Plant Pathology: Bacterial Leaf Scorch

Problem:

Bacterial leaf scorch disrupts the xylem/phloem column in trees causing starvation in the farthest extremities of leaves. It is characterized by a red and yellow pattern on leaf edges that is similar to a flame.

In spring, the leaves of trees affected by bacterial leaf scorch tend to show leaves a week later than those not affected.

Spring Leaves:

The tree in the foreground has bacterial leaf scorch. Compare it to the full canopies of the trees in the background.

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The susceptibility of trees is sporadic. In a row of trees, only the middle-most one is affected; The others are normal.

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The left side of this tree is normal, showing leaves; the right side appears to still be in the budding stage of growth.

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Summer Leaves:

These pictures were taken in August though the reddish foliage appears typical of trees during autumn.

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Experiments:

In order to determine which insect is the vector for bacterial leaf scorch, fogging is used to gather the insects on a tree without damage to the insects' fragile bodies.

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PLANT HEALTH: MANAGING INSECT PESTS AND DISEASES OF LANDSCAPE PLANTS
Project Number 08601 Starting 10/01/2001 Ending 09/30/2006

OBJECTIVES: Encourage pathologists and entomologists to interact and develop multi-disciplinary management tactics for pest control. Foster development of sound IPM methods including cultural, biological, and selective chemical approaches for protecting nursery stock and landscape plants from damage by insects and diseases. Coordinate and promote new and ongoing research and technology transfer projects dealing with insects and diseases affecting landscape plants of regional interest. Develop multi-state IPM programs to help individual states deal with diseases and insect pests on the tremendous range of plant species and cultivars available.

APPROACH: The investigators have developed research projects that address issues of importance to ornamental clientele in New Jersey as well as in the Northeastern/Mid-Atlantic United States. In accordance with the Regional Project goals, primary objectives in each study include the development of management options for insects and diseases of high priority (for use in IPM and standard management programs), as well as the study of factors that affect plant and pest/disease relationships. Of primary interest is Bacterial leaf scorch of shade trees, a disease that has reached epidemic proportions in parts of the northeast, Mid-Atlantic States, and the mid-west. In this multi-disciplinary project, the epidemiology, vector relationships, host range, management, and economic impact of this disease are investigated. Other projects include the study of factors in recycled irrigation water in nurseries that affect disease development and plant nutrition; use of insect predators to manage hemlock wooly adelgid and fiorinia scale; and control of oriental beetle in nursery crops and Christmas trees. Technology transfer to appropriate audiences is of high importance in all projects. This includes development of Web sites and video, Extension bulletins, and journal articles as appropriate. Multidisciplinary cooperation is necessary to achieve the objectives for most studies as well as cooperation with the United States Forest Service on the Bacterial leaf scorch and hemlock wooly adelgid projects. In addition, multi-state (or regional) cooperation is needed to address some of the larger issues associated with Bacterial leaf scorch.

Impact Statement:
As more pesticides become restricted for use, there will be a growing need for new pest management tools for the economically important ornamental plants. Research from this study will provide information on which tools are most effective in managing plant diseases and pests.

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EPIDEMIOLOGY, VECTOR ECOLOGY AND ECONOMIC IMPACT OF BACTERIAL LEAF SCORCH IN NEW JERSEY
Project Number 12312 Starting 01/18/2002 Ending 01/18/2005

OBJECTIVES:

1. Develop sampling techniques for vectors of bacterial leaf scorch of oak.
2. Establish relationships between Xylella & potential insect vectors.
3. 3. Assess the impact of alternative hosts on disease development.
4. 4. Determine within- and between-tree movement of the pathogen and vectors.
5. 5. Assess potential economic impact of Bacterial Leaf Scorch to New Jersey urban forest.
6. 6. Technology transfer to community foresters and shade tree commissions.

APPROACH: Collect and identify potential insect vectors of Xylella fastidiosa; do transmission studies to verify that recovered insects are vectors of the disease; identify alternative hosts of the pathogen and insect vectors; assess the economic impact of the disease by estimating tree value in communities around the state; present research results in the form of presentations and written material to community foresters, arborists, and the general public.

Impact Statement:
2002/01 TO 2002/12 In spite of the widespread distribution of BLS in New Jersey, very little is known of the biology of the disease, its progression, and effective management. Methods for monitoring potential insect vectors in the canopy are primitive, and little is known regarding the transmission rate and spread of this disease both within and between trees. More information regarding the pattern of new infections, the seasonal cycles of insect vectors, and the role of alternative, "potential-reservoir" hosts on disease development is needed before effective management strategies can be devised. If uninvestigated and untreated, BLS will continue to debilitate municipalities where widespread overplanting of red and pin oaks has occurred.