Question
If your tree has been diagnosed with Dutch Elm Disease and the city has notified you to cut it down, do you have to remove the stump as well to keep the disease from spreading?

Answer
Dutch elm disease can spread through root grafts-it depends on if the dying tree was cut as soon as the disease was detected or did the trre die first before it was cut. If the later then the disease can be spread through the roots to a nearby healthy tree.

Root Graft Transmission

Spread through natural root grafts has accounted for a majority of new cases of Dutch elm disease each year in some Midwestern cities.

Elm trees which are growing close together (within 50 feet) over a period of years form root grafts. If one of the trees becomes diseased, the DED fungus will be transmitted along an entire street by moving directly through the root system into adjoining healthy trees. In other words, disease in just one tree in the row could cause infection and death of the remaining trees. Immediate removal of infected trees (see sanitation) reduces the chance of root graft spread by getting rid of the infected tree before the Dutch elm disease fungus reaches the roots.

The only way to prevent transmission through the roots is to create a barrier between diseased and healthy trees by severing or killing those roots between the trees. This can be done without harm to the healthy trees either by mechanical trenching or through the use of chemical barriers, which have been found to be quite effective in some situations.

Mechanical trenching for disruption of root grafts has the advantage of being quick and effective if the machinery is available and no pipes, underground cables or pavements are encountered. Two types of equipment are commonly used for me chanical root disruption ?ditch diggers or trenchers and the vibrating plow. The trench should be as narrow as practical and can be refilled immediately. Many cities and towns own or have access to small self-powered trenchers (such as "Ditch Witch") which will cut a trench 24-30 inches deep. Homeowners using such equipment (often from rental stores) should exercise EXTREME CARE not to contact buried power cables or gas lines. Severe injury or death could result

To be entirely certain of disruption, a trench depth of 48 inches is needed, but most roots are much nearer the soil surface and trenching to a depth of 24-30 inches is often adequate. The deeper trenching may require specialized equipment. A 30-inch trench cut immediately is probably better than a 48-inch trench delayed for days or weeks while waiting for the special machine.

A fumigant, sodium N-methydithiocarbamate (SMDC) sold under the trade names of Vapam and VPM, has been found effective as a chemical barrier. The chemical fumigant is dangerous and should be applied only by trained applicators. Homeowners should consult their city forester or a reputable, trained arborist.