DUTCH ELM DISEASE ON PRINCE EDWARD ISLAND

“Dutch e1m disease" - for those of

5 who have noted the gradua1 disappearance of the species in eastern Canada, the term invokes visions of stream borders 1ined with dead e1ms, their trunks devoid of bark, b1eached by the e1ements 1ike the bones of a beached wha1e. What is this terrib1e disease, and how has it arrived here?

Dutch e1m disease was first observed in the Netherlands in, 1918 and now occurs throughout the who1e of Western Europe. It was discovered on this continent in Ohio, in 1930, apparent1y having been introduced in a ship- ment of e1m 1095 from Europe. The disease had spread to Canada by 1944, and is now present at epidemic 1eve1s in Manitoba, Ontario, Quebec, New Brunswick and Nova Scotia. The first

infection was found on Prince tdward Is1and in 1979.

The disease is caused by a fungus, Ceratocystis u1mi, the spores of w 1c are transported from diseased to hea1thy trees by the native e1m bark beet1e, Hy1urgopines rufipes. A11 species of e1m may be so infected. The fungus enters the tree's water- conducting vesse1s, as adu1t bett1es feed in the upper

branches of hea1thy trees.

There it produces spores and toxic chemica1 byproducts which are carried in the sap stream to a11 parts of the tree. Eventua11y, vesse1s are b1ocked, and the 1eaves wi1t from 1ack of water.

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Ye11owing and sudden wi1ting of the 1eaves during Ju1y, on one

or more 1imbs in the upper crown, is the first obvious_sympton of Dutch e1m disease. It is .important that surveys be carried

out at this time as natura1 ye11owing, not associated with the disease, common1y begins in ear1y August. Diseased 1eaves turn brown, dry out and fa11, or they may shrive1, become britt1e, and remain attached to the twigs for many weeks.

F011owing deve1opment of the first fo1iar symptoms of Dutch e1m disease, affected branched die quick1y and the condition extends through a11 1arge 1imbs unti1 the tree dies. Depending on the initia1 condition of the tree, and the severity of attack, death may occur in from one to three years.

The first infections on Prince Edward Is1and, 1ocated at Conway and Northam in centra1 Prince County, were confirmed in

August, 1979. At that time, an attempt was made to contain the "hot spots” by removing and destroying a11 infected trees,

as we11 as other e1ms in their immediate vicinity. A11 areas of the Province have been surveyed for the disease in

1980. Though suspects have

once again been identified, a fina1 ana1ysis must await the resu1ts of 1aboratory testing.

Favored for its beauty and vigor, American e1m was p1anted exten- sive1y a1ong streets of new1y- sett1ed towns in the 1ast century. Significant popu1ations of our native e1m occur in centra1 Prince County, a1ong with scattered sma11 groups e1sewhere throughout the Province. Unfor— tunate1y, the future surviva1 of this species is in jeopardy. Un1ess a practica1 means is

found to ha1t its spread, Dutch e1m disease may very we11

resu1t in the eventua1 disappearance of American e1m from the 1andscape of P.E.I.

Jean-Pau1 Arsenau1t Forestry Branch

P.E.I. Dept. of Agricu1ture & Forestry