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<br />How to Identify and Manage Dutch Elm Disease <br /> <br /> <br />Figure 7. Macroinjection of fungicide into the root flare of an <br />elm tree. <br />(photo courtesy of Mark Ste""es, certified arbolist, & Paul, <br />MN) <br /> <br />Page 11 of 16 <br /> <br />thorough distribution of chemical in <br />the crown (figure 7). Microinjection <br />(injection of small volumes of <br />concentrated chemical) is also an <br />option, although it's efficacy <br />compared to macroinjection has not <br />been thoroughly researched. <br />Preferably, injections should be done <br />soon after the earliest leaves have <br />fully expanded, but may be done <br />from then to the end of the growing <br />season. Label rates of concentration <br />for chemical application are updated <br />to reflect the most recent findings on <br />effectiveness; always follow the <br />current labeL <br /> <br />Harmful effects of fungicide injection have sometimes been reported and include occasional <br />leaf "scorching" or loss. Elms generally recover from this damage. Also, drilling injection <br />holes results in wounding which, if repeated annually, may eventually result in significant <br />discoloration and decay. Following fungicide injection with a flush of clean water can <br />reduce damage to the cambium. Some chemicals are able to protect trees for up to three <br />seasons, thus minimizing the frequency of treatments. <br /> <br />Several fungicides are registered for injection to prevent DED infection. These chemicals <br />vary in duration of protective effects, means of application, risk of damage to the tree, <br />documentation of effectiveness, and cost. Certified arborists or Cooperative Extension <br />Services at land grant colleges are able to provide current recommendations on product <br />availability and effectiveness. <br /> <br />Eradicating Dutch elm disease <br />from newly infected trees. If a <br />new crown infection ofDED is <br />detected early enough, there is <br />opportunity to save a tree through <br />pruning, fungicide injection, or <br />both. Eradicative treatment is not <br />possible on trees that have become <br />infected via root graft transmission. <br />Pruning, which can literally <br />eradicate the fungus from the tree <br />by removing it, has a high <br />probability of "saving" a newly <br />infected tree that has less than 5% <br />of its crown affected. To be a <br />candidate for eradicative pruning, <br />the infection must be a new <br />infection (not a residual infection <br />from the previous season) and be <br />present only in the upper crown <br />(not yet present in the main stem). <br /> <br />http://www.na.fs.fed.uslspfolpubslhowtoslht_ded/hcded.htm <br /> <br />L_ <br /> <br /> <br />Figure 8. Eradicative pruning of branches infected with DED <br />may be effective if there is adequate length (5 to JO feet) of <br />clearwood between the infected tissue and the remainder of the <br />crown, or if the tree has been properly treated with fungicide. <br />(Artwork courtesy of Jim Lockyer, USDA Forest Service, <br />Radnor, PA) <br /> <br />8/25/2004 <br />