194 The Elm and its Insect Enemies. 



if the roots are aided by new soil and suitable nourishment, no 

 doubt the trees are benefited, and by the same processes every 

 good gardener would follow to reinvigorate old orchard trees 

 covered with rugged bark. 



But for this to be necessary, presupposes a state of disease 

 or debility in the trees operated on. This cannot be caused by 

 Scolytus, which, as we have shown, not only does not, but 

 cannot, attack a tree in full health and vigour. The tree firsfe 

 exhausts the soil in which it is growing, or some circumstance 

 renders that soil no longer suitable for it. It begins to languish; 

 the beetle then discovers that it is a suitable prey, and plays 

 the part of scavenger, which is its proper office in the scheme 

 of nature. To Scolytus has been assigned the task of eating 

 up dying elm-trees ; it never attacks a dead tree, never attacks 

 a healthy tree, but riots in the elm when its reparative powers 

 have already received a shock, and it is passing from life to 

 death by atrophy. The appearance of Scolytus is a sign only 

 that the tree has passed its heyday, then it may be possible to 

 recover it by judicious treatment of the roots, and the removal 

 of the epiphlseum, or corky layer ; but to leave the roots alone 

 and strip it to the cambium, will be but to hasten the process 

 which has begun already, and with which Scolytus has had 

 nothing at all to do. In a grove of elms, one here and there 

 will be found infested with Scolytus, but the rest are untouched. 

 Did Scolytus originate the diseased condition, all would be 

 attacked alike, but it selects those that are in such a languid 

 state, that when pierced for the deposition of eggs, they are 

 unable to close up the small wound and entomb the larva in a 

 mass of vegetable cells. There is one more proof for those 

 who will observe for themselves, and draw conclusions from 

 facts only. Whenever elm-trees seem to be decaying, it will be 

 found that there is a pavement, or a hard pathway, or a drain, or 

 something else over or near their roots, which prevents those 

 roots exercising their nutritive functions in a normal manner. 

 The elm roots near the surface ; it likes a strong loam and plenty 

 of moisture, and free access of air to its root fibres. When 

 these conditions do not exist, or where, having existed, some 

 change of circumstances has taken place, the trees will sooner 

 or later decline in health, and when the process of internal 

 decay has commenced, the insects peculiar to the elm take 

 possession, and make a speedy finish of their work. The 

 prudent forester will lay the axe at the root of an elm the 

 moment he finds Scolytus in it, and take warning from the fact 

 that the conditions of the soil are such that other elms must 

 follow, unless, as M. Robert remarks, some attention be paid to 

 the roots as the source of nourishment to the tree. 



