Economic Implications of Caliciopsis on the Lumber Industry

In the northeastern United States, eastern white pine (Pinus strobus L.) is a leading species in the forest products industry. The native pathogen  Caliciopsis pinea  Peck is associated with Caliciopsis canker of white pine, with symptoms including excessive resin production and cankers. This study processed 28.0 m3 of white pine lumber to: (1) quantify losses resulting from Caliciopsis canker, (2) assess how damage varies between Caliciopsis canker symptom severity and thinning, and (3) quantify economic loss resulting from damage. Caliciopsis canker damage was present in 37% of lumber, yet only 10% was downgraded due to canker damage. Of the downgraded lumber, the vast majority (77%) lost one grade. Additionally, severely symptomatic trees consistently had more damage, and their lumber was more likely to be downgraded than low severity trees. Caliciopsis canker damage resulted in average revenue losses of 2.3%. Yet much of the sampled lumber had other, more significant damage which resulted in downgrade: highly symptomatic trees averaged 63% of the revenue of low/asymptomatic trees. Caliciopsis canker, therefore, can be used as an indicator of poor quality trees. We recommend thinning Caliciopsis canker symptomatic trees to meet low-density stocking guidelines, which may minimize revenue loss while simultaneously minimizing stress to residual stock.

Site Selection: Three white pine sites that all had > 75% basal area white pine were selected in northern New England (N1 and N2 in New Hampshire, M3 in Maine). Each site had a history of Caliciopsis canker damage, and a portion of each site was thinned to approximately 250 trees per hectare (TPH) within the last 5-15 years. Paired stands were selected at each site: one thinned and one unthinned stand in close proximity to one another. All stands had similar climate regimes with mean annual temperatures from 6.9-7.6° C and mean annual precipitation from 111.2-117.9 cm. All stands occurred on fine sandy loam soils that were shallow, had limited rooting depth, and were moderately well drained to poorly drained.

Plots were established at the center of each stand and all trees greater than 12.7 cm dbh were measured. The following data was recorded: species, dbh, height, crown class, and uncompacted live crown ratio. All white pine trees were further for Caliciopsis canker symptoms. Tree boles were visually divided into thirds and the number of resin streaks were counted. These resin counts did not sufficiently distinguish low and high severity trees, thus additional symptoms were used to categorize trees (Figure 1). To ensure that a full range of damaged trees was sampled, 10 white pine trees were harvested from each stand: the five most severely affected trees (high severity) and the five least affected trees (low severity), for a total of 60 trees. While a key objective of this study was to measure the lumber value of Caliciopsis canker damaged trees, it is likely that thinning treatments targeted and removed highly symptomatic trees over less symptomatic trees in the New Hampshire thinned stands. As a result, the five most severely affected trees in thinned stands were likely some of the least affected trees prior to the original thinning.

Sample trees were harvested in summer 2015 (site N1) and summer 2016 (sites N2, M3), and a unique identifier was assigned to each tree and log. Standard logging procedures were followed: trees were felled by chainsaw, delimbed, bucked into 3.7 m sawlogs with a minimum 15.2 cm top, dragged to a landing, loaded onto a flatbed truck, and transported to a nearby mill for further processing. At M3, a few logs were cut to 4.3 m or 4.9 m at the discretion of the landowner. Variation in log length was accounted for in measurement and analysis.

Sample Processing: At the mill a certified scaler calculated the gross volume of each log prior to milling, using the International ¼” Log Rule. A sawyer then milled each log to maximize output. All boards were cut to 2.54 cm thickness, except N1 and N2 logs, where the center board was left at 5.08 cm thickness due to saw limitations. Logs were processed individually to ensure that unique tree and log identifiers were maintained, with two technicians standing at the end of the saw to mark boards. Unique board identifiers were also assigned as they came off the saw. All boards were transported to the University of Maine and loaded into a kiln in batches of 3.5 m3 per charge. They were dried for 6-8 days, at a maximum temperature of 54.5° C, until they reached a moisture content of 6-10% (dry basis). Although the lumber was equalized in the kiln, no conditioning was done due to the mild schedule. Boards were removed from the kiln, transported to a wood shop, and planed to 1.9 cm thickness. Boards passed through the planer one side at a time, and unique identifiers were transferred from one side of the board to the other.

