In previous issues of Nature Notes appeared a series of articles dealing with the efforts toward control and eradication of the Mountain Pine Beetle (Dendroctonus monticolae, Hopk.) which had attacked and threatened to destroy the pine forests of Crater Lake National Park and the surrounding areas.

As mentioned in those articles, the beetle is destructive, due to the fact that the larvae feed upon the cambium or living layer of the tree, horizontally from chambers in which the eggs are laid by the adult.

The solar method of control consists of felling the infested trees, exposing them to the sun. A sun temperature of 85 degrees for a period of one hour serves to destroy the eggs, larvae, pupae and immature beetles in the tree. The trees are subsequently rolled half over, thus exposing all surfaces.

Control work for a season must be completed or terminated by July 1 since by that time adult beetles emerge from the trees and subsequent work would be useless. The work for this season covered the period from April 30 to June 30. Due to a mild winter and early spring, and with experience gained in previous years the work was more rapidly advanced.

The number of trees treated this year totaled 14,747 over an area of 16,500 acres. This gives an average of .893 trees per acre. In 1930 the average was 2.2 and in 1929 it was 4.4 trees per acre.

When figures, covering the work of the past three seasons, are studied, they prove enlightening.

In areas completely treated in 1929, the average decrease of infestation in 1930 was 74 percent. The average decrease in 1931, over 86.1 percent.

In units incompletely treated the infestation showed an increase, in one instance, of 59.5 percent in one year and in another instance 82.8 percent in one year.

Observations in areas not treated indicate that the increase may run from 50 to 200 percent.

It may be concluded from the complete figures on file that partial or incomplete treatment is useless and that treating in areas subject to reinfestation is also unsatisfactory. Only complete treatment of all affected areas in one season will produce the desired results.

It may also be concluded that although the work has not been a complete success, yet, had nothing been done, the pine forests of the southern part of the park would present the same appearance of a "ghost forest" as is found upon 33,000 acres in the northern portion.

It is also obvious that the present incomplete treating will eventually eliminate all pine stands by cutting.

In conclusion it may be mentioned that the solar method of control was developed in Crater Lake National Park and that progress and results indicate that the method is successful, provided the treatment of all infested areas is thorough and complete.