LI E> RARY 
 
 OF THE 
 
 UNIVERSITY 
 OF ILLINOIS 
 
 no 
 
 AGRICULTURE 
 
CIRCULATING 
 
 CHECK FOR UNBOUND 
 CIRCULATING COPY 
 
3M 3-58 64998 
 
/^V^ I 
 
 BARKING - 
 
 BLACK OAK AND JACK PINE 
 
 FENCE POSTS 
 
 with Sodium Arsenite 
 
 By K. R. Peterson 
 C. S. Walters 
 W. L. Meek 
 
 BULLETIN 626 
 
 UNIVERSITY OF ILLINOIS 
 AGRICULTURAL EXPERIMENT STATION 
 
CONTENTS 
 
 PAGE 
 DEVELOPMENT AND EARLY STATUS OF CHEMICAL BARKING 3 
 
 CHEMICAL BARKING TESTS MADE IN ILLINOIS 4 
 
 MATERIALS AND METHODS 5 
 
 RESULTS 11 
 
 Part I: Effect of Season on Peeling Time 11 
 
 Part II: Effect of Length of Exposure to Poison on Peeling Time. . . .17 
 
 DISCUSSION OF RESULTS 23 
 
 Effect of Chemical Barking on Preservative Treatment 25 
 
 Chemical Peeling for the Woodland Owner 27 
 
 SUMMARY AND CONCLUSIONS 28 
 
 LITERATURE CITED 30 
 
 ACKNOWLEDGMENTS . . . 30 
 
 Until 1952 relatively little was known about the use of chemicals as an 
 aid in barking trees. The tests described in this report were initiated dur- 
 ing the winter of 1950 and completed in the fall of 1952. Since these data 
 were collected, much progress has been made toward a better under- 
 standing of the principles of chemical barking and its application. Many 
 results similar to those reported herein have already appeared in print. 
 Although the publication of the results of the Illinois tests was unavoidably 
 delayed, the authors believe that the information obtained was significant, 
 and that it will be of value in substantiating the results of other more 
 recent investigations. 
 
 Urbana, Illinois March, 1958 
 
 Publications in the Bulletin series report the results of investigations made 
 or sponsored by the Experiment Station 
 
SODIUM ARSENITE AS AN AID IN BARKING JACK PINE 
 AND BLACK OAK FENCE POSTS 
 
 By K. R. PETERSON, C. S. WALTERS, and W. L. MEEK" 
 
 THE TREATMENT OF LIVING TREES WITH CHEMICALS to facilitate the 
 removal of bark is a rather recent development. A number of re- 
 ports have been published on chemical barking research, many of them 
 by persons interested in peeling pulpwood (1, 3, 6, 9). b Several chem- 
 icals and methods have been tested. Although the results of the tests 
 have varied with regard to species and season and methods of treat- 
 ment, the technique appears promising as a means of barking trees to 
 be used for products other than pulpwood. 
 
 Small trees thinned from Illinois woodlands may be used as fence 
 posts. Most of the species, however, are not naturally durable in con- 
 tact with soil, requiring preservative treatment to make them so. Wood 
 preservatives do not penetrate bark. Therefore, it is essential that posts 
 be thoroughly barked or peeled before they are given preservative treat- 
 ment. Hand-peeling, however, is arduous and the best season for hand- 
 peeling is in the spring when the farm workload is heavy. If post-peeling 
 could be made easier or delayed by the use of chemicals until time 
 would be available for the work, more farmers would treat their fence 
 posts, thereby conserving time, money, and raw materials. 
 
 DEVELOPMENT AND EARLY STATUS 
 OF CHEMICAL BARKING 
 
 The use of chemicals to bark trees probably was first described in a 
 Canadian patent issued to A. R. White in September, 1942 (U. S. 
 Patent issued in July, 1943). Although 11 years earlier Cope and 
 Spaeth (2) described a method similar to White's, they recommended 
 their method for killing trees and not for barking them. 
 
 The results of formal tests of barking chemicals and techniques 
 began to appear in the literature about 1946 (3) when the Canadian 
 Forest Products Laboratory described the effectiveness of various 
 chemicals and seasons of treatment and cutting in barking several 
 
 K. R. PETERSON, Research Associate in Forestry ; C. S. WALTERS, Professor 
 of Forestry; and W. L. MEEK, formerly First Assistant in Forest Utilization 
 Research. 
 
 " Numbers in parentheses refer to literature citations listed at the end of this 
 report. 
 
4 BULLETIN No. 626 [March, 
 
 pulpwood species. In their early tests, the Canadian researchers applied 
 the barking chemicals to a girdle made at breast height on the tree with 
 a V-shaped knife. The knife was designed to cut a shallow, narrow 
 groove through the bark and into the sapwood. The chemical was pre- 
 pared as a paste and it was held in contact with the girdle by a band of 
 crinkled paper pulled tightly around the tree and fastened with a tack. 
 
 The conclusions drawn from the results of the Canadian tests were 
 published in a series of reports, many of which appeared between 1946 
 and 1950 (3, 5, 6, 8). In general, soluble arsenic proved to be the best 
 of the chemicals tested prior to 1950 for facilitating bark removal. 
 Trees which were girdled but not poisoned were found to be either 
 similar to untreated control trees in peeling qualities or, in some in- 
 stances, harder to peel. June, July, and possibly the first part of August 
 were found to be the best months for applying chemicals under Cana- 
 dian conditions if the bark were to be peeled easily during the fall of 
 the same year. Generally, a minimum period of two months was needed 
 between treating and felling the Canadian trees to obtain the best 
 barking results. 
 