After processing, a certified lumber grade inspector from the Northeastern Lumber Manufacturer’s Association ( NeLMA ) graded each planed board and provided two grades per board. Grades, from high to low, were C-select, D-select, 2 (finish), 3 (premium), 4 (standard), and 5 (industrial). The first grade was based on the board as-is, with the inspector following NeLMA published guidelines. For the second grade, the inspector graded as if pitch and canker damage were “removed” from the board. This second grade allowed us to quantify the loss in lumber quality specifically associated with Caliciopsis canker damage. The inspector also listed the primary defect that graded each board. For example, if a board had Caliciopsis canker damage but was graded as a finish board both as-is and with canker damage “removed,” the inspector recorded the primary defect (e.g., black knots) that kept the board graded as a finish board. Additional measurements were taken on each board, including length, width, thickness, presence/absence of pitch, presence/absence of cankers,number of cankers (only on N2 and M3 boards), and qualitative notes on board quality. Lastly, price data per thousand board feet, by grade and board width, were collected from the  Random Lengths Report . These data were converted to price per m3 of lumber, then used to calculate the value of each board based on size and grade. Additional calculations made for each board included board volume, value as is, and value if Caliciopsis canker damage were removed (all values in $USD). We also calculated value per unit of lumber ($USD/m3) to standardize the data.

Analysis: Basic summary statistics were calculated for each stand including mean tree dbh, height, volume, and UNCR prior to felling. The total number of boards and volume of lumber produced were also calculated, including both the finished volume (measured milled, dried, planed boards) and the gross volume (measured green logs). Two-way analyses of variance (anova) were run in R version 3.4.3 ( R Core Team 2018 ). Each metric (dbh, height, volume, UNCR, number boards, volume lumber, gross volume) was a response variable, while silvicultural treatment (thinned or unthinned) and Caliciopsis canker symptom severity class were fixed effects. Site was treated as a random factor. To assess Caliciopsis canker occurrence within boards and trees, summary statistics were also calculated for every board including volume of boards with Caliciopsis canker damage, as well as volume of boards downgraded due to Caliciopsis canker.

Decrease in lumber quality was assessed by quantifying the volume of boards downgraded due to Caliciopsis canker (Figure 2A-C), as well as downgraded due to other defects (Figure 2D-T). For all boards where Caliciopsis canker did not cause a grade reduction, the primary defect that graded the board was recorded. In addition to canker damage, 15 defects were identified and grouped into broad categories: (1) natural defects including bark and branch seams (Figure 2D-F), shake (Figure 2G), pitch not related to cankers (Figure 2H), and cross grain; (2) red knots (Figure 2I-J); (3) black knots (Figure 2K) and associated holes (Figure 2L-M); (4) biotic defects including incipient and advanced decay (Figure 2N-O) and wounds; (5) structural defects including compression failure (Figure 2P); (6) manufacturing defects including wane (Figure 2Q), stain (Figure 2R-S), and end split; and (7) no defects (Figure 2T), which are C-select boards that received the highest grade. If a board had two co-dominant grading defects, the defects were weighted (0.5 each). To assess which defects were associated with Caliciopsis cankers, the proportion of boards in each defect group was analyzed using two methods. First, boards were grouped by presence/absence of Caliciopsis cankers: boards that did not have canker damage vs. those that had canker damage but were assigned another defect that was the dominant grading factor (note: these two categories excluded canker-downgraded boards). Second, boards were grouped by Caliciopsis canker symptom severity class: boards from high severity trees vs. those from low severity trees. Peterson’s chi square test was performed using the “stats” package in R ( R Core Team 2018 ) to test if presence/absence of canker damage was associated with the primary grading defect, and also if high/low severity ratings were associated with the primary grading defect. Where there was a statistically significant difference between groups, standardized residuals were generated for post hoc analysis. Residuals > 2 or < -2 were considered to deviate substantially from the expected values, contributing to the significant chi square result. Chi square tests were performed on raw count data (number of boards graded by a given defect), but final data were reported by proportion of lumber volume graded by the defect.

