By Donella Meadows
–August 10, 1989–
Skeletons of elm trees still stand in the valley where I live. They have succumbed to Dutch elm disease so recently that they haven’t yet been cut down. The dead branches hold their curving V shapes, like huge elegant vases, reminders of a beauty that is now only a memory.
Only a memory, except on the Dartmouth College campus, where 150 American elms are still alive, graceful, and green, casting welcome summer shade on the lawns. About half of them are mature trees, their branches arching out 50 to 80 feet overhead. The other half are youngsters. Bob Thebodo is actually optimistic enough to plant new elms.
Thebodo is in charge of Dartmouth’s 1200 campus trees. He has every one of them mapped, has a computer printout with each tree’s vital statistics, knows each personally. “That big elm back of Baker Library, that’s my favorite. Hasn’t given me a bit of trouble.”
Though he likes all trees, Thebodo has a special respect for elms. They’re tough, he says, a good urban tree, tolerant of salt, pavement, and pollution. They’re only bothered by Dutch elm disease and construction. Every time Dartmouth digs up a phone line, a sewer line, or a steam pipe, the roots of an elm tree are likely to get cut. The weakened tree attracts the elm bark beetle, the carrier of the fungus that causes Dutch elm disease.
Elms may be tough, but Thebodo has to give them a lot of help these days. Sanitation is the first line of defense; Thebodo cuts back immediately any limb that shows a sign of infection. The second defense is fertilization, keeping the trees healthy enough to resist disease.
The third line of defense is chemotherapy — injecting into the vascular system of each tree a fungicide called Arbotect. The earth is carefully dug away to expose the root flare several feet down. Holes drilled into the roots are attached to tubes through which flows dilute Arbotect (“$215 a gallon — liquid gold”). One treatment is good for three years; one-third of the trees must be done each year.
The fungicide and the drilling do some damage to the tree’s tissues. Thebodo doesn’t know how long this treatment can be continued before it does more harm than good. He hopes he can keep it up indefinitely, because the chemical directly attacks the fungus, nothing and no one else — which cannot be said for the fourth and most controversial line of defense.
Every spring Thebodo sprays the insecticide Dursban to knock back the population of elm bark beetle. It isn’t easy to spray a full-size elm tree. You have to suit up in a rubber outfit, gloves, and a respirator, and either shoot down from a cherry-picker or up with a high-powered sprayer. Spraying can be done only on rainless, windless nights when the temperature is above 40 degrees. Back when he sprayed more trees more often, Thebodo had to wait many nights for the right weather, then work all night to get the job done.
Before Thebodo’s time the insecticide of choice was DDT and the spraying was frequent. Then DDT was banned and Dartmouth turned to methoxychlor, twice a year on all elms. Now Thebodo prefers Dursban, one of the most commonly used horticultural chemicals in America.
The active ingredient in Dursban is chorpyrifos, an organophosphate. It affects the membranes of nerve cells, disrupting the pattern of nerve firing. Therefore it deranges virtually every body function, not only in insects, but in any creature that has nerves.
Dursban is very toxic to birds, fish, crustaceans, and bees. In human beings it causes headache, confusion, convulsion, blurred vision, vomiting, fatigue, and tremor. Dursban has not been tested for its tendency to cause cancer. In fact it may not have been properly tested for anything, since its federal approval was based on data provided by Industrial Bio Test Labs, whose executives have been sent to jail for faking test results.
Every time Bob Thebodo sprays Dursban, he gets angry phone calls from a few people in the community. Thebodo sympathizes with them, but he says he has done everything he can think of to reduce his use of pesticides — everything except give up the battle against Dutch elm disease.
He has tried pheromones, hormones that attract insects into traps. He found they were only effective against European bark beetle; the beetle infesting the campus is a native one. He tried girdling a few trap trees, unwanted young elms, weakening them to attract beetles, so he could selectively spray only those trees. That didn’t slow down the disease. He planted “disease resistant” varieties and they promptly contracted the disease.
Until he thinks of something else to try, Thebodo has reduced the Dursban spraying to only the biggest, most scenic, most stressed trees around the central Dartmouth green, and he just endures the hostile phone calls.
“I try to be in the middle, not spraying every bug, but not avoiding all spray either. These people are yelling at me about something I don’t even like to do.”
With all his precautions, Thebodo loses five or so elm trees a year. He mourns every one that comes down, and so do I. I drive past the elm skeletons along the roadsides and then come to Dartmouth’s living trees and rejoice. That’s difficult to admit, because I also happen to be a pesticide hater. I know well and thoroughly distrust the federal pesticide regulatory system. I agonize when poisons are sprayed where people, bees, songbirds, and earthworms have to live. I refuse to use sprays on my farm, and I’ve lost every elm tree.
So here I am, a bundle of contradictions, hoping Bob Thebodo can keep those magnificent trees alive long enough and experiment persistently enough to find a way of protecting them without having to drench the land with poison. And next week I will write, also with sympathy and hope, the story of one of those people on the telephone trying to get him to stop spraying.
Copyright Sustainability Institute 1989