Bacterial Leaf Scorch of Landscape Trees

Similar documents
Bacterial Leaf Scorch of Landscape Trees Elizabeth A. Bush, Extension Plant Pathologist, School of Plant and Environmental Sciences, Virginia Tech

Bacterial Leaf Scorch

Bacterial Leaf Scorch of Blueberry

Tree morphology and identification. TreeKeepers March 18, 2017

Bacterial Leaf Scorch of Blueberry

A Planthopper in the Family Fulgoridae

Bacterial Leaf Scorch of Shade Trees

B - Requires a sheltered position. Prefers a moist soil.

Emergent diseases threatening California ecosytems

It is one of the most serious oak diseases in the United States, killing thousands of trees each year.

Certified Arborist. Diagnosis and Plant Disorders. What is a healthy plant?

Unit D: Controlling Pests and Diseases in the Orchard. Lesson 5: Identify and Control Diseases in the Orchard

The New Zealand Institute for Plant & Food Research Limited. Xylella fastidiosa: A pathogen with the X-factor

Leaf and Stem Feeding Aphids

STRATUM Sample Survey of Street Trees. For City of Richmond, Urban Forestry Division

Unit G: Pest Management. Lesson 2: Managing Crop Diseases

CAMBIUM, meristem, heartwood, and lenticel are

Diagnosing Plant Problems. A strategy to get started

Databases of host species to support research on plant pests: the case of Xylella fastidiosa

VILLAGE OF MAMARONECK

Basic Plant Pathology for Franklin County Master Gardener Volunteers. Nancy J. Taylor Plant Pathology Department Ohio State University

WSU and UI Master Gardeners March 1, 2016 Philip Shinn

ABSTRACT. Jordan L. Harris, Master of Science, Dr. Yilmaz Balci, Department of Plant Sciences and Landscape Architecture

Vol.23 No.3 November 2011

Adjacent Sewage Treatment Plant

ARBORICULTURE JOURNAL OF WATER TRANSPORT AT STEM-BRANCH JUNCTURES IN WOODY ANGIOSPERMS. November 1991 Vol. 17, No. 11.

Larval Hosts: plant these -- and feed baby birds! Common name Scientific name Growth form Leaf type Soil type Flower & fruit dates

PLANT TERMS Buds [V. Max Brown]

Village of Cazenovia, NY. Street Tree Inventory Report

To Understand How Trees Decline and Die, We Must: What is Stress? Tree Physiology. Understand stress and how it affects trees. Why Do Trees Die?

To Understand How Trees Decline and Die, We Must: What is Stress? Tree Physiology. Understand stress and how it affects trees. Why Do Trees Die?

Serviceberry Leaf scorch (Abiotic disorder)

Leaf Morphology Tree Biology-2012

The Athens-Clarke County Tree Species List

Dendrology 101 & Tree Identification Techniques

Two primary sources have been used for creating the species characteristic entries:

Florida Friendly Landscapes?

Master Gardener - Plant Pathology

Riparian Plants Along the Three Rivers of Pittsburgh

Possum-haw. Summary. Protection Endangered in New York State, not listed federally.

New Insect Pests of Golf Courses. Wendy Gelernter PTRI

Tree and Shrub Insects

Plant disease. Plant Diseases: Learning objectives: Plant Disease: Any physiological or structural abnormality that is harmful to the plant

Todd A.Steinlage, Alaska Department of Natural Resources, Division of Agriculture, Plant Materials Center

Phytophthora ramorum What Every Georgia Nursery Should Know

Heads Up! We Thank You. The Diagnostic Lab

Boxwood Blight. Enhanced First Detector Training

Chapter 901 APPENDIX A Approved And Prohibited Plant Forms And Tree Species

Cornell University Plant Disease Diagnostic Clinic. Diagnostic Review Report Confidence (to genus) Host. Diagnosis. Not Detected Suspected

Native Adaptive - Sm

Physiology of Pruning Fruit Trees

Biological Invasions: a threat to California Ecosystems

What Do Gardeners Think About Pruning Trees?

Interpreting Modern and Paleo-Environments by Analysis of Water-Stress in Xylem: Examples from Nebraska and Arkansas

Plant Disease Introduction. Larry A. Sagers Utah State University Extension Regional Horticulturist

Welcome to the Iowa Certified Nursery Professional Training program Module 7: Introduction to Plant Diseases and Insects.

Parasitic Diseases. Plants killing plants

What is a plant disease?

Plant Disease Introduction

Tree Identification Summer Phase. Learning to identify trees by looking at their leaves.

