Word: elm
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Those who are familiar with the Yard--as all of the students and alumni are--know that it can be divided into two parts, an east and west part, the dividing line being Thayer, University and Weld Halls. The magnificent old elms stand on the west section, while the eastern part, being newer, has a greater variety of trees, namely: elm, ash, maple and oak, which are younger and in much better condition, than the former ones...
...trees of the Yard have been practically free from insect pests in past years and it is only during the last few years that there has been any trouble at all. The first troublesome insect was the elm-leaf beetle. It is a small beetle which feeds on the leaves of the elms, in its larval stage, appearing in such numbers as to strip the trees entirely of their foliage, thereby killing them. The trees in the west part of the Yard were attacked by this pest and considerable damage was done before they were overcome...
...These elm-leaf beetles undoubtedly weakened the elms to a very great extent and it may be that this paved the way for other destructive insects which have followed...
While cutting the leopard moth larvae from the limbs of the elms last fall, a small beetle was found, which has since been identified as the European elm bark-borer--scolytus multistriatus-marsh. In Germany it is known as the "splint kafer" and it is one of their most injurious pests. It enters the bark and the newly hatched larvae work in the splint of the live wood causing the bark to loosen and eventually fall off. Scores of trees in the Yard and about Cambridge have been examined and without exception all of them are infected...
Insecticides fail to reach either the leopard moth or bark-borer. And such a spraying as the trees got when attacked by the elm-leaf beetle may have something to do with the apparent absence of insect enemies of the two above-named species. For the spraying of the trees could have easily killed their parasites, which might have been lurking about on the trees at the time the spray- ing was done. And one thing that favors this theory is,--the leopard moth is worst in that part of the Yard which was the most carefully sprayed...