Pathologists advocate 3-point program to control dreaded Dutch elm disease
By PAULA MYERS
Varying opinions concerning the most effective means of control for the Dutch elm disease has caused much controversy in afflicted towns and states.
Some pathologists have developed an effective three-point control program for Dutch elm disease which includes sanitation, root-graft and chemical protection.
THE THREE-POINT program, according to Harold S. McNabb Jr., professor of forest pathology at Iowa State University and member of the Dutch Elm Disease Control Advisory Committee, does control Dutch elm disease. Communities which have tried to foli-
Last of a series
low this program have experienced an annual elm loss of only one per cent or less.
If no control is practiced, communities in the Midwest can expect to lose 99 per cent of their elms in 10 years, says McNabb. Failure to control Dutch elm disease can always be traced to a lack of a complete control program.
The KU trees are constantly being pruned and checked, according to Harold Blitch, grounds supervisor. Sanitation has been the only control method KU has used for the last four years.
ACCORDING to R. W. Lichtwardt, professor of botany, and Raymond Hall, curator of the Natural History Museum and noted zoologist, the most important control measure is to promote identification of diseased trees and their removal.
Sanitation is the removal and destruction of all dead and dying elm wood with bark. This material, whether it be a dying or dead standing tree, in wood piles, or in broken branches of otherwise healthy trees, contains both disease fungus and bark beetles.
Most of the Jayhawk Boulevard elms were group-planned some 40 years ago. Since the elms have been planted so close together is it probably that roots of adjacent elm trees have formed natural connections through which the deadly fungus passes.
ROOT-GRAFT treatment would create a life-saving barrier between trees by cutting out connecting roots. This is done by digging a 30-inch-deep trench or by injecting chemicals into the soil.
KU sprayed the campus elms until 1963, but has stopped because of an administrative policy.
Chemical protection is aimed at the prevention of beetles feeding in the twigs of healthy elms. This prevents infection of the trees by the disease fungus carried on the beetles.
A CHEMICAL INSECTICIDE is applied either as a spray to the outside of the bark, or as a systemic chemical through the sap stream of the tree. This facet of the control protects only healthy trees. It is not a cure for diseased trees.
"Unless spraying is done on a large scale basis, I don't believe there is any great advantage in the spraying control program," Blitch said. "The spray reduces the beetle population, not the fungus."
Another approach to the Dutch
elm disease problem is to develop species or strains of elms that are resistant to the disease. Investigators working on the Dutch elm disease problem in the Netherlands have found several elms with a high degree of disease resistance among the commonly susceptible European elm species. The best are the Christian Buisman and Bea Schwartz elms.
SOME ELMS have natural resistance. In plant pathology, according to Lichtwardt, resistance is not like immunity, but the plant is able to get slight effects and yet not be particularly harmed. It is not an all or nothing idea, but more of a degree situation.
KU has lost 72 elms out of 1,800 in six years by Dutch elm disease alone. By a 1960 census, the Lawrence area had some 18,000 elms. Only 13,500 now exist on public and private property.
"Most of KU's afflicted elms are cut down in June and July. It is at this time that the symptoms are most prevalent," Blitch said.
Write books
Contributor to two books soon to be issued is John R. Willingham, associate professor and director of the freshman-sophomore English program. He has aided with the writing of "Dictionary of American Regional English" and "Mid-Century Authors."
"KU'S COST of removal and planting only entails that of labor, not the equipment cost. The average cost to remove a 24-inch diameter elm, if there aren't too many obstructions, is $50," he said.
Miss Beverly Boyd, associate professor of English, is the author of the newly issued "Chaucer and Liturgy."
A large elm is replaced by a sapling three inches in diameter and 15 to 18 feet tall. This replacement costs $20 to $25 depending on the size and type of tree.
The elm is known as a shade tree—it grows up, then arches out. It is relatively a fast growing tree.
KU replaces the removed diseased elms by a variety of trees. There must be a variety because if the streets were completely replanted with sycamores, oaks or maples, then there is a possibility that someday an epidemic will
begin to gnaw at them. The long process would all begin again.
LICHTWARDT and Hall recommend hard maples, oaks and sycamores.
Hard maples, oaks and sycamores have several good characteristics. Sycamores are higharching, but the shade is less dense. The maples and oaks are long-living with a dense shade, but do not get as tall or arch as widely as the elm.
Elms are slowly and steadily disappearing from the KU campus while the debate continues on what is the most effective control method or methods.
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