After trenching the soil may be replaced. Place another trench beyond the second tree in situations where there are multiple elms and the disease in the first tree was not diagnosed early. Unfortunately, obstacles such as sidewalks and fences may interfere with trenching. Root grafts still can occur in these locations, so modifications of trenching method described may be needed. A combination of trenching and fumigation is often required.
Fumigation is practical when sidewalks, utility lines, etc, prohibit trenching.
Pour the fumigant in each hole and tamp it shut. The chemical fumigant is dangerous and should be applied only by trained applicators. The use of insecticides to suppress early beetle populations has diminished in recent years. Sanitation and removal of firewood is more effective in controlling beetle populations. Certain insecticides may be applied to trees in April to prevent feeding by emerging beetles.