THE YARD ELMS

The tragedy of the Yard elms is too well known to most of us, but our attention is again called to the trees by a defence of the care taken to preserve them printed in another column. The trees have been sprayed with arsenate of lead for several seasons to protect them from the ravages of the brown-tail and gypsy moths and from the elm beetle, but the presence of the leopard moth was not discovered until last summer. A firm of practical foresters, the head of the Boston park department, and several eminent entomologists were immediately consulted.

The leopard moth is a comparatively new insect in this locality but its habits are well understood. As soon as it hatches the worm makes its way into the twigs, where it feeds and grows as it burrows into the larger limbs. These worms vary in size from three-eighths of an inch to over three inches in length, when they are the most destructive. They then bore across and completely girdle large limbs, and frequently even girdle the trunk, finally cutting a cell close to the bark and there turning into pupas. When these develop they push out through the bark and become moths, which in turn lay their eggs in the bark of the twigs. The elm beetle works in a similar manner, through it does not cut across the wood, but burrows mostly in the inner bark of the tree, so that the outer bark may become completely detached from the trunk. It will thus be seen that the borers are at no time exposed to the spraying, and so must be destroyed in some other way.

The experts consulted in regard to the Yard elms recommended that they be extensively pollarded, and that wherever the holes of the borers could be found they be filled with carbon bisulphide and sealed. This latter process was put into practice immediately, but only the dead or badly bored limbs were cut off. As the small limbs can not be reached it is impossible to exterminate the worms in them.

Under such conditions the elms are doomed within five years, but it is possible that they may be saved by an extreme pollarding. This, of course, would forever destroy the grace and beauty of the trees, and the question is whether to let them die in their present condition or to attempt to preserve them at the expense of what beauty they still retain.