loss was 13 percent in pole-size trees (5 to 8.9 inches d.b.h.), 40 percent in the sawlog portion (board-foot volume) of sawtimber trees (9 inches d.b.h. and over) and 70 percent in the portion above sawlog limits of merchantability (cubic volume).
White pine is not the only tree species attacked. Norway spruce plantations have been severely attacked by the weevil in the East, and jack pine plantations in the Lake States are also vulnerable. The weevil attacks all conifer trees except balsam fir and hemlock.
THE OBJECTIVE of our research program is to develop efficient methods of reducing losses of white pine due to the weevil. Although a great deal of valuable research has been done, many questions remain unanswered.
U.S. Forest Service research on the white-pine weevil has taken several courses. We are seeking more information about the insect itself. We are seeking more effective methods of control by spraying. We are also studying the tree species itself in its relationship to the insect.
The time in the spring when weevils emerge is an important factor in control. Godwin and Bean (3) have shown that there is a close correlation between emergence and average and maximum daily temperatures, and that weevil emergence can be predicted by using cumulative degree-hours above 40° F. A reasonably accurate estimate can be made of the degree and rate of weevil emergence in the spring. With this information, better spray treatments can be devised. This timing of spray applications is particularly important
