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EDMUND B. ROGERS, Superintendent DORR G. YEAGER, Editor
Volume V JUNE 1932 Number VI

The Black Hills Beetle

It appears that our unwelcome acquaintance of 1927 and 1928, the Black Hills Beetle, is again becoming active and, indeed, manifests signs of becoming epidemic. Reports have been coming to the park office of valuable Ponderosa pines dying, and then the reporter asks what can be done about it. Since this beetle, it seems, is to plague us locally for some time to come, every resident of this community should know something of its habits.

Rangers have been keeping an eye on the beetle ever since the big outbreak of 1927 and '28, when well over a thousand pine trees were killed in a summer. Our bark beetle belongs to the genus Dendroctonus and is one of the 24 species in the genus. The word Dendroctonus means "killer of trees" and this name surely is well applied to a genus of beetles which Mr. A. D. Hopkins of the Bureau of Entomology estimates has killed over $1,000,000,000 worth of standing timber in the last fifty years.

The Black Hills Beetle (Dendroctonus ponderosae) was first noted in the Black Hills, and it is now doing damage in the Black Hills region, Wyoming, Colorado, New Mexico, and Arizona. In the adult stage, the beetle is a very dark brown or black, and is approximately one-quarter of an inch in length. It attacks the Ponderosa and Limber pines and has been noted a few times in Lodgepole pine. Its life cycle is interesting. It spends practically all of its life, with the exception of a few hours in flight after it emerges from one tree and enters another, in two trees and at times, one tree. A mature beetle will enter a tree during June or early July: it bores galleries in the living part of the tree and deposits eggs in these galleries. These eggs usually hatch into larvae in August and the larvae continue active until the beginning of hibernation in the fall. During the next spring, these larvae extend the galleries and are transformed into pupae, and then to adults, and the process repeats itself. It is the galleries the beetle bores in the cambium layer that kills the tree, for the extension of these galleries has the same effect as girdling the tree. Wherever the beetle enters a healthy tree, a small spot of pitch appears; and if the beetles become too numerous, the tree's needles become red and it is dead by the following spring.

About the only practical method of combating this beetle on a large scale is to cut the infested tree and peel the bark in the infected area, which is usually confined to the lower trunks. Several years ago a citizen of Estes Park, Mr. Edward J. Walsh, developed a method of fighting this beetle in his ornamental and shade trees, and it appeared to have been in some instances at least, a successful check. It is a comparatively expensive process, but oftentimes a valuable tree near a summer home is more than worth the time and expense. Mr. Walsh cleaned the pitch from the holes where the beetle entered the tree, and then injected carbon bi-sulphide into the galleries. When the gallery was full of the liquid, he sealed the hole with putty. Some authorities regard this method of treatment as useless, but it seems to have produced the results, in some instances, and is at least worth a try.

(courtesy Nature Magazine)

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