Certified organic flue-cured tobacco (Nicotiana tabacum L.) production has experienced significant expansion in the United States. Despite this expansion, there is very little information available that outlines organic nitrogen (N) programs for seedling production. To develop grower recommendations, research was conducted to evaluate the effects of a Peruvian seabird guano (SG), sodium nitrate (SN), or a combination of the two (SN_SG) in a float system on float water chemistry and seedling vigor. A conventional treatment (Conv; SQM Ultrasol Premium) was included for comparison. A greenhouse study was conducted twice between June 2016 and January 2017. Nitrogen fertilizer treatments were applied to tobacco float system water twice during the germination and growth of tobacco transplants. Float system water was collected every 5 days and analyzed for N forms, pH, dissolved oxygen, and bicarbonate. At the end of each experiment, transplant dimensions were measured and percent of usable plants collected. Float water bicarbonate concentration was <1 meq L⁻¹ in treatments absent of SG for the duration of the study, but were in excess of 12 meq L⁻¹ 25 days after seeding (DAS) when SG was the exclusive N source. Despite high ammonium and bicarbonate concentrations with SG, neither factor negatively impacted seedling growth. Both SG and SN_SG produced as many usable plants as Conv; however, seedling height and diameter tended to be lower in SG compared to the other two treatments. No usable transplants were produced when SN was the sole fertility source, likely because of lack of nutrients other than N. Furthermore, many of the organic fertility products require biological activity to mineralize organic N to a plant-available form. This activity can have potentially detrimental outcomes on float system solution pH, dissolved oxygen, and bicarbonate levels.

Field studies were conducted in North Carolina in 2010/2011 and 2012/2013 to determine the effect of flumetralin applied for sucker control in tobacco (Nicotiana tabacum L.) on sweet potato (Ipomoea batatas L. Lam. storage root yield and quality) planted in the following year. Treatments in these studies consisted of flumetralin at 0, 0.67, 1.01, 1.34, 2.02, and 2.69 kg active ingredient (a.i.)/ha applied for sucker control to tobacco 2 weeks after topping (WAT) using a ground sprayer equipped with 3 nozzles per row. In 2012, 3 additional treatments included flumetralin at 1.01 and 2.02 kg/ha applied 2 WAT with a dropline method, and a lay-by treatment of 532 g a.i./ha pendimethalin at 4 to 5 weeks after tobacco transplanting followed by (fb) 1.01 kg/ha flumetralin at 2 WAT (using a 3-nozzle boom sprayer). Sweet potato planted the following year (2011) after tobacco had reduction in no. 1 sweet potato storage root yield in the 2.69 and 2.02 kg/ha flumetralin treatments applied with a 3-nozzle boom sprayer in 2011 and with both application methods (3-nozzle boom sprayer, dropline) in 2013, respectively. Flumetralin application rate (both years) or application method (2013) did not affect jumbo and marketable sweet potato yields. The lay-by treatment of pendimethalin followed by flumetralin in tobacco did not reduce yield (across all grades) of sweet potato planted the following year after tobacco. Overall, these results showed that no concern should exist for sweet potato planted the following year if flumetralin is applied at ≤1.34 kg a.i./ha (label-recommended dose) in tobacco.

Pesticide residues found on cured tobacco (Nicotiana tabacum L.) remain a large concern to the allied tobacco industry. To quantify maximum expected cured leaf residues, 3 active ingredients (fluopicolide, indoxacarb, and oxathiapiprolin) were applied to flue-cured tobacco grown in 6 North Carolina environments from 2016 to 2018. Fluopicolide residues were consistently among the highest documented in this evaluation (7.25 mg/kg maximum), which was most likely a result of the compound having the shortest preharvest interval (PHI; 7 days) among the products tested. The highest indoxacarb residue was 2.15 mg/kg, which was identified in lower-stalk-position samples collected from 1 environment in 2018. Additional data suggest that indoxacarb residues are likely to be <2.0 mg/kg. Oxathiapiprolin was below the limit of quantification (0.09 mg/kg) in 98.6% of the samples analyzed and averaged 0.10 mg/kg in the lower-stalk position of 1 environment in 2017. It is plausible that residues from commercial farming operations would be lower than those reported because of integrated pest management (IPM) practices. Further investigations are warranted to better identify residues resulting from applications delivered using recommendations put forth by Cooperative Extension Services in the southern United States.

