Common Name

Dutch Elm Disease

Habitat

Temperate zone

Physical Description

First occured in Britain in 7000BC, reoccured in 1960s due to violent strain, brought in from Canada, killed millions of Elms.

Life Cycle

Spreads to healthy plants by Elm bark beetles Scolytus scolytus and Scolytus multistriatus. The fungus produces yeast like cells which are transported in the water conducting tissues. These are blocked and prdoce wilt. Toxins are produced which are carried to the leaves. As the bark is weathered, the bettle is able to tunnel and lay eggs in fan shaped galleries. Spore forming bodies of the fungus are also formed here. The main types are small conidia bearing structures and tiny black flask shaped perithricia, which produce aecospores. In warm weather in the summer, mature bettles emerge bearing fungal spores which have been collected. These fly to healthy trees and feed on branches, the spores are introduced again. The dead tree remains a reservoir for 2 years for other beetles. The fungus will also spread by wind and root system.

Method Of Attack

Sap absorption

Damage Caused

Plants discolour, yellow, distort and debilitate plant into decline and death. Serious in warm, dry conditions.

Control Methods

Treatment is not practical. In areas where the disease is not established, fell all infected trees and burn them. If neccasary dig pits between infected trees. Protection has been observed by injection of systemic fungicides into trees, Benomyl. Do not plant above species, find resistant varieties.

Stage Vulnerable

At first signs of disease