White Pine Weevil Response to Oak Overstory Girdling—Results from a 16-Year-Old Study

Abstract A white pine release study initiated in 1973 on the Black River State Forest in central Wisconsin was evaluated in 1990. The study compared growth response and number and frequency of white pine weevil attacks of understory white pine under different canopy removal treatments. In addition, annual measurements of leader diameter and length growth for each treatment are reported for the period 1974-1979. The treatments were girdling of overstory hardwoods, predominantly oak, to produce 0, 30, 50, and 70 ft² of basal area/ac (BA) overstory and an ungirdled control of approximately 100-120 ft² BA. In 1990, white pine in the 0 and 30 ft² BA treatment blocks were taller and were larger in dbh than the other treatments. However, there were significantly more trees attacked by white pine weevils in the 0 and 30 ft² BA treatments (P = 0.05). In both treatments, within 4 years of over-story removal or partial removal, mean leader diameter was sufficiently large to support weevil larvae. The 50 ft² BA treatment was intermediate in growth and number of trees attacked by weevils. In 1990, the 50 ft² BA treatment had the greatest number of unattacked dominant, codominant, and intermediate white pine per acre. Maintaining 30-50 ft² BA appeared to be an appropriate compromise between increased growth while mitigating weevil damage. North. J. Appl. For. 9(2):51-54.