symptoms Industry, Florida Department of thin, spindly canopies, The flattened Agriculture and Consumer Services, with symptoms often Bugwood.org. cankers are sometimes starting in the lower difficult to see. Expose crown and moving upward toward the tree top (Fig. 5). them by scraping the Wet, rainy weather that splashes the spores throughout bark from the surface the canopy encourages infections and can eventually to reveal the dead, kill the tree. The pathogen spreads more quickly and brown tissue in the is more severe when trees are planted in tight groups. infected lesion; healthy These conditions impede air circulation that helps to tissue will be white dry foliage. under the bark sur- rounding the canker Management margins. Patterns of Treat Cercospora blight with copper-based fungi- branch and trunk die- cides and other types of commercially available fungi- Fig. 4. Botryosphaeria canker back are the same for cides. Valuable plantings may warrant the use of chem- on Juniperus deppeana. both bot and seiridium Source: John Ruter, University of ical controls, applied promptly upon proper diagnosis canker diseases (Fig. 4). Georgia, Bugwood.org. of the disease. Multiple applications may be necessary

2 during the summer, particularly during rainy periods. irrigation. In landscape specimens, remedial pruning In Texas, begin applications in May and continue them of diseased tips and branches during dry weather might every 2 to 3 weeks as long as conditions are conducive sufficiently manage the disease. Fungicides control the to disease development. disease in highly valuable landscape specimens.

Phomopsis blight Other tip blights Cause Cause The fungusPhomopsis juniperovora causes pho- Several fungal pathogens cause progressive dieback mopsis blight. It is more common on eastern redcedar, of the outer twigs and branches, mostly on junipers, although some true cedars (Cedrus spp.) and arborvitae including Kabatinia juniper, Sclerophoma pythiophila, (Thuja spp.) are also predisposed. and Seimatisporium berckmanssii (Berckmann’s blight). Although they rarely damage mature trees, they can be Symptoms serious on young trees and nursery . Unlike Cercospora blight, new, young nee- Symptoms dles on the ends of the As with many of the foliar diseases, symptoms nor- branch are more sus- mally appear first on the lower portions of the canopy ceptible (Fig. 6), caus- because the fungi that cause them produce spores on ing branches on trees the dead twigs lying on the ground beneath the tree. with phomopsis blight Over time, infections work up through the tree, causing to die from the tip to progressive branch dieback, and potentially killing the the base. Needles turn tree. light green, followed Management by red-brown, dead Regularly rake and destroy or discard all dead shoots that finally turn needles (leaves), twigs, and branches. Prune the same ash gray. Under a hand Fig. 6. Phomopsis blight on eastern redcedar. types of materials from the tree as well. When moving lens, the typical black Source: Robert L. Anderson, USDA between trees, clean the pruning tools with a 10 percent fruiting bodies of the Forest Service, Bugwood.org. solution of household bleach. Unlike phomopsis blight, fungus look like small, there are no chemical products available for treating black pimples embed- these other tip blights. ded in the dead tissues (Fig. 7). The pathogen Root diseases grows through the infected needles on the Phytophthora root rot – Phytophthora young shoots and even- cinnamomi tually advances to the Cause main stem where major A soil-inhabiting, fungal-like organism (an oomy- portions of the canopy cete), Phytophthora cinnamomi, causes phytophthora may be girdled and root rot. This pathogen increases in soils that retain die. These symptoms, high soil moisture levels for days because of overwater- Fig. 7. Close-up view of sometimes described as ing, poor drainage, or both. Phomopsis juniperivora tip blight, may begin in fruiting bodies on redcedar. Symptoms the spring and progress Source: Robert L. Anderson, USDA Phytophthora rots small feeder roots so the tree all summer. Forest Service Bugwood.org. cannot supply the canopy with the necessary water Management and nutrients it needs to grow and survive. As a result, Because phomopsis blight can be particularly portions of the crown turn a pale green or yellow that damaging in commercial nurseries, there are import- eventually progresses to brown over a few weeks (Fig. ant management protocols based on regular use of 8). The branches and leaves eventually become dry fungicides, removal of diseased plants, and judicious and brittle. Removing the bark at the base (crown) of watering to avoid wet, humid conditions and overhead the lower portion of the trunk reveals a distinct line

3 of necrotic (brown), dead tissue. This necrosis (death) occurs when infection kills the feeder roots and the pathogen grows up through the larger roots, eventually reaching the base of the tree. The roots will be brown and rotted. Spatially, in the landscape, the mortality appears to spread from one plant to adjacent ones, forming clusters of diseased trees (Fig. 8). Management Cultural practices such as supplying proper drain- age and reducing irrigation reduces soil moisture and environments conducive for the growth of the patho- gen. Commercially available fungicides labelled for use on phytophthora in the landscape also control root rot Fig. 8. Phytophthora root rot on leland cypress. on Italian cypress. Source: John Ruter, University of Georgia, Bugwood.org.

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