North American Bramble Growers Research Foundation 2016 Report. Fire Blight: An Emerging Problem for Blackberry Growers in the Mid-South

Scale Insects. Order: Hemiptera. Families: Diaspididae (armored scales), Coccidae (soft scales), Eriococcidae (Felt scales), others

Why Calcium is So Important

Japanese Beetle. Popillia japonica

Rose Black spot-diplocarpon rosae

Invasive Species Test. 30 Stations 90 seconds each -or- 15 stations (2/seat) 3 minutes each

Table 2-1. Quick reference guide to tree and shrub characteristics

Japanese Beetle. Popillia japonica

2018 Envirothon Wetland Plants Study Materials: diagrams and glossary

Office of the City Manager INFORMATION CALENDAR June 23, 2009

Pages in the Montana Master Gardener Handbook

TREES. Functions, structure, physiology

History INVASIVE INSECTS THREATENING YOUR BACKYARD: BROWN MARMORATED STINK BUG & VIBURNUM LEAF BEETLE. Identification. Common Look-A-Likes 1/12/2015

INVENTORY AVAILABILITY

Identifying Wheat Growth Stages

Basic Tree Biology a quick look

WHY LEAVES CHANGE COLOR. ~ ~- j. " ".., :: J~,

Core Training Manual, Ohio Certified Nursery Technician (OCNT) Chapter 1 - Safety & First Aid

Management Of Insect And Mite Vectors Of Vegetable Diseases

Field Identification Guide

Tree Anatomy. Arlington and Alexandria Tree Stewards Jim McGlone Urban Forest Conservationist Virginia Department of Forestry

ECOLOGICAL OBSERVATIONS ON TWO LEAFHOPPERS THAT TRANSMIT THE PIERCE'S DISEASE BACTERIUM1

Importance of Mycorrhizae for Agricultural Crops 1

Introduction to Taxonomy USU Extension Service Advanced Master Gardeners 2005

Basidiomycetes (the club fungi)

Identification of culturable endophytes isolated from apple tissues with antagonism towards Neonectria ditissima

Master Gardeners. Plant Nomenclature. Developed by Steve Dubik. 1

Module 2. Classification. The Classification of Plants. We will discuss a few ways of classifying plants: Big vs. Small. Grass vs.

Simplistic view of energy flow Linear path Lacks other possible pathways energy can be passed. Food Chain?

Grapevine Nutrition: Results of Tissue and Soil Analyses

Plant Growth and Development Part I. Levels of Organization

MNLA Certification Manual Learning Objectives

Tree Identification Techniques Rex Bastian, Ph.D. ISA Board Certified Master Arborist Il-0121B The Davey Institute Cobden, Illinois

Distance Learning course Plant pathology and entomology Covered topics

Leave That Willow Bee: Pollinators Need Trees and Shrubs too! Debbie Fluegel, Illinois Program Manager

What is a TREE? Woody plant (stems, branches, roots) Long lived (typically 100 s of yrs. sometimes 10

Good Morning! When the bell rings we will be filling out AP Paper work.

Tree Decay Fungi. Chelsi Abbott, MSc The Davey Tree Expert Company

Allelopathy In Trees

USDA FOREST SERVICE RESEARCH NOTE NE-198

Transcription:

Bacterial Leaf Scorch of Landscape Trees Elizabeth A. Bush, Extension Plant Pathologist, Department of Plant Pathology, Physiology and Weed Science, Virginia Tech Bacterial leaf scorch is an important and often lethal disease of many landscape trees, particularly in the southern and eastern U.S. In Virginia landscapes it is most often observed on oak, elm, and sycamore; however, many other landscape tree species are susceptible to this disease. The bacterium that causes bacterial leaf scorch colonizes the tree s water-conducting tissue (xylem) where it disrupts water movement and reduces water availability to the tree. The symptoms of bacterial leaf scorch are very similar to symptoms of other problems that limit water uptake. This is why marginal leaf scorch symptoms caused by other problems, such as drought-stress or root disease, are often mistaken for symptoms of bacterial leaf scorch. Laboratory identification of the causal bacterium (Xylella fastidiosa) from affected petiole and leaf tissue is necessary for positive confirmation of the disease. Symptoms Symptoms of bacterial leaf scorch usually appear in the latter part of summer and progress through the fall. The most characteristic symptom of this disease is marginal leaf scorch. Often a yellow band is evident between brown and green tissue (Figures 1 A and B). Figures 1 A and B. Characteristic marginal scorch symptoms of bacterial leaf scorch with a band of yellow between brown and green tissue on elm (A) and gingko (B) leaves. This yellow band is characteristic of bacterial leaf scorch. In contrast, when marginal leaf scorch is caused by other problems (e.g. drought, root disease, salt injury) no yellow band is typically observed between brown and green tissue. However, this symptom is not 2010 Virginia Polytechnic Institute and State University 3001-1433 Virginia Cooperative Extension programs and employment are open to all, regardless of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. An equal opportunity/affirmative action employer. Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Rick D. Rudd, Interim Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Wondi Mersie, Interim Administrator, 1890 Extension Program, Virginia State, Petersburg.