 Since 1950 a number of reports on chemical barking have been 
 published in this country and in Europe, only a few of which are cited 
 in this publication. The most comprehensive of these reports is prob- 
 ably the one made by Wilcox and his colleagues (11) in 1956 on the 
 work of the cooperative Chemical Debarking Research Project con- 
 ducted by the State University of New York. 
 
 CHEMICAL BARKING TESTS MADE IN ILLINOIS 
 
 In 1950 the Illinois Agricultural Experiment Station in cooperation 
 with the Illinois Department of Conservation, Division of Forestry, 
 initiated a study of the use of sodium arsenite for barking post-size 
 trees. The objectives of the investigation were to: 
 
 1. Find methods of reducing the cost of peeling fence posts for 
 preservative treatment. 
 
 2. Determine whether the method of peeling has an effect on the 
 treatability of posts that are to be cold-soaked in oil-soluble wood 
 preservatives. 
 
 3. Determine whether the peeling season could be prolonged by 
 killing the cambium at a time when growing conditions make peeling 
 easiest. 
 
 4. Develop a technique which would produce satisfactory results 
 under Illinois conditions. 
 
1958] CHEMICAL BARKING OF BLACK OAK AND JACK PINE 5 
 
 MATERIALS AND METHODS 
 
 Trees. Jack pine (Finns banksiana Lamb.) and black oak (Quercus 
 vclutina Lam.) were chosen for treatment because a satisfactory num- 
 ber of trees of post-size were readily available on the Mason County 
 State Forest. (The original design also included hickory, but an ade- 
 quate supply of satisfactory trees was not available in the test area.) 
 
 Two hundred and thirty-four pines in a fifteen-year-old plantation 
 were pruned to a height of 7 feet and identified with numbered metal 
 tags. The trees ranged from 2.3 to 5.2 inches in diameter (average 
 diameter was 3.4 inches) at the time they were poisoned. The total 
 height of the pine test trees ranged from 15 to 24 feet, averaging 19.8 
 feet. With one or two exceptions, the trees contained only one 7-foot 
 post. 
 
 One hundred and eight of the 234 oak test trees were located on an 
 area of approximately 2 acres, and the remaining trees were on a second 
 area of similar size and environment. The two areas, located about 3 
 miles apart, were portions of larger timber stands which apparently had 
 been clear-cut twenty-five years earlier. Only trees which had devel- 
 oped from seedlings, rather than sprouts, were selected for treatment. 
 Most of the trees had pruned themselves to a height of at least 7 feet. 
 
 Barking chemicals. At the time the investigation was initiated, 
 sodium arsenite appeared to be the most promising of the barking 
 chemicals, and the tests were limited to this compound. Two aqueous 
 solutions were prepared from a technical grade, powdered form of the 
 chemical. One solution, designated as "weak," contained 7.5 gm. of 
 toxicant per 100 ml. of water. The "strong" solution contained 20.0 gm. 
 of sodium arsenite per 100 ml. of water. 
 
 A paste form was prepared by mixing 2 parts (by weight) sodium 
 arsenite, 1 part cornstarch, and 12 parts water, and heating the mixture 
 approximately 5 minutes. 
 
 Design of experiment. This factorial experiment related the effect 
 of dosage, time of treatment, and duration of treatment to the length 
 of time required to hand-peel posts cut from the poisoned trees. Table 1 
 shows the schedule of treatments for 468 trees included in the study. 
 Tables 2 and 3 show the poisoning and cutting and peeling schedules 
 for 156 3-tree lots. The test trees were randomly assigned to treatments. 
 
 The study was divided into two parts. Part I (Table 2) was de- 
 signed to show the most effective time of the year for applying the 
 different concentrations of sodium arsenite. Thus, three trees of each 
 
BULLETIN No. 626 [March, 
 
 Table 1. Number of Trees Tested Grouped by Treatment 
 and by Species 
 
 Treatment Parti Part II Total 
 
 Weak solution 
 
 Black oak 
 36 
 
 36 
 
 72 
 
 Strong solution 
 
 36 
 
 36 
 
 72 
 
 Paste 
 
 
 36 
 
 36 
 
 Untreated controls 
 
 36 
 
 18 a 
 
 54 
 
 Subtotal 
 
 108 
 
 126 
 
 234 
 
 Weak solution 
 
 Jack pine 
 36 
 
 36 
 
 72 
 
 Strong solution 
 
 36 
 
 36 
 
 72 
 
 Paste 
 
 
 36 
 
 36 
 
 Untreated controls 
 
 . . 36 
 
 18" 
 
 54 
 
 Subtotal 
 
 108 
 
 126 
 
 234 
 
 Total 
 
 216 
 
 252 
 
 468 
 
 
 
 
 
 n Overlapping of schedules for Parts I and II reduced the requirements for control trees 
 to 18. 
 
 species were poisoned with the weak solution and a similar number 
 with the strong solution, each month from December, 1950, through 
 November, 1951. One year elapsed between poisoning the trees and the 
 time the posts were cut and peeled. Three untreated (control) trees of 
 each species also were cut each month, and the posts were peeled with 
 the poisoned posts. 
 
 Part II (Table 3) was designed to show the minimum amount of 
 exposure time required between poisoning and felling to obtain the best 
 peeling results. One hundred and twenty-six trees of each species were 
 poisoned May 15, 195 l, a a time that was judged to be favorable for 
 "sap-peeling" (barking posts during the spring when it is made easier 
 by physiological and anatomical changes in the tree). Nine treated trees 
 and three untreated controls of each species were cut, and the posts 
 were peeled each month following treatment. Thus, exposure times 
 ranged from one to twelve months in length. As Parts I and II over- 
 lapped for six months (December, 1951 through May, 1952), one set 
 of control trees served both parts for that period. 
 