Organically derived fatty alcohol is useful for the control of tobacco axillary buds (suckers) and is greatly needed by commercial organic tobacco farmers. Recently, its approval by the U.S. Department of Agriculture (USDA)-National Organic Program has been scrutinized. The objective of this research was to evaluate the suggested alternatives: pelargonic acid, vegetable oil, canola oil, and peppermint + spearmint oil using two different application methods, a standard 3-nozzle boom or a dropline. Chemical injury was not observed within any treatment except for those containing pelargonic acid. Injury was greatest when applied with the 3-nozzle boom and was reduced by nearly 50% with the dropline; however, injury after the dropline application was 2.5 to 7 times greater than any other treatment. Despite significant injury, sucker control was acceptable with pelargonic acid (≈90%) and was similar to that resulting from fatty alcohol (99–100%). Sucker control was <40% among all other treatments, with peppermint + spearmint oil providing better efficacy than canola (10 to 15%) or vegetable oil (−1 to −10%). Cured leaf yield, quality, and value were likewise greatest in fatty alcohol treatments because of maximized sucker control and minimized chemical injury. Producers are encouraged to utilize fatty alcohol until the alternative products can be reformulated and re-evaluated.

Experiments were initiated in 2015 to evaluate the efficacy of chemical topping for burley tobacco (Nicotiana tabacum L.). The major objectives for this study were to determine the optimum timing of suckercide application and appropriate cultivar maturity for effective chemical topping. Burley tobacco cultivars TN 90 (medium maturity), KT 210, and KT 215 (late maturity) were chemically topped at the 10% button, 50% button, and 10% bloom growth stages. The 10% button and 50% button application timings were best suited for chemical topping practices. Treatments that targeted the 10% bloom stage did not completely halt inflorescence growth; however, all application timings resulted in excellent sucker control. Both medium and late maturing burley cultivars proved to be acceptable for chemical topping methods; however, timing the suckercide application may be less difficult with later maturing cultivars. Chemically topped treatments generally resulted in shorter, narrower tip leaves than manually topped treatments. There were no significant differences in total yield of TN 90 when comparing tobacco that was manually topped at 10% bloom to tobacco that was chemically topped at 10% button, 50% button, or 10% bloom across all environments. In 4 out of 6 environments, total yield was not significantly different between manual topping and any chemically topped application timing in the late maturing burley cultivars; however, at least 1 chemically topped application timing had equivalent yield to manually topped tobacco in all environments.

The act of topping tobacco (Nicotiana tabacum L.) involves the removal of the terminal bud or inflorescence of the tobacco plant. This practice ordinarily is accomplished by manually removing the top of each tobacco plant in an entire field, which is labor intensive and costly. The major objectives for this research were to determine which labeled suckercides could be used effectively for chemical topping of burley tobacco and the effect of suckercide rate on sucker control, yield, leaf quality, maleic hydrazide (MH) residues, and leaf chemistry. A study was initiated at Murray, Princeton, and Lexington, KY that investigated the efficacy of suckercide applications using combinations of MH, butralin, and fatty alcohols (FA). The terminal bud was not well controlled with FA or butralin alone, nor was adequate sucker control or total yield achieved. A significant reduction in total yield and sucker control were observed when plants were chemically topped with MH alone compared to manually topped or chemically topped with a tank mixture of MH and butralin at Princeton only. At the other locations, all chemically topped plants had similar yield to manually topped plants. Our data suggested that chemical topping of burley tobacco with a tank mixture of MH and a local systemic can be an acceptable alternative to manual topping as total yield and leaf quality grade index were not significantly different at any location. Total tobacco-specific nitrosamine (TSNA) content and MH residues were significantly lower with chemical topping treatments in some years and locations.

Tobacco-specific nitrosamines (TSNAs) are known carcinogens in cured tobacco. They are produced primarily during the curing process, but agronomic practices occurring in the field as well as handling practices after curing may also influence TSNA levels, particularly if cured leaf is stored at high moisture. After curing and during market preparation, the cured leaf must be supple to avoid breakage. Ideally, this is after a period of wet weather during which the leaf absorbs moisture and comes into order or case. Often the weather remains dry for long periods after curing, and growers resort to artificial ordering to take down a sufficient amount of their crop to work on for several days, during which time the tobacco is bulked. The effect of this artificial ordering on TSNAs during short-term storage is not known. Field experiments were conducted in each of 3 years at two locations in Kentucky to evaluate TSNA accumulation following several ordering methods in dark air-cured and burley tobacco types. Treatments included natural ordering and variants of steaming and misting, which are both commonly used artificial ordering methods. At the Princeton location, samples were taken within 24 hr after the ordering treatments were done. In Lexington, samples were taken sequentially at takedown, after ordering, and after 14 d in the bulk. There were limited and inconsistent differences in total TSNAs between methods of ordering, and the TSNA levels were not affected by the moisture content of the leaf during bulking. There was a significant increase in TSNAs in the 24-hr period between takedown and bulking, which cannot be explained. We conclude that, in Kentucky, growers should use ordering methods that are best suited for their production system, but this may not be the case in warmer climates.