always present on bacterial leaf scorch-diseased leaves (Figure 2). Figure 3. A cluster of bacterial leaf scorch affected branches are apparent low on this Camperdown elm (Ulmus glabra Camperdownii ) while the rest of the tree appears unaffected by the disease. Figure 2. This oak was confirmed positive for bacterial leaf scorch, yet the leaf symptoms are not very characteristic of the disease. Other symptoms, depending on the host species, include leaf yellowing, browning and premature leaf drop. On many oak species, brown leaves do not drop prematurely; however, on pin oak (Quercus palustris) marginal scorch symptoms may not occur, but leaves may drop prematurely. On trees with an indeterminate growth habit, such as elm and sycamore, symptoms on infected branches begin on older leaves and move to younger leaves; on trees with a determinate habit, such as oak, all leaves on a diseased branch are the same age and show symptoms at the same time. Diseased trees may also leaf out later than normal in the spring and leaves may be stunted. Although this disease is a vascular disease, the vascular tissue does not discolor. The severity of bacterial leaf scorch on an individual tree can vary considerably from year to year and drought can contribute to greater disease severity. Over time, however, trees suffer a gradual decline and loss of vigor as defoliation and dieback continue to occur, and eventually the disease may be lethal. Initial symptoms of bacterial leaf scorch often appear on only one or two branches before gradually spreading to more and more branches in subsequent years (Figure 3). 2

Disease Cycle The pathogen that causes bacterial leaf scorch is spread by insect vectors. The primary vectors are leafhoppers called sharpshooters (Figure 4), but other insects, such as spittlebugs, also vector the bacterium. These insect vectors have piercing and sucking mouthparts that allow them to penetrate the tree s water-conducting tissue (xylem) and extract nutrients. An insect acquires the bacterium by feeding on infected plant tissue; subsequently, the insect may spread the bacterium to non-infected hosts while feeding. Once a plant is infected with the bacterium, the disease becomes systemic, since the bacteria move throughout the tree in the tree s water transport system. Susceptible Tree Species Figure 4. This adult glassy-winged sharpshooter (Homalodisca vitripennis) is a type of leafhopper and a known vector of Xylella fastidiosa. (Image courtesy of Reyes Garcia III, USDA Agricultural Research Service, Bugwood.org.) Many oaks are susceptible to bacterial leaf scorch and oaks in the red oak group are most commonly afflicted with this disease. Elms and sycamore are also relatively common hosts of the disease in Virginia. The disease is also reported on many other tree species, such as maple, hackberry, mulberry, sweet gum, and gingko. (Refer to Table 1 for a list of selected susceptible tree species.) 3

Table 1. Some trees on which bacterial leaf scorch has been reported. (Note: This list is not exhaustive regarding either species or genera and new hosts of bacterial leaf scorch continue to be identified.) Acer species Cornus species* Platanus species Quercus species Ulmus species other species Acer negundo boxelder A. rubrum red maple A. saccharinum silver maple A.saccharum sugar maple Cornus florida flowering dogwood C.kousa Kousa dogwood Platanus occidentalis American sycamore P. x acerifolia London planetree Quercus alba white oak Q. bicolor swamp oak Q. coccinia scarlet oak Q. falcata southern red oak Q. imbricaria shingle oak Q. incana bluejack oak Q. laevis turkey oak Q. laurifolia laurel oak Q. macrocarpa bur oak Q. nigra water oak Q. palustris pin oak Q. phellos willow oak Q. prinus chestnut oak Q. rubra northern red oak Q. shumardii shumard oak Q. stellata post oak Q. velutina black oak Q. virginiana live oak Ulmus americana American elm U. glabra wych elm U. pumila Siberian elm U. x hollandica Dutch elm Celtis occidentalis hackberry Gingko biloba gingko Liquidambar styraciflua sweetgum Morus rubra red mulberry * To date, Cornus species have not been diagnosed with bacterial leaf scorch in the Virginia Tech Plant Disease Clinic (http://www.ppws.vt.edu/~clinic). 4