 Application of barking chemical. All trees except the untreatec 
 controls were girdled at breast height with a girdling saw (Fig. 1 
 
 " Previous experience showed that the peak of the sap-peeling season in Illinois 
 occurs about ten days after the hardwood leaves attain full size. This "rule of 
 thumb" and periodic tests on nontest trees were used to set the poisoning date. 
 
1958] CHEMICAL BARKING OF BLACK OAK AND JACK PINE 
 
 Table 2. Schedule of Treatments for 3-Tree Lots: Part I 
 
 Date of 
 treatment 
 
 Black oak 
 
 Jack pine 
 
 
 Treatment 
 
 
 Treatment 
 
 Untreated 
 controls 
 
 Year Month 
 
 Weak Strong 
 solution solution 
 
 Untreated 
 controls Weak 
 solution 
 
 Strong 
 solution 
 
 1950 Dec 
 
 1 
 
 Trees girdled and poisoned 
 
 13 
 14 
 15 
 16 
 17 
 18 
 19 
 20 
 21 
 22 
 23 
 24 
 
 Butt posts cut and peeled a 
 
 13 49 
 14 50 
 15 51 
 16 52 
 17 53 
 18 54 
 19 55 
 20 56 
 21 57 
 22 58 
 23 59 
 24 60 
 
 25 
 26 
 27 
 28 
 29 
 30 
 31 
 32 
 33 
 34 
 35 
 36 
 
 25 
 26 
 27 
 28 
 29 
 30 
 31 
 32 
 33 
 34 
 35 
 36 
 
 37 
 38 
 39 
 40 
 41 
 42 
 43 
 44 
 45 
 46 
 47 
 48 
 
 37 
 38 
 39 
 40 
 41 
 42 
 43 
 44 
 45 
 46 
 47 
 48 
 
 61 
 62 
 63 
 64 
 65 
 66 
 67 
 68 
 69 
 70 
 71 
 72 
 
 1951 Jan 
 
 2 
 
 Feb. 
 
 3 
 
 Mar 
 
 4 
 
 Apr 
 
 5 
 
 May 
 
 6 
 
 June 
 
 7 
 
 July. . 
 
 8 
 
 Aug. 
 
 9 
 
 Sept 
 
 . . 10 
 
 Oct. . . 
 
 11 
 
 Nov 
 
 . . . 12 
 
 Dec 
 
 1 
 
 1952 Jan. 
 
 2 
 
 Feb. 
 
 3 
 
 Mar 
 
 4 
 
 Apr. . . 
 
 5 
 
 May 
 
 6 
 
 June 
 
 7 
 
 July. . 
 
 8 
 
 Auer. 
 
 9 
 
 Sept.. 
 
 . . . 10 
 
 Oct 
 
 ... 11 
 
 Nov 
 
 ... 12 
 
 
 
 * The three trees in each lot produced from 3 to 7 7-foot posts. For example, only 1 post 
 was cut from each of the 3 pines in Lot 37; 6 posts were cut from 3 oaks in Lot 13. 
 
 designed to cut a groove (kerf) 14 inch wide. The girdles were cut 
 through the bark and into the sapwood to a depth of 1/4 inch. 
 
 The sodium-arsenite solutions were applied to the girdles with a 
 pump-type oil can. No measurement was made of the volume of solu- 
 tion applied to each tree, but the dosage was "liberal" (Fig. 2). About 
 620 ml. of solution were required to treat 72 oaks, an average of 8.6 ml. 
 per tree. About 480 ml. of solution were applied to a similar number of 
 pines, an average of 6.7 ml. per tree. 
 
 Two men, one girdling and one applying the solution to the girdle, 
 treated 72 jack pine trees at an average rate of 3.4 man-minutes per 
 tree. 
 
 The paste was applied with a hand-operated caulking gun (the type 
 commonly used for home maintenance) equipped with a i/2-inch nozzle. 
 
BULLETIN No. 626 
 
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1958] 
 
 CHEMICAL BARKING OF BLACK OAK AND JACK PINE 
 
 This girdling saw, shown partially disassembled, was built of two pruning- 
 saw blades spaced about 1/4 inch apart with flat washers. Two stove 
 bolts and wing nuts held blades in position. Although the saw was used 
 to girdle all trees treated with sodium-arsenite solutions, it was rated as 
 an unsatisfactory tool for this purpose. Bark clogged the space between 
 the blades, and the girdle was believed to be too narrow for best results. 
 Wider spacing of the blades might have overcome the objectionable 
 features. Other features of the tool, such as its lightness and cutting 
 speed, were quite satisfactory. (Fig. 1) 
 
 A pump-type oil can was 
 used to apply the sodium- 
 arsenite solutions to girdled 
 trees. The first portion of 
 the solution applied was 
 readily absorbed; treatment 
 was stopped when the tree 
 no longer promptly ab- 
 sorbed the solution and the 
 liquid began to flow down 
 the trunk. A small paint 
 brush probably would be 
 a less tiring and quicker 
 method of applying the so- 
 lution than the oil can. 
 
 (Fig. 2) 
 
10 
 
 BULLETIN No. 626 
 
 [March, 
 
 The gun held about 430 gm. of paste and one loading treated about 20 
 pines, an average of 21 gm. of paste per tree or 6.5 gm. of paste per 
 inch of tree diameter. The authors concluded that the paste-gun method 
 of poisoning would not be practical for a commercial operation, par- 
 ticularly where girdles wider than 1/2 inch were used. 
 
 Collection and analysis of peeling data. An axe, a bark spud made 
 from a section of automobile springleaf, and a carpenter's draw knife 
 were used interchangeably to peel the posts. The choice of tool de- 
 pended on which one was best suited for the post being peeled. The 
 posts were supported in a "buck" during the peeling operation (Fig. 3). 
 Posts cut during freezing weather were stored overnight in a warm 
 room and peeled there the following day. 
 