Additional calculations were made to quantify losses in grade, as well as to assess how Caliciopsis canker damage varied between log position in the tree and Caliciopsis canker symptom severity class. Calculated metrics include the volume of boards that lost grade, value of lumber from high severity trees as a proportion of low severity value, value due to Caliciopsis canker damage, and which grade levels were affected. The value of lumber from high severity trees as a proportion of the value of lumber from low severity trees was calculated by dividing the present value of lumber from all 10 high severity trees by the present value of lumber from all 10 low severity trees, then multiplying by 100. The value lost due to Caliciopsis canker was calculated for each board by subtracting board value if canker damage were “removed” from the board value as-is. This metric was then summed by tree, symptom severity class, and site to produce total loss estimates for the sampled trees. Finally, loss estimates were divided by the volume of lumber produced to obtain a standardized metric: value lost per m3 of lumber. Value lost per m3 of lumber was then compared between Caliciopsis canker symptom severity class (high or low) and log position in the tree, where Log 1=0-3.75 m, Log 2=3.75-7.50 m, Log 3=7.50-11.25 m, Log 4=11.25-15.00 m, Log 5=15.00-18.75 m.

From July 2015 to August 2016, 60 trees were felled producing 1,747 boards totaling 28.00 m3 (11,868 board ft). When analyzing fixed effects, thinning treatment (thinned vs. unthinned) was only statistically significant for tree dbh, number of boards produced, and gross volume of lumber. Conversely, Caliciopsis canker severity was significant for all metrics except UNCR. Due to the minimal influence of thinning treatment on tree and lumber metrics, differences between these thinning treatments were not considered in further analyses. Instead, data and analyses are reported by site and Caliciopsis canker symptom severity class. On average, low severity trees were slightly larger (dbh, height, volume) and produced more lumber than high severity trees. Low severity trees also averaged greater UNCR values than high severity trees at two of the three sites (N1 and M3).

Of the 28.0 m3 of lumber produced, 10.43 m3 (37%) had evidence of Caliciopsis canker damage (Table 2). Only 2.7 m3 of the damaged lumber (10% of all lumber) was downgraded because of Caliciopsis canker (Table 2). At all sites, high severity trees produced a greater percentage of lumber with Caliciopsis canker damage (p=0.0257, Table 2). Similarly, high severity trees at all three sites had more lumber downgraded due to Caliciopsis canker damage than low severity trees, although ANOVA tests indicated it was not statistically significant (p=0.438, Table 2). For example, at N1 high severity trees produced three times the percentage of lumber downgraded due to Caliciopsis canker, while at M3 high severity trees produced nearly four times the percentage of downgraded lumber (Table 2).

Of the 10.43 m3 of lumber with Caliciopsis canker damage present, only 26% of that lumber was downgraded as a direct result of the canker damage (Table 2). For the remaining 74% of lumber, the presence and size of red knots was the leading cause of downgrade (Table 3). Natural defects (bark and branch seams, shake, non-Caliciopsis-canker-associated pitch, and cross grain), black knots and their associated holes, and biotic defects (wounding, incipient decay, and advanced decay) were also common causes of downgrade (Table 3). Other less common reasons for downgrade included structural defects (compression failure) and manufacturing defects (wane, staining, and end split). A small proportion of lumber was not downgraded because it received the highest grade (C select) and was classified as no defect (Table 3). Across each site, the leading defect grading lumber was different: predominant defects were red knots at N1 (55% of lumber), natural defects at N2 (45% of lumber), and black knots and holes at M3 (26% of lumber).

Presence/absence of Caliciopsis cankers was significantly associated with the primary downgrading defect for each board (x2=27.589, p<0.001; Table 3). Standardized residuals indicated two defect groups were significant: natural defects and biotic defects. Natural defects (bark and branch seams, holes, shake, cross grain, and non-Caliciopsis-canker-related pitch) were more common in lumber without cankers than in lumber with cankers (standardized residuals 2.96 and -2.96, respectively). Biotic downgrades (incipient or advanced decay, wounds) were twice as common in lumber with Caliciopsis cankers than in lumber without cankers (standardized residuals 4.37 and -4.37, respectively).

Similarly, Caliciopsis canker symptom severity class was significantly associated with the primary downgrading defect (x2=46.29, p<0.001; Table 4). For both severity classes, red knots were the leading cause of downgrade, although low severity trees had a greater proportion of lumber downgraded due to red knots than high severity trees (Table 4). Further, three defect groups were significantly different between high severity and low severity classes: red knots (29.32% vs 34.00%), structural defects (4.08% vs 1.12%), and Caliciopsis cankers (14.68% vs 6.45%). According to standardized residuals, Caliciopsis cankers were the most significant defect between severity classes, with lumber from high severity trees more than twice as likely to be downgraded by Caliciopsis cankers than lumber from low severity trees (Table 4).

