After another season of debate about how best to protect the elms, this summer’s results are in.
Approximately 500 Evanston elms were infected with Dutch Elm disease this summer, about 400 fewer than during the same period in 2004, according to the Evanston Department of Parks/Forestry and Recreation.
“It’s really something,” said Paul D’Agostino, superintendent of the parks department. This year the department used fungicide injections in about 1,800 trees, a little more than half the city’s elm population, he said.
In May Evanston City Council voted to inoculate 3,400 of Evanston’s elms, paying for half of the measure by adding a $24.33-charge to city water bills over three years. But the aldermen reversed the payment plan in June and decided only to inject trees with a diameter of 30 inches or more and those deemed “significant” based on their qualitative value – about 1,150 trees.
About 3.7 percent of Evanston’s elms died each year between 1995 and 2003. In 2004 that number jumped to 6.3 percent, according to city documents. Injections helped reduce the number of tree deaths this year, but it will take years to determine the full results of the procedure, D’Agostino said.
“The drought is probably going to take effect,” D’Agostino said. “And we’ll see the end result over the next year or two as we finish the three-year injection cycle.”
The parks department continued sanitation efforts in addition to inoculations, D’Agostino said. Sanitation saves trees 96 percent of the time. Inoculation has a 98 percent success rate.
Despite the improvement, Mimi Peterson and Virginia Mann, who co-founded To Rescue Evanston Elms in 2002, said the council should not have reduced the number of elms injected.
“No member of TREE is pleased by this,” Peterson said. “The decision was a very poor one.”
Trees catch Dutch Elm disease when beetles eat their bark and leave behind a fungus that blocks trees’ ability to pipe water through themselves. But the fungus also can travel through root grafts – the roots of trees near each other fusing together over time, according to a 1999 article in Plant Diagnosticians Quarterly. Injection does not prevent trees from catching the disease this way, Mann said. So trees not inoculated can continue to spread the fungus within a grove.
The two women also questioned the fiscal result from scaling back the number of trees inoculated.
“No matter how you look at it, if you cut down fewer trees it costs less,” Mann said. “My degree is in economics. Let’s not pretend it’s saving money.”
But Ald. Elizabeth Tisdahl (7th) said the city negotiated with Arbor Green to receive the same rate per tree for the inoculations as for the previous plan and spending money on inoculating smaller trees could actually result in more tree death. Smaller trees are less likely to recover from the hole drilled into them for the inoculation process. Six of the 317 inoculated trees with diameters of less than 30 inches had died as of June 25, Tisdahl said.
“The old council wanted to inoculate every elm tree above 10 inches,” she said. “The forestry department advised against it and trees died. Since we changed the plan, I haven’t heard of trees dying of the inoculation.”
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