At last, a vac­cine to kill Dutch elm dis­ease

Winnipeg Free Press - Section G - - HOMES - MIKE ALLEN

DUTCH elm dis­ease started to kill Amer­i­can elms in Win­nipeg in the mid-1970s. Many thou­sands have suc­cumbed to the dis­ease, which reap­pears ev­ery year on at least 1,000 to 2,000 elms.

Last Novem­ber, the fed­eral Pest Man­age­ment Re­view Agency ap­proved a vac­cine that has proved to be 99-per-cent ef­fec­tive against Dutch elm dis­ease (DED) in Canada.

The vac­cine is called Dutch Trig. It works in prin­ci­ple sim­i­lar to the way flu vaccines work in the hu­man body. Dutch Trig elic­its or trig­gers a re­sponse that causes a de­fence re­ac­tion in the con­duct­ing cells of elms lo­cated just be­low the bark.

If the tree de­tects the pres­ence of DED, it will quickly con­tain the dis­ease and stop it from spread­ing dur­ing the year of in­jec­tion. Like flu vaccines, the in­oc­u­la­tion is good for only one year. The vac­cine has been work­ing in Hol­land since 1992, and in sev­eral ar­eas in the United States since the late 1990s.

Dutch Trig is a liq­uid emul­sion of about one mil­lion mi­cro­scopic Ver­ti­cil­lium fun­gal spores that will not do any dam­age to elm trees. Us­ing a spe­cial tree in­jec­tor, one 0.15 ml (0.005 ounce) droplet of Dutch Trig is placed un­der the bark. In­jec­tions are spaced about 10 cm (4 inches) from each other, com­pletely around the cir­cum­fer­ence of the tree at about 1.4 m (4.5 feet) above the ground.

Tim­ing of the in­jec­tion/in­oc­u­la­tion is crit­i­cal. There is about a six-week win­dow in early to mid-spring when the in­jec­tion will be ef­fec­tive. In­jec­tions made later into the sum­mer have been shown through re­search to be in­ef­fec­tive. The best time to in­ject is when the elm leaves are just open­ing up from their win­ter buds. This nor­mally oc­curs in May, but this year’s early spring will force the leaves out ear­lier. It’s very im­por­tant to sched­ule clients who want their elms in­oc­u­lated as soon as pos­si­ble.

The in­jec­tion/in­oc­u­la­tion work is a joint ven­ture of Vibur­num Tree Ex­perts (204-831-6503) and Peren­nial Trees Inc. (204-896-0404). It takes some time to sched­ule prop­er­ties re­quir­ing this ser­vice as elm trees must be as­sessed, mea­sured and price quoted in ad­vance of the in­jec­tions. Please call one of the above num­bers for fur­ther in­for­ma­tion.

Re­mem­ber, to pre­vent your elm from get­ting Dutch elm dis­ease, there is only a six-week pe­riod that the work can be car­ried out.

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