Of the 2.7 m3 of lumber downgraded due to Caliciopsis canker damage, the vast majority (2.08 m3, 77%) lost one grade (Table 5). The remaining lumber lost two grades (0.58 m3, 21%), or three grades (0.04 m3, 2%; Table 5). The majority of lumber that was downgraded had lower grades to begin with. For example, no C select boards (highest grade) were downgraded due to Caliciopsis canker, and only two D select boards (second highest grade) were downgraded (Table 5).

Value lost due to Caliciopsis canker ranged from $4.16/m3 to $15.96/m3 of lumber, but averaged $7.27/m3 of lumber across all sites and symptom severity classes (Table 6). In each site and severity class, these losses equated to 1.23% to 5.12% of the value of the 10 trees sampled (Table 6). Further, high severity trees consistently lost a greater dollar value and percentage of their value than low severity trees, as a direct result of Caliciopsis canker damage (Table 6). When considering the reduced lumber volume and lower quality lumber, high severity trees yielded just 63% of the value of low severity trees from the same site (Table 6).

Value lost by a log’s height in the tree also varied significantly, with the “butt” log (first log in the tree, 0-3.75 m) losing the least amount of value due to Caliciopsis canker damage (Figure 3). In general, the higher up in the tree a log was cut, the more value was lost due to Caliciopsis canker damage (Figure 3). The exception was the fifth log cut (height 15-18.75 m): although no logs in that range lost value due to canker damage, only three trees had a fifth log, thus the sample size was small. Trees were further separated by Caliciopsis canker symptom severity class. High severity trees lost more value, on average, than the low severity trees from the same site, thinning treatment, and position in the tree (Figure 3). This was more pronounced in the first three logs (first 11.25 m), where the difference in value lost was statistically different between severity groups (Figure 3).

This study presents a unique evaluation of the primary reasons for white pine downgrades based on quantitative data. In our study, Caliciopsis canker damage was found in 37% of sampled lumber, but only 26% of that lumber (10% of all lumber) was y downgraded as a direct result of the canker damage (Table 2). From visual observations and conversations with grade inspectors, there were two primary explanations: (1) Caliciopsis canker damage and resin streaks were often small enough to be within the allowable limit for a given board size, and/or (2) other defects were present that had a greater impact on wood quality than Caliciopsis cankers. These reasons for downgrade are significant: while Caliciopsis cankers were present, clearly other factors influenced the value of our sampled white pine trees, producing poor quality trees and lumber.

Knots (red and black) made up the majority of primary downgrades in both non-Caliciopsis-canker-damaged lumber and canker-damaged lumber (60% and 56%, respectively; Table 3). Additionally, the proportion of natural downgrades (bark and branch seams, shake, pitch, and cross grain) was greater in all non-canker-damaged lumber compared with canker-damaged lumber (28.39% and 21.03%, respectively; Table 3). Also of note was the statistically significant increase in biotic defects (wounds, incipient decay, and advanced decay) in canker-damaged lumber compared with non-canker-damaged lumber (18.52% and 9.07%, respectively; Table 3). A portion of this biotic defect increase could be explained by harvesting damage, which can leave wounds that allow fungi to infect the tree and cause decay; there was, however, minimal indication of harvesting damage on sampled trees. Alternatively, we hypothesize that the increase in biotic defects, particularly decay, associated with canker-damaged may be a result of Caliciopsis cankers acting as an entry point for other fungi and organisms. Recent studies support this hypothesis, having documented large fungal communities associated with Caliciopsis cankers ( Costanza 2017b ,  Schulz et al. 2018 ). While the fungal species reported were not decay fungi, visual observations of early/young cankers showed decay at canker margins and surrounding some larger, older cankers. Thus, it is possible that decay fungi infect cankers at a later date, and additional sampling of older cankers may reveal decay fungi. Taken together, these results suggest that Caliciopsis canker is closely associated with lower quality lumber due to a range of defects.