 Peeling times were measured with a stop watch and recorded on 
 data forms together with a narrative description of results. 
 
 
 Test posts were held in a "buck" during the peeling operation. The 1 
 of the peeling buck were set in the soil to a depth of about 2 feet tc 
 give the equipment stability. The operator is using a carpenter's drav 
 knife to peel the post. (Fig. 
 
1958] CHEMICAL BARKING OF BLACK OAK AND JACK PINE 11 
 
 The measurement data were punched on cards, and the organiza- 
 tion and computation of the data were made by business machines. 
 
 Only one post was cut from each pine tree, but from one to three 
 posts were cut from each oak tree. Since missing values complicated the 
 analyses, the analyses of variance (Tables 5, 7, 9, 11) apply only to data 
 for the butt posts. 
 
 The diameters in inches and the peeling times in seconds for the 
 butt posts were analyzed statistically. Differences in diameters were not 
 a significant source of variation. However, the differences among peel- 
 ing times were found to be significant, and an analysis of variance was 
 made for each group of species data to determine the effects of treat- 
 ment, month, and the interaction of treatment and month. 
 
 A hypothesis that peeling times fitted a cyclical pattern over the four 
 seasons of the year was tested using first and second harmonics. The 
 test showed no significance and the hypothesis was rejected. 
 
 RESULTS 
 
 Part I: Effect of Season on Peeling Time 
 
 Pine. The month of treatment and average peeling times for jack 
 pine posts which were cut and peeled one year after the trees were 
 poisoned are shown in Table 4 and Figure 4. 
 
 An analysis of variance (Table 5) for the peeling data showed that 
 treatment, month, and their interaction were highly significant sources 
 of variation. This means that the variation of peeling time from month 
 to month was characteristic of the treatment applied, as shown in 
 Figure 4. Since the two sources of variation were interdependent in 
 their effects on peeling time, the average independent effects of the two 
 variables on peeling time become relatively unimportant. 
 
 Treating with the strong sodium-arsenite solution in August gave 
 the lowest peeling time for posts cut from jack pines that were poisoned 
 each month and felled one year later (Lots 25 to 72, Table 2). The 
 poisoned posts were peeled at a rate averaging 97 seconds per post, and 
 the untreated posts were peeled at the height of the sap-peeling season 
 at a rate averaging 62 percent slower (157 seconds per post). 
 
 The control trees peeled most rapidly from April through August. 
 During this time poisoning was detrimental, or at best neutral, except 
 for the strong solution applied in August. The sap-peeling season for 
 jack pine appeared to be somewhat longer than that for oak. 
 
12 
 
 BULLETIN No. 626 
 
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 CHEMICAL BARKING OF BLACK OAK AND JACK PINE 
 
 13 
 
 SQN003S-J.SOd 3d 
 
14 
 
 BULLETIN No. 626 
 
 [March, 
 
 Table 5. Analysis of Variance for Jack Pine Post-Peeling Data: Part I 
 
 Peeling times obtained from 7-foot butt posts cut from healthy trees and from 
 trees poisoned monthly. Treated trees exposed to poison one year before posts 
 were cut and barked. 
 
 Source of variation 
 
 Degrees of 
 freedom 
 
 Sum of 
 squares 
 
 Mean 
 square 
 
 Variance 
 ratio (F) a 
 
 Treatment 
 
 2 
 
 268,605 
 
 134302 
 
 16.02*** 
 
 Month 
 
 11 
 
 991,032 
 
 90093 
 
 10.75*** 
 
 Treatment by month 
 
 22 
 
 984,722 
 
 44760 
 
 5.34*** 
 
 Error 
 
 72 
 
 603,541 
 
 8382 
 
 
 Total 
 
 107 
 
 2,847,900 
 
 
 
 
 
 
 
 
 a *** _ s ig n ifi can t a t .001 level. 
 
 Oak. The effects of treatment at various months of the year on the 
 length of time required to peel black oak posts cut one year following 
 treatment are shown in Table 6 and Figures 5 and 6. Table 7 shows an 
 analysis of variance for the oak-peeling data. 
 
 Treatment and month, but not the interaction of these two variables, 
 were highly significant sources of variation (Table 7). Therefore, 
 standard errors and standard deviations for average peeling times for 
 each month and treatment are shown in Table 6. 
 
 The lowest average peeling time per post for all treatments com- 
 bined was recorded for June, 234 seconds (Table 6 and Fig. 6A). The 
 lowest of the average peeling times for the three methods of treatment 
 was for the strong sodium-arsenite solution (Table 6 and Fig. 6B), 
 313 seconds, although the time was only slightly lower than that for 
 the weak solution (332 seconds). The average peeling times for both 
 
 Table 7. Analysis of Variance for Black Oak Post-Peeling Data: Part I 
 
 Peeling times obtained from 7-foot butt posts cut from healthy trees and from 
 trees poisoned monthly. Treated trees exposed to poison one year before posts 
 were cut and barked. 
 
 Source of variation 
 
 Degrees of 
 freedom 
 
 Sum of 
 squares 
 
 Mean 
 square 
 
 Variance 
 ratio (F) a 
 
 Treatment 
 
 2 
 
 297,746 
 
 148873 
 
 20.32*** 
 
 Month . 
 
