. Field testing of Bacillus thuringiensis for control of western hemlock looper. Hemlock looper Control; Bacillus thuringiensis. Tree Damage Examination of plot trees in fall of 1963 showed that 5 of the 60 trees had suffered serious damage, with 90 percent or more of their foliage removed. One of these trees died in fall of 1963; three other trees had extensive top damage. In June 1964, foliage remaining on heavily defoliated trees was almost entirely 1963 needle growth. These trees showed progressive refoliation and no further mortality occurred. Two of three trees showing serious top damage
. Field testing of Bacillus thuringiensis for control of western hemlock looper. Hemlock looper Control; Bacillus thuringiensis. Tree Damage Examination of plot trees in fall of 1963 showed that 5 of the 60 trees had suffered serious damage, with 90 percent or more of their foliage removed. One of these trees died in fall of 1963; three other trees had extensive top damage. In June 1964, foliage remaining on heavily defoliated trees was almost entirely 1963 needle growth. These trees showed progressive refoliation and no further mortality occurred. Two of three trees showing serious top damage recovered in 2 years; the other survived even though the top was killed. One of the plot trees showing light defoliation succumbed to bear damage in spring of 1964. Tree recovery was abetted by the reduced looper population level in 1964; feeding was scarcely visible. For all practical purposes, no additional damage occurred in 1964 or 1965. Tree damage was correlated with number of larvae surviving the Thuri- cide application. The best relationship was obtained when damage was expressed by an average of percent defoliations recorded for low and middle thirds of the crown. A probit transfer (probit = 0. 44 + 2. 5 log N) produced the curve shown in figure 1 20. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carolin, V. M. (Valentine M. ), 1918-; Thompson, Clarence Garrison, 1918-; Pacific Northwest Forest and Range Experiment Station (Portland, Or. ). [Portland, Or. ] : Pacific Northwest Forest and Range Experiment Station, Forest Service, U. S. Dept. of Agriculture
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