HD9 - The Effect of Anthracnose on the American Flowering Dogwood

  • Published: 1992
  • Author: Department of Forestry and Department of Agriculture and Consumer Services and Virginia Cooperative Extension Service
  • Enabling Authority: House Joint Resolution 324 (Regular Session, 1991)

Executive Summary:
The 1991 Virginia General Assembly passed House Joint Resolution Number 324 to direct the Virginia Department of Forestry (DOF), Virginia Department of Agriculture and Consumer Services (VDACS), and Virginia Polytechnic Institute and State University (VPI & SU) to jointly study effects of dogwood anthracnose (DA) on dogwoods of the Commonwealth.

Within the forest, the disease has been identified from all Virginia mountain counties. Disease occurrence and mortality of dogwoods are greatest at high elevation where conditions conducive to fungal success are generally present. With several notable exceptions, the disease is not currently severe in Piedmont and Coastal Plain forests. Semi-permanent survey and impact plots have been established by the DOF in cooperation with a southwide effort to learn more about this disease complex.

The nursery situation within the Commonwealth involves media-generated concern more than infected nursery stock. Media attention has caused tremendous citizen apprehension resulting in reduced sales. With some exceptions, the VDACS believes the current inspection program is adequate to address nursery concerns.

Currently, there is probably the greatest opportunity for control strategies within the shade and ornamental dogwood area. For Virginia, such research would be centered at VPI & SU. Current funding and staffing problems have not permitted the resource allocation necessary to address questions involving fungal biology, environmental conditions conducive to disease success and control strategies.

WOODS

Finding #1:

The fungus-caused disease, DA, is well established in Virginia and probably was active before the initial find in 1988.

Recommendation: The DOF should continue to look for the disease in areas where it has not been located. Geographical/area limits on the fungus may assist in development of control techniques should some limit(s) be manageable.

Finding #2: Even with extensive media coverage and attempts to keep DOF personnel up-to-date, there remains considerable confusion regarding disease identification.

Recommendation: Increase the training available to DOF personnel pertaining to disease identification. This should be of major assistance in, not only better enabling personnel to answer questions from the public, but also support efforts directed toward the preceding recommendation.

Finding #3: There remain far more questions than answers regarding 1) disease origin, 2) disease variability, and 3) control strategies.

Recommendation: Answers, when available, will come from concerted survey efforts covering wide geographical areas. The DOF should continue cooperation with the southwide survey plot program. If funds become available, the number of Virginia plots should be increased to include many of the new counties where infection has been found since the effort began.

Finding #4: Present control tactics being considered for nursery and ornamental tree application have little applicability to forest-grown dogwood. There is simply no way that mulching, fertilization, pruning, fungicide application and the like will ever be feasible in the forest. It would seem the only hopes for forest-based control strategies rest with genetic resistance or manipulation of a natural control agent.

Recommendation: DOF personnel should look for healthy dogwoods in areas where the disease has caused serious mortality. Such trees may possess genetic resistance that could be used in a breeding program. Similarly, DOF personnel should look for areas where the disease would be expected to be severe, but is not. Biological control agents may be present in such areas that could reduce virulence of the DA organism. If such an agent could be manipulated, dogwoods in other areas may benefit.

Finding #5: Numerous agencies, both state and federal, as well as several universities are involved with survey and research statewide. It is difficult to stay current regarding the various efforts underway. Within the South, a DA working group has been formed. Participation in these meetings remains the best way of keeping abreast of current efforts so as to better inform other investigators.

Recommendation: Currently, DOF is represented on the working group and, if funding is available, attendance at the meetings, held once or twice yearly, should continue.

Finding #6: The disease has been present in the Northeast longer than the South. At a recent meeting, an investigator from New York indicated the disease seems to have stabilized in his area. Certainly, there are areas in the Northeast where the dogwood has been eradicated, but where dogwoods remain, they seem to be holding their own.

Recommendation: Support work in the Northeast aimed at defining how and why stabilization occurred. The reason may help determine what might be expected regarding Virginia's dogwoods.

NURSERY

Finding #1: The flowering dogwood, Virginia's state tree and flower, is susceptible to a fungus disease that is threatening its survival. This ominous scenario translates into consumer fears; homeowners, nurserymen, and nursery dealers are avoiding this valued and valuable species.

Recommendation: Consumers need to be informed and reassured that growing dogwoods in the landscape is not a futile effort. VDACS should continue to work cooperatively with nurserymen and nursery dealers to insure that flowering dogwoods in the channels of commerce are at a very low risk of being infected. Also, current information and technology on disease management should be funnelled through VDACS to the nursery industry so that homeowners can properly care for and maintain healthy dogwoods.

Finding #2: VDACS Agricultural Inspectors are knowledgeable front-line troops in the battle to detect and prevent this disease.

Recommendation: VDACS needs additional support for laboratory services to diagnose accurately this and other devastating diseases of flowering dogwoods. Because of unfilled vacancies due to budget reductions within VDACS, the State Plant Pathologist now is assigned to duties unrelated to plant pathology. Therefore, he is unable to adequately address the dogwood anthracnose epidemic for the nursery industry. Adequate staffing and monies are necessary to administer this objective.

Finding #3: No one organization or institution has a monopoly on the latest technology and information regarding dogwood anthracnose.

Recommendation: All interested parties must interact cohesively on state, regional and national levels so that current information on regulation, policy, and the biology of dogwood anthracnose is available to appropriate individuals. If adequate funding is available, VDACS personnel should be encouraged and allowed to attend state, regional, and national meetings were DA is discussed.

SHADE AND ORNAMENTAL

Finding #1: Dogwood anthracnose has been abundantly and positively identified in the home/city/highway/cemetery/historic shrine/gardens/parks situation in the Commonwealth. It has been identified for the first time on many of these sites, and the numbers of cases are rising greatly.

Recommendation: The Department of Plant Pathology, Physiology and Weed Science at VPI & SU has and will continue to monitor disease incidence, via the Plant Disease Clinic primarily. Additional funding is crucially needed to expand surveys.

Finding #2: Many facets of the biology of the disease are unknown at this time. A partial listing of fungicides is available for recommendation, but these compounds are in urgent need of testing at several sites.

Recommendation: Studies are needed to evaluate environmental conditions conducive to disease development under various Virginia conditions. There needs to be a search for strains that are adaptable in the warmer areas. Fungicidal options need to be tested in Virginia.

Finding #3: Specialists and related workers need to meet, exchange information, become informed, and develop teams to attack this problem.

Recommendation: Support is required to sponsor such meetings. A forthcoming regional workshop, chaired by R. J. Stipes, will be held at Pipestem, WV in April, 1992.

Finding #4: Publicity and public education on the identification, incidence and severity of the disease is lacking.

Recommendation: Support needs to be increased to provide information on this problem. This can be accomplished by public lectures/programs, purchase and distribution of literature (already printed), and additional TV/radio coverage.

Finding #5: Because of the dearth and decline of overall support at the university level for research and study of this and other plant diseases, more than ever before, help is needed in developing student research projects, in obtaining technical support and related assistance to attack this problem.

Recommendation: The Department of Plant Pathology, etc., could use graduate research assistantships, even partial ones, to underwrite student research projects. It is well known that graduate students provide more and better research data, since they are working on graduate degrees. A budget line item specifically for DA would ensure that this research area is addressed.