 11 
 
 408,108 
 
 37100 
 
 4.85*** 
 
 Treatment by month 
 
 . . . 22 
 
 191,120 
 
 8687 
 
 1 18 NS 
 
 Error 
 
 72 
 
 527,334 
 
 7324 
 
 
 Total 
 
 107 
 
 1,424,308 
 
 
 
 
 
 
 
 
 ** = significant at .001 level. 
 NS = not significant. 
 
CHEMICAL BARKING OF BLACK OAK AND JACK PINE 
 
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 BULLETIN No. 626 
 
 [March, 
 
 
 SQNOD3S-iSOd U3d 3WI1 9NH33d 39VH3AV 
 
1958} 
 
 CHEMICAL BARKING OF BLACK OAK AND JACK PINE 
 
 17 
 
 poison solutions, 313 and 332 seconds, were lower than that for the 
 untreated control posts (433 seconds). The lower standard deviations 
 for the poisoned posts (Table 6) indicates that the peeling times were 
 more uniform than they were for the control posts. 
 
 Part II: Effect of Length of Exposure to Poison on Peeling Time 
 Pine. Peeling times for jack pine posts poisoned in May, 1951, and 
 
 subsequently peeled at intervals of one to twelve months, are shown for 
 
 various treatments in Table 8 and Figure 7. 
 
 An analysis of variance for the peeling data (Table 9), shows that 
 
 the treatment-by-month interaction was very highly significant. This 
 
 FMAMJJASOND 
 MONTH OF TREATMENT 
 
 SODIUM ARSENITE 
 TREATMENT 
 
 A B 
 
 The effect of treatment on average peeling times for black oak butt posts 
 cut from healthy trees and from trees poisoned monthly with sodium 
 arsenite solutions (Part I). Treated trees exposed to poison one year 
 before posts were cut and barked. A: Peeling times by month of treat- 
 ment. B: Peeling times by kind of treatment. (Fig. 6) 
 
18 
 
 BULLETIN No. 626 
 
 [March, 
 
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1958] 
 
 CHEMICAL BARKING OF BLACK OAK AND JACK PINE 
 
 19 
 
 
 
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20 BULLETIN No. 626 [March, 
 
 Table 9. Analysis of Variance for Jack Pine Post Peeling: Part II 
 
 Peeling times obtained from 7-foot butt posts cut and peeled at intervals of one 
 to twelve months after poisoning in May 1951. 
 
 Source of variation 
 
 Degrees of 
 freedom 
 
 Sum of 
 squares 
 
 Mean 
 square 
 
 Variance 
 ratio (F) a 
 
 Treatment 
 
 3 
 
 216,163 
 
 72054 
 
 5.65** 
 
 Month 
 
 11 
 
 1,147,528 
 
 104320 
 
 7 59*** 
 
 Treatment by month 
 
 33 
 
 720 630 
 
 21837 
 
 1 59*** 
 
 Error 
 
 96 
 
 1,319,210 
 
 13741 
 
 
 Total 
 
 143 
 
 3 403 531 
 
 
 
 
 
 
 
 
 a ** significant at .01 level. 
 ** = significant at .001 level. 
 
 means that the amount of time required to peel posts varied with the 
 time that elapsed beween treatment and peeling in a manner character- 
 istic of the type of treatment applied. Thus, we should look in Table 8 
 for the combination of treatment and length of exposure to poison 
 before peeling that gave the lowest peeling time. 
 
 The untreated control posts cut and peeled in July had the lowest 
 average peeling time (220 seconds) for all lots shown in Table 8. 
 
 Although the poisoning treatments and length of exposure to the 
 poisons were different, three of the peeling times were somewhat 
 similar. For posts that were cut from trees poisoned with sodium- 
 arsenite paste in May and peeled 10 months later, the average peeling 
 time was 250 seconds. When the strong solution was used, the best 
 average peeling time, 263 seconds, occurred twelve months after poison- 
 ing. One group of posts from the trees treated with weak solution were 
 cut and peeled only four months after treatment, but the average peel- 
 ing time, 277 seconds, was almost as low as those previously mentioned. 
 
 Oak. Peeling times for oak posts poisoned in May, 1951, and sub- 
 sequently peeled at intervals of one to twelve months are shown in 
 Table 10 and Figure 8. In Table 11 an analysis of variance for the 
 peeling data shows that the treatment-by-month (elapsed time) inter- 
 action was highly significant, as it was for the pine. 
 
 The untreated trees peeled more rapidly in May than the trees 
 treated in May and allowed to stand one year before peeling, the aver- 
 age rates being 213 and 217 seconds, respectively. The lowest average 
 peeling time, 210 seconds, was obtained on the controls peeled in June. 
 This means that the time and chemical used to poison trees to be peeled 
 a year later were wasted. 
 
1958] 
 
 CHEMICAL BARKING OF BLACK OAK AND JACK PINE 
 
 21 
 
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22 
 
 BULLETIN No. 626 
 
 [March, 
 
 
1958] 
 
 CHEMICAL BARKING OF BLACK OAK AND JACK PINE 
 
 23 
 
 Table 11. Analysis of Variance for Black Oak 
 Post-Peeling Data: Part II 
 
 Peeling times obtained from 7-foot butt posts cut and peeled at intervals of one 
 to twelve months after poisoning in May 1951. 
 
 Source of variation 
 
 Degrees of 
 freedom 
 
 Sum of 
 squares 
 
 Mean 
 square 
 
 Variance 
 ratio (F) a 
 
 Treatment 
 
 3 
 
 119,308 
 
 39769 
 
 3.19* 
 
 Month 
 
 11 
 
 1,017,272 
 
 92479 
 
 7.43*** 
 
 Treatment by month 
 
 33 
 
 581,909 
 
 17633 
 
 1.42** 
 
 Error 
 
 96 
 
 1,194,028 
 
 12437 
 
 
 Total 
 
 ... 143 
 
 2,912,517 
 
 
 
 
 
 
 
 
 * = significant at .05 level. 
 '* = significant at .01 level. 
 '* = significant at .001 level. 
 
