NZ could lead way in saving elm trees

New Zealand may become the first nation to eradicate the fungal disease that has killed most of the Dutch elm trees in the United States and Europe, say forestry officials.

"Dutch elm disease is being controlled in New Zealand, and a successful conclusion to the 10-year response programme is now a distinct possibility," said the biosecurity director of the Ministry of Agriculture and Forestry, Dr Ruth Frampton.

The disease reached the United States in the 1930s and spread rapidly in the 1950s and 1960s, after apparently originating in Romania.

Dutch elm disease is thought to have wiped out between a third and a half of all the six species of elms common to the United States, and has killed many varieties common to Europe. An estimated 50 million trees have died in the United States and 14 million in Britain.

The disease is caused by fungi called ophiostoma novo-ulmi and ophiostoma ulmi, which cause trees to wilt and die as water-conducting tissues in branches and trunks become clogged.

In New Zealand the beetle carrier of the fungi, Scolytus multistriatus, was discovered in Auckland in 1989 and quickly spread south.

The ministry responded by restricting movement of elms and stopped the sale or planting of the trees in Auckland City, the North Shore, Waitakere, Manukau and part of Papakura District.

A pheromone trapping programme in 1990-91, luring the beetles with sex scents, helped to check their spread into the Waikato.

In the summer of 1993, the disease was also found in the Sturms Gully Reserve area on Bluff Hill in Napier, where it had been spreading through contact between the tree roots.

About 200 trees were removed and destroyed.

The control methods have been effective, with no new infections detected in Auckland for three years.

Over the next five years, all elms in Auckland will be tested for asymptomatic infection, hidden in the inner growth rings, and infected trees will be destroyed.

- NZPA