Some other woody plants that are reported hosts of X. fastidiosa include oleander (Nerium oleander), peppervine (Ampelopsis arborea), beauty berry (Callicarpa americana, Virginia creeper (Parthenocissus quinquefolia), American elder (Sambucus canadensis), southern highbush blueberry (interspecific Vaccinium corymbosum hybrids), and grape (Vitis species). X. fastidiosa is also an economically significant pathogen of several important fruit and nut trees (e.g. almond, citrus, plum, peach, pecan) and many weeds and grasses are hosts to X. fastidiosa. Many plant species have also been identified as asymptomatic hosts of X. fastidiosa. The host list of this pathogen continues to grow. Diagnosis Late summer or early fall are the best times to test for bacterial scorch, since this is when X. fastidiosa is most active and bacterial populations in the tree s water conducting tissue are highest. Testing too early in the growing season has sometimes been demonstrated to result in a false negative result. Samples consisting of a dozen symptomatic leaves with the petioles still attached are sufficient for testing for this disease. In the Virginia Tech Plant Disease Clinic (http://www.ppws.vt.edu/~clinic/) an extremely sensitive assay, real-time polymerase chain reaction, is used to test for X. fastidiosa. Plant samples for diagnosis may be submitted through your local Virginia Cooperative Extension office (http://www.ext.vt.edu/offices/index.html). Control There are currently no curative controls for bacterial leaf scorch. Injection of antibiotics into diseased trees has been shown to slow the spread of the disease, but will not cure the tree. Antibiotic injection is an expensive option and trees must be treated on an ongoing basis. Injection holes are also prone to colonization by wood decay fungi that can negatively impact the health of the tree. Control of leafhoppers and other vectors of X. fastidiosa is not effective in preventing spread of bacterial leaf scorch to non-infected trees. Avoiding stress to trees and maintaining them in optimal health can help trees better withstand the effects of bacterial leaf scorch, resulting in a longer period of time in which they are aesthetically acceptable and survive. Since bacterial leaf scorch progresses gradually over a period of years, this is a reasonable approach to controlling the disease. Providing water to trees during hot, dry periods of the summer and during drought are the most critical tactics to help trees avoid stress. This is particularly important if a tree has been already been diagnosed with bacterial leaf scorch. Mulching trees can also help avoid water stress. Ensuring adequate nutrient uptake by having soil tested by the Virginia Tech Soil Testing Lab (http://www.soiltest.vt.edu/) is also recommended. Soil samples should be submitted through your local Virginia Cooperative Extension office (http://www.ext.vt.edu/offices/index.html). Soil test results will give details on correcting the soil ph if ph is found to be a problem. Inspecting diseased trees on an annual basis to determine the extent of dieback is also recommended, so that pruning and/or removal options may be considered. Pruning out dead wood is recommended: remove branches back to healthy tissue (white or cream-colored in cross-section). Replacing diseased trees is another option for homeowners and urban landscapers. Trees with extensive dieback are best removed. Choose replacement trees that are not reported hosts of bacterial leaf scorch or other major pests and 5

that are well-adapted to the location. (New hosts of bacterial leaf scorch continue to be identified, so it is prudent to avoid all species of tree genera on which the disease has been reported.) Some trees to consider as replacements include: European black alder (Alnus glutinosa), European beech (Fagus sylvatica), black gum (Nyssa sylvatica), yellow buckeye (Aesculus flava), northern catalpa (Catalpa speciosa), katsuratree (Cercidophyllum japonicum), Kentucky coffeetree (Gymnocladus dioicus)**, American linden (Tilia americana), littleleaf linden (T. cordata), silver linden (T. tomentosa), cucumbertree (Magnolia acuminata), Osage orange (Maclura pomifera)**, tulip poplar (Liriodendron tulipifera), and Japanese zelkova (Zelkova serrata). Refer to the Virginia Cooperative Extension fact sheet: Problem-free Trees for Virginia Landscapes (publication #450-237) [http://www.pubs.ext.vt.edu/450/450-237/450-237.html] for recommendations on relatively trouble-free trees for Virginia landscapes. **Purchasing fruitless male cultivars of these species may be desirable, since the fruits may be a nuisance. References Gould, A. B. and J. H. Lashomb. 2005. APS Feature Story: Bacterial Leaf Scorch of Shade Trees. Online: http://www.apsnet.org/online/feature/bls/ Hopkins, D. L. 1989. Xylella fastidiosa: Xylemlimited bacterial pathogen of plants. Annual Review of Phytopathology 27:271-290. Schaad, N. W., D. Opgenorth, and P. Gaush. 2002. Real-time polymerase chain reaction for one-hour on-site diagnosis of Pierce s disease of grape in early season asymptomatic vines. Phytopathology 92:721-728. Schaad N. W., J. B. Jones, W. Chun. 2001. Laboratory guide for Identification of Plant Pathogenic Bacteria. 3 rd ed. The American Phytopathological Society, St. Paul, MN. Sherald, J. L. 2007. Bacterial leaf scorch of landscape trees: what we know and what we do not know. Arboriculture and Urban Forestry 33(6): 376-385. Sinclair, W.A., and H.H. Lyon. 2005. Diseases of Trees and Shrubs, 2nd ed. Ithaca, N.Y.: Cornell University Press. Acknowledgements This publication benefited from the advice of Dr. Alex Niemiera, Horticulture Department, Virginia Tech and Mary Ann Hansen, Plant Pathology, Physiology and Weed Science Department, Virginia Tech. 6