 DISCUSSION OF RESULTS 
 
 The statistical analyses discussed earlier indicated that ease of peel- 
 ing usually depended on a particular combination of type of treatment 
 and elapsed time since poisoning. It would be helpful to the reader to 
 know the combination that might be used most effectively under condi- 
 tions similar to those that existed when the experimental treatments 
 were made, but the data do not show clearly the most effective poisoning 
 schedule. 
 
 One reason for the confusion is this: Peeling time recorded for a 
 post represented "average" peeling conditions over the 7- foot length. 
 If the post had been poisoned and the cambium only partially killed, 
 however, then peeling time did not represent the true effects of the 
 treatment. As a matter of fact, incomplete kill of the cambium, partic- 
 ularly the area below the girdle, often made peeling more difficult and 
 resulted in an increase in peeling time. Thus peeling times must be 
 balanced by general observations recorded in narrative records. 
 
 In general, better results were secured with strong sodium-arsenite 
 solution than with the weak solution or the paste mixture. The strong 
 solution contained about 17 percent toxicant. Although the solution was 
 saturated at all seasons of the year, the toxicant concentration was still 
 below the 30 to 50 percent solutions now recommended for barking 
 trees. 
 
 The sap-peeling season for jack pine was from May 15 to August 
 15 in 1951 and from June 15 to August 15 in 1952. The black oak 
 sap-peeling season appeared to be of shorter duration, May 15 to about 
 Tune 15 in both 1951 and 1952. 
 
24 BULLETIN No. 626 [March, 
 
 In addition to differences in season and type of treatment, peeling 
 time was probably affected by weather conditions at time of peeling, 
 skill of the peelers, size and quality (knottiness and straightness) of 
 the post, thickness of bark, and the girdling technique used. 
 
 Some posts were peeled during freezing weather, and the effect of 
 frozen moisture in the post on ease of peeling is unknown. However, it 
 is believed that posts stored overnight in a heated building and peeled 
 indoors were easier to peel than frozen posts, other conditions being 
 equal. 
 
 Most of the peeling was done by two of the authors, although five 
 members of the Forestry Department participated. Every attempt was 
 made by those peeling posts to work at a steady "normal" rate. No 
 acceptable method of evaluating or correcting differences in hand- 
 peeling skill was developed. Wilcox designed a tool which evaluated 
 the effects of treatment (10) by measuring peeling resistance in terms 
 of a gram-centimeter unit of stress, but it too proved a source of 
 variation (7, 11) that could not be measured. 
 
 The experimental error probably would have been smaller if all the 
 posts could have been pruned and the pruning scars allowed to heal 
 before the trees were poisoned. The jack pine trees were pruned to a 
 height of about 7 feet from four to twenty months before the trees 
 were cut into posts, but not all the pruning scars had completely healed 
 by the time the posts were peeled. The oaks often developed epicormic 
 branches, which appeared singly or in clusters on the bole of the tree 
 below the girdle. These "knots" created a peeling problem, the effect of 
 which could not be measured in terms of peeling time. 
 
 At the time the investigation was designed (1949), it was believed 
 that a }4-inch girdle located at breast height would be satisfactory. 
 When the posts were peeled, however, it was noted that the cambium 
 on some posts was killed only in narrow streaks (Fig. 9) or spots, 
 whereas the objective was to kill all of the cambium. An incomplete 
 kill of the cambium area usually made such posts more difficult to peel 
 than nonpoisoned posts. More recent studies (7, 8, 9) have shown that 
 girdles 4 to 12 inches wide are needed to bark post-and-pole-size trees 
 satisfactorily. 
 
 In many instances the entire cambium above the girdle was killed 
 and barking results were satisfactory, whereas the cambium below the 
 girdle was only partially killed and the bark was more difficult to re- 
 move than that on healthy trees (Fig. 10) It is believed that barking 
 times would have been lower in such cases if the girdle had been located 
 
1958] 
 
 CHEMICAL BARKING OF BLACK OAK AND JACK PINE 
 
 25 
 
 These two black oak posts were cut from a tree that was girdled and 
 treated with sodium-arsenite paste in May, 1951; the posts were cut and 
 peeled in January, 1952, eight months after treatment. Note the narrow 
 streaks of dead tissue alternated with wide bands of live tissue. The in- 
 complete kill of the cambium area is believed to have resulted mainly 
 from improper girdling of the tree. (Fig. 9) 
 
 at a point nearer the root collar. However, girdling the tree at a point 
 below the worker's knees with a tool other than one similar to the 
 Cornell tree-killing tool (2) would be more arduous than girdling the 
 tree at a point on the bole between waist-height and breast-height. 
 
 Effect of Chemical Barking on Preservative Treatment 
 
 One of the objectives of this investigation was to determine what 
 effect chemical barking had on the absorption and penetration of oil- 
 soluble wood preservatives. This phase of the study was temporarily 
 abandoned because an adequate supply of suitable posts of a particular 
 barking treatment was not available for the tests. However, Lindgren 
 (4) reported that some fungi increased the permeability of southern 
 pine posts to oil- and water-borne preservative chemicals. In heavily 
 
26 
 
 BULLETIN No. 626 
 
 [March, 
 
 This black oak post was cut from a tree which was girdled and treated 
 with strong sodium-arsenite solution in May, 1951 at the height of the 
 sap-peeling season; the post was cut and peeled in January, 1952, 8 
 months following treatment. Note that the bark above the girdle (right 
 hand side) was dead and easily removed. The bark also was dead and 
 loose for about one foot below the girdle, but the remainder of the bark 
 below the girdle was green and tight. Fungi were present in the dead, 
 loose bark adjacent to the girdle. (Fig. 10) 
 
 molded wood, the absorptions he obtained from nonpressure treatments 
 often were five times greater than those in uninfected wood. 
 
