Mr. Koch and Mr. Mitchell* have very ably considered the cost and necessity of slash disposal from a fire-protection standpoint. That the protection of our forests from insects is probably of as great importance is beginning to be recognized by foresters in the United States and Canada. I will cite one instance of damage from insects, resulting from unavoidable slash, as an illustration of the importance of this phase of the question in America.
During the winter of 1912-1913, the southern part of the Sierra Nevada mountains, extending from the Merced river on the north to Kings river on the south, was visited by a storm which caused a large amount of snowbreak, especially in the pole and sapling stands. This slash bred a bark borer (Ips cola f uses), which is very destructive to young growth of western yellow pine and the tops of mature trees of the same species. The bettles increased in this slash to such an extent that, in the spring and summer of 1914, groups of 75 and 100 dying trees were not uncommon. Strenuous efforts have been made to check this epidemic in some of the more important commercial stands, at a cost of approximately $5,000. What the ultimate cost will be it is impossible to estimate at the present writing. This was a natural cause, and only serves to illustrate the immense damage resulting from fresh material which is not promptly burned, or at least before the broods escape to near-by standing timber.
Settlers and commercial activities in our wooded areas, especially in the western United States, have added another cause for epidemics of insects in our forests. Visitors and residents in these sections are continually reporting the increase of dying timber due to this cause. Prof. E. P. Stebbing,f a well-known English forester, says:
"Experience has shown that in countries where very large tracts are covered with a single species of conifer, such, e.g., as is the case in America and to a lesser extent perhaps in India, uncontrolled fellings have resulted in the most disastrous infestations of bark-boring beetle pests."
Unburned slash constitutes " uncontrolled fellings." I do not mean to state, nor does Professor Stebbing, that all uncontrolled fellings start epidemics, but that many of them do, and that the damage and consequent loss is so large that it will greatly exceed any expenditures for slash disposal. Certain investigations in California have proved that the annual loss of timber from the depredations of forest insects has increased from year to year. If only natural causes, such as snow-break, windbreak, and climatic conditions, were responsible, the loss
*Proceedings of the Society of American Foresters, Vol. VIII, No. 3, 1913. flndian Forest Memoirs, by E. P. Stebbing, Vol. III, Pt. 1, page 1, 1911.