At the time of site selection and sampling, this study intended to focus on the difference in canker damage between thinned and unthinned stands. It was originally hypothesized that the potential positive impacts of thinning on tree growth and yield would result in increased tree vigor and decreased canker damage. Our results did show that trees from different thinning treatments (thinned vs unthinned) differed significantly in tree dbh values and amount of lumber produced (both number of boards and gross green volume; Supplementary Table 1). However, thinning treatment was not consistently significant across all tree and stand metrics (Supplementary Table 1). For example, the percent of lumber downgraded by Caliciopsis canker was highly variable between sites and thinning treatments. These thinning results were likely confounded for three reasons. First, thinning treatments potentially reduced Caliciopsis canker damage by removing the unhealthiest, most heavily infected and slower growing trees, leaving higher quality residual trees compared to the paired unthinned stands. This is apparent in the size and amount of lumber produced from the sampled trees: trees in thinned stands produced 14.85 m3 of lumber, while those in unthinned stands produced 13.16 m3 (data not shown). Trees in thinned stands also had a larger average dbh (35.67 cm) than those in unthinned stands (34.33 cm), and greater average crown ratios (34.97% vs 28.10%; Supplementary Table 1). Second, thinnings were conducted relatively recently, between 2000 and 2010, thus trees may not have had enough time to respond differently to Caliciopsis canker infections post-treatment. Additionally, the majority of lumber analyzed from these trees was formed prior to 2000, indicating most of our data came from pre-thinned lumber. Finally, in two of the three stands, trees were already growing at different rates before the thinning took place, making it difficult to discern the specific impact of thinning ( Costanza 2017a ). As a result, the effects of thinning were not rigorously explored in this analysis, but future studies would benefit from a more comprehensive assessment on the impacts of thinning.

Instead, differences in Caliciopsis canker symptom severity class were analyzed in detail. High severity trees consistently produced lower quantities of lumber than low severity trees (10.83 m3 vs 17.17 m3 of lumber respectively; Table 6). Further, all lumber with Caliciopsis cankers (regardless of whether or not it was downgraded due to cankers) averaged $297.98/m3, while lumber without canker damage averaged $315.04/m3 (data not shown). Taking into account volume and quality, lumber from high severity trees, on average, yielded just 63% of the revenue that low severity trees yielded (Table 6).These volume and price differences between high and low severity trees suggest that removal of the most severely affected trees can result in larger, more valuable residual trees.

Removing high severity trees is consistent with white pine management recommendations that focus on low-density thinning to maximize health and vigor of pine stands, with targets of 330 stems per hectare and 25 m2/ha basal area ( Seymour 2007 ,  Leak and Yamasaki 2013 ,  Livingston and Kenefic 2018 ). From our study, the M3 thinned stand was the only one that approached these levels, with 270 trees per hectare and 29 m2/ha basal area (data fully reported in Haines et al. 2018). Both N1 and N2 thinned stands had 405 stems per hectare, and 26 m2/ha (N1) or 36 m2/ha (N2) basal area ( Haines et al. 2018 ). The trees sampled from the low-density M3 thinned stand produced more lumber than the more densely stocked thinned stands at N1 or N2 (5.31 m3 vs 4.49 m3 and 5.05 m3, respectively). Further, low severity trees at M3 produced similar volumes of lumber in thinned versus unthinned stands (3.07 m3 vs 3.23 m3), but high severity trees produced nearly 50% more volume in thinned stands versus unthinned stands (2.24 m3 vs 1.54 m3), again supporting the recommendation to remove high severity trees and maintain low-density stands.