 Mold fungi, of course, have little or no harmful effect on the 
 mechanical properties of wood, whereas decay fungi reduce all 
 strength properties. The first evidence of decay attack on the experi- 
 mental posts was observed in November, six months after the poisoning 
 treatment. The posts that were easily peeled in this investigation also 
 were infected with cerambycid and buprestid a larvae and mold fungi. 
 
 The borers were present in the cambial area within one month 
 following treatment of the oak. The first observation of borers in the 
 
 " The cerambycidae larvae were identified by Dr. C. F. W. Muesebeck, U. S. 
 National Museum, as Acanthoderes sp. and Batyle sp.; Dr. J. C. Krall, State Uni- 
 versity of New York, College of Forestry, identified the buprestid larvae as 
 Chrysobothris sp. 
 
1958] CHEMICAL BARKING OF BLACK OAK AND JACK PINE 27 
 
 jack pine was made in September following treatment with sodium 
 arsenite in May. Fewer borers were found in the pine than in the oak. 
 Unless the preservative treatment can effect deep penetration, the 
 mycelial strands will remain active as long as conditions are favorable 
 for decay. Conditions probably will become favorable for decay of 
 fence posts as soon as the post is set in the fence line. Thus, cold- 
 soaking posts already infected with decay fungi appears to be a ques- 
 tionable practice. 
 
 Chemical Peeling for the Woodland Owner 
 
 From the woodland owner's standpoint, a schedule that would 
 permit him to poison the trees when the treatment would be most effec- 
 tive and cut and peel the posts (or pulpwood) later in the fall or winter 
 when the farm workload is relatively light would be most beneficial. 
 
 Many Illinois farm operators find the period from the middle of 
 April to the middle of May their busiest season of the year. a The 
 seasons of relatively light workloads fall in late summer and during 
 the winter, that is, from the middle of July to about the first of Sep- 
 tember and from the middle of November to the first of February. The 
 peak or depression periods, of course, vary among various types of 
 farms and from one part of the state to another. 
 
 Early summer is a busy farming period and farmers ordinarily do 
 not care to schedule peeling or poisoning activities during this period. 
 There are, of course, only a limited number of working hours. For 
 those farmers who cut and treat their own posts, however, an invest- 
 ment of a few hours poisoning trees for a supply of posts might sub- 
 sequently save several hours of peeling labor, even though the poison- 
 ing work conflicted with other farming activities. Although nothing in 
 the study indicated that poisoning jack pine was desirable, since sap- 
 peeling extended over a relatively long period and took no more time 
 than peeling poisoned posts at other seasons, it is believed that chemical 
 barking when properly done is less arduous than sap-peeling. 
 Thus, poisoning the trees at the height of the sap-peeling season and 
 cutting and peeling the posts in late summer or during the winter 
 would, it seems, better balance the work schedule on many Illinois 
 farms. Peeling, however, should not be delayed beyond the winter 
 season, because of the danger of insects and decay attacking the dead 
 trees. 
 
 a Based upon unpublished data collected by R. A. Hinton, Research Associate 
 in Farm Management, Department of Agricultural Economics. 
 
28 BULLETIN No. 626 [March, 
 
 SUMMARY AND CONCLUSIONS 
 
 Three hundred and sixty post-size trees were girdled at breast 
 height and poisoned with sodium arsenite at various times of the year. 
 One hundred and eight healthy nongirdled trees served as controls. 
 Half of the trees were jack pine and half were black oak. The test 
 trees were subsequently cut into fence posts and the posts were hand- 
 peeled. The sodium arsenite was applied as a "weak" or "strong" 
 aqueous solution, or in mixture with starch paste. Poisoning and cutting 
 schedules were designed to show the effect of poison dosage, time of 
 poison application, and the duration of poison treatment on the length 
 of time required to hand-peel butt posts cut from test trees. 
 
 The main results of the poisoning treatments were these: 
 
 1. When the trees were poisoned monthly and the posts cut and 
 peeled a year following treatment: 
 
 a. There was an interacting effect of treatment and month of 
 treatment on the time required to peel jack pine posts. Applying a 
 relatively strong concentration of an aqueous sodium-arsenite solution 
 to girdled trees in August gave the lowest average peeling time for the 
 species, 97 seconds per post. In comparison, the best average peeling 
 time for nonpoisoned posts occurred in June, when 62 percent more 
 peeling time was required. 
 
 b. The interacting relationship between treatment and month of 
 treatment had no statistically significant effect on peeling time for black 
 oak posts, but the independent effects of "month" and "treatment" 
 were statistically significant. The best average peeling time for a par- 
 ticular month was obtained in June, 234 seconds. The average peeling 
 time for posts treated with strong sodium arsenite solution was 313 
 seconds, results that were superior to all other poisoning treatments. 
 
 2. When the trees were poisoned in May, a time that was judged to 
 be favorable for sap-peeling, and peeled at intervals of one to twelve 
 months after treatment: 
 
 a. The interaction of treatment and length of exposure to poison 
 had a statistically significant effect on peeling time for jack pine posts. 
 The nonpoisoned control posts peeled in July had the lowest average 
 peeling time, 220 seconds. The poisoning treatments gave inconclusive 
 and somewhat poorer results. Although no single poisoning treatment 
 was outstandingly superior, an exposure period of at least ten months 
 appeared to be needed for best results. 
 
 b. The type of treatment given the black oak trees and the 
 amount of time which elapsed between treatment and peeling had an 
 
1958] CHEMICAL BARKING OF BLACK OAK AND JACK PINE 29 
 
 interacting and statistically significant effect upon peeling time. The 
 poisoning treatments gave peeling times that were slightly poorer than 
 those for the sap-peeled controls, although the differences probably 
 were not statistically significant. The lowest average peeling time was 
 secured on nonpoisoned control posts peeled in June, 210 seconds. The 
 average peeling time for control posts peeled in May was 213 seconds 
 per post, and that for posts poisoned with a strong sodium-arsenite 
 solution and peeled twelve months later was 217 seconds. 
 The authors concluded that: 
 
 1. There were a number of factors in addition to differences in 
 season and type of poisoning treatment that probably had an effect on 
 peeling time; namely, weather conditions at time of peeling, skill of the 
 peelers, size and quality of the post, thickness of bark, and the girdling 
 technique used. No acceptable method of evaluating or correcting for 
 differences in peeling times due to these and other similar factors was 
 developed. 
 
