EFFECT OF LOWER LEAF REMOVAL ON WRAPPER LEAF PRODUCTION IN CONNECTICUT BROADLEAF TOBACCO

INTRODUCTION

Connecticut Broadleaf is most similar to dark air-cured tobacco grown in Kentucky. However, it has enhanced leaf quality characteristics that increase its value for cigar production (1). In its traditional production area of the Connecticut River Valley in Connecticut and Massachusetts, there has been a decrease in production while there has also been an increased demand for natural leaf cigar wrappers. Therefore, tobacco dealers have been forced to seek other places for production of Connecticut Broadleaf. Kentucky and Tennessee have been of recent interest as a new area for Connecticut Broadleaf production (2).

Wrapper cuts make this crop profitable. The term wrapper refers to an excellent quality leaf that is large enough to have 6 to 8 wrapper cuts, which will be used to wrap the outside of a cigar. Binder refers to the portion of the cigar that is just below the wrapper. The rest of the cigar is comprised of filler, which makes up the center portion of the cigar. Wrapper cuts are approximately 8 cm in width and 13 cm in length. To be considered a wrapper cut, this leaf area cannot have any holes, defects, or discoloration. Even the slightest defect can disqualify a wrapper cut. There are 3 wrapper grades for this type of tobacco, and at least 50% of the crop needs to fall into these “wrapper” grades for the crop to be profitable based on current input costs (1).

Lower leaves on tobacco plants are commonly of the lowest quality. Growers have been known to remove these lower leaves after the first nitrogen side dressing to increase upper stalk grades and yield in flue cured tobacco (6). Leaf purchasers for flue-cured tobacco have been interested in lower-leaf removal programs that will reduce lug grades without negatively impacting yield or profit. Studies showed removing 4 or 8 leaves increased leaf and tip grades compared to treatments without leaf removal. However, leaf removal programs reduced total cured leaf yield and value. The reduction in income due to reductions in total yield incurred from lower leaf removal showed this management practice may have limited value in flue-cured tobacco (5). Other studies have been conducted with similar results, with 8 leaves removed significantly decreasing yield and value and 4 leaves removed having minimal impact on yield and value (4).

In Connecticut Broadleaf tobacco, the effects of removing lower leaves for wrapper leaf production has not been extensively studied. Removal of lower leaves could put more of the plant’s energy into upper stalk leaf production and result in broader upper leaves, thereby increasing the probability of wrapper grades. The objective of this research was to evaluate the use of lower leaf removal to improve wrapper production as a management strategy for Connecticut Broadleaf in Kentucky and Tennessee.

MATERIALS AND METHODS

Field trials were conducted on a private farm near Mayfield, KY and at the Highland Rim Research & Education Center in Springfield, TN in 2022 and 2023. The soil types for these locations were Grenada silt loam (Fine-silty, mixed, active, thermic Oxyaquic Fraglossudalfs) near Mayfield, and Sango silt loam (Coarse-silty, siliceous, semiactive, thermic Glossic Fragiudults) at Springfield (8). Tobacco was transplanted on May 14, 2022, and May 25, 2023, at Mayfield, and June 1, 2022, and May 4, 2023, at Springfield. All field management practices at both locations followed current University of Kentucky extension recommendations (3), except for leaf removal and fungicide applications. Plot size at the Mayfield, KY, location in both years was 12 m long and 4 rows wide, with row spacing of 101 cm and in-row plant spacing of 81 cm (12,109 plants/ha). At the Springfield, TN location, plots were 12 m long and 4 rows wide, with a row spacing of 106 cm and in-row plant spacing of 60 cm (15,277 plants/ha). All trials were arranged in a randomized complete block design with 4 replications. The variety used in all trials was a selection of a standard Connecticut Broadleaf variety known as “C9” (7).

Treatments are shown in Table 1. The treatment design was a 4 by 2 factorial with leaf removal at 4 levels (no lower leaf removal, lower leaf removal at layby [4 weeks posttransplant], lower leaf removal at topping [7 weeks posttransplant], or lower leaf removal at harvest), and fungicide application at 2 levels (fungicide or no fungicide applications). The lowest 4 leaves on the bottom of the plant were removed in all treatments that included lower leaf removal.

Table 1.Treatments for lower leaf removal trial, 2022 and 2023.

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In all trials, plants were topped to 12 leaves when approximately 35% of the plants in the trial had at least 1 open flower. Treatments that included lower leaf removal had 8 leaves that were harvested. In treatments that received fungicide applications, azoxystrobin (146 g ai/ha) was applied at the time of topping, and Bacillus amyloliquefaciens strain D747 (4.74^13 cfu/ha) was applied 3 days prior to harvest. TX-18 hollow cone nozzles were used at 374 L/ha in broadcast applications for all fungicide treatments.

The center 2 rows of all plots were harvested July 25, 2022, and July 26, 2023, at Mayfield, and August 17, 2022, and July 25, 2023, at Springfield. After cutting, the tobacco was allowed to wilt until leaves were pliable enough to withstand being put on sticks. Six plants were then evenly spaced on each stick. After plants were put on sticks, they were loaded onto scaffold wagons and transported to a standard air-curing barn. Tobacco was then housed at 30-cm stick spacing in standard tier-rail air-curing barns. Barn vents and doors were managed to optimize curing conditions for air-curing.

After air curing was complete, tobacco was removed from the barns when adequate leaf moisture was present to allow handling and leaf removal without breakage. Tobacco was then stripped of “trash grade” leaves (lower leaves on the stalk with obvious ground injury or other physical damage). After trash leaves were removed, stalks were stripped of all remaining leaves, and these leaves were graded into trash, filler, 2-cut, binder, and wrapper grades. Each grade was weighed and yield per hectare was calculated. Yield per hectare was calculated on a plot-by-plot basis by weighing each grade to determine the yield of the plot.