In addition to information on Caliciopsis canker, foresters and industry professionals want quantifiable grade loss and financial loss estimates for damaged trees. The majority of sampled lumber (77%) only lost one grade as a result of Caliciopsis canker damage, and select lumber (C and D select, the highest value lumber) was typically not downgraded. Instead, it was moderate- to low-quality lumber which was most frequently downgraded. For example, 63% of Caliciopsis canker-downgraded lumber was reduced from a grade 3 to a grade 4 as a result of canker damage, and another 29% was downgraded from a grade 2 to a grade 3 or 4 (Table 5). When comparing grades between high and low severity trees, low severity trees had a greater proportion of lumber that only lost one grade, instead of two or three grades. This trend occurred at N2 and M3 (Table 5), which suggests that removal of high severity trees can result in fewer grades lost in the residual trees. Further, high severity trees consistently lost a greater percentage of value due to Caliciopsis canker damage (Table 6). As Munck et al. ( 2015a ) suggest, external severity ratings can be extremely useful in conducting field surveys to classify trees and target high severity trees for removal. Due to the additional symptoms associated with Caliciopsis canker and the difficulty in using fresh resin streaks to categorize severity, we suggest that future surveys consider multiple symptoms (e.g., old, blackened resin; roughened bark; reddish sunken lesions; and/or bark seams/cracks) in addition to fresh resin streaks. This study’s detailed severity ratings successfully predicted which trees would have the greatest damage and revenue losses associated with Caliciopsis canker, and thus should be used in future white pine management protocols.

While differences between thinning treatments were generally not statistically significant throughout this study, stand histories and observational data from these three sites is important in understanding our results, particularly value loss estimates. According to management recommendations for white pine ( Seymour 2007 ,  Ostry et al. 2010 ,  Leak and Yamasaki 2013 ,  Livingston and Kenefic 2018 ), N2 was optimally managed: a curative thinning was conducted a few years after moderate Caliciopsis canker symptoms were observed, and the thinning did not overlap with other known stressors (i.e., avoided environmental stressors like drought). Highly affected trees were removed from the stand, and the stand was thinned to approximately 250 trees per hectare. At the time of sampling (2015), differences between high and low severity trees were minimal (Table 2, Table 6, Supplementary Table 2). Also, the proportion of lumber graded by biotic defects was lowest at N2; just 3.62%, compared to 8.04% at N1 and 19.74% at M3 (Supplementary Table 3). These results support the idea that proactive thinning can result in better outcomes, removing the worst trees and leaving residual trees that are healthier and more vigorous, and more likely to compartmentalize future infections ( Haines et al. 2018 ). Conversely, N1 was thinned 15-20 years after initial Caliciopsis canker reports, at which point symptoms were already severe. The N1 thinning was also conducted two months after a large-scale New England hurricane, where trees were already stressed, further exacerbating their predisposition to other stress agents. Finally, droughts occurred in the two summers post-thinning, making the thinned stand at N1 highly stressed. Indeed, lumber from the thinned stand at N1 was twice as likely to have Caliciopsis canker damage than the unthinned stand, and three times as likely to be downgraded due to canker damage than lumber from the unthinned stand (Table 2). Proactive management, coupled with appropriately timed thinnings and removal of high severity trees, can result in increased lumber production and reduced canker damage, but thinning must be properly timed to avoid other stressors.

In general, logs are typically worth less the higher in the tree from which they are cut, with the butt log being the most valuable. Based on our standardized estimates of value loss from Caliciopsis cankerby position, it is clear that log position also influences the amount of downgrade and loss. For example, Log 1 lost $2.09/m3 of lumber on average, while Log 4 lost $23.45/m3 of lumber on average (Figure 3). Minimal canker damage occurs below 7 m, and if damage does occur the cankers are usually small ( Costanza 2017a ). Instead, most of the cankers are occurring in Logs 3 and 4 ( Costanza 2017a ), which in turn results in higher value loss estimates than in Logs 1 and 2 (Figure 3). Interestingly, trees with different external Caliciopsis symptom severity classes (high vs low) differed significantly. At all log positions, high severity trees lost more value. This was particularly evident in Logs 1 and 2, the most valuable logs, where high severity trees lost more than twice as much value as low severity trees. These results are similar to Nevill et al. (1989), who quantified downgrade losses in lodgepole pine trees (P. contorta Dougl.) resulting from Atropellis canker (Atropellis piniphila (Weir)), and likewise found that trees with greater external symptoms lost greater value compared to trees with fewer symptoms. Consequently, high severity trees should be removed, leaving low severity trees that can recover what would otherwise be lost value due to Caliciopsis canker damage.

