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Dutch Elm Disease -- Real Killer

Hampton Union

Thursday, August 2, 1956

Dutch Elm disease -- the inexorable killer of elm trees -- is on the increase in New Hampshire and spreading rapidly in the seacoast area, it was learned by the Union yesterday in an interview with Dr. James G. Conklin, state entomologist of the N. H. Dept. of Agriculture, at Durham.

Known to have first been sighted in the Granite State in 1949, the elm tree killer -- for which there is no known way to halt the disease, once a tree is infected -- has spread rapidly throughout the southeastern part of the state with Nashua, Salem, and Exeter being hardest hit, and is now on the increase in Hampton.

Dr. Conklin told the Union that various methods of "chemo-therapy" -- the injection of chemicals into an elm tree to stop further progress of the disease -- have been tried with little success -- and that there is actually no known way to halt the disease once a tree is infected.

The only way to stop the spreading of Dutch Elm disease, according to the state entomologist, is to cut down the infected tree and burn it.

A spraying program utilizing a dormant spray, twice the usual strength of DDT, must be applied before the foliage comes out in the spring. According to the state expert, it is possible to get good protection for the elms through proper spraying.

New England elms have two enemies -- the leaf beetle and the bark beetle. It is the bark beetle which causes the greatest damage, according to Dr. Conklin, who told the Union that contrary to most popular beliefs, the leaf beetle does not spread the Dutch Elm disease.

The leaf beetle is responsible for the early browned leaves on the elm which can be seen on nearly every highway at this time of the year, but this is not the Dutch Elm disease. The effect of the leaf beetle's damage to the foliage, however, weakens the elm tree and makes it more susceptible to the Dutch Elm disease.

Dr. Conklin also pointed out that the hurricanes of the past two summers, severely damaged the tops of many tall elms, which also had a weakening effect upon the trees making them easy prey to the bark beetle.

According to state entomologists, the bark beetle lives and breeds in dead elms or in fallen branches, but just before depositing its larvae, the bark beetle must feed on a live tree. The beetle flies to a healthy tree and bites into the bark, thereby transmitting the fungus of the Dutch Elm disease into a live elm.

A real healthy elm can withstand many attacks, according to tree experts, but once weakened through defoliation by the leaf beetle or hurricane damage, it becomes easy prey to the Dutch Elm disease, which means sure death to the tree, sometimes within a matter of hours, depending on the condition of the tree.

The only alternative then, is to cut down the diseased tree and burn it.

Dr. Conklin pointed out that persons desiring to replace the elms, should plant the "Christine Buisman" elm, which is the only species known to be resistant to the Dutch Elm disease. Contrary to public opinion, he stated, the Chinese elm is not disease resistant.

Presence of the Dutch Elm disease in a tree is first spotted by scouting crews through a yellowing of the foliage, a failure of the tree to leave out, or a single branch not bearing foliage.