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How to Identify and Manage Dutch Elm Disease Page 9 of 16 ',;; "jh Figure 6. Where elms are closely spaced, the Dulch elm disease ftmgus may move down a row of trees through grafted roots. Removing trees without breaking root grafts may not keep the ftmgus from moving into adjacent trees. (photo courtesy of Dr. Joseph O'Brien. USDA Forest Service, St. Paul, UN) Managing Dutch Elm Disease OED is managed by interrupting the disease cycle. The most effective means of breaking the cycle is early and thorough sanitation to limit the population of the insects that transmit the fungus from tree to tree. Other useful means of affecting the disease cycle include using insecticides to kill the insect vector, breaking root grafts between trees, injecting individual trees with fungicides to prevent or halt the fungus, pruning out early infections, and planting OED tolerant or resistant elm cultivars or other tree species. Sanitation to reduce insect vectors. Many communities have been able to maintain a healthy population of mature elms through a vigilant program of identification and removal of diseased elms and systematic pruning of weakened, dying or dead branches. Sanitation by prompt removal of diseased trees or branches reduces breeding sites for elm bark beetles and eliminates the source of the OED fungus. To be completely effective in interrupting the spread of the disease by elm bark beetles, stems and branches of OED infected trees must be de-barked, destroyed, or utilized before the bark beetles emerge. During the growing season, removal should be completed within 2 to 3 weeks of detection. During the dormant season, removal should be completed before April, when overwintering beetles may begin to emerge. Wood from infected trees can be destroyed by chipping, burning or burying. Wood may be http://www.na.fs.fed.uslspfo/pubs/howtos/ht_ded!hCded.htm 8/25/2004 I