This study is one of the first to quantify tree-level lumber quality and value loss resulting from canker-forming fungi. Further, we produced a comprehensive assessment of primary defects in white pine lumber in the northeastern United States. However, there were limitations to this study that should be acknowledged. First, only three locations were sampled, all with known, high occurrences of Caliciopsis canker. This study, therefore, likely reflects some of the worst white pine damage associated with Caliciopsis canker. There was also no opportunity to harvest control (asymptomatic) trees, so there is no comparison of yield, grade, or defects between canker-infected and non-canker-infected trees. Additional locations need to be sampled, especially those with asymptomatic trees, in order to better understand the range of lumber defects and value loss across a broad spectrum of white pine stands. This comprehensive sampling would allow us to better understand if Caliciopsis canker damage can occur independent of other defects. Second, when assessing lumber for Caliciopsis canker damage, we only evaluated the processed wood. Visual observations, however, led us to believe that several new, fresh cankers were removed at the sawmill when logs were squared. For stands with newer infestations, the estimates provided here are likely conservative.

The fact that 37% of lumber had Caliciopsis canker damage but only 10% of all lumber was downgraded shows that the value of most lumber was not adversely affected by canker damage. Even if Caliciopsis canker is already present in a stand, thinning can reduce competition, increase resource availability, and in turn improve tree vigor. More vigorous trees respond better to fungal attack, sealing infection areas or defending against initial attack ( Manion 1991 ,  Vasiliauskas 2001 ). In another Caliciopsis canker study, Haines et al. ( 2018 ) reported faster white pine compartmentalization rates (time to seal over the damage) of cankers in thinned, more vigorous trees. Overall, presence of Caliciopsis canker damage is associated with other defects, and appears to be indicative of moderate- to low-quality lumber. Managing for improved health and vigor of white pine will reduce the risk of several common downgrades, improving the overall value of white pine stands.

Based on the results presented here, in conjunction with other studies, we suggest that management plans for stands susceptible to Caliciopsis canker be focused on maintaining adequate, low-density stocking levels and favoring trees with few to no symptoms. Ideally, thinning should be implemented before the first canker symptoms appear, consistently maintaining adequate stocking levels for tree size and basal area. Our recommendations are supported by Munck et al. ( 2016 ), who found that overstocked stands were at higher risk of Caliciopsis canker than well-spaced stands. However, because the response to thinning was insignificant between stands, it is critical to examine additional paired thinned/unthinned stands to assess the influence of specific thinning treatments.

For example, if we assume that Caliciopsis cankers are indicative of poor quality lumber, as our results demonstrate, then management recommendations should focus on removing the most symptomatic trees and maintaining or improving the quality of residual trees. For the residual trees, pruning is one recommendation that can reduce knots in lumber, and is also recommend for reducing white pine susceptibility to white pine blister rust and correcting white pine weevil damage ( Ostry et al. 2010 ). However, Ostry et al. ( 2010 ) also note that pruning will temporarily reduce growth and could provide a short window of time for other fungal agents to enter the tree. Therefore, pruning should either be done early (stands < 15 years old;  Lavallée 1991 ,  Ostry et al. 2010) , or on vigorously growing trees ( Zenner et al. 2005 ,  Ostry et al. 2010 ) if doing a curative treatment in heavily damaged stands. In summary, early intervention that removes symptomatic trees and promotes the quality of residual trees, while avoiding other stressors, is recommended. 

While Caliciopsis canker is an emerging health issue of eastern white pine forests in North America, it is possible that its impact on forest products can be effectively managed and reduced. A total of 37% of harvested white pine lumber had Caliciopsis canker damage, but only 10% of all lumber was downgraded and lost value as a result of the damage. Financially, sampled trees lost 2.3% of their value on average (3.28% in high severity trees, 1.67% in low severity trees), which can represent significant revenue losses. In addition, high severity trees produced less volume and lower quality lumber, yielding just 63% of the revenue of lumber from low severity trees. Together the results of this study indicate that with preemptive, thoughtful management plans it is feasible to remove highly symptomatic trees in order to maintain productive, profitable white pine stands in the Northeast. We therefore recommend resource managers (1) monitor stands routinely to maximize the likelihood of early Caliciopsis canker detection, (2) selectively thin to remove symptomatic trees and leave asymptomatic and low severity trees, (3) maintain adequate spacing and stocking levels, (4) carefully time thinning and harvest operations to minimize damage and avoid other stressors, and (5) attentively mill and process to maximize value (e.g., trim a 4 m board to 3 m if it removes Caliciopsis canker damage, improves grade, and increases value). As a result, these recommendations can reduce the economic impact of Caliciopsis canker on eastern white pine.