Dutch Elm Disease Eradication by Pruning

Abstract

A pruning study was conducted in an Illinois city having a comprehensive sanitation and spraying program to control Dutch elm disease. When pruning was restricted to trees having 5 percent or less of the crown showing wilt symtpoms, about two of three naturally infected elms were saved by prompt removal of infected branches. When pruning was delayed 1 to 4 weeks after wilt symptom detection, only one of three trees was saved. Pruning success was attributed to early detection of infected trees. Pruning American elm trees to remove the Dutch elm disease fungus, Ceratocystis ulmi, has been attempted for the past 40 years by various research agencies. Pruning studies based on the use of small elm trees 10 to 20 feet tall gave results that did not encourage further research on this method of control. Few researchers have published studies that would refute or support the practice of pruning large diseased elms.