Leaves were removed from the stalk and evaluated to be placed into 5 grades (trash [$1.32/kg], filler [$3.10/kg], number 3 wrapper [$6.62/kg], number 2 wrapper [$9.92/kg], and number 1 wrapper [$15.10/kg]). Leaves that are placed in the trash grade have no area on the leaf that can produce a wrapper cut. Filler grade leaves are leaves that can produce 1 wrapper cut. The next 3 grades are considered “wrapper” grades. Number 3 wrapper grade, also known as “2-cut”, are leaves that have 2 or 3 wrapper cuts within the leaf. Number 2 wrapper grade, also known as “binder”, are leaves that have 4 or 5 wrapper cuts within the leaf. The last grade is the number 1 wrapper grade, also known as “wrapper”, this grade is the highest quality and has 6 or more wrapper cuts within the leaf. Once the leaves were separated into these grades, each grade was weighed separately for each plot.

Data were analyzed using Statistical Analysis Software (SAS) version 9.4 (SAS, 2013). For the lower leaf removal trial in both years, a randomized complete block design analysis was used to determine the effect of treatments on production of wrapper grades. Treatments were partitioned to reflect the factorial treatment arrangement and evaluate the main effects and interactions of lower leaf removal and fungicide application. Analysis of variance (ANOVA) was used to look for differences in the response variables between the treatments. Response variables included total yield, yield of wrapper grades, and gross revenue. Treatment was considered a fixed effect and rep was considered a random effect. Locations were analyzed separately, and years were analyzed together unless there was an interaction between year and treatment. Differences were considered significant when P < 0.1. When there were significant differences between the treatments, all pairwise comparisons were made using Fisher’s Protected LSD test with alpha = 0.1.

RESULTS AND DISCUSSION

ANOVA showed significant reductions in total yield for lower leaf removal treatments compared to treatments where no lower leaves were removed in 2022 (P = 0.0001) and 2023 (P = 0.0158) at the Mayfield, KY location (Table 2). Total yield reductions were greatest where lower leaves were removed at harvest.

Table 2.Effects of lower leaf removal on total yield^a at Mayfield, KY, 2022 and 2023.

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There were no significant effects of lower leaf removal on yield of wrapper grades in 2022 or 2023 at the Mayfield, KY location. However, in 2023, there was a significant effect of fungicide treatment on total yield, total wrapper grade yield, and total revenue, with all 3 of these parameters being reduced where fungicide applications were made at the Mayfield, KY location in 2023 (Table 3). These reductions in total yield, wrapper yield, and total revenue were likely due to phytotoxicity (flecking injury) occurring due to azoxystrobin applications made at topping. Azoxystrobin in known to cause this flecking injury to tobacco under certain environment conditions (3), and this injury appears to be more common in Connecticut Broadleaf than in other types of tobacco.

Table 3.Effects of fungicide on total yield^a, total wrapper^b, and total revenue^c at Mayfield, KY, 2023.

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At the Springfield, TN location, similar treatment effects on total yield were found in 2022 (P = 0.0115) and 2023 (P = 0.0035) due to lower leaf removal (Table 4). Compared with no lower leaf removal in 2022, total yield was reduced by 444 to 488 kg/ha where lower leaves were removed at layby or topping, respectively, and further reduced by 808 kg/ha where lower leaves were removed at harvest. In 2023, lower leaf removal reduced total yield by 233 kg/ha when removed at layby, 243 kg/ha when removed at topping, and 587 kg/ha when removed at harvest (Table 4).

Table 4.Effects of lower leaf removal on total yield^a at Springfield, TN, 2022 and 2023.

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At Springfield, TN, there were significant reductions in wrapper yields in 2022 (P = 0.0363) due to leaf removal, but only where lower leaves were removed at harvest (Table 5). In addition, there were significant reductions in gross revenue of $2,024 to $2,899/ha with lower leaf removal at any timing at the Springfield, TN location in 2022 (Table 5). There were no significant differences in wrapper yields or total revenue at the Springfield, TN location in 2023 (data not shown).

Table 5.Effects of lower leaf removal on total wrapper^a yield and total revenue^b at Springfield, TN, 2022.

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Also, to be noted, estimated labor time trials were conducted at a separate on-farm location in 2023 to evaluate the labor time and resulting cost that would be incurred to remove lower leaves at topping. Based on current labor cost and efficiency of the labor, it was estimated that it would cost $432 to $482/ha to remove the 4 lower leaves from plants at topping.

CONCLUSION

Significant reductions in total yield were seen from lower leaf removal treatments at both locations in both years. There were also no significant increases in wrapper grade yield observed from lower leaf removal at any timing at either location in either year. There were no significant differences found for gross revenue where lower leaves were removed or not removed at the Mayfield, KY location. However, phytotoxicity from azoxystrobin applications made at topping resulted in significant reductions in wrapper yield and total revenue at the Mayfield, KY location in 2023. There were also significant reductions in gross revenue from the lower leaf removal treatments at the Springfield, TN location in 2022. These data suggest that removing lower leaves at layby, topping, or harvest decreases total yield, does not increase wrapper production, and may decrease gross revenue. Therefore, based on these results, the practice of removing lower leaves at layby, topping, or harvest in Connecticut Broadleaf cigar tobacco to increase wrapper grade leaves would not be recommended. However, from experience in these trials, removing lower leaves did seem to improve efficiency during harvest and stripping, although data to support this observation were not collected.