 2. Trees should be girdled and poisoned at a point on the bole near 
 the root collar. Girdling a tree at this point, however, would probably 
 be more arduous than girdling at waist-height. 
 
 3. The ^-inch-wide girdle used to poison the trees apparently was 
 too narrow to permit adequate poisoning of the cambium; removing a 
 band of bark at least 4 inches wide is suggested for trees of post size. 
 
 4. The sodium-arsenite solution containing 20 gm. of toxicant per 
 100 ml. of water was superior to one containing 7.5 gm. of the com- 
 pounds per 100 ml. of water, and to a boiled-paste mixture containing 
 13 percent toxicant, 7 percent cornstarch, and 80 percent water. 
 
 5. The sodium-arsenite solutions were easier and quicker to apply 
 than the paste mixture. 
 
 6. Applying the toxic solution with a brush would be easier, quicker, 
 and less tiring than using a hand-operated pump-type oil can. 
 
 7. If chemically barked trees are to be cold-soaked in a wood pre- 
 servative and used as fence posts, the peeling operation probably should 
 be done within six months of the time they are poisoned; otherwise the 
 posts may become heavily infested with decay fungi. 
 
 8. The sap-peeling season for jack pine lasted longer than that for 
 black oak. Although the duration and peak of the sap-peeling season 
 varies from year to year in Illinois, black oak probably peels best from 
 the middle of May to the middle of June, and jack pine from the middle 
 of May to the middle of August. 
 
30 BULLETIN No. 626 
 
 LITERATURE CITED 
 
 1. COOK, D. B., and HAMILTON, L. S. Chemi-peeling pulpwood in New York. 
 
 Jour. Forestry 51(8) : 566-569. 1953. 
 
 2. COPE, J. A., and SPAETH, J. N. The killing of trees with sodium arsenite. 
 
 Jour. Forestry 29 (5): 775-783. 1931. 
 
 3. HALE, J. D., and MC!NTOSH, D. C. Report on effect of chemical treatment on 
 
 the ease of peeling bark from trees felled in November, 1946. Canad. Forest 
 Prod. Lab. Mimeo. No. 116. 1946. 
 
 4. LINDGREN, R. M. Permeability of southern pine as affected by mold and other 
 
 fungus infection. Proc. Amer. Wood-Pres. Assoc. 48:158-168. 1952. 
 
 5. MclNTOSH, D. C. Effects of chemical treatment of pulpwood trees. Canad. 
 
 Forest Prod. Lab. Bui. No. 100. 1951. 
 
 6. MclNTOSH, D. C., and HALE, J. D. Effect of chemical treatment of trees on 
 
 ease of peeling. Canad. Forest Prod. Lab. Mimeo. 0-140. 1949. 
 
 7. RAPHAEL, H. J., PANSHIN, A. J., and DAY, M. W. Chemical bark peeling of 
 
 aspen, 1952 and 1953 field tests. Mich. Agr. Exp. Sta. Quart. Bui. 37(2): 
 230-240. 1954. 
 
 8. RISI, J. L'ecorage chimique des arbres on foret. Canad. Forest Prod. Lab. 
 
 Bui. No. 14. 1954. 
 
 9. Staff of the Chemical Debarking Research Project. Producing peeled pulp- 
 
 wood by chemical debarking. Unnumbered leaflet, State Univ. of N. Y. Col. 
 of Forestry. 1955. 
 
 10. WILCOX, HUGH, CZABATOR, F. J., and GIROLAMI, GUIDO. Seasonal variations in 
 
 bark-peeling characteristics of some Adirondack pulpwood species. Jour. 
 Forestry 52 (5): 338-342. 1954. 
 
 11. WILCOX, HUGH, CZABATOR, F. J., GIROLAMI, GUIDO, MORELAND, D. E., and 
 
 SMITH, R. F. Chemical debarking of some pulpwood species. Tech. Pub. 
 No. 77, State Univ. of N. Y. Col. of Forestry. 1956. 
 
 ACKNOWLEDGMENTS 
 
 The authors express their appreciation to the Illinois Department of 
 Conservation, Division of Forestry, for the use of the Mason County 
 State Forest; H. B. Wycoff, Superintendent of the State Tree Nursery 
 for use of facilities; and Rudolph Wahlfeld, former Superintendent of 
 the Mason County State Forest, for help in early phases of the field 
 work. 
 
 For their contributions to the study, the authors thank H. W. Norton, 
 Professor of Statistical Design and Analysis for suggestions regarding 
 the analyses and his review of the manuscript; D. A. Kulp, former mem- 
 ber of the Department of Forestry, for help in planning the investigation 
 and assisting in its early phases; J. J. Jokela, G. R. Cunningham, and 
 T. W. Curtin for their help in cutting and peeling the posts, and J. N. 
 Spaeth, Head of the Department of Forestry, for his counsel during the 
 study and his review of the manuscript. 
 
5M 3-59 67331 
 
 
UNIVERSITY OF ILLINOIS-URBAN*